Ras general science=biology
Anabolism consists of chemical reaction that forms complex substances from simpler substances resulting in the
formation of more protoplasm and growth.
Catabolism consisting of chemical reactions that breaks down complex substances resulting in the release of energy.
02) Cell membrane: It is found both on plants and animals.
It is a thin covering surrounding the cytoplasm.
It is present just beneath the cell wall in plants.
It is a semi permeable membrane which permits the passage
of certain substances but prevents the passage of others.
03) Protoplasm: All components internal to cell. Cytoplasm is
the portion of protoplasm without nucleus. It contains water
(85 to 90 %), proteins (7-10%), fats (1-2%) and sugar and
starches (1-2%) . Protoplasm contains a number of specialised
structure called cell organelles and chemical compounds called
cell inclusions.
04) Nucleus: The presence of a nucleus distinguishes the more
complex eukaryotic cells of cells of plants and animals from
simpler prokaryotic cells of bacteria that lack a nucleus. It is
typically round and occupies about 10% of cells volume.
The nucleus contains the nucleolus, which manufactures
protein producing structures called ribosome. Genetic information in the form of DNA is stored in thread like structures called chromatin within nucleus. The chromatid is composed of nucleoproteins that are combinations of proteins and nucleic acids i.e. DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).The DNA in the nucleus also contains the instructions for regulating the amount and types of proteins made by the cell. These instructions are copied, or transcribed, into a type of ribonucleic acid (RNA) called messenger (mRNA). The mRNA is transported from the nucleus to ribosomes, where proteins are assembled.
05) Vacuole: It is found more common in plants than animals and separated from cytoplasm by a membrane tonoplast.
06) Plastids: These are found only in plant cells and three different types are found
08) Endoplasmic reticulum (ER): It is an extensive network of tubes that manufacture, process, and transport materials within nucleated cells. The ER consists of a continuous membrane in the form of branching in the form of braching tubules and flattened sacs that extend throughout the cytoplasm and connect to the double membrane that surrounds the nucleus. There are two types of ER rough and smooth depending on the presence of ribosomes. Ribosomes contain RNA and are the sites of protein synthesis in the cells.
09) Mitochondria : These are the sites of energy release and called power houses of the cells.
10) Golgi apparatus : Also Golgi body or Golgi complex , network of stacked sacs found within nucleated cells that store, package and distribute the proteins and lipids made in ER. The Golgi apparatus in plants is known as dictyosome.
11) Lysosomes. These are vacuole like bodies that secrete enzymes to digest food substances. It is also involved in defence against bacteria and viruses, destroys old and worn out organelles and results in the death of the cell. So they are called suicide bags of the cell.
Mitosis: This is the process in which a cell’s nucleus replicates and divides in preparation for the division of the cell. It results in 2 cells that genetically identical and occurs in 4 successive stages ; prophase, metaphase, anaphase and telophase. These four stages are preceded by a resting phase called interphase. In this phase, chromosomes undergo self duplication. Mitosis is vital for growth and replacement of damages or worn out cells and for asexual reproduction.
Meiosis: It is a type of cell division in which the cell’s genetic information, contained in chromosomes, is mixed and divided into sex cells (gametes) with half the normal number of chromosomes. The random sorting of chromosomes during meiosis assures that each new sex cell, and therefore each new offspring, has a unique genetic inheritance. Thus it results in the reduction of chromosomes in the daughter cells by half. So gametes are haploid and when they fuse together the produce a diploid zygote.Hence it is a source of new genetic variation.
The five kingdoms are
Prokaryotes (pro-KAR-ee-oht) are organisms, such as bacteria and archaea, that lack nuclei and other complex cell structures. Eukaryotes share a common origin, and are often treated formally as a superkingdom, empire, or domain. In the domain system, eukaryotes have more in common with archaean prokaryotes than bacterial prokaryotes. The name comes from the Greek ευ, meaning good/true, and κάρυον, meaning nut, in reference to the cell nucleus.
Aerobic bacteria uses oxygen for respiration and anaerobic bacteria maintain respiration without free oxygen and this process is known as fermentation. So it is used in the production of vinegar and other substances. Some bacteria decompose organic matter and fix nitrogen by converting atmospheric nitrogen into nitrates. These are mainly found in the roots of legumes such as peas, clover and alfalfa. In human beings, intestinal bacteria produce lactic acid which promotes digestion.
Bioremediation: It is the use of microorganisms such as bacteria to remove environmental pollutants from soil, water or gases.
Ferns allies have a vascular system to transport fluids through their bodies but like mosses, they reproduce from spores rather than seeds. Three other phyla are included are The horsetails, club mosses and whisk ferns.
The gymnosperms add the next level of complexity to plant evolution: They reproduce from seeds instead of spores. The seeds however are “naked” not covered by an ovary. Usually the seed is produced inside a cone like structure such as a pine cone hence the name “conifer.” Conifers are fairly easy to identify. In addition to these cones trees and shrubs have needle-like, scale-like or awl-like leaves and they never have flowers. Approximately 600 species are counted as conifers including the pines, firs, spruces, cedars, junipers and yew. Species within the conifer ranks give us pine nuts, turpentine and rosin are prepared from pine resin. Pine seeds are eaten by man and animals. Ephedrine, a drug from Ephedra, is used for the relief of asthma and other respiratory ailments.
Angiosperms add the final improvement to plant reproduction: They grow their seeds inside an ovary (Greek : angeion = vessel) which is, itself, embedded in a flower. After it is fertilized, the flower falls away and the ovary swells to become a fruit. The angiosperms are classified as Monocotyledons and Dicotyledons.
Within the leaf, there is a layer of cells called the mesophyll. The word mesophyll is greek and means "middle" (meso) "leaf" (phyllon). Mesophyll can then be divided into two layers, the palisade layer (F) and the spongy layer (G). Palisade cells are more column-like, and lie just under the epidermis, the spongy cells are more loosely packed and lie between the palisade layer and the lower epidermis. The air spaces between the spongy cells allow for gas exchange. Mesophyll cells (both palisade and spongy) are packed with chloroplasts, and this is where photosynethesis actually occurs.
Epidermis also lines the lower area of the leaf (as does the cuticle). The leaf also has tiny holes within the epidermis called stomata (H). Specialized cells, called guard cells (I) surround the stomata and are shaped like two cupped hands. Changes within water pressure cause the stoma (singular of stomata) to open or close. If the guard cells are full of water, they swell up and bend away from each other which open the stoma. During dry times, the guard cells close.
1) Dermal - It covers the outer surface of herbaceous plants and prevent water loss. e.g guard cells.
2) Ground - It comprises the bulk of the primary plant body. e.g. Parenchyma, collenchyma, and sclerenchyma cells.
3) Vascular - It transports food, water, hormones and minerals within the plant. xylem, phloem, parenchyma, and cambium cells.
Parenchyma: A generalized plant cell type, parenchyma cells are alive at maturity. They function in storage, photosynthesis, and as the bulk of ground and vascular tissues.
Collenchyma: These cells support the plant. It consists of living cells that are characterized by thickening of cells particularly at corners.
Sclerenchyma: These cells support the plant but they are dead at maturity. They often occur as bundle cap fibers. Sclerenchyma cells are characterized by thickenings in their secondary walls. The fibers from jute and coconut are best examples of these cells.
Xylem: These cells conduct water and minerals from roots to leaves. The common name of Xylem is wood. Tracheids and vessels are major cells types both of which are dead at maturity.
Phloem: It transports food from the leaves to rest of the plant. They are alive at maturity. The two most common cells in the phloem are the companion cells and sieve cells. Companion cells retain their nucleus and control the adjacent sieve cells. Dissolved food, as sucrose, flows through the sieve cells.
Cambium: It is layer of actively dividing cells lying between xylem and phloem; forms additional xylem and phloem layers during secondary thickening. The layers formed in each year forms a distinctive series of concentric rings called annual rings. By counting the annual rings, we can find out the age of the tree.
Cork: It is the out layer of bark. These increases in girth as new layers of xylem and phloem are formed. It develops abundantly in certain trees. Commercial cork is taken from oak tree.
This most primitive unicellular organisms which reproduce by fission, budding,spores or sexually. e.g. Amoeba, Entamoeba, paramecium, vorticella, plasmodium, Euglena & trypanosoma. They move a variety of ways. The ameba has a false foot that extends as it moves. The paramecium is covered with hairs and the euglena has a whip-like tail(flagella) to move. A protozoa takes in oxygen through the cell membrane and gives off carbon dioxide through the cell membrane. Some protozoans are harmful to man as they can cause serious diseases. Others are
helpful because they eat harmful bacteria and are food for fish and other animals.
a) Gastropod: The Gastropoda (Greek gaster,"stomach"; pous,"foot") are generally characterized by a single shell and an asymmetric body. E.g. snails and slugs.
b) Bivalves: It is characterized by a shell divided into two valves hinged at one side, gills specialized for feeding, and a reduced head. E.g clam, cockle, mussel, oyster, scallop, and shipworm. Pearl is actually a secretion by bivalves induced by factors such as foreign substances etc
c) Cephalpods: The word cephalopod means "head footed," and the animals are so named because the arms surround the mouth. These are predatory marine mollusks which includes squid, octopus, and nautilus.
b) Arachnids: The annelids are similar to insects. However, they have eight legs, wings are different and they have no antenna. The arachnids are spiders, scorpions, etc.
c) Crustaceans: These are predominantly aquatic arthropods with protective carapace and compound eyes. E.g. Prawns, Lobsters and Crabs.
d) Myriapods: include millipedes and centipedes. The centipedes have two pairs of legs per segment while millipedes have one pair.
i) Agnatha: They are fish like forms with the absence of Jaws and scales. Their skeleton is cartilaginous. The best examples of this type are lamprey and the hagfish They have two chambered heart and gills used for respiration.
ii) Gnathostomata: These are vertebrates with jawed mouth. These are subdivided into fishes, amphibians, reptiles, birds and mammals.
a) Fishes: These are diverse group of cold blooded animals that live and breathe in water. Most fish have gills for breathing, two chambered heart, fins for swimming, scales for protection, and a streamlined body for moving easily through the water. The swim (or gas) bladder allows fish to maintain a constant buoyancy regardless of the changing water pressure at varying depths. Its eyes are positioned on either side of its body and are quite large, with no eyelid. They have an inner ear but no outer ear opening. Fishes are broadly classified into
i) Chondrichthyes (Cartilaginous fish): Their skeleton made of cartilage and their body covered with triangular Placoid scales. They lack a swim bladder but have air sacs to regulate buyonancy. E.g Sharks ,Rays and Skates. Sharks are viviparous.
ii) Osteichthyes (bony fishes): They have a bony endoskeleton. These are oviparous and fertilization is external. E.g. Salmon, Labeo (rohu), Mrigal etc.
b) Amphibians: Amphibian means both sides of life. it begins its life in the water and then finishes it mainly on land. It uses gills in larval stage (tadpole) and lungs and skins in the adult stage. Their heart is three chambered. Skin is often kept moist for gas exchange. These are cold blooded animals and have to be near water to complete their life cycle. So these are severely affected by environmental pollutants, destruction and modification of amphibian habitats, such as the cutting of forests and the draining of wetlands .E.g. Frogs, toad, Salamander, caecilians, sirens etc.
c) Reptiles: Reptiles are cold blooded animal with tough, dry skin covered with horny scales adapted for life in dry places. Some forms are aquatic. Reptiles breathe air with lungs alone. They have teeth except in tortoises and turtles. They have three chambered heart (crocodile has a four chambered heart). The females eggs are fertilized in her body by the male. The eggs are laid in a shell that has a leathery covering to protect it in the wilds. E.g. turtles, lizards, snakes, crocodiles, gavial (Gharial),alligators and dinosaurs.
d) Birds: They are unique in the fact that they are covered with feathers and fly. They are descended from reptiles, feathers are modified limbs and their eggs resemble reptilian eggs. But like mammals they are warm blooded and have four chambered heart. The bones of many adult birds are hollow rather than filled with marrow, making them lighter and enabling them to disperse heat in flight. A bird has relatively large eyes that allow it to judge distance well and an excellent sense of hearing. They exhibit migratory behaviour, nest building and parental care. The study of birds is ornithology. The Smallest bird is humming bird. The heaviest bird is bustard
e) Mammals: Mammals are warm blooded animals having distinctive characteristics such as milk producing mammary glands, hair on their body, external ears, sweat glands, give birth to young rather laying eggs and nurse their young
Major mammal groups
a) Monosaccharides are simple sugars consisting of three or more carbon atoms. e.g. Ribose, deoxyribose(pentoses),glucose, fructose (fruit sugar) and galactose( hexoses). (Our body digests them quickly and easily; it is sweat tasting and found in fruits)
b) Disaccharides are formed by the union of two monosaccharids. Maltose(malt sugar) = glucose+glucose
Lactose(Milk sugar) = glucose+galactose
Sucrose(cane sugar) = glucose+fructose.
(These takes longer to be digested than Monosaccharides. Found in foods like bread, noodles, rice, vegetables.)
c) Polysaccharids are made up of large number of monosaccharids units(300 to over 1000). E.g. starch, cellulose in plants , glycogen, chitin in animals.
The nutrional role of carbohydrate is the production of energy. These are main sources of blood glucose and stored in tissues as glycogen in liver and muscles for further use when necessary.
The deficiency causes Kwashiorkor in children below 5 years who instead of mothers milk take mainly carbohydrate diet. If the mothers milk is replaced to children below 1 year it causes Marasmus.
Anaemia is caused due to iron deficiency and characterised by deficiency of haemoglobin in red blood cells.
Hypokalemia is caused by loss of potassium and characterised by kidney damage, rise in hear beat, paralysis of muscles.
Hyponatremia is due to the increased loss of sodium which leads to dehydration, low blood pressure and loss of body weight.
Simple Goitre is casued by deficiency of iodine which regulates the secretion of the thyroxine from the thyroid gland. It causes the increased production of thyroid stimulating hormone which brings about the enlargement of gland.
The process occurs in two phases:
1) glycolysis, the breakdown of glucose to pyruvic acid
2) the complete oxidation of pyruvic acid to carbon dioxide and water. This process called aerobic respiration. When the respiration takes place with out oxygen it is known as anaerobic respiration. The end product of anaerobic respiration is carbon dioxide and chemical such as lactic acid and ethanol. When the micro organisms respire anaerobically we call it as fermentation. e.g. fermentation of yeast in the preparation of ethanol.
Features of blood cells: Red blood cells, white blood cells, and platelets grow from a single precursor cell, known as a haematopoietic stem cell.
It is internal mechanisms of animals to prevent blood loss at the time of injury. During the blood clotting, the blood platelets produce an enzyme called thromokinase which forms prothrombin protein in the plasma. It combines with calcium ion to form thrombin. It convert the soluble plasma protein(fibrinogen) to form fibrin threads. corpuscles get entangled in these threads and forms clot.
The wall of the heart is very muscular and does not tire. It consists of three distinct layers. The first is the outer epicardium which is composed of a layer of flattened epithelial cells and connective tissue. Beneath this is a much thicker myocardium made up of cardiac muscle. The endocardium is a further layer of flattened epithelial cells and connective tissue.
A large blood supply is necessary to power the heart itself. It is supplied by the left and right coronary arteries, which branch off from the aorta.
Main components of nephron -
Urine formation
The formation of urine had three processes: filtration, reabsorption, and tubular excretion During filtration, or glomerular excretion, blood pressure forces all the small molecules in the blood into the lumen of the nephron through the pores both in the walls of the glomerular capillaries and in the wall of the Bowmans capsule. The filtrate has the same concentration of dissolved substances as the blood minus the formed elements and the plasma proteins which are too large to fit through the pores of the capillaries and the Bowmans capsule. As the filtrate passes through the tubules of the nephron, water and many dissolved materials are reabsorbed by the blood. In fact, during the filtrates passage through the tubules up to 99 percent of the water is reabsorbed. In addition, the tubules also remove substances from the blood. This process, called tubular excretion, supplements the initial glomerular filtration.
Hormones of the Kidneys: The human kidney is also an endocrine gland secreting two hormones: 1) Erythropoietin (EPO) 2) Calcitriol, the active form of vitamin D as well as the enzyme renin.
The functions of our body are controlled and coordinated by two systems namely the nervous and endocrine system. The nervous system consists of animals within the animal organisms that are concerned with the reception of stimuli, the transmission of nerve impulses, or the activation of muscle mechanisms. A nerve tissue composed primarily of cells called neurons. A neuron consists ofdendrites, a cell body and an axon. The dendrites generate nerve impulses in response to stimulation from a sense receptor or from another neuron and carry impulses toward the cell body, which contains the cell’s nucleus. The axon carries an impulse
transmitted to it by the cell body to another neuron or to an effector muscle or gland. There are three types of neuron sensory, motor and association. A synapse is the junction between two neuron.
In mammals these neuron comprise 2 types of nervous system i.e.Central nervous system and peripheral nervous system. The brain and spinal cord make up the central nervous system (CNS).
The Central Nervous System (CNS) is composed of the brain and spinal cord.
b) parietal : It has somaesthetic area or general sensory area is the seat for general sensation like pain, touch and temperature.
c) temporal lobe :The temporal lobes are anterior to the occipital lobes and lateral to the Fissure of Sylvius. Temporal lobes are associated with emotional responses, hearing, memory and speech.
d) occipital lobes : It has a visual area ( visual sensation) and auditory area ( hearing)
(ii) Hypothalmus : The hypothalamus is composed of scattered masses of grey matter in white matter at the base of the brain. Although it is the size of only a pea (about 1/300 of the total brain weight), the hypothalamus is responsible for some very important functions. It is responsible for regulation of temperature, hunger, thirst and emotional reactions. The hypothalamus also controls the pituitary.
b) Brainstem : The brain stem is a general term for the area of the brain between the thalamus and spinal cord. Structures within the brain stem include the medulla, pons, tectum, reticular formation and tegmentum. Some of these areas are responsible for the most basic functions of life such as breathing, heart rate and blood pressure.
Spinal Cord: spinal cord is about 43 cm long in adult women and 45 cm long in adult men and weighs about 35-40 grams. The vertebral column, the collection of bones (back bone) that houses the spinal cord, is about 70 cm long. Therefore, the spinal cord is much shorter than the vertebral column. It is covered by the same meninges as the brain and its main function is conduct impulses to and from the brain and acts as a reflex centre.
a) spinal nerves are those nerves emerge from the spinal cord . There are 31 pairs of spinal nerves all of them are mixed nerves consisting of sensory and motor neurons .
b) cranial nerves are those nerves that emerge from the brain. There are twelve pairs of them. Some are sensory, some are motor and some are mixed nerves.
c) autonomic nervous system : This is organised into two distinct regions along the central nervous system forming the sympathetic and parasympathetic system. These two systems act opposite to each other in their action in their muscles and glands they control. It controls the rate and force of the heart beat, the contraction of involuntary muscles and the size of pupils of eye.
1. external (an exoskeleton)
The phyla arthropoda and mollusca both have exoskeletons. An internal skeletal system consists of rigid structures within the body, moved by the muscular system. Hydrostatic skeletons are similar to a water-filled balloon. Located internally in cnidarians and annelids, among others, these animals can move by contracting the muscles surrounding the fluid-filled pouch, creating pressure within the pouch that causes movement. Cartilage is another common component of skeletal systems, supporting and supplementing the skeleton. The human ear and nose are shaped by cartilage. Some organisms have a skeleton consisting entirely
of cartilage and without any calcified bones at all, for examplesharks. The bones or other rigid structures are connected by ligaments and connected to the muscular system via tendons.
