What are Communicable Diseases?

Communicable disease is an illness caused due to a specific infectious agent or its toxic products capable of being directly or indirectly transmitted from man to man, animal to animal or from environment to man or animal. These diseases are grouped as water-borne, air borne, vector borne, fomite – borne diseases etc. The mode of transmission may be through oro- faecal route, parasites, air, vectors, animals and by direct contact
Infection : The entry and development or multiplication of an infectious agent in the body of man or animals.
Contamination : The presence of infections agent on a body surface, also on or in clothes, beddings, toys, surgical instruments or dressings or other inanimate articles or substances including water, milk and food.
Infestation : For persons or animals the lodgment, development and reproduction or arthropods on the surface of the body or in the clothing (e.g) ice, itch mite.
Host : A person or other animal including birds and arthropods that affords subsistence or lodgment to an infectious agent under natural condition.
Communicable diseases : An illness due to specific infections agent or its toxic products capable of being directly or indirectly transmitted from man to man, animal to animal or from the environment to man or animal.
Epidemic : The unusual occurrence or sudden outbreak of disease in a community or region.
Endemic : It refers to the constant presence of a disease or infections agent within a givengeographic area or population group.
Sporadic : The word sporadic means scattered about. The diseases are so few and separated
widely in space.
Pandemic : An epidemic usually affecting a large proportion of the population, occurring over a wide geographic area such as a section of a nation.
Zoonosis : An infection or infections disease transmissible under natural conditions from vertebrate animals to man.
Eradication : Termination of all transmission of infection by extermination of infections agent through surveillance and containment.
Carriers : A carrier is defined as “an infected person or animal that harbours a specific infections
agent in the absence of clinical manifestation but potentially source of infection.
Infectious agents and examples of
diseases
The organisms that cause disease vary in size from viruses, which are too small to be seen by a light microscope to intestinal worms which may be over a metre long. The groups of infectious agents are listed with examples of diseases they cause.
Bacteria
Pneumonia, tuberculosis, enteric fever, gonorrhoea
Viruses
Measles, varicella, influenza, colds, rabies
Fungi
Ringworm, tinea pedis (athlete’s foot)
Protozoa
Malaria, giardia
Metazoa
Tapeworm, filariasis, onchcerciasis (river blindness), hookworm
Prions
Kuru, Creutzfeld-Jacob disease, Bovine spongiform encephalopathy (BSE)

Lecture notes on Gastro Intestinal Hormones

Endocrine cells present in different regions of the gastro-intestinal tract secrete four major peptide hormones, namely
 gastrin, secretin, cholecystokinin (CCK) and gastric inhibitory peptide (GIP).
. Secretin acts on the exocrine pancreas and stimulates secretion of water and bicarbonate ions.
CCK acts on both pancreas and gall bladder and stimulates the secretion of pancreatic enzymes and bile juice, respectively.
Gastrin is produced by the mucosal cells of the pyloric region ofthe stomach and is the most effective activator of gastric acid secretion.Two gastrins, Gastrin I and Gastrin II have been identified. Gastrin I has
17 amino acids and Gastrin II has 14 amino acids. Gastrin secretion increases with age, vagal stimulation, acetyl choline and intake of foods rich in proteins and amino acids particularly glycine. The terminal four
amino acids of gastrin are responsible for its hormonal action.
Secretin is a polypeptide with 27 amino acids of which 14 amino acids are identical to that of glucagon. It is formed in the duodenal mucosal cells. The secretion is stimulated by HCl and it increases the secretion of
electrolytes and fluid components of pancreatic juice. It is one of the factors that increase the secretion of bile by the liver. It can act like glucagon by increasing the cardiac output and lipolysis.
Cholecystokinin and Pancreozymin are two hormones that stimulate the secretion of pancreatic juice. Pancreozymin also stimulates the pancreas to secrete insulin and glucagons. Due to this action of pancreozymin, insulin secretion is higher when glucose is given orally than intravenously. Out of the 33 amino acids present in the pancreozymin, the eight C terminal amino acids are biologically active.
Cholecystokinin causes contraction of the gall bladder and discharge the bile into the duodenum. Discharge of bile is also stimulated by secretin and bile salts.
Other gut hormones
Hepatocrinin stimulates the formation of bile, which is low in bile salts. Motilin increases gastric motility. Enterogastrone and gastric inhibitory polypeptide inhibit gastric acid secretion and gastric motility. Enterocrinin stimulates the secretion of enzymes by the intestinal mucosa. Chymodenin stimulates the secretion of chymotrypsin from pancreas

Brief notes on Cell Membrane Transport

One of the vital functions of the plasma membrane is membrane transport. Such a transport is important to carry out the life processes of the cell. Hydrophobic molecules and small polar molecules rapidly diffuse in the membrane. Uncharged large polar molecules and charged molecules do not diffuse and they need proteins to get transported Depending upon the energy required and movement of the solute for or against the concentration gradient, the transport can be classified into two, active transport and passive transport.
Passive transport: Passive transport is also called as passive diffusion. In passive transport, the substances move from higher concentrations to lower concentrations generally without the help of any protein. The transportcontinues until the concentration of the substance becomes same on both the sides of the membrane. O2, CO2 and urea can easily diffuse across the membrane.
Facilitated Diffusion
Eventhough, the concentration of certain hydrophilic substances  like glucose are high across the membrane, they cannot pass through the membrane and need a carrier for their transport. Such a transport is
called as facilitated diffusion. The proteins involved in such processes are called as carrier proteins. Carrier proteins are present in all biological membranes. Some important characteristics of carrier proteins are
1. They facilitate transport from high concentrations of the solute to low concentrations.
2. They speed up the process of attaining equilibrium
3. They do not need energy for their transport.
4. They are highly specific in nature.
Some common examples are glucose transporter and anion transporters in red blood cell membranes.
Carrier proteins are classified into three major types.
1. Uniporters that transport single solute from one side of the membrane to the other.
2. Symporters that transport two different solute molecules simultaneously in the same direction.
3. Antiporters that transport two different solute molecules inopposite directions.
Active transport
Cells have to transport substances against the concentration gradient, i.e. from low concentrations to high concentrations. This transport called active transport is a thermodynamically unfavourable reaction.
Hence, it needs energy to drive the reaction which is acquired by ATP hydrolysis. Active transport is also mediated by carrier proteins and they are called as pumps. Na+K+ ATPases that is required to maintain the
potassium concentration high inside the cell and sodium concentrations low is an example for pumps.
Endocytosis: Endocytosis is the active process of engulfing large size particles of food substances or foreign substances. Depending upon the nature of the material that is ingested, endocytosis may be classified into two.
Pinocytosis, in which the fluid material is engulfed and phagocytosis, in which large sized solid material is engulfed. During the process, the plasma membrane invaginates into tiny pockets, which draw fluids from the surroundings into the cell. Finally, these pockets pinch off and are known as pinosomes or phagosomes,
which fuse with lysosomes and liberate their contents into the cell cytosol
Exocytosis is the process of exudating the secretory products from the cells. Vesicles containing secretory materials fuse with the plasma membrane and discharge their contents into the exterior. Pancreatic cells
pass out their enzyme secretions to the exterior by exocytosis

Cell Membrane structure and function

The outer living boundary of the cell is called as the cell membrane or ‘Plasma membrane’. The term cell membrane was coined by C.J. Nageli and C. Crammer in 1855. Apart from the cell membrane, each
and every organelle in the cell is also covered by membranes. The cell membrane not only limits the cell cytosol, but it has a variety of functions like membrane transport, signal transduction and neuro transmission.

Chemical Composition.: Four major constituents are present in the cell membrane. They are (i) lipids (28 – 79%) (ii) proteins (20 – 70%). (iii) oligosaccharides (only 1 – 5%) and (iv) water (20%).

Lipids: Depending upon the tissue from which the cell membrane isisolated, the composition also differs. Nearly 80% of the myelin sheath is made up of lipids, while in liver, it constitutes only 28%.The main lipid components of the membranes are phospholipids, cholesterol and glycolipids. The major phospholipids present are phophatidyl choline (lecithin), phophatidyl ethanolamine, phophatidyl serine and phophatidyl inositol.
Membrane lipids are amphipathic in nature and they have a head portion, which is hydrophilic and a tail portion which is hydrophobic. As the membranes are exposed to the hydrophilic environments, the lipids
arrange themselves to form a bilayer in which the hydrophobic core is buried inside the membrane.
Proteins:All the major functions of the plasma membrane are executed by the proteins present in the membrane. Proteins account for about 20 – 70% of the membrane depending on the type of the cell. They can be classified into two types. Integral membrane proteins and peripheral membrane proteins
Integral Proteins:Some of the membrane proteins are tightly embedded in the membrane and they cannot be isolated unless, the membrane is disintegrated. They are called as Integral or Intrinsic membrane proteins.
They are again classified into two. (a). Transmembrane proteins, which traverse (pass through) or span the membrane. These proteins will have domains on either side of the membrane. Many cell surface receptors
belong to this class. (b). Lipid anchored proteins that are present either on the cytosolic side or on the extracytosolic side. They insert themselves in the membrane by a lipid (acyl chain) attached to the N terminal end.
Transmembrane proteins are of two types. Single pass transmembrane proteins that traverse the membrane only once. Multipass transmembrane proteins that traverse the membrane more than once.
Peripheral Proteins:Those proteins that are present on the surface of the membrane are called as peripheral proteins. They can be easily isolated from the membrane. eg. spectrin present in the RBC membrane.
Models proposed for the plasma membrane
Monolayer Model:Overton was the pioneer to postulate that plasma membrane is a thin layer of lipid. He proposed this because he found that lipid soluble substances are easily transported across the membrane.
 Lipid Bilayer Model
The amount of lipids present in the erythrocyte membrane was nearly twice that of its total surface area. This made Gorten and Grendelto propose that lipids in the membrane exist as bilayers.
 Unit Membrane Model
This model was proposed by Davson and Danielli and was shapedby Robertson. Experiments showed that the surface tension of the biologicalmembranes are lower than that of the pure lipid bilayers, suggesting the
presence of proteins in them. Based upon this, Davson and Danielliproposed that proteins are smeared over the lipid bilayer.When electron microscope was invented, plasma membraneappeared as three layers. With this observation, Robertson formulated aunit membrane model, which states that the proteins are present on either side of the lipid bilayer. According to this model, the membrane will be like a lipid layer sandwiched between two protein layers.
 Fluid Mosaic model
This is the universally accepted model for plasma membrane. On the basis of several experiments, S.J. Singer and G.L. Nicolson in 1972 proposed this model.
The essential features of the Fluid mosaic model are
1. Lipids and proteins are present in a mosaic arrangement within the bilayer.
2. Phospholipids act as a fluid matrix, in which some proteins are integral and others are associated with the surface of the membrane.
3. Lipids and proteins are mobile in the membrane.
4. They can move laterally, rotate but not from one monolayer to the other.
5. The membrane is asymmetric in nature, the outer and inner leaflets of the bilayer differ in composition.

Isolation and isolation mechanisms-Lecture notes on evolution

A species may be defined as “a group of organisms that are reproductively isolated from other such groups”. Thus the maintenance of a species as a dintinct group is due to several isolating mechanisms. They are
1. Geographical isolation
It is a common type of isolation. The isolation between populations is caused due to geographical barriers such as mountains, rivers, oceans, forests or deserts. These natural barriers prevent interbreeding between them. Thus mutations formed in one population will lead to the formation of new species. The existence of closely related species of frogs in Southern India and Srilanka is a classical example. These fresh water animals are prevented from interbreeding due to a narrow sea namely Gulf of Mannar. Because of
isolation for a fairly long time they have evolved into distinct species.
2. Premating isolations – such mechanisms prevent interspecific crosses.
a) Ecological isolation – Members of the populations occur in different habitates in the same general region.
b) Seasonal or Temporal isolation – Mating or flowering periods occur at different seasons.
c) Sexual, Psychological or Ethological isolation – It is a behavioural isolation where males and females of the same species get attracted to each other.
d) Mechanical isolation – Physical non-correspondence of the genitalia or floral parts.
e) Gametic isolation – Spermatozoa, or pollen tubes of one species arenot attracted to the eggs or ovules of another species.
3. Postmating or postzygotic isolations – These isolating mechanisms while allowing fertilization may prevent the hybrid zygote from further development.
a) Hybrid inviability – The hybrid zyotes are inviable.
b) Hybrid sterility – The hybrids develop but they remain sterile. They are incapable of producing a normal complement of functional sex cells.
c) Hybrid breakdown – F1 hybrids are normal and fertile, but F2 containsmany weak or sterile individuals.