The human skeleton consists of 206 bones. We are actually born with more bones (about 300), but many fuse together as a child grows up. These bones support your body and allow you to move. Bones contain a lot ofcalcium (an element found in milk, broccoli, and other foods). Bones manufacture blood cells and store important minerals.
The longest bone in our bodies is the femur (thigh bone). The smallest bone is the stirrup bone inside the ear. Each hand has 26 bones in it. Your nose and ears are not made of bone; they are made of cartilage, a flexible substance that is not as hard as bone.
Bones are connected to other bones at joints.T here are many different types of joints, including
fixed joints (such as in the skull, which consists of many bones)
hinged joints (such as in the fingers and toes)
ball-and-socket joints (such as the shoulders and hips)
A typical bone has an outer layer of hard or compact bone, which is very strong, dense and tough. Inside this is a layer of spongy bone, which is like honeycomb, lighter and slightly flexible. In the middle of some bones is jelly-like bone marrow, where new cells are constantly being produced for the blood.
Differences in males and females
2) Budding: In this process an offspring grows out of the body of the parent e.g. Hydra
4) Fragmentation: In this form, the body of the parent breaks into distinct pieces, each of which can produce an offspring. Planariansexhibit this type of reproduction.
5) Regeneration: In this form, if a piece of a parent is detached, it can grow and develop into a completely new individual.Echinoderms & Crustaceans exhibit this type of reproduction.
Male reproductive system
During sexual intercourse, semen containing millions of sperms discharges into vagina. The sperms swim up to the fallopian tube and only one sperm fuses with the ovum to produce zygote. The embryo is formed from this zygote.
During the fetal stage, which lasts from 9 weeks after fertilization to birth, development continues as cells multiply, move, and change. The fetus floats in amniotic fluid inside the amniotic sac. The fetus receives oxygen and nourishment from the mothers blood via the placenta. The amniotic fluid and membrane cushion the fetus against bumps and jolts to the mothers body.
Pregnancy lasts an average of 280 days - about 9 months. When the baby is ready for birth, its head presses on the cervix, which begins to relax and widen to get ready for the baby to pass into and through the vagina. The mucus that has formed a plug in the cervix loosens, and with amniotic fluid, comes out through the vagina when the mothers water breaks.
When the contractions of labor begin, the walls of the uterus contract as they are stimulated by the pituitary hormone oxytocin.The contractions cause the cervix to widen and begin to open. After several hours of this widening, the cervix is dilated (opened) enough for the baby to come through. The baby is pushed out of the uterus, through the cervix, and along the birth canal. The babys head usually comes first; the umbilical cord comes out with the baby and is cut after the baby is delivered. The last stage of the birth process involves the delivery of the placenta, which is now called the afterbirth. After it has separated from the inner lining of the uterus, contractions of the uterus push it out, along with its membranes and fluids.
2. Law of segregation : when the factors that determine a pair of contrasting characters are brought together in a hybrid, they do not freely intermix but maintain their individualities. When the hybrid forms gametes, the factors of the pair become separated from each other and enter separate gametes.
3. Law of independent assortment : In the inheritance of more that one pair of characters considered together in a cross, the factors responsible for each pair of characters are distributed independently to the gametes i.e assorted independent of those of the other pair.
Traits controlled by genes found on X and Y chromosomes are said to be sex linked. Recessive traits appear more frequently in malesthan females due to the fact that males have only one X chromosomes. A female will not exhibit the traits unless the recessive gene is on both her X chromosomes.
Erythroblastosis foetalis : This is a haemolytic disease of new born infants that occur due to incompatibility between mother and foetus.
Colour blindness : defect of vision affecting the ability to distinguish between red and green colours. This happens more commonly in males than females.
Downs syndrome (mongolism) : people with disease may have mild to severe learning disabilities and physical symptoms that include a small skull,extra folds of skin under the eyes, flattened nose bridge,a large,protruding tongue.such persons have 47 chromosomes.
Haemophilia: a hereditary blood disease characterised by inability of blood to clot or coagulate,leading to hemorrhage, or excessive bleeding even from minor injuries.
Harelip : It is abnormal clefts between upper lip and the base of nose. Cleft palate : It is the incomplete closure of palate or roof of mouth.
Sickle cell anaemia : Disease affecting black Africans . The RBC assume sickle shape when blood is deprived of oxygen.
Phenylketonuria: It causes inability to metabolise the amino acid Phenylpyruvic acid.
Albinism:Albinism (from Latin albus, meaning "white") is a lack of pigmentation in the eyes, skin and/or hair. Albinism is an inherited condition resulting from the combination of recessive alleles passed from both parents of an individual.
Cystic fibrosis : It causes body to secrete an abnormally thick, sticky mucus that clogs pancreas,lungs leading to problems with breathing, infection and ultimately death.
(i) pentose sugar(deoxyribose)
(ii) Phosphate molecule
(iii) nitrogenous bases (purines : adenine, guanine pyrimidines : cytosine,thymine).
Among these bases, adenine pairs specifically with thymine whereas cytosine does so with guanine. Hence the molecule is dependent on the sequence of bases in the other, The two chains are, therefore said to be complementary to each other. The base molecules of the two chains are linked through weak hydrogen bonds. Exceptionally,
DNA molecule may be single stranded and circular as in some bacteriophages.
The RNA molecule has generally a single stand of an unbranches polynucleotide chain. Its constituents are the same as in DNA except that the pentose sugar is ribose and among the nitrogenous bases,uracil is present as the pyrimidine in place of thymine. In some instances .the RNA strand is coiled on itself to form helices that may be connected by weak hydrogen bonds.
The genetic code is the sequence of nitrogen bases in deoxyribonucleic acid. The DNA carries the instructions for the production of protein. A protein is composed of smaller molecules called amino acids and the structure and function of the protein is determined by the sequence of its amino acids . The sequence of amino acids in turn is determined by the sequence of nucleotide bases DNA . A sequence of three nucleotide bases, called a triplet, is the genetic code word, or codon, that specifies a particular amino acid.
According to Syllabus of General Science for IAS : BIOLOGY
BIOLOGY
IAS General studies -General science :BIOLOGY
Summary of topics in this article
Intoduction ;Fundamental & Basics of biological sciences
(the study of living organisms).
(the study of living organisms).
Cell biology :Animal vs plant cell,Anatomy of cells & subcellular comonents &
Cell functions.
Cell functions.
Gene:Genetics material, Chromosomes, DNA & Genetic disorder.
Human system: cardiovascular system, digestive system, Endocrine system,
Immune system, Intergumentary system, Lymphatic system, Muscular system,
Nervous system, Reproductive system,Respiratory system , Skeletal system,
Excretory system.
Immune system, Intergumentary system, Lymphatic system, Muscular system,
Nervous system, Reproductive system,Respiratory system , Skeletal system,
Excretory system.
Diseases:causes, transmission of disease, agents and symptoms of hereditary
and communicable diseases. Pathogens of various diseases.
and communicable diseases. Pathogens of various diseases.
Nutrition: Essential nutrients needed for animals and plants, food and its
components like vitamin, protein, carbohydrates, minerals etc.
components like vitamin, protein, carbohydrates, minerals etc.
Biological Diversity: Includes division of animals and plants into various
groups according to their nature of living.
groups according to their nature of living.
Discoveries: Scientists and their discoveries in the field of Biology.
Plant Biology: Nutition elements, photosysthesis,and respiration,
Medicine and materials.
Medicine and materials.
Cell - The Basic Unit of Life
1. Cell - The Basic Unit of Life
Cell is the basic unit of life. These are smallest structure capable of basic life process, such as taking in nutrients,
expelling waste, and reproducing. All living things are composed of cells. Some organisms are unicellular such
as bacteria and protozoa and the rest are multicellular. Different kinds of cells are organised into specialised
groups called tissues such as tendons and bones. Different tissues types are assembled into organs, which are
structures specialised to perform particular functions. Examples are heart, stomach and brain. Organs , in turn, are
organised into systems such as the circulatory, digestive or nervous systems . All together, these assembled organ
systems form Human body.
expelling waste, and reproducing. All living things are composed of cells. Some organisms are unicellular such
as bacteria and protozoa and the rest are multicellular. Different kinds of cells are organised into specialised
groups called tissues such as tendons and bones. Different tissues types are assembled into organs, which are
structures specialised to perform particular functions. Examples are heart, stomach and brain. Organs , in turn, are
organised into systems such as the circulatory, digestive or nervous systems . All together, these assembled organ
systems form Human body.
Important contributions
- Robert Hooke was the first to identify cells and gave them their name.
- Mathias schleiden , theodor Schwann and others formulated a cell theory.
- Virchow stated that new cells are formed due to the divisions of previously existing cells.
- Purkinje found that the protoplasm in a cell is instrumental for all the living activities of a plant.
- Robert Brown discovered nucleus.
- Strasburger and Weismann stated that the nucleus is concerned with the inheritance of characteristics
- of a living body
Activities with in cell
Metabolism is the sum total of biochemical reactions involved in the release and utilisation of energy within the
organism is called Metabolism.
organism is called Metabolism.
Anabolism consists of chemical reaction that forms complex substances from simpler substances resulting in the
formation of more protoplasm and growth.
Catabolism consisting of chemical reactions that breaks down complex substances resulting in the release of energy.
Structure of cell
01) Cell wall: It is absent in animals but found in most of the plants.
It is a semi rigid, permeable structure consisting of cellulose,
lignin and other substances, gives shape to the cell.
It is a semi rigid, permeable structure consisting of cellulose,
lignin and other substances, gives shape to the cell.
02) Cell membrane: It is found both on plants and animals.
It is a thin covering surrounding the cytoplasm.
It is present just beneath the cell wall in plants.
It is a semi permeable membrane which permits the passage
of certain substances but prevents the passage of others.
03) Protoplasm: All components internal to cell. Cytoplasm is
the portion of protoplasm without nucleus. It contains water
(85 to 90 %), proteins (7-10%), fats (1-2%) and sugar and
starches (1-2%) . Protoplasm contains a number of specialised
structure called cell organelles and chemical compounds called
cell inclusions.
04) Nucleus: The presence of a nucleus distinguishes the more
complex eukaryotic cells of cells of plants and animals from
simpler prokaryotic cells of bacteria that lack a nucleus. It is
typically round and occupies about 10% of cells volume.
The nucleus contains the nucleolus, which manufactures
protein producing structures called ribosome. Genetic information in the form of DNA is stored in thread like structures called chromatin within nucleus. The chromatid is composed of nucleoproteins that are combinations of proteins and nucleic acids i.e. DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).The DNA in the nucleus also contains the instructions for regulating the amount and types of proteins made by the cell. These instructions are copied, or transcribed, into a type of ribonucleic acid (RNA) called messenger (mRNA). The mRNA is transported from the nucleus to ribosomes, where proteins are assembled.
05) Vacuole: It is found more common in plants than animals and separated from cytoplasm by a membrane tonoplast.
06) Plastids: These are found only in plant cells and three different types are found
- leucoplasts – found in sex cells, roots and underground cells
- Chromoplasts – It contains pigments that colour parts of plants
- Chloroplasts – That contain chlorophyll, green substance which converts carbon dioxide and water into sugar.
07) Centrosomes: It is a dense area of protoplasm which close to the nucleus. In the middle of the centrosomes are two small dot like, rod shaped or v shaped bodies called centrioles.
08) Endoplasmic reticulum (ER): It is an extensive network of tubes that manufacture, process, and transport materials within nucleated cells. The ER consists of a continuous membrane in the form of branching in the form of braching tubules and flattened sacs that extend throughout the cytoplasm and connect to the double membrane that surrounds the nucleus. There are two types of ER rough and smooth depending on the presence of ribosomes. Ribosomes contain RNA and are the sites of protein synthesis in the cells.
09) Mitochondria : These are the sites of energy release and called power houses of the cells.
10) Golgi apparatus : Also Golgi body or Golgi complex , network of stacked sacs found within nucleated cells that store, package and distribute the proteins and lipids made in ER. The Golgi apparatus in plants is known as dictyosome.
11) Lysosomes. These are vacuole like bodies that secrete enzymes to digest food substances. It is also involved in defence against bacteria and viruses, destroys old and worn out organelles and results in the death of the cell. So they are called suicide bags of the cell.
Cell division
The growth and development of all organisms depend upon the growth and division of cells. All these cell divisions starts from one cell called a fertilized egg cell or zygote. These are two types of cell divisions mitosis and meiosis. The two important events in cell divisions are nuclear division (Karyokinesis) followed by the division of cytoplasm(Cytokinesis).
Mitosis: This is the process in which a cell’s nucleus replicates and divides in preparation for the division of the cell. It results in 2 cells that genetically identical and occurs in 4 successive stages ; prophase, metaphase, anaphase and telophase. These four stages are preceded by a resting phase called interphase. In this phase, chromosomes undergo self duplication. Mitosis is vital for growth and replacement of damages or worn out cells and for asexual reproduction.
Meiosis: It is a type of cell division in which the cell’s genetic information, contained in chromosomes, is mixed and divided into sex cells (gametes) with half the normal number of chromosomes. The random sorting of chromosomes during meiosis assures that each new sex cell, and therefore each new offspring, has a unique genetic inheritance. Thus it results in the reduction of chromosomes in the daughter cells by half. So gametes are haploid and when they fuse together the produce a diploid zygote.Hence it is a source of new genetic variation.
2. Classification of life
Binomial system of nomenclature
Carolus Linnaeus developed Binomial system of nomenclature. It has two parts one generic name with a capital letter and specific name with a small letter e.g. Homo sapiens. In the modern system each living thing belongs to species , genus, family ,order ,class, phylum(or divisions in plants) and kingdom.
The five kingdoms are
Kingdom
|
Structural organisation
|
Method of Nutrition
|
Types of organisms
| |
Monera
|
small simple single prokaryotes.
|
absorb food
|
bacteria, blue green algae, spirochetes
| |
Protista
|
Large, single Eucariotic cell
|
Absorb, ingest
|
Protozoans and algae of various types.
| |
Fungi
|
Multi cellular filamentous form with specialized Eukaryotic cell
|
absorb food
|
funguses, mushrooms, molds, yeast, smuts and mildew.
| |
Plante
|
Multi cellular; Eukaryotic; do not have own mean of locomotion
|
Photosynthesize food
|
mosses, ferns, woody and non woody flowering plants
| |
Animalia
|
Multicellular; eukaryotic with own means of locomotion
|
ingest food
|
sponges, reptiles, amphibians, mammals etc.
|
Eukaryote and Prokaryote
An eukaryote (yoo-KAR-ee-ot) is an organism with a complex cell or cells, in which the genetic material is organized into a membrane-bound nucleus or nuclei. Eukaryotes (also spelled "eucaryotes") comprise animals, plants, and fungi—which are mostly multicellular—as well as various other groups that are collectively classified as protists (many of which are unicellular).
Prokaryotes (pro-KAR-ee-oht) are organisms, such as bacteria and archaea, that lack nuclei and other complex cell structures. Eukaryotes share a common origin, and are often treated formally as a superkingdom, empire, or domain. In the domain system, eukaryotes have more in common with archaean prokaryotes than bacterial prokaryotes. The name comes from the Greek ευ, meaning good/true, and κάρυον, meaning nut, in reference to the cell nucleus.
3. Virus
Structure
A complete virus particle, known as a virion , is little more than a gene transporter, consisting of nucleic acid either deoxyribonucleic acid (DNA) or ribonucleic acid (RNA) surrounded by a protective coat of protein called a capsid. A capsid is composed of proteins encoded by the viral genome and its shape serves as the basis for morphological distinction. Virally coded protein units calledprotomers will self-assemble to form the capsid, requiring no input from the virus genome - however, a few viruses code for proteins which assist in the construction of their capsid. Proteins associated with nucleic acid are known as nucleoproteins, and the association of viral capsid proteins with viral nucleic acid is called anucleocapsid.
Viruses are dead outside the
cells multiply only inside living cells and moves along blood or Phloem sap in animals and plants respectively. The nucleic acid of the virus enters the cell and control the host cell to produce identical virus nucleic acid and protein coat and thus it multiplies. Continuous multiplication of virus, exhaust the protoplasmic contents and it finally the cell ruptures and realises virus. This process is known as lysis of the host cell. The new viruses repeat the entire multiplication process.
cells multiply only inside living cells and moves along blood or Phloem sap in animals and plants respectively. The nucleic acid of the virus enters the cell and control the host cell to produce identical virus nucleic acid and protein coat and thus it multiplies. Continuous multiplication of virus, exhaust the protoplasmic contents and it finally the cell ruptures and realises virus. This process is known as lysis of the host cell. The new viruses repeat the entire multiplication process.
Human diseases caused by virus
Disease
|
Name of Virus
|
AIDS (Acquired immune deficiency syndrome
|
Human T cell Leukemia Virus (HTLV III)
|
Chicken Pox
|
Varicella Virus
|
Common Cold
|
Rhino Virus
|
Herpes Zoster
|
Herpes Zoster
|
Influenza/ Flu
|
Orthomixo Virus
|
Measles
|
Paramyxo Virus
|
Mumps
|
Mumps Virus
|
Rabies
|
Rhabdovirus
|
Dengue Fever
|
Arbovirus
|
Poliomyelitis
|
poliovirus
|
Herpes Simplex
|
Herpes Simplex
|
Treatement
Although viruses cannot be treated with antibiotics, which are effective only against bacteria, the body's immune system has many natural defences against virus infections. Infected cells produce interferon and other cytokines (soluble components that are largely responsible for regulating the immune response), which can signal adjacent uninfected cells to mount their defences, enabling uninfected cells to impair virus replication. Virus are widely used in genetic engineering. Viruses that are parasites of bacteria are called bacteriophage.
Although viruses cannot be treated with antibiotics, which are effective only against bacteria, the body's immune system has many natural defences against virus infections. Infected cells produce interferon and other cytokines (soluble components that are largely responsible for regulating the immune response), which can signal adjacent uninfected cells to mount their defences, enabling uninfected cells to impair virus replication. Virus are widely used in genetic engineering. Viruses that are parasites of bacteria are called bacteriophage.
Viroids and prions
Viroids and prions are smaller than viruses, but they are similarly associated with disease. Viroids are plant pathogens that consist only of a circular, independently replicating RNA molecule. The mutated protein, known as a prion, has been implicated in some neurological diseases such as Creutzfeldt-Jakob disease and Bovine Spongiform Encephalopathy. There is some evidence that prions resemble viruses in their ability to cause infection. Prions, however, lack the nucleic acid found in viruses.
Viroids and prions are smaller than viruses, but they are similarly associated with disease. Viroids are plant pathogens that consist only of a circular, independently replicating RNA molecule. The mutated protein, known as a prion, has been implicated in some neurological diseases such as Creutzfeldt-Jakob disease and Bovine Spongiform Encephalopathy. There is some evidence that prions resemble viruses in their ability to cause infection. Prions, however, lack the nucleic acid found in viruses.