Lecture notes on evolution-Theory of Natural selection by Charles Darwin

Charles Robert Darwin proposed the  natural selection concept   in 1859. His theory provided the correct idea to explain all processes and intricate mechanisms of evolution.  The monumental work of Darwin was titled as “The Origin of species” (the original full title of the book was ‘On the Origin of species by means of Natural Selection, or the Preservation of favoured Races in the struggle for life’).

The book of Darwin convincingly demonstrates the fact of evolution. Further, it elaborates on the theory of natural selection as a convincing mechanism for providing evolutionary transformations. Charles Darwin was born in Shrewsbury, England on February 12, 1809. While studying in college at England through his friendship with Professor J.S. Henslow, Darwin became familiar with Botany. Later he accepted the job of a naturalist aboard the ship H.M.S Beagle. The ship was to spend five years, in exploration around South America (1829 - 34). During the period of five years, Darwin visited pacific islands and many parts of the world. He returned to England in 1836. Later he worked for a further period of 20 years to develop his theory of natural selection. While Darwin prepared his work for publication, a similar idea to explain

evolution was proposed by another naturalist, Alfred Russel Wallace (1823-1913) from Malay archipelago. Charles Darwin gracefully accepted for the publication of his theory as a joint paper with Wallace. Thus the theory of natural selection is actually titled as ‘Darwin-Wallace theory of evolution’.

The Theory of Natural SelectionDuring his period of study Darwin has made several observations and collected facts. Through these facts he arrived at certain conclusions. These conclusions constitute Darwinism. Thus Darwinism or the theory of Natural selection includes the following elements.

1. Overproduction or Prodigality of nature:All living beings have an innate desire to reproduce and form their own progeny. In this attempt they have the capacity to multiply in a geometrical manner. Such an enormous reproductive potentiality can be observed in all species of organisms. For example a single female salmon fish can produce 28,000,000 eggs in a season. A common oyster of the Atlantic coast may release as many as 80 million eggs in one season. At the time ofbreeding the ovaries of a cod fish may contain 10 million eggs. If natural processes of reproduction are allowed without any check a single pair of English sparrows can produce 275 billion descendents in 10 years. The elephants are the slowest breeders. An elephant begins to breed at 30 years of age. It goes on breeding till it is 90 years old. A female elephant can give birth to 6 young ones during its life time. Under these conditions, a pair of male and female elephants can cause the production of 19 million elephants in 750 years. Thus, the reproductive capacity is an innate nature of living organisms.

2. Struggle for existence:According to Darwin while the population increases in geometric ratio there is no corresponding increase in food production. This causes an intensive struggle for living. The struggle happens for food, space for living and for coping with environmental conditions. The struggle may be  intraspecific or interspecific. In an intraspecific struggle there is a competition among the individuals of the same species. Such a struggle is severe because the needs of the competing organisms are identical. Struggle might happen with environment too. Conditions like heat, cold, drought, storms, floods and other natural changes can affect organisms resulting in struggle for existence.

3. The universal occurrence of variations

The occurrence of variations is a characteristic feature of all groups of animals and plants. The variations may be morphological , anatomical, physiological or behavioral. (However during Darwin’s time the actual cause

and nature of variations were not known). As a result of variations, no two animals would look alike. Even the progeny of the same parents are not exactly alike in all respects. Eventhough variations are universal all such variations need not be significant from an evolutionary point of view. Certain variations that get established in the population and get inherited continually are termed, heritable variations.Such variations form the raw material for evolution.

4. Survival of the fittest:While all living organisms face the struggle for existence, certainorganisms possessing adequate modifications are able to escape and survive. Such modifications are due to inherent variations. Hence favourable variations make an animal or a plant to be successful in life. They survive as fittest organisms in an environment which gets altered frequently.

5. Natural Selection:According to Darwin ‘the fittest’ forms that are allowed to survive are chosen by ‘Natural Selection’ (an imaginative concept which includes all real aspects of the natural environment that supports the life of organisms). The forces of natural selection will encourage only those that have suitable variations as adaptive features, to survive. Darwin designated them as ‘fittest’ forms. All other organisms having non adaptive or deleterious modifications shall be disqualified. Natural selection will eliminate such organisms from the populations. The selected group of modified individuals will occupy the next level in the evolutionary ladder. Darwin strongly believed that using the natural selection concept, all

evolutionary processes in the living world can be explained. As an example he differed from the explanation provided by Lamarck while explaining the lengthening of neck in giraffe. According to Darwin the

population of giraffes had individuals having varying neck lengths. Those that had longer necks had more survival value, since they had more food andremained healthy. Gradually natural selection encouraged them to survive. Thus in course of time the average length of the neck increased.

Objections to Darwinism

While the ideas of Darwin, related to reproductive capability, prevalence of variations, concept of struggle and survival of suitable forms are all commonly accepted, there are certain drawbacks in his original theory.

1. Darwin could not explain, the origin and cause for variations while insisting their importance in progressive evolution.

2. He overemphasized the importance of the ‘fittest’ organisms. During later periods it has been suggested that ‘fit’ and fitter forms can also exist alongwith the fittest.

3. As the principle of inheritance as explained in the later years were not available during Darwin’s time. Hence he believed in the theory of ‘pangenesis’. According to this concept from every organ in the body very minute such replicate structures will orginate. Later they are transferred to

the gonads for transmission to future generations.

4. ‘Over-specialization’ as in Irish deer and its consequent harmful effect on animals had not been accounted for by Darwin

Defnition of Pleiotropy

It is an established fact that a specific gene controls a specific phenotypic trait. This finding is not always true. Studies on ‘gene expression’ have revealed that a gene often influences more than one phenotypic trait.
This phenomenon of multiple effects of a single gene is called pleiotropism. In such a genic influence more conspicuous expression of a phenotypic trait by a gene is called its major effect. If the gene causes other less conspicuous phenotypic changes, it is known as secondary effect. Such genes responsible for multiple effects are called pleiotropic genes. Vestigeal wings in Drosophila are caused by a recessive gene in homozygous condition. A keen observation has shown that this gene affectsother traits as well. They are
(i) the small halters or balancers behind the wing
(ii) structure of reproductive organs
(iii) egg production
(iv) life duration and
(v) bristles on the body.

What are Fossils ?

The fossils are the preserved remains of animals, plants or their parts found in various strata of earth. Fossils may be of entire organisms or a part which got buried, a mould or cast, foot prints or imprints of a leaf on a stone.
Fossilization :- Fossils can result by several methods. However these methods are purely accidental. There are many methods of fossilization.
1. Petrifaction :- It is the commonest method. In this method dead and buried organisms turn into stones. This is due to formation of sedimentary rocks under water. While the soft parts disappear due to decaying, hard parts get preserved due to mineralisation. The preservation happens in the original strata.
2. Petrifaction of soft parts :- Under certain conditions muscles and other soft organs may get mineralised and form rocky fossils. Several such plant fossils had been obtained.
3. Preservation of foot prints :- Moving animals on soft mud can leave foot prints. These prints, if left undisturbed, can get hardened and form rocky fossils. A study of such imprints can provide clues regarding the body form and characteristics of the extinct animal.
4. Moulds and casts :- Fossilized moulds are found in volcanic ashes. Several invertebrate fossils had been obtained as moulds. They provide details about the exact physical features of the animal.
5. Fossilization in resins and amber :-Normally, insects get entangled in soft sticky secretions of trees called
resin. The dried material can get fossilized. These fossils can even reveal the colour of the organism.
6. Preservation in ice :- Entire animals can get frozen and may be preserved in ice. In such fossils the body parts remain intact without change. Fossils of woolly mammoth from Siberia are classical fossils of this nature.
7. Dating of fossils :- The age of the fossils to a large extent can be assessed accurately, using radioisotope method. It is known that all elements exist as isotopes. Isotopes are atoms having slightly different atomic weights. e.g c12 and c14. Some isotopes remain unstable. They undergo decay and release sub
atomic oe and ß particles till they become more stable.
 Examples are
Uranium238 :lead206
Potassium40: Calcium40+argon39
Carbon14 : Carbon12
The time required for the breakdown of half the given quantity of unstable isotope is called the half-life. The half-life of many isotopes isuseful to assess the age of the rock accurately by measuring the ratio of
unstable : stable nuclides. Eg. c14 : c12 of the rock in which the fossil wascollected.
Evolutionary significance of fossils
1. Fossils tell us the full story of evolution. Fossil studies reveal the course ofevolution.
2. Through fossils the origin and evolution of specific groups of organisms canbe understood e.g. Horse evolution.
3. Fossils provide us clues regarding climatic conditions of various prehistoricperiods.
4. Study of fossils simplifies phylogenetic discussions.
5. Some fossils like woolly mammoth can provide vital clues regarding geneticalmake up.
Important fossils
Ichthyostega - interconnecting link between fishes and amphibians.
Seymouria - Interconnecting link between Amphibians and Reptiles.
Archaeopteryx - Ancestral form of birds
Dinosaurs - Extinct group of reptiles.
Hyracotherium - Early ancestor of horses.

Features o Cenozoic Era

Cenozoic Era :- (65 million years ago till date)
Plenty of fossil of organisms belonging to this era had been obtained. All modern animals and plants were represented in these fossils. This era is subdivided into Tertiary and Quarternary periods. Further this era contains seven epochs. Through fossils we can trace the origin and evolution of independent
groups of animals, camels and man.
1. Paleocene epoch :-
Modern placental mammals originated during this time.
2. Eocene Epoch :-
Ungulates originated. The ancestral form of modern horses livedduring this epoch.
3. Oligocene epoch :-
Several animals with ancient characteristics became extinct. Modernmammalian families were established. The apes originated during this epoch.
4. Miocene epoch :-
Several varieties of grasses evolved in Europe and N. America. Thuslarge Priaries were formed. These changes encouraged the evolution of fast running herbivorus mammals and their predators. Thus the carnivorousmammals came to prominence.
5. Pliocene Epoch :-
The priaries enlarged still further in several regions. The rodentsbecame more successful. The mammals increased in number.
6. Pleistocene epoch :-
Several glaciations happened during this time. This epoch ispopularly called the ‘Ice age’. The evolution of horses and man reached thefinal stages during this period. The melting of ice that happened 1,500 years
ago is considered as the last stage of this epoch. Today we are living in an
inter-glacial Period.

Features of Mesozoic Era

Mesozoic Era :-
This middle period in the history of life was marked by the  prominence of land living forms. Among animals the reptiles became more dominant. They increased in size and in number. Hence this era is named as
the Golden age of reptiles.
1. Triassic Period :- (210 to 160 million years ago)
For the first time fossils of turtles, crocodiles, and dinosaurs have beenobtained from this period. Fossil evidences show that aquatic andflying reptiles thrived during this time. The mammals orginated from reptiles
during this period.
2. Jurassic Period :- (160 to 130 million years ago)
There was a marked adaptive radiation among dinosaurs. They diversifiedinto carnivorus and herbivorus forms. The first birds originated from thereptiles. The earlist bird thus originated is known as the Archeopteryx. Theorigin of birds was a major physiological change among animals. From a more
common poikilothermic condition through feathers the birds became homeothermic.The modern bony fishes were diversified into several groups.

Cretaceous Period :- (130 to 65 million years ago)
The larger marine molluscs became extinct. The fossils of such organisms are available in places like Ariyaloor, of Tamil Nadu, today. The Dinosaurs of the Mesozoic era abruptly became extinct during
this period. Several reasons are given for the extinction of the dinosaurs. Fossilsof dinosaurs were not obtained from later periods.