4. Bacteria
Structure
Bacteria are microorganisms that lack a nucleus and have a cell wall composed of peptidoglycan, a protein-sugar molecule. Bacteria are the most common organisms on earth and are intimately connected to the lives of all organisms. The common structural forms are
Bacteria are microorganisms that lack a nucleus and have a cell wall composed of peptidoglycan, a protein-sugar molecule. Bacteria are the most common organisms on earth and are intimately connected to the lives of all organisms. The common structural forms are
- Spherical or ovoid (coccus )
- rod shaped or cylindrical (bacillus )
- spiral or screw (spirillum) Many forms of bacteria are not capable of independent movement,. Some Bacteria which live in liquid often have thread like projections called flagella (e.g Salmonella bacterium)
Reproduction
Reproduction in bacteria is largely by binary fission i.e. it splits into two. In some case due to some extreme environmental conditions, they
form tiny structures is called Spores. It is formed by condensation of protoplasm into a spherical or egg shaped body and they germinate under favourable conditions. Some bacteria exhibit a type of sexual reproduction.
form tiny structures is called Spores. It is formed by condensation of protoplasm into a spherical or egg shaped body and they germinate under favourable conditions. Some bacteria exhibit a type of sexual reproduction.
Human Diseases caused by bacteria
Disease
|
Name of Bacteria
|
Mode of Transmission
|
Septic sore throat
|
Streptococccus
|
By direct contact & droplets
|
Diptheria
|
Corynebacterim diptheriae
|
Infect respiratory tract by carrier, direct contact, droplets and food
|
Pneumonia
|
Diplococcus pneumoniae
|
respiratory tract,lungs by direct contact, droplets and food.
|
Tuberculosis
|
Mycobacterium
|
Lungs, bones etc by direct contact
|
Plague or Babonic Plague
|
Yersinia pestis
|
Rat flea spreads from rat to man
|
Tetanus
|
Clostridium tetani
|
Bacteria in soil, enter through wounds
|
Typhoid
|
Samonella typhi
|
Flies, food, faeces, water and carriers
|
Typhoid
|
Samonella typhi
|
Flies, food, faeces, water and carriers
|
Cholera
|
Vibrio Cholerae
|
Flies, food, faeces, water and carriers
|
Bacillary dysentery
|
Shigella dysenteriae
|
Flies, food, faeces, water and carriers
|
Whooping Cough
|
Hemophilus pertussis
|
Droplets
|
Gonorrhoea
|
Neisseria gomorrhoeae
|
Sexual intercourse
|
Syphilis
|
Treponema Pallidum
|
Sexual intercourse
|
Leprosy
|
Mycobacterium leprae
|
Sexual intercourse
|
Leprosy
|
Mycobacterium leprae
|
Long and close contact with infected
|
Botulism
|
Clostridium botulinum
|
Organism produces poison in food
|
Treatment
Vaccination or Immunization or inoculation is a method of stimulating resistance in the human body to specific diseases using microorganisms -bacteria or viruses-that have been modified or killed. These vaccines do not cause diseases but stimulates the production of antibodies in its blood. It build a defense mechanism that continuously guards against the disease. If a person immunized against a particular disease later comes into contact with the disease-causing agent, the immune system is immediately able to respond defensively. Bacterial vaccines are used chiefly in immunizing human beings and animals against such diseases on diphtheria, cholera and typhoid fever.
Uses
Aerobic bacteria uses oxygen for respiration and anaerobic bacteria maintain respiration without free oxygen and this process is known as fermentation. So it is used in the production of vinegar and other substances. Some bacteria decompose organic matter and fix nitrogen by converting atmospheric nitrogen into nitrates. These are mainly found in the roots of legumes such as peas, clover and alfalfa. In human beings, intestinal bacteria produce lactic acid which promotes digestion.
Bioremediation: It is the use of microorganisms such as bacteria to remove environmental pollutants from soil, water or gases.
Serum
Serum is a preparation from blood of an animal that has been inoculated with bacteria. This contains antibodies that formed as a consequence of the disease. The important antibodies produced with the help of bacteria are streptomycin, Aureomycin, Terramycin. Please note that penicillin is produced by an Fungi .
Important scientists who studied bacteria
- Antoni van Leeuwenhoek : The first person to systematically study bacteria.
- Louis Pasteur: Showed that microbes do not arise from nonliving matter (germ theory). He also founded the science of microbiology, invented the process of pasteurization, and developed vaccines for several diseases, including rabies.
- Robert Koch: showed that bacteria could cause disease.
5. Fungi
Introduction
The fungi (singular fungus) are a kingdom of eukaryotic organisms. Fungi lack chlorophyll; consequently they cannot synthesize their own food. In order to feed fungi release digestive enzymes that break down food outside their bodies. The fungus then absorbs the dissolved food through their cell walls. It is a simple plant body that has no roots, stems, flowers and seeds. It includes mushrooms, molds, yeasts, truffles etc. The branch of biology involving the study of fungi is known as mycology.
Types of fungi
The major divisions (phyla) of fungi are mainly classified based on their sexual reproductive structures. Currently, five divisions are recognized:
- The Chytridiomycota are commonly known as chytrids. These fungi produce zoospores that are capable of moving on their own through liquid menstrua by simple flagella.
- The Zygomycota are known as zygomycetes and reproduce sexually with meiospores called zygospores and asexually with sporangiospores. Black bread mold (Rhizopus stolonifer) is a common species that belongs to this group; another is Pilobolus, which shoots specialized structures through the air for several meters. Medically relevant genera include Mucor, Rhizomucor, and Rhizopus. Molecular phylogenetic investigation has shown the zygomycota to be a polyphyletic group.
- Members of the Glomeromycota are also known as the arbuscular mycorrhizal fungi. Only one species has been observed forming zygospores; all other species only reproduce asexually. This is an ancient association, with evidence dating to 350 million years ago.
- The Ascomycota, commonly known as sac fungi or ascomycetes, form meiotic spores called ascospores, which are enclosed in a special sac-like structure called an ascus. This division includes morels, some mushrooms and truffles, as well as single-celled yeasts and many species that have only been observed undergoing asexual reproduction. Because the products of meiosis are retained within the sac-like ascus, several ascomyctes have been used for elucidating principles of genetics and heredity (e.g. Neurospora crassa).
- Members of the Basidiomycota, commonly known as the club fungi or basidiomycetes, produce meiospores called basidiospores on club-like stalks called basidia. Most common mushrooms belong to this group, as well as rust (fungus) and smut fungi, which are major pathogens of grains.
Major uses
- The enzyme forming activities are used by man in brewing, baking, cheese making. Some cause diseases in animals and plants.
- The symbiotic relationship between fungus and roots are called mycorrhizal. Similarly Lichens are living partnership of a fungus and an alga.
- Litmus, a dye used in chemistry to determine the presence of acid and bases in a solution. Acid turn blue litmus red and bases turn red litmus blue.
- Fungi and bacteria are the primary decomposers of organic matter in most terrestrial ecosystems.
- Some of these fungi can be used as biopesticides, like the ones that kill insects (entomopathogenic fungi). Specific examples of fungi that have been developed as bioinsecticides are Beauveria bassiana, Metarhizium anisopliae, Hirsutella, Paecilomyces fumosoroseus, and Verticillium lecanii.
Major diseases in human caused by Fungi
- Ringworm
- Athletes foot
- Madura foot
- Dhobie itch
6. Algae
Introduction
These are chiefly plant like organisms found usually in water bodies and moist environments that are not subjected to direct sunlight. They make their own food by photosynthesis but theylack roots, leaves and other structures typical of true plants. They capture more of sun’s energy than all plants combined and form the foundation of most aquatic food webs. These are divided into 7 divisions one belonging to monera and the rest to plant kingdom.
These are chiefly plant like organisms found usually in water bodies and moist environments that are not subjected to direct sunlight. They make their own food by photosynthesis but theylack roots, leaves and other structures typical of true plants. They capture more of sun’s energy than all plants combined and form the foundation of most aquatic food webs. These are divided into 7 divisions one belonging to monera and the rest to plant kingdom.
Blue green algae (Cyanobacteria)
This belongs to the moneran division and contain a blue pigmentphycocyanin ,which in addition to chlorophyll but the chlorophyll is not located in chloroplasts rather it is found in chromatophores, infoldings of the plasma memrane where photosynthesis is carried out. It fixes atmospheric nitrogen. Some of this group likeGloeocapsa and Nostoc coexist with fungi to form Lichens. They give reddish colour to the Red sea. Euglenophycota is like Euglena found in stagnant water causes greenish colour and unpleasant flavour. Extensive quantities not desirable for drinking.
This belongs to the moneran division and contain a blue pigmentphycocyanin ,which in addition to chlorophyll but the chlorophyll is not located in chloroplasts rather it is found in chromatophores, infoldings of the plasma memrane where photosynthesis is carried out. It fixes atmospheric nitrogen. Some of this group likeGloeocapsa and Nostoc coexist with fungi to form Lichens. They give reddish colour to the Red sea. Euglenophycota is like Euglena found in stagnant water causes greenish colour and unpleasant flavour. Extensive quantities not desirable for drinking.
Green algae (chlorophyta)
These are found in fresh water and add more oxygen to water. Their excessive growth contaminate water . This unwanted growth can be removed by adding copper sulphate (CuSo4). Chlamydomonasis a green alage found in ditches,pools and even in artic . Spirogyrais green alage with a unique arrangement of its chlorophyll like a spirally twisted ribbon.
These are found in fresh water and add more oxygen to water. Their excessive growth contaminate water . This unwanted growth can be removed by adding copper sulphate (CuSo4). Chlamydomonasis a green alage found in ditches,pools and even in artic . Spirogyrais green alage with a unique arrangement of its chlorophyll like a spirally twisted ribbon.
Brown algae
The Brown colour is due to the presence of brown pigment,Flucoxanthin. They are the important sources of food for fish and other marine animals. They are also used as cattle feed, fertilizer. Its well known forms include Kelp (largest algae) and the sargassum weed.
The Brown colour is due to the presence of brown pigment,Flucoxanthin. They are the important sources of food for fish and other marine animals. They are also used as cattle feed, fertilizer. Its well known forms include Kelp (largest algae) and the sargassum weed.
Diatoms
They have colour ranging from yellowish green to yellowish brown containing silica. When they die, their skeletons are accumulated on the bottom of earth. This diatomaceous earth is used as insulating material for boilers, blast furnaces and refrigerators. It is also used as mild abrasive in polishes and scouring powders.
They have colour ranging from yellowish green to yellowish brown containing silica. When they die, their skeletons are accumulated on the bottom of earth. This diatomaceous earth is used as insulating material for boilers, blast furnaces and refrigerators. It is also used as mild abrasive in polishes and scouring powders.
Red algae
These are characterized by reddish pigment phycobilin pigments . Most species grow near tropical and subtropical shores below the low tide mark and quite few are found on fresh water. Some secrete lime and there fore helped to build numours coral reefs . important edible varieties are Irish moss and laver(porphyra). Iris moss is used in curing leather, shoe polish and as an ingredient for creams and shampoos. Ceylon moss yield a gelatinous material known asagar-agar which is used as a medium for growing bacteria and fungi. Carrageenin obtained from Irish moss used as substitute for gelatin.
These are characterized by reddish pigment phycobilin pigments . Most species grow near tropical and subtropical shores below the low tide mark and quite few are found on fresh water. Some secrete lime and there fore helped to build numours coral reefs . important edible varieties are Irish moss and laver(porphyra). Iris moss is used in curing leather, shoe polish and as an ingredient for creams and shampoos. Ceylon moss yield a gelatinous material known asagar-agar which is used as a medium for growing bacteria and fungi. Carrageenin obtained from Irish moss used as substitute for gelatin.
7. The Plant Kingdom (Plantae) - 1
Introduction
Plants are multicellular photosynthetic producers of biosphere. With the help of protists and fungi, plants provide the oxygen we breathe. The plant kingdom consists of 260,000 known species of mosses, liverworts, ferns, herbaceous and woody plants, bushes, vines, trees etc.
The land plant belongs to two major divisions Bryophytes & Tracheophytes.
Plants are multicellular photosynthetic producers of biosphere. With the help of protists and fungi, plants provide the oxygen we breathe. The plant kingdom consists of 260,000 known species of mosses, liverworts, ferns, herbaceous and woody plants, bushes, vines, trees etc.
The land plant belongs to two major divisions Bryophytes & Tracheophytes.
Bryophytes
Bryophytes are non vascular
embryo bearing plants consisting of three plant divisions: Bryophyta (Mosses), the Hepatophyta(liverwort) and the Anthocerophyta(Hornworts). Mosses cannot transport fluids though their bodies. Instead, they must rely on surrounding moisture to do this job for them. They reproduce by spores, never have flowers, and can be found growing on rocks, and on other plants. All species of bryophytes are characterized by the alteration of generations. The embryo from the sexual plant matures into a small asexual plant that remains attached to and dependent on the sexual plant. The asexual plant produces spores produced by lower plants, and they are spread by wind and other carriers to produce new sexual plants. Sterilized peat moss is used for surgical dressings.
Bryophytes are non vascular
embryo bearing plants consisting of three plant divisions: Bryophyta (Mosses), the Hepatophyta(liverwort) and the Anthocerophyta(Hornworts). Mosses cannot transport fluids though their bodies. Instead, they must rely on surrounding moisture to do this job for them. They reproduce by spores, never have flowers, and can be found growing on rocks, and on other plants. All species of bryophytes are characterized by the alteration of generations. The embryo from the sexual plant matures into a small asexual plant that remains attached to and dependent on the sexual plant. The asexual plant produces spores produced by lower plants, and they are spread by wind and other carriers to produce new sexual plants. Sterilized peat moss is used for surgical dressings.
Tracheophytes (Vascular Plants)
The characteristic organs of vascular plants are roots, stems and leaves and have vascular tissue xylem, which conducts water and minerals from ground to stems and leaves and phloem which conducts food produced in the leaves to stems, roots and storage and reproductive organs. Vascular plants are divided into Ferns (vascular plants without seed), gymnosperm ( seeds without fruit) and angiosperms(fruit & seed).
Ferns
The characteristic organs of vascular plants are roots, stems and leaves and have vascular tissue xylem, which conducts water and minerals from ground to stems and leaves and phloem which conducts food produced in the leaves to stems, roots and storage and reproductive organs. Vascular plants are divided into Ferns (vascular plants without seed), gymnosperm ( seeds without fruit) and angiosperms(fruit & seed).
Ferns
Ferns allies have a vascular system to transport fluids through their bodies but like mosses, they reproduce from spores rather than seeds. Three other phyla are included are The horsetails, club mosses and whisk ferns.
Gymnosperms( Conifers and Allies )
The gymnosperms add the next level of complexity to plant evolution: They reproduce from seeds instead of spores. The seeds however are “naked” not covered by an ovary. Usually the seed is produced inside a cone like structure such as a pine cone hence the name “conifer.” Conifers are fairly easy to identify. In addition to these cones trees and shrubs have needle-like, scale-like or awl-like leaves and they never have flowers. Approximately 600 species are counted as conifers including the pines, firs, spruces, cedars, junipers and yew. Species within the conifer ranks give us pine nuts, turpentine and rosin are prepared from pine resin. Pine seeds are eaten by man and animals. Ephedrine, a drug from Ephedra, is used for the relief of asthma and other respiratory ailments.
Angiosperms ( Flowering Dicot Plants )
Angiosperms add the final improvement to plant reproduction: They grow their seeds inside an ovary (Greek : angeion = vessel) which is, itself, embedded in a flower. After it is fertilized, the flower falls away and the ovary swells to become a fruit. The angiosperms are classified as Monocotyledons and Dicotyledons.
- Monocotyledons: Monocots have only one seed leaf in the embryo. The main veins of their foliage leaves are usually unbranched and nearly parallel to each other. These include orchids, lilies, rises, palms, grasses, bamboo and sugarcane. Monocots provide us with our primary sources of nutrition, supplying us and the animals we eat with grains such as wheat, oats and corn as well as fruits such as dates and bananas.
- Dicotyledons: Angiosperms in this class grow two seed-leaves(cotyledons). In addition, foliage leaves typically have a single, branching, main vein originating at the base of the leaf blade, or three or more main veins that diverge from the base. The vast majority of plants are Dicots. Most trees, shrubs, vines and flower belong to this group of around 200,000 species. Most fruits, vegetables, legumes and all the hardwood tree species come from this class.
Photosynthesis
It is a process by which green plants and certain other organisms use light energy to convert carbon dioxide and water to simple sugar glucose. In doing so, it provides the basic energy sources for all organisms and releases oxygen on which most organisms depend. Photosynthesis occur in green plants, seaweeds, algae and certain bacteria. Plant photosynthesis occurs in leaves and green stems within specialised cell structures called chloroplasts. The chloroplast is divided by membranes into numerous disk shaped compartments called thylakoids . These are arranged vertically in the chloroplast like a stack of plates is called a granum; the grana lie suspended in a fluid known as stroma. Embedded in the membranes of the thylakoids are hundreds of molecules of chlorophyll, a light trapping pigment required for photosynthesis. Minute structures called plastids contain the chlorophyll within the leaf. The chloroplast traps light energy and covert it into a chemical energy contained in nicotinamide adenine dinucleotide phospate (NADPH) and adenosine triphosphate(ATP),two molecules used in the second stage of photosynthesis. In the second stage, called the light independent reaction, NADPH provides the energy for this and other reactions used to synthesize glucose. The carbohydrates manufactured in the leaves of higher plants are distributed to roots and storage organs along phloem. This long distance movement of organic compounds is called translocation. Sucrose is the principal form in which the carbohydrates are translocated.
8. The Plant Kingdom (Plantae) - 2
Morphology
A plant has two organ systems: 1) the shoot system, and 2) the root system. The shoot system is above ground and includes the organs such as leaves, buds, stems, flowers. The root system includes those parts of the plant below ground, such as the roots, tubers, and rhizomes.
A plant has two organ systems: 1) the shoot system, and 2) the root system. The shoot system is above ground and includes the organs such as leaves, buds, stems, flowers. The root system includes those parts of the plant below ground, such as the roots, tubers, and rhizomes.
Root
The major functions of roots are hold a plant in the ground, to absorb water and minerals from the soil, in some cases store food and in rare cases produce a new plant. There are two main types of root. In one type, the taproot system, a single large root grows straight down.
In the other type, the fibrous root system, there are several main roots with many smaller branching roots of almost equal diameter.
The major functions of roots are hold a plant in the ground, to absorb water and minerals from the soil, in some cases store food and in rare cases produce a new plant. There are two main types of root. In one type, the taproot system, a single large root grows straight down.
In the other type, the fibrous root system, there are several main roots with many smaller branching roots of almost equal diameter.
Primary root
|
The first toot to develop, thickest and grows downwards ( primary root)
|
Secondary Root
|
All roots arises from primary root and grow sidewise
|
Apical meristem
|
tip of the root and stems is capable of rapidly dividing cells responsible for primary growth
|
Root hair
|
hair-like outgrowth of some surface cells of plant roots that greatly increases the area available for the absorption of water & minerals.
|
adventitious roots
|
roots that arise from stems or leaves. If formed high up on a stem are termed aerial or prop roots (seen in banayan and certain orchids.)
|
Stem
It is the portion of vascular plants that commonly bears leaves and buds. It is usually is aerial, upright and elongate, but may be highly modified in structure. Stems that grow above ground are called aerial stems and below the ground are called Subterranean stems. There are two classes of aerial stems – herbaceous and woody. Herbaceous stems are slender, greenish and comparatively soft. The plants with herbaceous stems are called herbs. Woody stems are thicker, taller and harder than herbaceous stems. These may be either trees or shrubs. A tree has a thick main stems called the trunk, which branch abundantly. In shrub there are a number of comparatively slender main stems which branch abundantly.