Features of Paleozoic era

I. Paleozoic era :- This era produced revolutionary changes in the biosphere. Further this era saw the origin and the radiation of several groups of animals and plants that remained as the forefathers for the modern groups. Thus this era is known as the Cradle of ancient life.
1. Cambrian period :- (600 to 440 million years ago) The period preceeding cambrian is known as Pre-cambrian period. During precambiran time simple algae, protozoans, poriferans, annelids, were
well established. Thus the cambrian started with the plants and animals that were suceessful during the precambrian period. During cambrian among plants thallophytes were well establised. They diversified into various groups. (Chlorophyceae, Rhodophyceae etc.,). Among animals the aquatic arthropods
and echinoderms came to prominence. The fossils of such organism were obtained from several places.
2. Ordovician period :- (440 to 350 million years ago)
This period was marked by formation of coral rocks and molluscs and echinoderms. Among plants the semi terrestrial bryophytes were getting established. Interestingly this period saw the origin of first vertebrates. These were the now extinct agnatha. (Jawless, armoured fishes). The origin of early vertebrates was the major event that happened in the evolution of animals.Among arthopods, the trilobites were more prominent during this period.
3. Silurian period :- (350 to 315 million years ago)The oldest land plant originated in this period. These plants possesedconducting tissues. They colonised the land. Among invertebrates except forinsects all others flourised. The corals diversified. Several coral islands wereformed. Jawed fishes originated. The fishes developed scales and paried fins, for the first time jaws originated in fishes. Origin of paired fins and jaws is
considered as major events in chordate evolution.
4. Devonian Period :- (315 to 275 million years ago It is a significant period in the paleozoic era. During this period land living plants were more successful. The forests were filled with varieties of ferns and cycas. (non-flowering plants). Among aquatic animals fishes became dominant. They diversified by adapting themselves to live in various aquatic ecosystems. The forefathers of almost all modern fishes lived during
this period. Due to these reasons this period is called as the Age of fishes.
5. Mississippian Period :- (275 to 255 million years ago) Several changes happened to the land structure. There were massive upraising of land in several places. This resulted in the formation of several mountain ranges. Huge water bodies were broken into smaller lakes. These major changes on earth’s surface were known as revolutions(eg. Caledonian revolution). Such changes were the cause for the origin of lungs in fishes. Lungs evolved for the purpose of living temporaily on land. It helped such fishes to find new water bodies. Such practises encouraged the origin of the amphibians. The origin of land living amphibians were further increased by the proliferation of several land living insects.
6. Pennsylvanian :- (255 to 235 million years ago)
The land living forms became more successful during this period. There were huge forests of ferns and cycas. Due to geotectonic changes several forests got burried under the soil. Today’s coal and petroleum are obtained from such resources only. Hence the Pennsylvanian and the earlier Mississippian were collectively krown as Carboniferous (carbon bearing) period.
7. Permian Period :- (235 to 210 million years ago) It was the last period in the Paleozoic era. This period was marked by extinctions of several older groups of animals and plants. Nearly 60% of the organism that survived at that time became extinct. Some of the amphibians dramatically laid land eggs (cleidoic eggs). Specifically the group of organisms that laid such eggs are identified as Seymouria. These areconsidered as inter-connecting links between amphibians and reptiles.

Lecture notes on evolution-Geological time scale

The oldest known rocks are about 3.8 billion (3800 million) years old.It corresponds to 38, 000, 000 centuries. According to Geologists and Geophysicists our planet earth is 4.7 billion (4,700 million) years old.
In this ancient time scale evidenes showed that the first life originated 2.5 billion (2,500 million) years ago. Hence from the formative stage for nearly 2,200 billion years there was no life on earth. Such a period in earth’s history is known as the Azoic era (2,200 to 5,000 billion years ago). Evidences show that during this era the earth was a hot sphere.Gradually the upper surface of the earth cooled down. It resulted in solidification and formation of rocks and rocky terrain. Further water molecules were formed resulting in accumulation of water and water reservoirs as wate masses and land surface were established. These transformations provided a suitable condition for the origin of the first life.
                               Once the life originated and established, evolutionary changes tookplace. Changes happened in the structure, organisation and living methods of,organisms, depending on natural surroundings and changes in natural surroundings.Thus fauna and flora started flourishing on earth. The water masses
were fully exploited. Later land surfaces were invaded by plants and animals.The Geological time succeeding Azoic Era, was dramatic and rich is life. This period is divided into three eras. These were significant periods in earth’s history. Of these, the oldest era was the Paleozoic era. It ranged from 600 to 210 million years ago. Thus its duration was nearly 390 million years. This era saw the origin and adaptive radiation of sponges, starfishes snails, insects, crabs, and terrestialised amphibians and reptiles.
The Paleozoic era was followed by middle period named as Mesozoic era. This era ranged from 65 to 210 million years ago. Its duration was145 million years. During this era, among animals the reptiles came to prominence. Hence this era is known as the golden age of reptiles. Further this era saw the origin and development of birds and reptiles. The period ranging from 65 million years till date is named as the
Coenozoic era. This era is characterised by rapid evolutionary changes in mammals. This era is known as the Age of mammals. Geological time scale A geological calendar has been formulated by assessing the age of
rocks and rock sediments. Based on age, and events, the ancient period from earth’s history is formulated into eras-periods-epochs. Each division in the geological calender is clearly identified and demarcated. Incidents pertaining to earth surface, plant and animals life are neatly recorded. The influence of
geological and climatic changes on the life and the evolution of the living organism had been well analysed.