Types of stems
It is the portion of vascular plants that commonly bears leaves and buds. It is usually is aerial, upright and elongate, but may be highly modified in structure. Stems that grow above ground are called aerial stems and below the ground are called Subterranean stems. There are two classes of aerial stems – herbaceous and woody. Herbaceous stems are slender, greenish and comparatively soft. The plants with herbaceous stems are called herbs. Woody stems are thicker, taller and harder than herbaceous stems. These may be either trees or shrubs. A tree has a thick main stems called the trunk, which branch abundantly. In shrub there are a number of comparatively slender main stems which branch abundantly.
Types of stems
stolons or runners
|
stems that grow horizontally above the surface e.g. strawberry
|
rhizomes
|
underground stems looks like roots e.g. ginger, turmeric, arrowroot
|
Tubers
|
thickened underground stems. e.g. potato
|
bulb
|
short underground stem that bears a cluster of thick, overlapping leaves and stores food. e.g. Onions, tulips ,lilies
|
tendrils
|
climbing organs called are some times modified stems
|
twiner
|
stem that spirals around a solid support.
|
cladodes (Phylloclades)
|
These are leaf like stems. They appear because the real leaves are very small, therefore non functional. e.g. butchers broom and the prickly pear.
|
Succulent stems
|
They become very fat because of water accumulation. They use it as a reservoir for the long dry periods they have to stand. e.g. cacti
|
Leaf
It is part of plant that serves primarily as the plant’s food making organ and takes part in transpiration and respiration. It may store food and water and provide structural support. A leaf is an extension of a plants stem. Some plants whose leaves change colour and lose their leaves in the autumn called deciduous. Those plants such as laurels and pines, the leaves do not change colour and do not fall off in autumn and are called evergreens.
Leaf consists of a flattened portion, called the blade, that is attached to the plant by a structure called the petiole.
The outer surface of the leaf has a thin waxy covering called the cuticle (A), this layer's primary function is to prevent water loss within the leaf. (Plants that leave entirely within water do not have a cuticle). Directly underneath the cuticle is a layer of cells called the epidermis (B). The vascular tissue, xylem and phloem are found within the veins of the leaf. Veins are actually extensions that run from to tips of the roots all the way up to the edges of the leaves. The outer layer of the vein is made of cells called bundle sheath cells (C), and they create a circle around the xylem and the phloem. One the picture, xylem is the upper layer of cells (D) and is shaded a little lighter than the lower layer of cells - phloem (E). Recall that xylem transports water and phloem transports sugar (food).
It is part of plant that serves primarily as the plant’s food making organ and takes part in transpiration and respiration. It may store food and water and provide structural support. A leaf is an extension of a plants stem. Some plants whose leaves change colour and lose their leaves in the autumn called deciduous. Those plants such as laurels and pines, the leaves do not change colour and do not fall off in autumn and are called evergreens.
Leaf consists of a flattened portion, called the blade, that is attached to the plant by a structure called the petiole.
The outer surface of the leaf has a thin waxy covering called the cuticle (A), this layer's primary function is to prevent water loss within the leaf. (Plants that leave entirely within water do not have a cuticle). Directly underneath the cuticle is a layer of cells called the epidermis (B). The vascular tissue, xylem and phloem are found within the veins of the leaf. Veins are actually extensions that run from to tips of the roots all the way up to the edges of the leaves. The outer layer of the vein is made of cells called bundle sheath cells (C), and they create a circle around the xylem and the phloem. One the picture, xylem is the upper layer of cells (D) and is shaded a little lighter than the lower layer of cells - phloem (E). Recall that xylem transports water and phloem transports sugar (food).
Within the leaf, there is a layer of cells called the mesophyll. The word mesophyll is greek and means "middle" (meso) "leaf" (phyllon). Mesophyll can then be divided into two layers, the palisade layer (F) and the spongy layer (G). Palisade cells are more column-like, and lie just under the epidermis, the spongy cells are more loosely packed and lie between the palisade layer and the lower epidermis. The air spaces between the spongy cells allow for gas exchange. Mesophyll cells (both palisade and spongy) are packed with chloroplasts, and this is where photosynethesis actually occurs.
Epidermis also lines the lower area of the leaf (as does the cuticle). The leaf also has tiny holes within the epidermis called stomata (H). Specialized cells, called guard cells (I) surround the stomata and are shaped like two cupped hands. Changes within water pressure cause the stoma (singular of stomata) to open or close. If the guard cells are full of water, they swell up and bend away from each other which open the stoma. During dry times, the guard cells close.
Plant tissues
Plant cell types rise by mitosis from a meristem. A meristem may be defined as a region of localized mitosis. Meristems may be at the tip of the shoot or root (a type known as the apical meristem) or lateral, occurring in cylinders extending nearly the length of the plant. A cambium is a lateral meristem that produces (usually) secondary growth. Secondary growth produces both wood and cork (although from separate secondary meristems).
Plant cell types rise by mitosis from a meristem. A meristem may be defined as a region of localized mitosis. Meristems may be at the tip of the shoot or root (a type known as the apical meristem) or lateral, occurring in cylinders extending nearly the length of the plant. A cambium is a lateral meristem that produces (usually) secondary growth. Secondary growth produces both wood and cork (although from separate secondary meristems).
1) Dermal - It covers the outer surface of herbaceous plants and prevent water loss. e.g guard cells.
2) Ground - It comprises the bulk of the primary plant body. e.g. Parenchyma, collenchyma, and sclerenchyma cells.
3) Vascular - It transports food, water, hormones and minerals within the plant. xylem, phloem, parenchyma, and cambium cells.
Parenchyma: A generalized plant cell type, parenchyma cells are alive at maturity. They function in storage, photosynthesis, and as the bulk of ground and vascular tissues.
Collenchyma: These cells support the plant. It consists of living cells that are characterized by thickening of cells particularly at corners.
Sclerenchyma: These cells support the plant but they are dead at maturity. They often occur as bundle cap fibers. Sclerenchyma cells are characterized by thickenings in their secondary walls. The fibers from jute and coconut are best examples of these cells.
Xylem: These cells conduct water and minerals from roots to leaves. The common name of Xylem is wood. Tracheids and vessels are major cells types both of which are dead at maturity.
Phloem: It transports food from the leaves to rest of the plant. They are alive at maturity. The two most common cells in the phloem are the companion cells and sieve cells. Companion cells retain their nucleus and control the adjacent sieve cells. Dissolved food, as sucrose, flows through the sieve cells.
Cambium: It is layer of actively dividing cells lying between xylem and phloem; forms additional xylem and phloem layers during secondary thickening. The layers formed in each year forms a distinctive series of concentric rings called annual rings. By counting the annual rings, we can find out the age of the tree.
Cork: It is the out layer of bark. These increases in girth as new layers of xylem and phloem are formed. It develops abundantly in certain trees. Commercial cork is taken from oak tree.
9. The Animal Kingdom
Protozoa
This most primitive unicellular organisms which reproduce by fission, budding,spores or sexually. e.g. Amoeba, Entamoeba, paramecium, vorticella, plasmodium, Euglena & trypanosoma. They move a variety of ways. The ameba has a false foot that extends as it moves. The paramecium is covered with hairs and the euglena has a whip-like tail(flagella) to move. A protozoa takes in oxygen through the cell membrane and gives off carbon dioxide through the cell membrane. Some protozoans are harmful to man as they can cause serious diseases. Others are
Human Diseases Caused by protozoa
Disease
|
Name of Prozoa
|
Mode of transmission
|
Ameobic dysentery (Amoebiasis)
|
Entamoeba histolytica
|
thru ingestion of cysts in drinking water and food
|
Diarrhoea
|
Glardia intestinalis
|
thru ingestion of cysts in drinking water and food
|
Kala-Azar(Black sickness)
|
Leishmania donovani
|
thru’ the bite of infected Sandfly
|
Malaria
|
Plasmodium vivax
|
thru’ the bite of infected anophelise - mosquito
|
Sleeping sickness
|
Trypanosoma brucei
|
thru’ the bite of infected tse-tse fly
|
Oriental Sore or Delhi boil
|
Leishmania tropica
|
thru’ the bite of infected Sandfly
|
Vaginitis
|
Trichomonas vaginalis
|
During coitus in female vagina , shared towels and toilet seats
|
Porifera (Sponges)
These are most primitive of multi cellular animals. They live in water bodies. They were the first group of animals that has specialized cells to do special jobs. A sponge is a hollow tube with many pores or openings. The skeleton is made of lime or silicon. A sponge takes in food via the water that flows through the pores. Commercial sponge is only porous skeleton. e.g. Euspongia (bath sponge),sycon ,spongilla(fresh water) , hyalonema(Glass sponge).
These are most primitive of multi cellular animals. They live in water bodies. They were the first group of animals that has specialized cells to do special jobs. A sponge is a hollow tube with many pores or openings. The skeleton is made of lime or silicon. A sponge takes in food via the water that flows through the pores. Commercial sponge is only porous skeleton. e.g. Euspongia (bath sponge),sycon ,spongilla(fresh water) , hyalonema(Glass sponge).
Cnidaria (Coelenterata)
These are mostly marine species except hydra which is fresh water form. These are radially symmetrical animals which posses 2 distinct germ layers ectoderm and endoderm . Polyp and medusa are 2 basic form. Medusa is free floating and represents sexual phase of the animal. These are comparable to alteration of generation among plants. The corals consists of polyp colonies. These are soft bodied organisms having a thick calcium carbonate shell to protect it. The living coral develop on dead corals and thus coral reefs are found. Important coelentrates are coral, hydra, jellyfish, sea anemone, Portuguese man of war.
These are mostly marine species except hydra which is fresh water form. These are radially symmetrical animals which posses 2 distinct germ layers ectoderm and endoderm . Polyp and medusa are 2 basic form. Medusa is free floating and represents sexual phase of the animal. These are comparable to alteration of generation among plants. The corals consists of polyp colonies. These are soft bodied organisms having a thick calcium carbonate shell to protect it. The living coral develop on dead corals and thus coral reefs are found. Important coelentrates are coral, hydra, jellyfish, sea anemone, Portuguese man of war.
Platyhelminths(Flat worms)
Flat worm is a common name for soft bodied, usually parasitic animals, the simplest of animals possessing heads. A flatworm has a gastrovascular cavity with one opening. It takes food in and gets rid of wastes through the same opening. They are bilaterally symmetrical and somewhat flattened and are elongated. E.g. Tape worm, flukes.
Flat worm is a common name for soft bodied, usually parasitic animals, the simplest of animals possessing heads. A flatworm has a gastrovascular cavity with one opening. It takes food in and gets rid of wastes through the same opening. They are bilaterally symmetrical and somewhat flattened and are elongated. E.g. Tape worm, flukes.
Nemathelminthes(round worms)
These are roundworms which are usually found in soil, water, plants and in animals as a parasite. A roundworm has a definite digestive system that runs the length of their bodies. It has a mouth, pharynx, intestine and anus. e.g. Ascaris(round worm),oxyuris(pinworm), ancylostoma(hook worm),wucheria(Filaria worm).
These are roundworms which are usually found in soil, water, plants and in animals as a parasite. A roundworm has a definite digestive system that runs the length of their bodies. It has a mouth, pharynx, intestine and anus. e.g. Ascaris(round worm),oxyuris(pinworm), ancylostoma(hook worm),wucheria(Filaria worm).
Annelida
These are known as segmented worms whose body is made up of similar segments. A true closed circulatory system with hearts and oxygen carrying blood is found for the first time in them. A earthworm has a nervous system with a simple brain and nerve cord. Earth worms are useful in agriculture because they loosen the soil for roots to grow and its wastes help to fertilize the soil. Earthworms are hermaphroditic, possessing both male and female internal reproductive organs. Some blood sucking leech produce a compound known as Hirudin from their salivary gland to prevent blood clotting. E.g. earth worms, leech and clamworm.
These are known as segmented worms whose body is made up of similar segments. A true closed circulatory system with hearts and oxygen carrying blood is found for the first time in them. A earthworm has a nervous system with a simple brain and nerve cord. Earth worms are useful in agriculture because they loosen the soil for roots to grow and its wastes help to fertilize the soil. Earthworms are hermaphroditic, possessing both male and female internal reproductive organs. Some blood sucking leech produce a compound known as Hirudin from their salivary gland to prevent blood clotting. E.g. earth worms, leech and clamworm.
Mollusca
It is the common name for members of a phylum soft-bodied animals with a hard external shell (so called shell fishes). It is the second largest kingdom after arthropods. The three major groups are gastropods, bivalves and cephalopods.
It is the common name for members of a phylum soft-bodied animals with a hard external shell (so called shell fishes). It is the second largest kingdom after arthropods. The three major groups are gastropods, bivalves and cephalopods.
a) Gastropod: The Gastropoda (Greek gaster,"stomach"; pous,"foot") are generally characterized by a single shell and an asymmetric body. E.g. snails and slugs.
b) Bivalves: It is characterized by a shell divided into two valves hinged at one side, gills specialized for feeding, and a reduced head. E.g clam, cockle, mussel, oyster, scallop, and shipworm. Pearl is actually a secretion by bivalves induced by factors such as foreign substances etc
c) Cephalpods: The word cephalopod means "head footed," and the animals are so named because the arms surround the mouth. These are predatory marine mollusks which includes squid, octopus, and nautilus.
Arthropods
It is the largest animal kingdom. These are animals with hard outer skeleton and jointed body and limbs. The arthropods are the first animal group to have jointed legs. The major groups are
a) Insects : The largest class of arthropods. They have six legs and three body parts, a head, a thorax and an abdomen. They also have an outer or exoskeleton made of chitin, containing cellulose. All insects grow from eggs. They go through various stages until they reach adulthood. This transformation through these stages is called metamorphosis. Insects undergo either complete(butterfly, bee, ant, beetle) and fly or incomplete (dragonfly, termite, grasshopper and true bug) metamorphosis. Complete metamorphosis has four stages: egg, larvae, pupae and adult where as in incomplete metamorphosis has three stages called egg, nymph and adult. A insect has a circulatory system that carries food, but not oxygen throughout its body. Since it does not carry oxygen, insect blood is green, not red like mammal blood. The insect heart is a simple tube running along their backs.
It is the largest animal kingdom. These are animals with hard outer skeleton and jointed body and limbs. The arthropods are the first animal group to have jointed legs. The major groups are
a) Insects : The largest class of arthropods. They have six legs and three body parts, a head, a thorax and an abdomen. They also have an outer or exoskeleton made of chitin, containing cellulose. All insects grow from eggs. They go through various stages until they reach adulthood. This transformation through these stages is called metamorphosis. Insects undergo either complete(butterfly, bee, ant, beetle) and fly or incomplete (dragonfly, termite, grasshopper and true bug) metamorphosis. Complete metamorphosis has four stages: egg, larvae, pupae and adult where as in incomplete metamorphosis has three stages called egg, nymph and adult. A insect has a circulatory system that carries food, but not oxygen throughout its body. Since it does not carry oxygen, insect blood is green, not red like mammal blood. The insect heart is a simple tube running along their backs.
b) Arachnids: The annelids are similar to insects. However, they have eight legs, wings are different and they have no antenna. The arachnids are spiders, scorpions, etc.
c) Crustaceans: These are predominantly aquatic arthropods with protective carapace and compound eyes. E.g. Prawns, Lobsters and Crabs.
d) Myriapods: include millipedes and centipedes. The centipedes have two pairs of legs per segment while millipedes have one pair.
Echinoderm
It consists of phylum of marine animals such as starfish, brittle stars, sea urchins, sand dollars and sea cucumbers. They usually show a superficial five part radial symmetry. The phylum name is derived from spiny skin. A Echinoderm is a male or female. The males and females discharge their eggs and sperm into the water where they are fertilized. A female can release one hundred million eggs at once. If a piece of certain echinoderms is chopped off, a new piece or even a new echinoderm can regrow.
It consists of phylum of marine animals such as starfish, brittle stars, sea urchins, sand dollars and sea cucumbers. They usually show a superficial five part radial symmetry. The phylum name is derived from spiny skin. A Echinoderm is a male or female. The males and females discharge their eggs and sperm into the water where they are fertilized. A female can release one hundred million eggs at once. If a piece of certain echinoderms is chopped off, a new piece or even a new echinoderm can regrow.
Chordate
It refers to the common name for animals of the phylum Chordata, which includes vertebrates as well as some invertebrates that possess, at least some time in their lives, a stiff rod called notochord lying above the gut and beneath a single hollow dorsal nerve cord. It is the third largest animal phylum. The Phylum chordate has been divided into Proto chordate and Vertebrate.
I) Proto Chordate: They are primitive lower chordates possess notochord but lacks vertebral column or back bone. They are represented by cephalo chordates e.g. small marine fish (Amphioxus), urochordata (Ascidian) and Hemichordata (Balanoglossus)
II) Vertebrate: It represents the largest group of chordates.
It refers to the common name for animals of the phylum Chordata, which includes vertebrates as well as some invertebrates that possess, at least some time in their lives, a stiff rod called notochord lying above the gut and beneath a single hollow dorsal nerve cord. It is the third largest animal phylum. The Phylum chordate has been divided into Proto chordate and Vertebrate.
I) Proto Chordate: They are primitive lower chordates possess notochord but lacks vertebral column or back bone. They are represented by cephalo chordates e.g. small marine fish (Amphioxus), urochordata (Ascidian) and Hemichordata (Balanoglossus)
II) Vertebrate: It represents the largest group of chordates.
i) Agnatha: They are fish like forms with the absence of Jaws and scales. Their skeleton is cartilaginous. The best examples of this type are lamprey and the hagfish They have two chambered heart and gills used for respiration.
ii) Gnathostomata: These are vertebrates with jawed mouth. These are subdivided into fishes, amphibians, reptiles, birds and mammals.
a) Fishes: These are diverse group of cold blooded animals that live and breathe in water. Most fish have gills for breathing, two chambered heart, fins for swimming, scales for protection, and a streamlined body for moving easily through the water. The swim (or gas) bladder allows fish to maintain a constant buoyancy regardless of the changing water pressure at varying depths. Its eyes are positioned on either side of its body and are quite large, with no eyelid. They have an inner ear but no outer ear opening. Fishes are broadly classified into
i) Chondrichthyes (Cartilaginous fish): Their skeleton made of cartilage and their body covered with triangular Placoid scales. They lack a swim bladder but have air sacs to regulate buyonancy. E.g Sharks ,Rays and Skates. Sharks are viviparous.
ii) Osteichthyes (bony fishes): They have a bony endoskeleton. These are oviparous and fertilization is external. E.g. Salmon, Labeo (rohu), Mrigal etc.
b) Amphibians: Amphibian means both sides of life. it begins its life in the water and then finishes it mainly on land. It uses gills in larval stage (tadpole) and lungs and skins in the adult stage. Their heart is three chambered. Skin is often kept moist for gas exchange. These are cold blooded animals and have to be near water to complete their life cycle. So these are severely affected by environmental pollutants, destruction and modification of amphibian habitats, such as the cutting of forests and the draining of wetlands .E.g. Frogs, toad, Salamander, caecilians, sirens etc.
c) Reptiles: Reptiles are cold blooded animal with tough, dry skin covered with horny scales adapted for life in dry places. Some forms are aquatic. Reptiles breathe air with lungs alone. They have teeth except in tortoises and turtles. They have three chambered heart (crocodile has a four chambered heart). The females eggs are fertilized in her body by the male. The eggs are laid in a shell that has a leathery covering to protect it in the wilds. E.g. turtles, lizards, snakes, crocodiles, gavial (Gharial),alligators and dinosaurs.
d) Birds: They are unique in the fact that they are covered with feathers and fly. They are descended from reptiles, feathers are modified limbs and their eggs resemble reptilian eggs. But like mammals they are warm blooded and have four chambered heart. The bones of many adult birds are hollow rather than filled with marrow, making them lighter and enabling them to disperse heat in flight. A bird has relatively large eyes that allow it to judge distance well and an excellent sense of hearing. They exhibit migratory behaviour, nest building and parental care. The study of birds is ornithology. The Smallest bird is humming bird. The heaviest bird is bustard
e) Mammals: Mammals are warm blooded animals having distinctive characteristics such as milk producing mammary glands, hair on their body, external ears, sweat glands, give birth to young rather laying eggs and nurse their young
Major mammal groups
Egg Laying Mammals
|
platypus and anteater
|
Flying Mammals
|
bats
|
Toothless Mammals
|
sloth, armadillo and and anteater
|
Pouched Mammals (marusupials)
|
kangaroo, koala, opossum and wallaby
|
Flesh-eating Mammals
|
bear and the raccoon - Flat-footed; cats, dogs, lions, tigers, wolves and coyotes – walk on their toes; skunk, weasel, otter and mink walk partly on their toes and partly on soles
|
Flexibly Fingered Mammals (Primates)
|
monkey, lemur, orangetan, chimpanzee, gorilla, gibbon and man
|
Insect Eating Mammals (insectivores)
|
mole, shrew and hedgehog
|
Gnawing Mammals (Rodents)
|
the rat, mouse, squirrel, chipmunk, prairie dog, rabbit, hare and beaver
|
Hoofed Mammals (Ungulates)
|
Even toed cud chewers - cow, sheep, goat, camel, giraffe and deer even-toed noncud chewers- pig and the hippopotamus
|
Trunk Nosed Mammals
|
elephant
|
Marine Mammals
|
whale, dolphin and porpoise
|
10. Human Body - Digestive system
Introduction
The human body is composed of different systems that have specific tasks to complete. It is better to study each system and associated organs in some details to get best picture of our body and how it works. There are nine organ systems in our body.
The human body is composed of different systems that have specific tasks to complete. It is better to study each system and associated organs in some details to get best picture of our body and how it works. There are nine organ systems in our body.
Food and its composition
Food, anything eaten to satisfy appetite and to meet physiological needs for growth, to maintain all body processes, and to supply energy to maintain body growth, to maintain all body process, and to supply energy to maintain body temperature and activity. Foods differ markedly in the amount of nutrients they contain; they can be classified on the basis of their composition. They can be classified as
Food, anything eaten to satisfy appetite and to meet physiological needs for growth, to maintain all body processes, and to supply energy to maintain body growth, to maintain all body process, and to supply energy to maintain body temperature and activity. Foods differ markedly in the amount of nutrients they contain; they can be classified on the basis of their composition. They can be classified as
- Carbohydrates
- Lipids(Fats)
- Proteins
- Vitamins
- Minerals
Carbohydrates
They are compounds containing carbon, hydrogen and oxygen and have a general formular Cx(H20)y. It is the major component of our food as it all energy need by our cells. So athletes, labourers doing heavy work need carbohydrates in their food. The main sources are rice, wheat, maize, potato, banana, sugar etc. Carbohydrates are divided into
a) Monosaccharides are simple sugars consisting of three or more carbon atoms. e.g. Ribose, deoxyribose(pentoses),glucose, fructose (fruit sugar) and galactose( hexoses). (Our body digests them quickly and easily; it is sweat tasting and found in fruits)
b) Disaccharides are formed by the union of two monosaccharids. Maltose(malt sugar) = glucose+glucose
Lactose(Milk sugar) = glucose+galactose
Sucrose(cane sugar) = glucose+fructose.
(These takes longer to be digested than Monosaccharides. Found in foods like bread, noodles, rice, vegetables.)
c) Polysaccharids are made up of large number of monosaccharids units(300 to over 1000). E.g. starch, cellulose in plants , glycogen, chitin in animals.
The nutrional role of carbohydrate is the production of energy. These are main sources of blood glucose and stored in tissues as glycogen in liver and muscles for further use when necessary.
Lipids(Fats)
These are a group of fatty substances found in all living organisms and these contain less amount of oxygen than in carbohydrates but yield twice the amount of energy than carbohydrates. Fats are not soluble in water but in alcohol, ether, or organic solvents. Fat is more suitable as stored food, insulates our body from cold, provides cushioning effects for our organs, and helps the fat soluble vitamins to be transported through when they are needed. The important sources are fatty acids and glycerol. Fatty acids can be grouped into saturated fatty acid and unsaturated fatty acids. These are designated as saturated or unsaturated, depending on whether the chemical bonds between the carbon atoms of the fat molecules contain all the hydrogen atoms they are capable of holding (saturated) or have capacity for additional hydrogen atoms (unsaturated). Saturated fats generally are solid at room temperature; unsaturated and polyunsaturated fats are liquids. Unsaturated fats may be converted to saturated fats by adding hydrogen atoms in a process known as hydrogenation. Saturated fatty acids come from animal foods like meat, milk, cheese, and some oils that come from plants. Unsaturated fatty acids are different - they come from plants and fish. Together, these two substances are grouped and called the fat content in food.
These are a group of fatty substances found in all living organisms and these contain less amount of oxygen than in carbohydrates but yield twice the amount of energy than carbohydrates. Fats are not soluble in water but in alcohol, ether, or organic solvents. Fat is more suitable as stored food, insulates our body from cold, provides cushioning effects for our organs, and helps the fat soluble vitamins to be transported through when they are needed. The important sources are fatty acids and glycerol. Fatty acids can be grouped into saturated fatty acid and unsaturated fatty acids. These are designated as saturated or unsaturated, depending on whether the chemical bonds between the carbon atoms of the fat molecules contain all the hydrogen atoms they are capable of holding (saturated) or have capacity for additional hydrogen atoms (unsaturated). Saturated fats generally are solid at room temperature; unsaturated and polyunsaturated fats are liquids. Unsaturated fats may be converted to saturated fats by adding hydrogen atoms in a process known as hydrogenation. Saturated fatty acids come from animal foods like meat, milk, cheese, and some oils that come from plants. Unsaturated fatty acids are different - they come from plants and fish. Together, these two substances are grouped and called the fat content in food.
Proteins
Proteins are complex compounds formed from about 20 amino acids which are needed for the synthesis of protoplasm. These amino acids are composed of carbon, hydrogen, oxygen, nitrogen and sometimes sulphur. These are essential for body growth. Some of the amino acids are not produced in the animal body and it must by supplied with food. These are called essential amino acids and the rest are non essential amino acids. ( It does not mean that is not essential for our body but not essential in our food!)
The deficiency causes Kwashiorkor in children below 5 years who instead of mothers milk take mainly carbohydrate diet. If the mothers milk is replaced to children below 1 year it causes Marasmus.
Food
|
Calorific Value
|
Physiological Value
|
Carbohydrates
|
4.1 kcal
|
4kcal
|
Fat
|
9.45 kcal
|
9 kcal
|
Protein
|
5.65 kcal
|
4 kcal
|
Vitamins
http://competitionaffairs.blogspot.com/2010/11/vitamins.html
These organic substances of various types which cannot be synthesised in sufficient quantities by the body and have to be supplied in its diet. Vitamins can be classified into water soluble vitamins and fat soluble vitamins. Fat soluble vitamins are stored in our body and water soluble dont get stored as much in our body. Instead, they travel through your blood stream. The deficiency of vitamins causes various diseases. A detailed list containing the sources, benefits and deficiency of vitamins are given below
These organic substances of various types which cannot be synthesised in sufficient quantities by the body and have to be supplied in its diet. Vitamins can be classified into water soluble vitamins and fat soluble vitamins. Fat soluble vitamins are stored in our body and water soluble dont get stored as much in our body. Instead, they travel through your blood stream. The deficiency of vitamins causes various diseases. A detailed list containing the sources, benefits and deficiency of vitamins are given below
VITAMIN
|
FOOD SOURCES
|
HEALTH BENEFIT
|
DEFICIENCY
|
Fat Soluble
| |||
A (Retinol)
|
Eggs, butter, whole milk, vegetables and liver.
|
Component of light-sensitive pigments in eye, epithelial tissue maintenance
|
Night blindness, Xerophthalmia or dry eye, extremely dry skin (Dermatosis)
|
D (Calciferol)
|
Fish, egg yolks and the rays of the sun
|
Calcium absorption, bone formation
|
Rickets (bone deformities) in children, Osteomalacia in Adult.
|
E (Tocopherol)
|
Margarine, seeds, green leafy vegetables
|
Protects fatty acids and cell membranes from oxidation
|
Sterility
|
K
|
Green leafy vegetables
|
Blood clotting
|
Uncontrolled bleeding
|
Water Soluble
| |||
B1 (Thiamine)
|
Organ meats, pork, grains, legumes
|
Carbohydrate metabolism, nerve and heart function
|
Beriberi (weakened heart, edema, nerve and muscle degeneration
|
B2 (Riboflavin)
|
Milk products, liver, eggs, grains, legumes
|
Energy metabolism
|
Ariboflavinosis-Eye irritation, inflammation and breakdown of skin cells
|
B3 (Niacin or Nicotinic Acid)
|
Liver, lean meats, grains, legumes
|
Oxidation-reduction reactions in cellular respiration
|
Pellegra (skin and gastrointestinal disorders, nerve inflammation, mental disorders)
|
B5 (Pantothenic Acid)
|
Milk products, liver, eggs, grains, legumes
|
Energy metabolism
|
Fatigue, loss of coordination
|
B5 (Pantothenic Acid)
|
Milk products, liver, eggs, grains, legumes
|
Energy metabolism
|
Fatigue, loss of coordination
|
B6 (Pyridoxine)
|
Whole-grain cereals, vegetables, meats
|
Amino acid metabolism
|
Convulsions, irritability, kidney stones
|
B12 (Cobalamin)
|
Red meats, eggs, dairy products
|
Nucleic acid production
|
Pernicious anemia, neurological disorders
|
Biotin
|
Meats, vegetables, legumes
|
Fat synthesis and amino acid metabolism
|
Depression, fatigue, nausea
|
C (Ascorbic Acid)
|
Citrus fruits, green leafy vegetables, tomatoes
|
Collagen formation in teeth, bone, and connective tissue of blood vessels; may help in resisting infection
|
Scurvy (breakdown of skin, blood vessels, and teeth
|
Folic Acid
|
Whole-wheat foods, green vegetables, legumes
|
Nucleic acid metabolism
|
Anemia, diarrhea
|
Minerals
Mineral salts are needed in very small quantities but very essential for the functioning of the body. Blood contains 0.9 per cent salt, most of which is sodium chloride, very essential for maintaining osmotic pressure.
Mineral salts are needed in very small quantities but very essential for the functioning of the body. Blood contains 0.9 per cent salt, most of which is sodium chloride, very essential for maintaining osmotic pressure.
Anaemia is caused due to iron deficiency and characterised by deficiency of haemoglobin in red blood cells.
Hypokalemia is caused by loss of potassium and characterised by kidney damage, rise in hear beat, paralysis of muscles.
Hyponatremia is due to the increased loss of sodium which leads to dehydration, low blood pressure and loss of body weight.
Simple Goitre is casued by deficiency of iodine which regulates the secretion of the thyroxine from the thyroid gland. It causes the increased production of thyroid stimulating hormone which brings about the enlargement of gland.
MINERAL
|
FOOD SOURCES
|
HEALTH BENEFIT
|
DEFICIENCY
|
Major
| |||
Calcium
|
Milk, cheese, dried legumes, vegetables
|
Bone and teeth formation, blood clotting, and nerve transmission
|
Rickets, osteoporosis, convulsions
|
Chlorine
|
Foods containing salt; some vegetables and fruits
|
Fluid regulation between cells or cell layers
|
Acid-base imbalance in body fluids (very rare)
|
Magnesium
|
Whole grains; green, leafy vegetables
|
Enzyme activation, protein synthesis
|
Growth failure, behavior problems, spasms
|
Phosphorus
|
Milk, cheese, yogurt, fish, poultry, meats,
|
Bone and teeth formation, acid-base balance
|
Weakness, loss of calcium
|
Potassium
|
Bananas, leafy vegetables, potatoes, cantaloupe, milk, meats
|
Acid-base balance and fluid balance maintenance, nerve transmission
|
Muscle cramps, mental confusion, loss of appetite, irregular cardiac rhythm - hypokalamia
|
Sulfur
|
Fish, poultry, meats
|
Acid-base balance maintenance and liver function
|
Disorders unlikely if body gets small amounts needed
|
Sodium
|
Table salt
|
Acid-base balance and body water balance maintenance, nerve function
|
Hyponatremia-Muscle cramps, reduced appetite, mental apathy
|
Trace
| |||
Chromium
|
Legumes, cereals, organ meats, fats, vegetable oils, meats, whole grains
|
Glucose metabolism
|
Adult onset diabetes
|
Copper
|
Meats, drinking water
|
Red blood cell formation
|
Anemia, impairs bone and nervous tissue development
|
Fluorine
|
Drinking water, tea, seafood
|
Bone structure maintenance, decay-resistant teeth
|
Osteoporosis; tooth decay
|
Iodine
|
Salt-water fish, shellfish, dairy products, vegetables, iodized salt
|
Component of thyroid hormone
|
Enlarged thyroid (goiter)
|
Iron
|
Lean meats, eggs, whole grains, green leafy vegetables, legumes
|
Hemoglobin formation in blood; energy metabolism
|
Anemia
|
Selenium
|
Seafood, meat, grains
|
Prevents breakdown of fats and other body chemicals
|
Anemia
|
Zinc
|
Lean meat, whole-grain breads and cereals, dried beans, seafood
|
Component of many enzymes included in digestion, cell repair, sexual reproduction
|
Growth failure, small sex glands, delayed wound healing
|
Enzymes
Enzymes are biological catalysts. These are the secretions of digestive gland with ducts. These are composed of amino acids(proteins); it t generally accelerate biochemical reaction by reducing the energy requirement, however certain substances called inhibitors slow down the rate of enzymatic reaction. These are specific in their action and on a particular substrate only. Each enzyme has its own pH and temperature at which it works. It show maximum activity at body temperature known as optimal temperature. Some enzymes are formed in an inactive form called the precursors or zymogens and are later activated by a number of agents, including co-enzymes or co factors.
Digestion in Humans
Now let us see, how our body digests the food consumed by us. Ingestion and mastication or chewing takes place in the mouth and it is passed along the oesophagus to the stomach by peristalsis (a type of movement). In stomach food mixes with gastric juices such as hydrochloric acid and pepsin and become a watery paste called chyme and enters into wider part of small intestine called duodenum. (the rest is called ileum). The later stage of digestive process is taken place with the help of bile which is stores in gall bladder and intestinal juices. When it reaches the large intestine or colon it absorbs large amount of water and vitamin K which is synthesized by bacteria. The newly absorbed material other than emulsified fat first brought to liver by portal vein. The liver helps to keep the blood sugar(glucose) level constant and make toxic by product into harmless substances and produces wide variety of substances such as proteins and bile. The numerous chemical reactions in liver produces significant amount of heat and helps to maintain a constant body temperature. Most of the digested food and minerals are absorbed in small intestine with the help of small intestine with the help of folds called villi and microvilli. The glycerids and fatty acids are transported via lymph vessels.
Now let us see, how our body digests the food consumed by us. Ingestion and mastication or chewing takes place in the mouth and it is passed along the oesophagus to the stomach by peristalsis (a type of movement). In stomach food mixes with gastric juices such as hydrochloric acid and pepsin and become a watery paste called chyme and enters into wider part of small intestine called duodenum. (the rest is called ileum). The later stage of digestive process is taken place with the help of bile which is stores in gall bladder and intestinal juices. When it reaches the large intestine or colon it absorbs large amount of water and vitamin K which is synthesized by bacteria. The newly absorbed material other than emulsified fat first brought to liver by portal vein. The liver helps to keep the blood sugar(glucose) level constant and make toxic by product into harmless substances and produces wide variety of substances such as proteins and bile. The numerous chemical reactions in liver produces significant amount of heat and helps to maintain a constant body temperature. Most of the digested food and minerals are absorbed in small intestine with the help of small intestine with the help of folds called villi and microvilli. The glycerids and fatty acids are transported via lymph vessels.
Jaundice (Icterus)
It is yellowing of the skin, conjunctivae and muscous membranes caused by excessive amounts of bile pigments in blood tissues. These pigments are present in blood as a result of the breakdown of haemoglobin in red blood cells. These are filtered through the liver and excreted in feces.
It is yellowing of the skin, conjunctivae and muscous membranes caused by excessive amounts of bile pigments in blood tissues. These pigments are present in blood as a result of the breakdown of haemoglobin in red blood cells. These are filtered through the liver and excreted in feces.
Liver
The liver is an organ in vertebrates including humans. It plays a major role in metabolism and has a number of functions in the body including detoxification, glycogen storage and plasma protein synthesis. It also produces bile which is important for digestion. Medical terms related to the liver often start in hepato- or hepatic from the Greek word hepar for "liver". It converts excess glucose to glycogen (glycogen synthesis). When the cells needs glucose, liver converts the glycogen into glucose (glycogenolysis). It neutralises toxins. It is the main site of red blood cell production of an embryo(upto 42nd week of gestation).
The liver is an organ in vertebrates including humans. It plays a major role in metabolism and has a number of functions in the body including detoxification, glycogen storage and plasma protein synthesis. It also produces bile which is important for digestion. Medical terms related to the liver often start in hepato- or hepatic from the Greek word hepar for "liver". It converts excess glucose to glycogen (glycogen synthesis). When the cells needs glucose, liver converts the glycogen into glucose (glycogenolysis). It neutralises toxins. It is the main site of red blood cell production of an embryo(upto 42nd week of gestation).
Pancreas
The pancreas has both an exocrine and an endocrine secretion. The exocrine secretion is made up of a number of enzymes that are discharged into the intestine to aid in digestion. The endocrine secretion, insulin, is important in the metabolism of sugar in the body. Insulin is produced in small groups of especially modified glandular cells in the pancreas; these cell groups are known as the islets of Langerhans.
The pancreas has both an exocrine and an endocrine secretion. The exocrine secretion is made up of a number of enzymes that are discharged into the intestine to aid in digestion. The endocrine secretion, insulin, is important in the metabolism of sugar in the body. Insulin is produced in small groups of especially modified glandular cells in the pancreas; these cell groups are known as the islets of Langerhans.