The basic principles of biological nomenclature

1. Providing stability in the naming and classification of organisms is emphasized. Any taxon must have only one correct name.
2. If two or more names are already in use the correct name will be the one that was published earlier. This system is referred to as the law of priority.
3. If two or more workers at one particular time describe the same organism using different names, it results in synonyms. However only one name will be held as a valid name. The validity is provided to the senior synonym.(law of priority)
4. When names referring to two separate taxa of the same nomenclatural level are spelt the same, the two names are called homonyms. This situation arises when two separate authors used the same name to refer to two different taxa. This condition is called homonymy. In this situation the junior name is invalid and a new replacement has to be proposed.
5. A material on which an original description is based, gets a special status. It will form the basis for any future identity of a taxon. This idea is called the type concept. Thus the concept of a genus and species are fixed by their type genus or type species.
6. Names that were used prior to those included by Linnaeus in the “Systema Naturae”, tenth edition, 1758 are not recognised.
7. Scientific names must be either Latin or latinized. The name should be mentioned in italics.
8. The genus name should be a single word beginning with a capital letter.
9. The species name sholud be a single or compound word beginning with a smalll letter.

Early Development and Axis Formation in Amphibians

               Amphibian cleavage is holoblastic, but unequal due to the presence of yolk in the vegetal hemisphere. Amphibian gastrulation begins with the invagination of the bottle cells, followed by the
coordinated involution of the mesoderm and the epiboly of the ectoderm. Vegetal rotation plays a
significant role in directing the involution. The driving forces for ectodermal epiboly and the convergent extension of the mesoderm arethe intercalation events in which several tissue layers merge. Fibronectin plays a critical role in enabling the mesodermal cells to migrate into the embryo.The dorsal lip of the blastopore forms the organizer tissue of the amphibian gastrula. This tissue dorsalizes the ectoderm, transforming it into neural tissue, and it transforms ventralmesoderm into lateral mesoderm.The organizer consists of pharyngeal endoderm, head mesoderm, notochord, and dorsal blastopore lip. The organizer functions by secreting proteins (Noggin, chordin, and follistatin) that block the BMP signal that would otherwise ventralize the mesoderm and activate theepidermal genes in the ectoderm. In the head region, an addition set of proteins (Cerberus, Frzb, Dickkopf) block the Wnt signal from the ventral and lateral mesoderm.The organizer is itself induced by the Nieuwkoop center, located in the dorsalmost vegetal cells. This center is formed by cortical rotation during fertilization, which translocates the Dishevelled protein to the dorsal side of the egg.The Dishevelled protein stabilizes β-catenin in the dorsal cells of the embryo. Thus, the Nieuwkoop center is formed by the accumulation of β-catenin, which can complex with Tcf3 to form a transcription factor complex that can activate the transcription of the siamois gene.The siamois product and a TGF-β signal (perhaps from Vg1) can activate the goosecoid gene in the organizer. The goosecoid gene can activate other genes that cause the organizer to function.Other posteriorizing signals (Wnt3a, retinoic acid, eFGF) can influence the anterior-posteriorspecification of the neural tube.The left-right axis appears to be initiated at fertilization through the Vg1 protein. In a still unknownfashion, this protein activates a Nodal protein solely on the left side of the body. As in other vertebrates, theNodal protein activates expression of Pitx2, which is critical in distinguishing left-sidedness from rightsidednessin the heart and gut tubes.

Development and Axis Specification in drosophila

1. Drosophila cleavage is superficial. The nuclei divide 13 times before forming cells. Before cell
formation, the nuclei reside in a syncytial blastoderm. Each nucleus is surrounded by an actinfilled
cytoplasm.
2. When the cells form, the Drosophila embryo undergoes a midblastula transition, wherein the
cleavages become asynchronous and new mRNA is made. The amount of chromatin determines
the timing of this transition.
3. Gastrulation begins with the invagination of the most ventral region, the presumptive
mesoderm. This causes the formation of a ventral furrow. The germ band expands such that the
future posterior segments curl just behind the presumptive head.
4. Maternal effect genes are responsible for the initiation of anterior-posterior polarity. Bicoid
mRNA is sequestered by its 3´ UTR in the future anterior by the cytoskeleton; nanos mRNA is
sequestered by its 3´ UTR in the future posterior pole. Hunchback and caudal messages are seen
throughout the embryo.
5. At fertilization, bicoid and nanos messages are translated. A gradient of Bicoid protein
activates more hunchback transcription in the anterior. Moreover, Bicoid inhibits the translation
of caudal mRNA. A gradient of Nanos in the posterior inhibits the translation of hunchback
mRNA. Caudal protein is made in the posterior.
6. Bicoid and Hunchback proteins activate the genes responsible for the anterior portion of the
fly; Caudal activates genes responsible for posterior development.
7. The unsegmented anterior and posterior are regulated by the activation of the Torso protein at the
anterior and posterior poles of the egg.
8. The gap genes respond to concentrations of the maternal effect gene proteins. Their protein products
interact with each other such that each gap gene protein defines specific regions of the embryo.
9. The gap gene proteins activate and repress the pair-rule genes. The pair-rule genes have modular
promoters such that they become activated in the seven "stripes." Their boundaries are defined by the gap
genes. These genes form seven bands of transcription along the anterior-posterior axis, each one
comprising two parasegments.
10. The pair-rule gene products activate engrailed and wingless expression in adjacent cells. The engrailedexpressing
cells form the anterior boundary of each parasegment. These cells form a signaling center that
organizes the cuticle formation and segmental structure of the embryo.
11. The homeotic selector genes are found in two complexes on chromosome 3 of Drosophila. Together
these are called Hom-C, the homeotic gene complex. The genes are arranged in the same order as their
transcriptional expression. These genes specify each segment, and mutations in these genes are capable of
transforming one segment into another.
12. The expression of each homeotic selector gene is regulated by the gap and pair-rule genes. Their
expression is refined and maintained by interactions whereby the protein products interact with genes,
preventing the transcription of neighboring Hom-C genes.
13. In Ultrabithorax mutations, the third thoracic segment becomes specifed as the second thoracic
segment. This converts the halteres into wings. When Antennapedia is expressed in the head as well as in
the thorax, it represses antenna formation, allowing legs to form where the antenna should be.
14. The targets of the Hom-C proteins are the realisator genes. These include Distal-less and Wingless
genes (in the thoracic segments).
15. Dorsal-ventral polarity is regulated by the entry of the Dorsal protein into the nucleus. Dorsal-ventral
polarity is initiated by the nucleus being positioned in the dorsal-anterior of the oocyte and transcribing the
gurken message. This message is transported to the region above the nucleus and adjacent to the follicle
cells.
16. The gurken mRNA is translated into the Gurken protein, which is secreted from the oocyte and binds to
its receptor, Torpedo, on the follicle cells. This dorsalizes the follicle cells, preventing them from
synthesizing Pipe.
17. The Pipe protein in the ventral follicle cells modifies an as yet unknown factor that modifies the Nudel
protein. This allows the Nudel protein to activate a cascade of proteolysis in the space between the ventral
follicle cells and the ventral cells of the embryo.
18. As a result of the cascade, the Spätzle protein is activated and binds to the Toll protein on the ventral
embryonic cells.
19. The activated Toll protein activates Pelle and Tube to phosphorylate the Cactus protein, which has been
bound to the Dorsal protein. Phosphorylated Cactus protein is degraded, allowing Dorsal protein to enter
the nucleus.
20. Once in the nucleus, Dorsal protein activates the genes responsible for the ventral cell fates and
represses those genes whose proteins would specify dorsal cell fates. Since a gradient of Dorsal protein
enters the various nuclei, those at the most ventral surface become mesoderm, those more lateral become
neurogenic ectoderm.
21. Organs form at the intersection of dorsal-ventral and anterior-posterior regions of gene expression.
Ref:Developmental biology Gilbert