11. Human Body - Respiratory system
Respiratory system
The primary function of the respiratory system is to supply the blood with oxygen in order for the blood to deliver oxygen to all parts of the body. The respiratory system does this through breathing. When we breathe, we inhale oxygen and exhale carbon dioxide. This exchange of gases is the respiratory systems means of getting oxygen to the blood. Respiration is achieved through the mouth, nose, trachea, lungs, and diaphragm. Oxygen enters the respiratory system through the mouth and the nose. The oxygen then passes through the larynx (where speech sounds are produced) and the trachea which is a tube that enters the chest cavity. In the chest cavity, the trachea splits into two smaller tubes called the bronchi. Each bronchus then divides again forming the bronchial tubes. The bronchial tubes lead directly
into the lungs where they divide into many smaller tubes which connect to tiny sacs called alveoli. The average adults lungs contain about 600 million of these spongy, air-filled sacs that are surrounded by capillaries. The inhaled oxygen passes into the alveoli and then diffuses through the capillaries into the arterial blood. Meanwhile, the waste rich blood from the veins releases its carbon dioxide into the alveoli. The carbon dioxide follows the same path out of the lungs when you exhale.
into the lungs where they divide into many smaller tubes which connect to tiny sacs called alveoli. The average adults lungs contain about 600 million of these spongy, air-filled sacs that are surrounded by capillaries. The inhaled oxygen passes into the alveoli and then diffuses through the capillaries into the arterial blood. Meanwhile, the waste rich blood from the veins releases its carbon dioxide into the alveoli. The carbon dioxide follows the same path out of the lungs when you exhale.
- The total lung capacity of an adult is 5.0 litres
- Tidal air : Volume of air entering and leaving the lungs during normal breathing (.5 litres)
- Vital capacity : Volume of air exhaled after a forceful breathing (3.5 litres)
- Residual air : Volume of air which remains after forceful expiration (1.5 litres)
The diaphragms job is to help pump the carbon dioxide out of the lungs and pull the oxygen into the lungs. The diaphragm is a sheet of muscles that lies across the bottom of the chest cavity. As the diaphragm contracts and relaxes, breathing takes place. When the diaphragm contracts, oxygen is pulled into the lungs. When the diaphragm relaxes, carbon dioxide is pumped out of the lungs.
Cellular respiration
Cellular respiration is the process of oxidizing food molecules, like glucose, to carbon dioxide and water. The energy released is trapped in the form of ATP (adenosine triphosphate) for use by all the energy-consuming activities of the cell.
The process occurs in two phases:
1) glycolysis, the breakdown of glucose to pyruvic acid
2) the complete oxidation of pyruvic acid to carbon dioxide and water. This process called aerobic respiration. When the respiration takes place with out oxygen it is known as anaerobic respiration. The end product of anaerobic respiration is carbon dioxide and chemical such as lactic acid and ethanol. When the micro organisms respire anaerobically we call it as fermentation. e.g. fermentation of yeast in the preparation of ethanol.
Human Circulatory system
12. Human Body - Circulatory system
Circulatory system
Blood is the circulatory fluid of circulatory system. A healthy person has around 4-5 litres of blood. It is slightly alkaline in nature. It is composed of plasma and three types of corpuscles. Plasma is yellow coloured fluid consisting of water (92%), proteins(6-9%) and 1% minerals. Plasma transports red and white blood cells and platelets throughout the body. It also delivers nutrients to cells and picks up cell waste products.
Features of blood cells: Red blood cells, white blood cells, and platelets grow from a single precursor cell, known as a haematopoietic stem cell.
RBC (erythrocates)
|
WBC(leucocyts)
|
Platelets (thrombocytes)
|
5 million (per cu mm of blood)
|
5 to 9 thousand
|
300,000
|
life span 110-120 days
|
life span of < 2 weeks
|
life span of few hours
|
devoid of nuclei
|
contains one nucleus
|
enucleated
|
discs in concave shape
|
irregular shaped cells
|
spherical bodies
|
formed in bone marrow
|
red bone marrow
|
formed in bone marrow
|
destroyed by spleen
|
destroyed by spleen
|
destroyed by spleen
|
consists of haemoglobin which transports oxygen
|
provides immunity to the body
|
important role in blood cloting
|
Blood clotting
It is internal mechanisms of animals to prevent blood loss at the time of injury. During the blood clotting, the blood platelets produce an enzyme called thromokinase which forms prothrombin protein in the plasma. It combines with calcium ion to form thrombin. It convert the soluble plasma protein(fibrinogen) to form fibrin threads. corpuscles get entangled in these threads and forms clot.
Blood groups
The colour of human blood is red. However it does not mean that anyone can receive blood from others without agglutination. The differences in human blood are due to the presence or absence of certain protein molecules called antigens and antibodies. The antigens are located on the red blood cells and the antibodies are in the blood plasma. based on this, four blood groups are identified. They are denoted by the letter A,B, AB, O (null). There are two type of antigen A and B and two types of anti bodies anti A and Anti B.
The colour of human blood is red. However it does not mean that anyone can receive blood from others without agglutination. The differences in human blood are due to the presence or absence of certain protein molecules called antigens and antibodies. The antigens are located on the red blood cells and the antibodies are in the blood plasma. based on this, four blood groups are identified. They are denoted by the letter A,B, AB, O (null). There are two type of antigen A and B and two types of anti bodies anti A and Anti B.
Blood Group
|
Antigens
|
Antibodies
|
Can give blood to
|
Can receive blood from
|
AB
|
A and B
|
None
|
AB
|
AB, A, B, O
|
A
|
A
|
B
|
A and AB
|
A and O
|
B
|
B
|
A
|
B and AB
|
B and O
|
O
|
None
|
A and B
|
AB, A, B, O
|
O
|
Blood transfusion
The general rule for blood transfusion is the donors red cells must be compatible with recipients plasma. Anti A plasma agglutinates A red cells, and anti B plasma agglutinates B red cells. People with O blood group can give blood to any group because they do not contain A and B anti bodies. So they are called universal donors. People with AB blood group are called universal recipients because they can accept blood from any group. So they are known as universal receipients.
The general rule for blood transfusion is the donors red cells must be compatible with recipients plasma. Anti A plasma agglutinates A red cells, and anti B plasma agglutinates B red cells. People with O blood group can give blood to any group because they do not contain A and B anti bodies. So they are called universal donors. People with AB blood group are called universal recipients because they can accept blood from any group. So they are known as universal receipients.
Rhesus (Rh) factor
About 85% of people also have a so called Rh factor on the red blood cells surface. This is also an antigen and those who have it are called Rh+. Those who have not are called Rh-. A person with Rh- blood does not have Rh antibodies naturally in the blood plasma (as one can have A or B antibodies, for instance). But a person with Rh- blood can develop Rh antibodies in the blood plasma if he or she receives blood from a person with Rh+ blood, whose Rh antigens can trigger the production of Rh antibodies. The antibodies stay for life. A person with Rh+ blood can receive blood from a person with Rh- blood without any problems. This problem becomes dangerous the blood of mother is Rh + and she conceives a fetus that has inherited the Rh-positive factor from its father, the antibodies in her blood during her pregnancy pass through the placenta into the fetus and attack the fetus blood. This antibody will not harm her first child but if she conceives again, the antibody destroys the red cell of the embryo. This is known as erythroblastosis. If not treated, the fetus suffers severe anemia, which leads to brain retardation or death. Nobel Laureate Karl Landsteiner was involved in the discovery of both the AB0 and Rh blood groups.
About 85% of people also have a so called Rh factor on the red blood cells surface. This is also an antigen and those who have it are called Rh+. Those who have not are called Rh-. A person with Rh- blood does not have Rh antibodies naturally in the blood plasma (as one can have A or B antibodies, for instance). But a person with Rh- blood can develop Rh antibodies in the blood plasma if he or she receives blood from a person with Rh+ blood, whose Rh antigens can trigger the production of Rh antibodies. The antibodies stay for life. A person with Rh+ blood can receive blood from a person with Rh- blood without any problems. This problem becomes dangerous the blood of mother is Rh + and she conceives a fetus that has inherited the Rh-positive factor from its father, the antibodies in her blood during her pregnancy pass through the placenta into the fetus and attack the fetus blood. This antibody will not harm her first child but if she conceives again, the antibody destroys the red cell of the embryo. This is known as erythroblastosis. If not treated, the fetus suffers severe anemia, which leads to brain retardation or death. Nobel Laureate Karl Landsteiner was involved in the discovery of both the AB0 and Rh blood groups.
Lymph
It is a yellowish fluid carried in the lymphatic system. Lymph is like blood but it contains white blood cells especially lymphocytes and red blood cells are absent. It acts as a medium for the exchange of material between cells and blood. It fights against germs.
It is a yellowish fluid carried in the lymphatic system. Lymph is like blood but it contains white blood cells especially lymphocytes and red blood cells are absent. It acts as a medium for the exchange of material between cells and blood. It fights against germs.
The human heart
The heart is a fist-sized, muscular organ that pumps blood through the body. Oxygen-poor blood enters the right atrium of the heart (via veins called the inferior vena cava and the superior vena cava). The blood is then pumped into the right ventricle and then through the pulmonary artery to the lungs, where the blood is enriched with oxygen (and loses carbon dioxide). The oxygen-rich (oxygenated) blood is then carried back to the left atrium of the heart via the pulmonary vein. The blood is then pumped to the left ventricle, then the blood is pumped through the aorta and to the rest of the body. This cycle is then repeated. Every day, the heart pumps about 7,600 liters of blood, beating about 100,000 times.
left atrium
|
Upper left chamber of the heart; It receives oxygen-rich blood from the lungs via the pulmonary vein.
|
right atrium
|
The right upper chamber of the heart. It receives oxygen-poor blood from the body through the inferior vena cava and the superior vena cava.
|
left ventricle
|
The left lower chamber of the heart. It pumps the blood into the aorta (biggest and longest artery in human body). The left ventricle is much thicker than the right because it must pump blood around the entire body; this involves exerting a considerable force to overcome the pressure caused by the body.
|
right ventricle
|
The right lower chamber of the heart. It pumps the blood into the pulmonary artery.
|
Heart valves & muscle
Heart contains valves which prevents mixing of blood in the four chambers.
Heart contains valves which prevents mixing of blood in the four chambers.
- septum - the muscular wall that separates the left and right sides of the heart.
- pulmonary valve - the flaps between the right ventricle and the pulmonary artery. When the ventricle contracts, the valve opens, causing blood to rush into the pulmonary artery. When the ventricle relaxes, the valves close, preventing the back-flow of blood from the pulmonary artery to the right atrium.
- mitral valve - the valve between the left atrium and the left ventricle. It prevents the back-flow of blood from the ventricle to the atrium.
- tricuspid valve - the flaps between the right atrium and the right ventricle. It is composed of three leaf-like parts and prevents the back-flow of blood from the ventricle to the atrium.
The wall of the heart is very muscular and does not tire. It consists of three distinct layers. The first is the outer epicardium which is composed of a layer of flattened epithelial cells and connective tissue. Beneath this is a much thicker myocardium made up of cardiac muscle. The endocardium is a further layer of flattened epithelial cells and connective tissue.
A large blood supply is necessary to power the heart itself. It is supplied by the left and right coronary arteries, which branch off from the aorta.
Regulation of the cardiac cycle
Cardiac muscle is myogenic, which means that it is self-exciting. This is in contrast with skeletal muscle, which requires either conscious or reflex nervous stimuli. The hearts rhythmic contractions occur spontaneously, although the frequency or heart rate can be changed by nervous or hormonal influences such as exercise or the perception of danger.
The rhythmic sequence of contractions is coordinated by the sinoatrial node and atrioventricular nodes. The sinoatrial node, often known as the cardiac pacemaker, is located in the upper wall of the right atrium and is responsible for the wave of electrical stimulation that initiates the atria to contract. Once the wave reaches the atrioventricular node, situated in the wall between ventricular chambers, it is conducted through the bundles of His and causes contraction of the ventricles. The time taken for the wave to reach this node from the sinoatrial nerve creates a delay between contraction of the two chambers and ensures that each contraction is coordinated simultaneously throughout all of the heart. In the event of severe pathology, the Purkinje fibers can also act as a pacemaker; this is usually not the case because their rate of spontaneous firing is considerably lower than that of the other pacemakers and hence is overridden.
The blood pressure for youg adult is 120 (systolic) and 80 (diastolic) mm of Hg. The Pulse is the throbing of arteries due to sudden detension of their walls after the ventricular systole. It it 72 in adult male and faster in women and children.
Cardiac muscle is myogenic, which means that it is self-exciting. This is in contrast with skeletal muscle, which requires either conscious or reflex nervous stimuli. The hearts rhythmic contractions occur spontaneously, although the frequency or heart rate can be changed by nervous or hormonal influences such as exercise or the perception of danger.
The rhythmic sequence of contractions is coordinated by the sinoatrial node and atrioventricular nodes. The sinoatrial node, often known as the cardiac pacemaker, is located in the upper wall of the right atrium and is responsible for the wave of electrical stimulation that initiates the atria to contract. Once the wave reaches the atrioventricular node, situated in the wall between ventricular chambers, it is conducted through the bundles of His and causes contraction of the ventricles. The time taken for the wave to reach this node from the sinoatrial nerve creates a delay between contraction of the two chambers and ensures that each contraction is coordinated simultaneously throughout all of the heart. In the event of severe pathology, the Purkinje fibers can also act as a pacemaker; this is usually not the case because their rate of spontaneous firing is considerably lower than that of the other pacemakers and hence is overridden.
The blood pressure for youg adult is 120 (systolic) and 80 (diastolic) mm of Hg. The Pulse is the throbing of arteries due to sudden detension of their walls after the ventricular systole. It it 72 in adult male and faster in women and children.
The cardiac cycle
Every beat of the heart involves a sequence of events called the cardiac cycle. This consists of three major stages: the atrial systole, the ventricular systole, and the complete cardiac diastole. The atrial systole consists of the contraction of the atria and the corresponding influx of blood in to the ventricles. Once the blood has fully left the atria, the atrioventricular valves, which are situated between the atria and ventricular chambers, close. This prevents any backflow into the atria. It is the sound of the valves closing which produces the familiar beating sounds of the heart.
The ventricular systole consists of the contraction of the ventricles and flow of blood into the circulatory system. Again, once all the blood has left, the pulmonary and aortic semilunar valves close. Finally complete cardiac diastole involves the relaxation of the atria and ventricles in preparation for new blood to enter the heart.
Every beat of the heart involves a sequence of events called the cardiac cycle. This consists of three major stages: the atrial systole, the ventricular systole, and the complete cardiac diastole. The atrial systole consists of the contraction of the atria and the corresponding influx of blood in to the ventricles. Once the blood has fully left the atria, the atrioventricular valves, which are situated between the atria and ventricular chambers, close. This prevents any backflow into the atria. It is the sound of the valves closing which produces the familiar beating sounds of the heart.
The ventricular systole consists of the contraction of the ventricles and flow of blood into the circulatory system. Again, once all the blood has left, the pulmonary and aortic semilunar valves close. Finally complete cardiac diastole involves the relaxation of the atria and ventricles in preparation for new blood to enter the heart.
Diseases and treatments
The study of diseases of the heart is known as cardiology. Important diseases of the heart include:
The study of diseases of the heart is known as cardiology. Important diseases of the heart include:
- Coronary heart disease is the lack of oxygen supply to the heart muscle; it can cause severe pain and discomfort known as Angina.
- A heart attack occurs when heart muscle cells die because blood circulation to a part of the heart is interrupted.
- Congestive heart failure is the gradual loss of pumping power of the heart.
- Endocarditis and myocarditis are inflammations of the heart.
- Cardiac arrhythmia is an irregularity in the heartbeat. It is sometimes treated by implanting an artificial pacemaker.
Other important points If a coronary artery is blocked or narrowed, the problem spot can be bypassed with coronary artery bypass surgery or it can be widened with angioplasty.
Beta blockers are drugs that lower the heart rate and blood pressure and reduce the hearts oxygen requirements. Nitroglycerin and other compounds that give off nitric oxide are used to treat heart disease as they cause the dilation of coronary vessels.
At Groote Schuur Hospital in Cape Town, South Africa, 53-year-old Lewis Washkansky on December 3, 1967 became the first human to receive a heart transplant (however he died 18 days later from double pneumonia). The transplant team was headed by Christiaan Barnard.
Beta blockers are drugs that lower the heart rate and blood pressure and reduce the hearts oxygen requirements. Nitroglycerin and other compounds that give off nitric oxide are used to treat heart disease as they cause the dilation of coronary vessels.
At Groote Schuur Hospital in Cape Town, South Africa, 53-year-old Lewis Washkansky on December 3, 1967 became the first human to receive a heart transplant (however he died 18 days later from double pneumonia). The transplant team was headed by Christiaan Barnard.
The hearts of other animals
The structure of the heart of other mammals is quite similar to that of humans, with four chambers. Birds also have a four-chambered heart, however it is thought that this evolved independently of that of mammals. Amphibians have a three-chambered heart. Fish have a single circulation system and a heart with two chambers. The hearts of arthropods and mollusks have a single chamber. The earthworm has a series of multiple primitive hearts.
The structure of the heart of other mammals is quite similar to that of humans, with four chambers. Birds also have a four-chambered heart, however it is thought that this evolved independently of that of mammals. Amphibians have a three-chambered heart. Fish have a single circulation system and a heart with two chambers. The hearts of arthropods and mollusks have a single chamber. The earthworm has a series of multiple primitive hearts.
Heartbeat
Smaller animals have faster heartbeat. This is evident within a species as well, as the young beat their hearts faster than the adults. Gray Whale beats 9 times per minute, Harbour Seal 10 when diving, 140 when on land, elephant 25, human 70, sparrow 500, shrew 600, and hummingbird 1,200 when hovering.
Smaller animals have faster heartbeat. This is evident within a species as well, as the young beat their hearts faster than the adults. Gray Whale beats 9 times per minute, Harbour Seal 10 when diving, 140 when on land, elephant 25, human 70, sparrow 500, shrew 600, and hummingbird 1,200 when hovering.
13. Human Body - Excretary system
Excretary system
Excretory systems regulate the chemical composition of body fluids by removing metabolic wastes and retaining the proper amounts of water, salts, and nutrients. Components of this system in vertebrates include the kidneys, liver, lungs, and skin. The main waste products in all organisms are carbon dioxide (from carbohydrates and fat oxidation) and nitrogenous wastes (ammonia, urea & uric acid) from protein metabolism. Ammonia is very toxic and usually is excreted directly by marine animals. Terrestrial animals usually need to conserve water. Ammonia is converted to urea, a compound the body can tolerate at higher concentrations than ammonia. Birds and insects secrete uric acid that they make through large energy expenditure but little water loss. Amphibians and mammals secrete urea that they form in their liver. Amino groups are turned into ammonia, which in turn is converted to urea, dumped into the blood and concentrated by the kidneys.
Excretory systems regulate the chemical composition of body fluids by removing metabolic wastes and retaining the proper amounts of water, salts, and nutrients. Components of this system in vertebrates include the kidneys, liver, lungs, and skin. The main waste products in all organisms are carbon dioxide (from carbohydrates and fat oxidation) and nitrogenous wastes (ammonia, urea & uric acid) from protein metabolism. Ammonia is very toxic and usually is excreted directly by marine animals. Terrestrial animals usually need to conserve water. Ammonia is converted to urea, a compound the body can tolerate at higher concentrations than ammonia. Birds and insects secrete uric acid that they make through large energy expenditure but little water loss. Amphibians and mammals secrete urea that they form in their liver. Amino groups are turned into ammonia, which in turn is converted to urea, dumped into the blood and concentrated by the kidneys.
Kidney
ALL vertebrates have paired kidneys. These are two bean-shaped organs, one on each side of the backbone. Kidneys regulate body fluid levels as a primary duty, and remove wastes as a secondary one. The nephron is the kidneys functional unit. Each kidney contains from one to two million nephrons.
Main components of nephron -
- Glomerulus: mechanically filters water and solutes from the blood. Bowmans Capsule: mechanically filters blood .
- Proximal Convoluted Tubule: Reabsorbs 75% of the water, salts, glucose, and amino acids.
- Distal Convoluted Tubule: Tubular secretion of H ions, potassium, and certain drugs.
Urine formation
The formation of urine had three processes: filtration, reabsorption, and tubular excretion During filtration, or glomerular excretion, blood pressure forces all the small molecules in the blood into the lumen of the nephron through the pores both in the walls of the glomerular capillaries and in the wall of the Bowmans capsule. The filtrate has the same concentration of dissolved substances as the blood minus the formed elements and the plasma proteins which are too large to fit through the pores of the capillaries and the Bowmans capsule. As the filtrate passes through the tubules of the nephron, water and many dissolved materials are reabsorbed by the blood. In fact, during the filtrates passage through the tubules up to 99 percent of the water is reabsorbed. In addition, the tubules also remove substances from the blood. This process, called tubular excretion, supplements the initial glomerular filtration.
Hormones of the Kidneys: The human kidney is also an endocrine gland secreting two hormones: 1) Erythropoietin (EPO) 2) Calcitriol, the active form of vitamin D as well as the enzyme renin.
Diseases of Kidney
Acute Renal Failure: No urine is formed by kidney and the wastes and water accumulates in the body. It can be treated by dialysis, by an artificial filtration of blood through semi permeable membaranes.
Kidney stone: It is also known as renal calculi, kidney stones are the result of crystallization of certain substances found in urine, including calcium, phosphate, oxalic acid, and uric acid. Stones may form in the urine collecting area (pelvis) of the kidney, as well as the ureters (narrow tubes connecting the kidney to the urinary bladder).
Acute Renal Failure: No urine is formed by kidney and the wastes and water accumulates in the body. It can be treated by dialysis, by an artificial filtration of blood through semi permeable membaranes.
Kidney stone: It is also known as renal calculi, kidney stones are the result of crystallization of certain substances found in urine, including calcium, phosphate, oxalic acid, and uric acid. Stones may form in the urine collecting area (pelvis) of the kidney, as well as the ureters (narrow tubes connecting the kidney to the urinary bladder).
14. Human Body - Endocrine system
Endocrine system
The endocrine system is a collection of glands that secrete chemical messages known as hormones. A hormone is a specific messenger molecule synthesized and secreted by a group of specialized cells called an endocrine gland. These glands are ductless, which means that their secretions (hormones) are released directly into the bloodstream and travel to elsewhere in the body to target organs, upon which they act. Note that this is in contrast to our digestive glands, which have ducts for releasing the digestive enzymes.
Hormones are grouped into three classes based on their structure:
a) steroids: Steroids are lipids derived from cholesterol. e.g. Testosterone is the male sex hormone. Steroid hormones are secreted by the gonads, adrenal cortex, and placenta.
b) peptides: Peptides are short chains of amino acids; most hormones are peptides. They are secreted by the pituitary, parathyroid, heart, stomach, liver, and kidneys.
c) amines: Amines are derived from the amino acid tyrosine and are secreted from the thyroid and the adrenal medulla.
Hormones are grouped into three classes based on their structure:
a) steroids: Steroids are lipids derived from cholesterol. e.g. Testosterone is the male sex hormone. Steroid hormones are secreted by the gonads, adrenal cortex, and placenta.
b) peptides: Peptides are short chains of amino acids; most hormones are peptides. They are secreted by the pituitary, parathyroid, heart, stomach, liver, and kidneys.
c) amines: Amines are derived from the amino acid tyrosine and are secreted from the thyroid and the adrenal medulla.
1)Pheromones are also communication chemicals, but are used to send signals to other members of the same species. Pheromones are used to mark territory, signal prospective mates, and communicate. Queen bees, ants, and naked mole rats exert control of their respective colonies via pheromones 2) Interferons are proteins released when a cell has been attacked by a virus. They cause neighboring cells to produce antiviral proteins. Once activated, these proteins destroy the virus. 3) Prostaglandins are fatty acids that behave in many ways like hormones. They are produced by most cells in the body and act on neighbouring cells.
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Hormones: Sources, Targets and Functions
Source
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Hormone
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Target
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Physiologic effect
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Anterior pituitary
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Follicle-stimulating hormone (FSH)
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Ovary and Testes
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Growth of ovarian follicles or seminiferous tubules
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Anterior pituitary
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Luteinizing hormone (LH)
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Ovary and Testes
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Production of estrogen and progesterone or testosterone
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Anterior pituitary
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Prolactin (LTH)
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Ovary and Mammary
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Stimulate milk production in breast maintain secretion of estrogen and progesterone by ovary
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Anterior pituitary
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Thyroid stimulating hormone (TSH)
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Thyroid
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Stimulates secretion of thyroid hormones
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Anterior pituitary
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Adrenocorticotropic hormone (ACTH)
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Adrenal cortex
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Stimulates secretion of adrenal cortex hormones
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Anterior pituitary
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Growth hormone (GH)
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General
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Stimulates growth
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Anterior pituitary
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Melanocyte-stimulating hormone (MSH)
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Melanocytes
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Stimulates dispersal of pigment in chromatophores
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Hypothalamus via posterior pituitary
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Oxytocin
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Uterus and Mammary
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Stimulates contraction and secretion of milk
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Hypothalamus via posterior pituitary
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Antidiuretic hormone (ADH)
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Kidney
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Stimulates reabsorption of water
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Thyroid gland
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Thyroxin and triodothyroxin
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General
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Stimulates metabolism, growth and development
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Thyroid gland
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Calcitonin
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Bone
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Lowers blood calcium level by inhibiting bone breakdown
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Parathyroid gland
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Parathyroid hormone
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Bone, kidney digestive tract
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Increases blood calcium by stimulating bone breakdown
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Adrenal cortex
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Mineralocorticoids (aldosterone)
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Kidney
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Maintain sodium and phosphate balance
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Adrenal cortex
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Glucoocorticoids (cortisol)
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General
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Adrenal cortex
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Dehydroepiandrosterone (DHEA)
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Stimulate sex drive induce labor
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Adrenal medulla
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Epinephrine (adrenalin)
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Muscle, liver
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Stimulates glucose release short term cope with stress
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Adrenal medulla
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Norepinephrine
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Blood vessels
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Constricts blood vessels increase heart rate
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Pineal gland
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Melatonin
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Gonads, pigment cells other cells
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Control biorhythms influence reproduction
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Pancreas alpha cells
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Glucagon
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Liver fatty tissue
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Raise blood glucose concentration stimulate gluconeogenesis
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Pancreas beta cells
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Insulin
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General
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Lower blood glucose concentration stimulate glycogen synthesis.
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Ovary
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Estrogen estradiol
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General uterus
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Develop/maintain female characteristics stimulate growth of uterine lining
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Ovary
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Progestrogen
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Uterus breast
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Stimulate development of uterine lining
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Ovary and placenta
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Relaxin
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Pelvic ligaments
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Relaxes pelvic ligaments
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Placenta
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Chorionic gonadotropin
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Anterior pituitary
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Stimulates release of FSH and LH
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Testes
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Testosterone
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General and reproductive structures
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Develops and maintains male sex characteristics promotes spermatogenesis
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Testes
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Inhibin
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Anterior lobe of pituitary
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Inhibits FSH release
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Testes
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Testosterone
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General and reproductive structures
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Develops and maintains male sex characteristics promotes spermatogenesis
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Testes
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Testosterone
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General and reproductive structures
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Develops and maintains male sex characteristics promotes spermatogenesis
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Duodenal mucosa
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Secretin
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Pancreas
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Stimulates secretion of pancreatic juice
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Duodenal mucosa
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Cholecystokinin
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Gallbladder
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Stimulates release of bile by gallbladder
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15. Human Body - Nervous system
Nervous system
The functions of our body are controlled and coordinated by two systems namely the nervous and endocrine system. The nervous system consists of animals within the animal organisms that are concerned with the reception of stimuli, the transmission of nerve impulses, or the activation of muscle mechanisms. A nerve tissue composed primarily of cells called neurons. A neuron consists ofdendrites, a cell body and an axon. The dendrites generate nerve impulses in response to stimulation from a sense receptor or from another neuron and carry impulses toward the cell body, which contains the cell’s nucleus. The axon carries an impulse
transmitted to it by the cell body to another neuron or to an effector muscle or gland. There are three types of neuron sensory, motor and association. A synapse is the junction between two neuron.
In mammals these neuron comprise 2 types of nervous system i.e.Central nervous system and peripheral nervous system. The brain and spinal cord make up the central nervous system (CNS).
The Central Nervous System (CNS) is composed of the brain and spinal cord.
Composition of the brain
The average adult human brain weighs 1.3 to 1.4 kg (approximately 3 pounds). The brain contains about 100 billion nerve cells (neurons) and trillons of "support cells" called glia. The brain consists of gray matter (40%) and white matter (60%) contained within the skull. The brain has three main parts: the cerebrum, the cerebellum, and the brain stem (medulla). Cerebrospinal fluid (CSF) surrounds the brain. Although the brain is only 2% of the bodys weight, it uses 20% of the oxygen supply and gets 20% of the blood flow.
Brain contained in the skull called cranium. The brain appears as three distinct but connected parts: the cerebrum, cerebellum and the brain stem a central core that gradually becomes the spinal chord.
Brain contained in the skull called cranium. The brain appears as three distinct but connected parts: the cerebrum, cerebellum and the brain stem a central core that gradually becomes the spinal chord.
(i) cerebrum The cerebrum is the largest part of brain and makes up 85% of the brains weight. This is the thinking part of the brain.The cerebrum is made up of two halves, with one on either side of the head. The right half of the cerebrum controls the left side of your body, and the left half controls the right side. These two hemisphere is jointed by a nerve fibres known as corpus callosum. The surface of each cerebral hemisphere shows many convolutions called Gyri separated by sulci(depressions). Each cerebral hemisphere is divided into
a) frontal lobe : It has motor area ( controls voluntary movements of the muscles), pre motor area ( involuntary movement and automatic nervous system) and association area (association between various sensation and movements)
a) frontal lobe : It has motor area ( controls voluntary movements of the muscles), pre motor area ( involuntary movement and automatic nervous system) and association area (association between various sensation and movements)
b) parietal : It has somaesthetic area or general sensory area is the seat for general sensation like pain, touch and temperature.
c) temporal lobe :The temporal lobes are anterior to the occipital lobes and lateral to the Fissure of Sylvius. Temporal lobes are associated with emotional responses, hearing, memory and speech.
d) occipital lobes : It has a visual area ( visual sensation) and auditory area ( hearing)
(ii) Hypothalmus : The hypothalamus is composed of scattered masses of grey matter in white matter at the base of the brain. Although it is the size of only a pea (about 1/300 of the total brain weight), the hypothalamus is responsible for some very important functions. It is responsible for regulation of temperature, hunger, thirst and emotional reactions. The hypothalamus also controls the pituitary.
Hind Brain
a) Cerebellum: The cerebellum is at the back of the brain, below the cerebrum. It is smaller than the cerebrum at only 1/8 of its size. It controls our balance, movement, and coordination (how your muscles work together). Because of our cerebellum, we can stand upright, keep your balance, and move around.
a) Cerebellum: The cerebellum is at the back of the brain, below the cerebrum. It is smaller than the cerebrum at only 1/8 of its size. It controls our balance, movement, and coordination (how your muscles work together). Because of our cerebellum, we can stand upright, keep your balance, and move around.
b) Brainstem : The brain stem is a general term for the area of the brain between the thalamus and spinal cord. Structures within the brain stem include the medulla, pons, tectum, reticular formation and tegmentum. Some of these areas are responsible for the most basic functions of life such as breathing, heart rate and blood pressure.
Spinal Cord: spinal cord is about 43 cm long in adult women and 45 cm long in adult men and weighs about 35-40 grams. The vertebral column, the collection of bones (back bone) that houses the spinal cord, is about 70 cm long. Therefore, the spinal cord is much shorter than the vertebral column. It is covered by the same meninges as the brain and its main function is conduct impulses to and from the brain and acts as a reflex centre.
Mid Brain
It contains many groups of nerve cells scatterd in white matter such as the superior and inferior colliculi and red nucleus. They are involved in controlling the muscle tone and modify some motor activities initiated by the cortex.
It contains many groups of nerve cells scatterd in white matter such as the superior and inferior colliculi and red nucleus. They are involved in controlling the muscle tone and modify some motor activities initiated by the cortex.
Peripheral nervous system
The nerves that connect the CNS to the rest of the body are called the peripheral nervous system.
The nerves that connect the CNS to the rest of the body are called the peripheral nervous system.
a) spinal nerves are those nerves emerge from the spinal cord . There are 31 pairs of spinal nerves all of them are mixed nerves consisting of sensory and motor neurons .
b) cranial nerves are those nerves that emerge from the brain. There are twelve pairs of them. Some are sensory, some are motor and some are mixed nerves.
c) autonomic nervous system : This is organised into two distinct regions along the central nervous system forming the sympathetic and parasympathetic system. These two systems act opposite to each other in their action in their muscles and glands they control. It controls the rate and force of the heart beat, the contraction of involuntary muscles and the size of pupils of eye.
Our sensory organs - Eye
Eye is the light sensitive organ of vision. The function of the eye is to translate the electromagnetic vibrations of light into patterns of nerve impulses that are transmitted to the brain. The eye sits in a little hollow area (the eye socket) in the skull and protected by the eyelid. The eyelid helps keep the eye clean and moist. Tear is a clear, salty liquid that is produced by Lacrimal glands in the eyes. The eyelid also has great reflexes, which are automatic body responses that protect the eye.
Let us see various parts of our eye and how it functions.
The white part of the eyeball is called the sclera made of tough material covers the eye ball. The part of the sclera in front of the colored part of the eye is called the cornea which is transparent allows light to pass through it. Behind the cornea are the iris and the pupil. The iris is the colorful part of the eye. When you see people with brown or blue eyes, it really means that the colour of iris. The iris has muscles attached to it that change its shape. This allows the iris to control how much light goes through the pupil. The pupil is the black circle in the center of the iris and it changes size as the amount of light changes (the more light, the smaller the hole). Between the iris and cornea is the anterior chamber. This chamber is filled with a special transparent fluid that gives the eye oxygen, protein, and glucose (a type of sugar in the body) to keep it healthy. Retina is a sensory tissue that lines the back of the eye. It contains millions of photoreceptors (rods and cones) that convert light rays into electrical impulses that are relayed to the brain via the optic nerve. Lens, a crystalline structure located just behind the iris - it focuses light onto the retina whose shape is adjusted by the ciliary body. The biggest part of the eye sits behind the lens and is called the vitreous body. The vitreous body forms two thirds of the eyes volume and gives the eye its shape. It is filled with a clear, jelly-like material called the vitreous humor.
The retina uses special cells called rods and cones to process light. Rods see in black, white, and shades of gray and tell us the form or shape that something has. Rods cannot tell the difference between colors, but they are super-sensitive, allowing us to see when it is very dark.
Cones sense color and they need more light than rods to work well. Cones are most helpful in normal or bright light. The retina has three types of cones - red, green, and blue - to help you see different ranges of color. Together, these cones can sense combinations of light waves that enable our eyes to see millions of colors.
There are 2 types of eyes found in animals: single (found in Humans ) and compound eyes. Compound eyes are only found in arthropods such as insects and crustaceans.
Let us see various parts of our eye and how it functions.
The white part of the eyeball is called the sclera made of tough material covers the eye ball. The part of the sclera in front of the colored part of the eye is called the cornea which is transparent allows light to pass through it. Behind the cornea are the iris and the pupil. The iris is the colorful part of the eye. When you see people with brown or blue eyes, it really means that the colour of iris. The iris has muscles attached to it that change its shape. This allows the iris to control how much light goes through the pupil. The pupil is the black circle in the center of the iris and it changes size as the amount of light changes (the more light, the smaller the hole). Between the iris and cornea is the anterior chamber. This chamber is filled with a special transparent fluid that gives the eye oxygen, protein, and glucose (a type of sugar in the body) to keep it healthy. Retina is a sensory tissue that lines the back of the eye. It contains millions of photoreceptors (rods and cones) that convert light rays into electrical impulses that are relayed to the brain via the optic nerve. Lens, a crystalline structure located just behind the iris - it focuses light onto the retina whose shape is adjusted by the ciliary body. The biggest part of the eye sits behind the lens and is called the vitreous body. The vitreous body forms two thirds of the eyes volume and gives the eye its shape. It is filled with a clear, jelly-like material called the vitreous humor.
The retina uses special cells called rods and cones to process light. Rods see in black, white, and shades of gray and tell us the form or shape that something has. Rods cannot tell the difference between colors, but they are super-sensitive, allowing us to see when it is very dark.
Cones sense color and they need more light than rods to work well. Cones are most helpful in normal or bright light. The retina has three types of cones - red, green, and blue - to help you see different ranges of color. Together, these cones can sense combinations of light waves that enable our eyes to see millions of colors.
There are 2 types of eyes found in animals: single (found in Humans ) and compound eyes. Compound eyes are only found in arthropods such as insects and crustaceans.
Diseases and disorders of eye
1) Myopia (nearsightedness or short sightedness) is a refractive defect where the person affected usually can see nearby objects clearly but distant objects appear blurred. The eye is slightly elongated front to back,causing images to be focused in front of the retina rather than directly on it. This defect can be corrected by wearing a biconcave or diverging lenses.
1) Myopia (nearsightedness or short sightedness) is a refractive defect where the person affected usually can see nearby objects clearly but distant objects appear blurred. The eye is slightly elongated front to back,causing images to be focused in front of the retina rather than directly on it. This defect can be corrected by wearing a biconcave or diverging lenses.
2) Hypermetropia is also known and long-sightedness, and it is a defect of vision caused by an impefection in the eye, causing inablility to focus on near objects and in extreme cases causing a sufferer to be unable to focus on objects at any distance. It is corrected by a using glasses with lenses of positive curvature ("magnifying glasses").
3) Presbyopia is a condition that occurs with growing age and results in the inability of the human eye to focus on objects in varying distances. Presbyopia cannot be cured, but the loss of focusing ability can be compensated by wearing glasses with varying power, so-called multifocal lenses or progressive addition lenses.
4) Astigmatism is a refractive defect of the eye characterized by an aspherical cornea in which one axis of corneal steepness is greater than the perpendicular axis. Astigmatism causes difficulties in seeing fine detail, and can be often corrected by glasses with a cylindrical lens or by toric contact lenses.