What are various events in Fertilization?

1. Fertilization accomplishes two separate activities: sex (the combining of genes derived from
two parents) and reproduction (the creation of a new organism).
2. The events of conception usually include: (1) contact and recognition between sperm and egg;
(2) regulation of sperm entry into the egg; (3) fusion of genetic material from the two gametes;
and (4) activation of egg metabolism to start development.
3. The sperm head consists of a haploid nucleus and an acrosome. The acrosome is derived from
the Golgi apparatus and contains enzymes needed to digest extracellular coats surrounding the
egg. The neck of the sperm contains the mitochondria and the centriole that generates the
microtubules of the flagellum. Energy for flagellar motion comes from mitochondrial ATP and a
dynein ATPase in the flagellum.
4. The egg contains a haploid nucleus, and an enlarged cytoplasm storing ribosomes, mRNAs,
and nutritive proteins. Other mRNAs and proteins, used as morphogenetic factors, are also stored
in the egg. Cortical granules lie beneath the egg's plasma membrane. Many eggs also contain
protective agents needed for survival in their particular environment.
5. Surrounding the egg plasma membrane is an extracellular layer often used in sperm
recognition. In most animals, this extracellular layer is the vitelline envelope. In mammals, it is
the much thicker zona pellucida.
6. In many species, eggs secrete diffusible molecules that attract and activate the sperm.
7. In sea urchins, the acrosome reaction is initiated by compounds in the egg jelly. The acrosomal
vesicle undergoes exocytosis to release its enzymes. Globular actin polymerizes to extend the
acrosomal process. Bindin on the acrosomal process is recognized by a protein complex on the
sea urchin egg surface.
8. In mammals, sperm must be capacitated in the female reproductive tract before they are
capable of fertilizing the egg.
9. Mammalian sperm bind to the zona pellucida before undergoing the acrosome reaction. In the
mouse, this binding is mediated by ZP3 (zona protein 3) and one or many sperm proteins that
recognize it. The mammalian acrosome reaction is initiated on the zona pellucida, and the
acrosomal enzymes are concentrated there.
10. Fusion between sperm and egg is mediated by protein molecules whose hydrophobic groups
can merge the sperm and egg plasma membranes. In sea urchins, bindin may mediate gamete
fusion. In mammals, fertilin proteins in the sperm bind to integrins in the egg and allow the
membranes to fuse.
11. Polyspermy results when two sperm fertilize the egg. It is usually lethal, since it results in
three sets of chromosomes divided among four cells.
12. There are often two blocks to polyspermy. The fast block is electrical and is mediated by
sodium ions: the egg membrane resting potential rises, and sperm can no longer fuse with the egg.
The slow block is physical and is mediated by calcium ions. A wave of calcium ions propagates
from the point of sperm entry, causing the cortical granules to fuse with the egg cell membrane.
The released contents of the granules cause the vitelline membrane to rise and to harden into the
fertilization envelope.
13. In mammals, blocks to polyspermy include the modification of the zona proteins by the
contents of the cortical granules. Sperm can no longer bind to the zona.
14. Inositol 1,4,5-triphosphate (IP3) is believed to be responsible for releasing calcium ions from
storage in the endoplasmic reticulum. DAG (diacylglycerol) is thought to initiate the rise in egg
pH. The free calcium ions, supported by the alkalization of the egg, activate egg metabolism,
protein synthesis, and DNA synthesis.
15. The male pronucleus and the female pronucleus migrate toward each other, replicating DNA
as they move.
16. In sea urchins, the two pronuclei merge and a diploid zygote nucleus is formed. In mammals,
the pronuclei disintegrate as they approach each other, and their chromosomes gather around a
common metaphase plate.
17. Some genes are transmitted differently depending on whether they are from the egg or the
sperm. Methylation differences determine if these genes are to be expressed in the early embryo.
18. Microtubular changes cause cytoplasmic movements. These rearrangements of cytoplasm can
be critical in specifying which portions of the egg are going to develop into which organs.

Defnition o Fertilization

Fertilization is the process whereby two sex cells (gametes) fuse together to create a new
individual with genetic potentials derived from both parents.
Fertilization accomplishes two separate ends: sex or the combining of genes derived from the two parents and reproduction  or the creation of new organisms.
 Thus, the first function of fertilization is to transmit genes fromparent to offspring, and the second is to initiate in the egg cytoplasm those reactions that permitdevelopment to proceed.
Conception generally
consists of four major events:
1. Contact and recognition between sperm and egg. In most cases, this ensures that the sperm and
egg are of the same species.
2. Regulation of sperm entry into the egg. Only one sperm can ultimately fertilize the egg. This is
usually accomplished by allowing only one sperm to enter the egg and inhibiting any others from
entering.
3. Fusion of the genetic material of sperm and egg.
4. Activation of egg metabolism to start development.