5) Arc eye is a painful condition sometimes experienced by welders who have failed to use adequate eye protection. It can also occur due to light reflected from snow (known as snow blindness), water or sand. The intense ultraviolet light emitted by the arc causes a superficial and painful keratitis.
6) A cataract is any opacity which develops in the crystalline lens of the eye or in its envelope. Cataracts form for a variety of reasons, including ultraviolet exposure, secondary effects of diseases such as diabetes, or simply due to advanced age; they are usually a result of denaturation of lens proteins.
7) Conjunctivitis is an inflammation of the conjunctiva (the outermost layer of the eye that covers the sclera), often due to infection. There are three common varieties of conjunctivitis, viral, allergic, and bacterial. Viral and bacterial conjunctivitis are contagious.
8) Blindness caused by cloudiness or scarring of the cornea can sometimes be cured by surgical removal of the affected portion of the corneal tissue. Only corneal tissue is taken from deceased persons for eye grafts.
9) Glaucoma is an eye disease that is defined as a characteristic optic neuropathy, or disease of the optic nerve. The most common cause of glaucoma is increased intraocular pressure. Both laser and conventional surgeries are performed to treat glaucoma.
Our sensory organs - Nose
Nose is the smell receptors or olfactory organs. Nose has two holes called Nostrils. The nostrils and nasal passage is separated by septum made of cartilage. There is a space in the middle of our face called nasal cavity which connect to the back of the throat which in turn connects trachea. When we inhale air, membrane warms and moistens it. mucous traps dust, gems and other particles. Cilia are the name given to small hairs in your nose. An olfactory epithelium is situated on the roof of mouth has very small receptors which are sensitive to odour molecules. odour stimulate different receptor and olfactory nerve sends message to brain and it interprets different smells.
Ear
An ear is an organ of hearing and balance. Human ear consists of of three sections: the outer, middle, and inner ear. The outer and middle ears function only for hearing, while the inner ear also serves the functions of balance and orientation. In the outer hear, the visible part is called the pinna, or auricle, and functions to collect and focus sound waves. From the pinna, the sound pressure waves p (Pascal) moves into the ear canal, a simple tube running to the middle ear.The middle ear includes the eardrum (tympanum or tympanic membrane) and the ossicles, three tiny bones of the middle ear. i.e. malleus, incus, and stapes(smallest bone in human body). Mammals are unique in having three ear bones. These bones form the linkage between the tympanic membrane and the oval window that leads to the inner ear. The tympanum turns vibrations of air in the ear canal into vibrations of the ossicles. The ossicles in turn transmit the vibrations through the membrane of the oval window into the fluid of the inner ear. The inner ear comprises both the organ of hearing (the cochlea) and the labyrinth or vestibular apparatus, the organ of balance located in the inner ear that consists of three semicircular canals and the vestibule. The eustachian tube helps keep the eardrum intact by equalizing the pressure between the middle and outer ear. For example, if a person travels from sea level to a mountaintop, where air pressure is lower, the eardrums may cause pain because the air pressure in the middle ear becomes greater than the air pressure in the outer ear.
Non-mammalian hearing organs Spiders have hairs on their legs which are used for detecting sound.; Reptilian ears only have one bone - the malleus.
Non-mammalian hearing organs Spiders have hairs on their legs which are used for detecting sound.; Reptilian ears only have one bone - the malleus.
Skin
Skin is the biggest organ in our body. It covers and protects our body. The skin is made up three layers. The outermost is epidermis. It consists mostly of dead skin cells. It has a substance called melanin which gives the skin its colour. Dermis is situated below the epidermis. It contains blood vessels, nerve endings, oil glands (sebaceous), and sweat glands. The nerve endings help us to sense touch by communicating to brain. The third and bottom layer is called the subcutaneous layer. It is made mostly of fat and helps your body stay warm, absorb shocks, here we find hair follicles.
Tongue
Tongue is primary organ of taste, plays an important role in chewing and swallowing of food. The tongue is covered with dozens of pimple-like projections called papillae. These grip and move food when you chew. Around the sides of the papillae are about 10,000 microscopic taste buds. Different parts of the tongue are sensitive to different flavours: sweet, salt, sour and bitter.
Tongue is primary organ of taste, plays an important role in chewing and swallowing of food. The tongue is covered with dozens of pimple-like projections called papillae. These grip and move food when you chew. Around the sides of the papillae are about 10,000 microscopic taste buds. Different parts of the tongue are sensitive to different flavours: sweet, salt, sour and bitter.
16. Human Body - Muscular system
Muscular system
Muscles contribute half of our body weight. It is made up special tissues, muscle fibers that can contract or expand depending on the signals from brain and helps us to move. There are 650 muscles. The muscle actions are voluntary and involuntary. We can move our hand according to our wish. It is an involuntary muscle movement. The muscles are attached to bones by stretchy tissue called tendons. When the muscles contract, they pull on the tendons which pull on the bones and cause our limbs to move. Involuntary muscles, such as the heart, diaphragm and intestines, are automatically controlled by the brain.
17. Human Body - Skeletal system
Skeletal system
In biology, the skeleton or skeletal system is the biological system providing support in living organisms. Skeletal systems are commonly divided into three types
1. external (an exoskeleton)
2. internal (an endoskeleton)
3. fluid based (a hydrostatic skeleton)
3. fluid based (a hydrostatic skeleton)
The phyla arthropoda and mollusca both have exoskeletons. An internal skeletal system consists of rigid structures within the body, moved by the muscular system. Hydrostatic skeletons are similar to a water-filled balloon. Located internally in cnidarians and annelids, among others, these animals can move by contracting the muscles surrounding the fluid-filled pouch, creating pressure within the pouch that causes movement. Cartilage is another common component of skeletal systems, supporting and supplementing the skeleton. The human ear and nose are shaped by cartilage. Some organisms have a skeleton consisting entirely
of cartilage and without any calcified bones at all, for examplesharks. The bones or other rigid structures are connected by ligaments and connected to the muscular system via tendons.
The human skeleton consists of 206 bones. We are actually born with more bones (about 300), but many fuse together as a child grows up. These bones support your body and allow you to move. Bones contain a lot ofcalcium (an element found in milk, broccoli, and other foods). Bones manufacture blood cells and store important minerals.
The longest bone in our bodies is the femur (thigh bone). The smallest bone is the stirrup bone inside the ear. Each hand has 26 bones in it. Your nose and ears are not made of bone; they are made of cartilage, a flexible substance that is not as hard as bone.
Joints
Bones are connected to other bones at joints.T here are many different types of joints, including
fixed joints (such as in the skull, which consists of many bones)
hinged joints (such as in the fingers and toes)
ball-and-socket joints (such as the shoulders and hips)
A typical bone has an outer layer of hard or compact bone, which is very strong, dense and tough. Inside this is a layer of spongy bone, which is like honeycomb, lighter and slightly flexible. In the middle of some bones is jelly-like bone marrow, where new cells are constantly being produced for the blood.
Differences in males and females
Males and females have slightly different skeletons, including a different elbow angle. Males have slightly thicker and longer legs and arms; females have a wider pelvis and a larger space within the pelvis, through which babies travel when they are born.
18. Human Body - Reproductive system
Reproductive system
Life could not exist without reproduction. This does not mean that all species reproduce in the same way. Humans reproduce slightly differently from other species and are even capable of controlling reproduction. There are two types of reproduction viz. asexual reproduction and sexual reproduction. Sexual reproduction produces offspring that are genetically different from their parents. Asexual reproduction produces offspring genetically identical to their parent. These offspring are produced by mitosis.
1) Fission : A unicellular organisms such as paramaecium, amoeba split into two cells (binary fission) that are similar to the parent cell whereas plasmodium undergo multiple fission to produce many daughter cells.
1) Fission : A unicellular organisms such as paramaecium, amoeba split into two cells (binary fission) that are similar to the parent cell whereas plasmodium undergo multiple fission to produce many daughter cells.
2) Budding: In this process an offspring grows out of the body of the parent e.g. Hydra
4) Fragmentation: In this form, the body of the parent breaks into distinct pieces, each of which can produce an offspring. Planariansexhibit this type of reproduction.
5) Regeneration: In this form, if a piece of a parent is detached, it can grow and develop into a completely new individual.Echinoderms & Crustaceans exhibit this type of reproduction.
Sexual reproduction
In sexual reproduction new individuals are produced by the fusion of haploid gametes to form a diploid zygote. Sperm are malegametes, egg or ova (ovum singular) are female gametes. Meiosis is a type of cell division that produces cells with half number of chromosomes of the original cell(haploid). Fertilization is the fusion of two such distinctive cells that produces a unique new combination of alleles. Thus Zygote has the full number of chromosomes typical of the species.
In sexual reproduction new individuals are produced by the fusion of haploid gametes to form a diploid zygote. Sperm are malegametes, egg or ova (ovum singular) are female gametes. Meiosis is a type of cell division that produces cells with half number of chromosomes of the original cell(haploid). Fertilization is the fusion of two such distinctive cells that produces a unique new combination of alleles. Thus Zygote has the full number of chromosomes typical of the species.
Male reproductive system
These are the testicles; duct system, including the epididymis and vas deferens; accessory glands; and penis. The two testicles, or testes, produce and store the tiny sperm cells. The counterpart of the ovaries in the female, the testicles are oval shaped and grow to be about 1 inch long. The testicles also produce hormones, including testosterone, which stimulates the production of sperm and facilitates male maturation.
The duct system includes the epididymis and the vas deferens, a muscular tube that passes upward alongside the testes and transports the sperm-containing fluid called semen. Each epididymis is a set of coiled tubes that lies against the testes, connecting them with the vas deferens. With the testes, they hang in a pouchlike structure behind the penis called the scrotum.
The accessory glands, including the seminal vesicles and the prostate gland, provide fluids that lubricate the duct system and nourish the sperm. The seminal vesicles are saclike structures attached to the vas deferens to the side of the bladder. The prostate gland, which produces some of the components of semen, surrounds the ejaculatory ducts at the base of the urethra, just below the bladder. The urethra carries the semen through the penis, a cylindrical structure located between the legs, to the outside. The urethra also discharges urine, which is filtered in the kidneys and stored in the bladder.
The duct system includes the epididymis and the vas deferens, a muscular tube that passes upward alongside the testes and transports the sperm-containing fluid called semen. Each epididymis is a set of coiled tubes that lies against the testes, connecting them with the vas deferens. With the testes, they hang in a pouchlike structure behind the penis called the scrotum.
The accessory glands, including the seminal vesicles and the prostate gland, provide fluids that lubricate the duct system and nourish the sperm. The seminal vesicles are saclike structures attached to the vas deferens to the side of the bladder. The prostate gland, which produces some of the components of semen, surrounds the ejaculatory ducts at the base of the urethra, just below the bladder. The urethra carries the semen through the penis, a cylindrical structure located between the legs, to the outside. The urethra also discharges urine, which is filtered in the kidneys and stored in the bladder.
Female reproductive system
A females internal reproductive organs are the vagina, uterus, fallopian tubes, and ovaries. The main function of this system is to produce eggs, protect and nourish fertilized egg and give birth to offspring. The vagina is a muscular, hollow tube that extends from the vaginal opening to the uterus. The fallopian tubes connect the uterus to the ovaries. They produce, store, and release eggs into the fallopian tubes in the process called ovulation. An ovary sends a tiny egg into one of the fallopian tubes. Unless the egg is fertilized by a sperm while in the fallopian tube, the egg dries up and leaves the body about 2 weeks later through the uterus. This process is called menstruation. On average, the monthly cycle for an adult woman is 28 days, but the range is from 23 to 35 days.
During sexual intercourse, semen containing millions of sperms discharges into vagina. The sperms swim up to the fallopian tube and only one sperm fuses with the ovum to produce zygote. The embryo is formed from this zygote.
During the fetal stage, which lasts from 9 weeks after fertilization to birth, development continues as cells multiply, move, and change. The fetus floats in amniotic fluid inside the amniotic sac. The fetus receives oxygen and nourishment from the mothers blood via the placenta. The amniotic fluid and membrane cushion the fetus against bumps and jolts to the mothers body.
Pregnancy lasts an average of 280 days - about 9 months. When the baby is ready for birth, its head presses on the cervix, which begins to relax and widen to get ready for the baby to pass into and through the vagina. The mucus that has formed a plug in the cervix loosens, and with amniotic fluid, comes out through the vagina when the mothers water breaks.
When the contractions of labor begin, the walls of the uterus contract as they are stimulated by the pituitary hormone oxytocin.The contractions cause the cervix to widen and begin to open. After several hours of this widening, the cervix is dilated (opened) enough for the baby to come through. The baby is pushed out of the uterus, through the cervix, and along the birth canal. The babys head usually comes first; the umbilical cord comes out with the baby and is cut after the baby is delivered. The last stage of the birth process involves the delivery of the placenta, which is now called the afterbirth. After it has separated from the inner lining of the uterus, contractions of the uterus push it out, along with its membranes and fluids.
19. Genetics
Principles of inheritance
It is the scientific study of how physical, biochemical and behavioural traits are transmitted from parents to their offspring. Gene is the unit of inheritance and are carried by chromosomes in the nucleus and are arranges in a line along each chromosome. An Austrian monk, Gregor Mendel made the first truly scientific study of heredity by conducting experiments with garden peas. On the basis of these experiments, he formulated the following principles of inheritance.
It is the scientific study of how physical, biochemical and behavioural traits are transmitted from parents to their offspring. Gene is the unit of inheritance and are carried by chromosomes in the nucleus and are arranges in a line along each chromosome. An Austrian monk, Gregor Mendel made the first truly scientific study of heredity by conducting experiments with garden peas. On the basis of these experiments, he formulated the following principles of inheritance.
2. Law of segregation : when the factors that determine a pair of contrasting characters are brought together in a hybrid, they do not freely intermix but maintain their individualities. When the hybrid forms gametes, the factors of the pair become separated from each other and enter separate gametes.
3. Law of independent assortment : In the inheritance of more that one pair of characters considered together in a cross, the factors responsible for each pair of characters are distributed independently to the gametes i.e assorted independent of those of the other pair.
Fertilisation
Fertilisation is necessary to produce a single cell that contains a full complement of genes. When a cell undergoes meiosis, gametes are formed – a sperm cell or an egg cell. Each gamete contains only half of the genetic material of the original cell. During sperm and egg fusion in fertilisation , the full amount of genetic material is restored. Half contributed by male parent and half contributed by female. In humans there are 46 chromosomes in each human body cell –except in sperm and egg which each have 23 chromosomes. As soon as fertilisation is complete , the zygote that is formed has a complete set of 46 chromosomes containing genetic information from both parents. Male gametes (sperm) contains has only 22 paired homologous chromosomes and two unpaired chromosomes called X and Y. Each somatic cells of female has 23 pairs including a pair of X chromosomes. At fertilisation if a male gamete containing X chromosomes unites with a female gamete, a female organism is produced. If the male gamete containing a Y chromosomes unites with a female gamete a male organisms will be produced. The male is said to determine the sex of the off spring.
Fertilisation is necessary to produce a single cell that contains a full complement of genes. When a cell undergoes meiosis, gametes are formed – a sperm cell or an egg cell. Each gamete contains only half of the genetic material of the original cell. During sperm and egg fusion in fertilisation , the full amount of genetic material is restored. Half contributed by male parent and half contributed by female. In humans there are 46 chromosomes in each human body cell –except in sperm and egg which each have 23 chromosomes. As soon as fertilisation is complete , the zygote that is formed has a complete set of 46 chromosomes containing genetic information from both parents. Male gametes (sperm) contains has only 22 paired homologous chromosomes and two unpaired chromosomes called X and Y. Each somatic cells of female has 23 pairs including a pair of X chromosomes. At fertilisation if a male gamete containing X chromosomes unites with a female gamete, a female organism is produced. If the male gamete containing a Y chromosomes unites with a female gamete a male organisms will be produced. The male is said to determine the sex of the off spring.
Traits controlled by genes found on X and Y chromosomes are said to be sex linked. Recessive traits appear more frequently in malesthan females due to the fact that males have only one X chromosomes. A female will not exhibit the traits unless the recessive gene is on both her X chromosomes.
Genetic disorders
Congenital heart defects: a hole in the atrial septum that permits passage of blood from one atrial chamber to the other may be present at birth.
Congenital heart defects: a hole in the atrial septum that permits passage of blood from one atrial chamber to the other may be present at birth.
Erythroblastosis foetalis : This is a haemolytic disease of new born infants that occur due to incompatibility between mother and foetus.
Colour blindness : defect of vision affecting the ability to distinguish between red and green colours. This happens more commonly in males than females.
Downs syndrome (mongolism) : people with disease may have mild to severe learning disabilities and physical symptoms that include a small skull,extra folds of skin under the eyes, flattened nose bridge,a large,protruding tongue.such persons have 47 chromosomes.
Haemophilia: a hereditary blood disease characterised by inability of blood to clot or coagulate,leading to hemorrhage, or excessive bleeding even from minor injuries.
Harelip : It is abnormal clefts between upper lip and the base of nose. Cleft palate : It is the incomplete closure of palate or roof of mouth.
Sickle cell anaemia : Disease affecting black Africans . The RBC assume sickle shape when blood is deprived of oxygen.
Phenylketonuria: It causes inability to metabolise the amino acid Phenylpyruvic acid.
Albinism:Albinism (from Latin albus, meaning "white") is a lack of pigmentation in the eyes, skin and/or hair. Albinism is an inherited condition resulting from the combination of recessive alleles passed from both parents of an individual.
Cystic fibrosis : It causes body to secrete an abnormally thick, sticky mucus that clogs pancreas,lungs leading to problems with breathing, infection and ultimately death.
Hereditary material
Genes are chemically composed of deoxyribonucleic acid (DNA). It is the DNA that transmits the hereditary characters in a coded form one generation to the next in the living organisms. However in some virus ribonucleic acid carries the genetic information. The DNA and RNA are nucleic acids. The correct structure of DNA and RNA was first deduced by Watson and Crick in 1953. They proposed that DNA exits as a double helix in which the two polynucleotide chains are coiled about one another in a spiral. Each nucleotide chains consist of sequence of nucleotides. The nucleotides in each chain consists of
(i) pentose sugar(deoxyribose)
(ii) Phosphate molecule
(iii) nitrogenous bases (purines : adenine, guanine pyrimidines : cytosine,thymine).
Among these bases, adenine pairs specifically with thymine whereas cytosine does so with guanine. Hence the molecule is dependent on the sequence of bases in the other, The two chains are, therefore said to be complementary to each other. The base molecules of the two chains are linked through weak hydrogen bonds. Exceptionally,
DNA molecule may be single stranded and circular as in some bacteriophages.
The RNA molecule has generally a single stand of an unbranches polynucleotide chain. Its constituents are the same as in DNA except that the pentose sugar is ribose and among the nitrogenous bases,uracil is present as the pyrimidine in place of thymine. In some instances .the RNA strand is coiled on itself to form helices that may be connected by weak hydrogen bonds.
The genetic code is the sequence of nitrogen bases in deoxyribonucleic acid. The DNA carries the instructions for the production of protein. A protein is composed of smaller molecules called amino acids and the structure and function of the protein is determined by the sequence of its amino acids . The sequence of amino acids in turn is determined by the sequence of nucleotide bases DNA . A sequence of three nucleotide bases, called a triplet, is the genetic code word, or codon, that specifies a particular amino acid.
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