GASTRULATION IN FROG DIAGRAM-

REF-Principles of development in biology-Gilbert

Recessive epistasis

• Epistasis due to recessive genes is called recessive epistasis. In mice albinism (white coat) is
• produced by a recessive gene aa. 
• There is a different gene B which in the dominant state (BB and Bb) produces grey coat colour called agouti, and when recessive (bb) leads to black coat colour. 
• The recessive gene for albinism (aa) is found to be epistatic to the gene for agouti(BB and Bb), and also to its recessive, homozygous allele (bb) for black.
•  The presence of thedominant allele (AA) of the epistatic gene allows expression of gene B so that agouti (BB andBb) and black (bb) coat colours can be produced
• 
• The 9 : 3 : 4 ratio obtained is a modification of the classical 9 : 3 : 3 : 1 in which the last
  two classes (3 : 1) are phenotypically identical and are therefore added up together.
•  In human
  beings also the recessive gene for albinism shows epistasis in a similar manner.
•  Epistaticeffect is usually only in one direction, from one particular gene pair to another.

LECTURE NOTES ON EPISTASIS

Due to the phenomenon of dominance a recessive allele remains obscure in the hybrid. But
when two different genes which are not alleles, both affect the same character in such a way
that the expression of one masks, inhibits or suppresses the expression of the other gene, it is
called epistasis. The gene that suppresses is said to be epistatic, and the gene which remains
obscure is hypostatic.
   

DOMINANT EPISTASIS

In poultry white birds belong to two different varieties namely white leghorns or white
wyandottes.
 Experiments reveal that the gene for white plumage of white leghorns is dominant
over the gene for coloured plumage of coloured varieties.
 But the gene for white plumage of
white wyandottes is recessive to the gene for coloured plumage of coloured varieties.
 Therefore
the gene which produces white plumage in white leghorns is different from the gene for white
plumage in white wyandottes.
A cross between a white leghorn and a white wyandotte gives an F1 of white birds with
small dark flecks.
When such birds are inbred, the F2 progeny segregates in the ratio of 13
white to 3 coloured birds.
The experiment is explained below by postulating two genes C and I
for the white leghorns
Out of sixteen genotypes, that is iiCC, iiCc, iiCc produce coloured birds.
The white leghorns
obviously contain a gene I, which in the dominant state inhibits or suppresses the expression
of the dominant colour gene C, resulting in white plumage.
The recessive alleles of the inhibitor
gene (ii) produce coloured birds due to expression of gene C.
 In other words gene I is epistatic
to gene C.
 This is a case of dominant epistasis because even one dominant allele of gene I is
able to express itself.

BRIEF NOTE ON COMPLEMENTARY GENES

•     Bateson and Punnett crossed two different white flowered varieties of sweet pea and obtained
  an F1 progeny of red flowered plants. 
• On self pollination the F1 plants gave an F2 progeny of 9red and 7 white flowered plants.
•  Single crosses between the red flowered variety and the twodifferent white flowered varieties showed that the gene for red colour was dominant over the gene for each of the two white varieties.
  The cross between the two white varieties can be explained by assuming two genes for
  red colour which must be present together, i.e., must act in a complementary way to each
  other.
•  Thus each gene independently contributes something different but essential for synthesis
  of red pigment.
•  If one of the two genes for red colour is absent, the result is a white flower. 
• The inheritance of the colour of aleurone layer in corn also demonstrates interaction of
  complementary genes. 
• The outermost layers of endosperm in the maturing corn kernels become
  modified into a specialised aleurone tissue, so named because the cells have rich deposits of
  aleurone grains.
•  In corn the aleurone layer is coloured due to anthocyanin pigments in the
  cells, and is controlled by complementary effect of two genes
• 
  

INCOMPLETE DOMINANCE AND CODOMINANCE

A monohybrid cross between a red-flowered snapdragon (Antirrhinum majus) and a white flowered variety does not produce red or white flowered plants in F1 as expected from mendelism. Instead the flowers are pink, i.e. intermediate between the two parents. This is because neither red flower colour nor white is dominant, but each allele has its influence in color development and the hybrid appears pink. If the F1 pink flowers are self-pollinated, the F2 progeny shows red, pink and white flowered plants in the proportion 1 : 2 : 1. It may be recalled that this is the same genotypic ratio that Mendel obtained in garden peas. The difference is that in the present case the heterozygous progeny is distinct in appearance from the homozygotes. The name intermediate inheritance is also given to crosses where F1 hybrids show incomplete or partial dominance with no phenotypic resemblance to either parent. This type of inheritance has been found in crosses involving many other plants.

In 1900 Bateson and his colleagues studied inheritance of comb shape in fowls. There are four types of combs in fowls: rose, pea, walnut and single. Bateson first performed a cross between rose and single. The F1 hens all had a rose comb, and on inbreeding gave rise to an F2 progeny of rose and single in the ratio 3 : 1. The cross indicates that rose and single comb are controlled by a single gene and that rose is dominant over single. In the second cross when chickens with pea comb were mated with single comb, the F1 progeny had pea comb, and F2 had pea and single in the proportion 3 : 1. Obviously, the gene for pea comb is dominant over single.  Bateson then crossed rose and pea. Surprisingly, the F1 birds had an altogether different comb of the walnut type! An F2 progeny raised by inbreeding the walnut type consisted of four types ofchickens—walnut, rose, pea and single  in the ratio 9 : 3 : 3 : 1. As this ratio is typical for dihybrid inheritance it became clear that rose and pea combs were controlled by two pairs
of genes.

NEET MCQ-ANIMAL TISSUES

1.         Non-keratinised stratified squamous epithelium is found in

a) Epidermis of skin of land vertebrate    b) oral cavity and pharynx

c) Vagina and cervix                                   d) Both (b) and (c) 

e) None of the above

2.         Endothelium lining of a blood vessel is formed of

            a) ciliated epithelium                                       b) columnar epithelium           

c) cuboidal epithelium                                     d) simple squamous epithelium          

e) transitional epithelium

3.         Which blood corpuscle is largest in diameter?

            a) Erythrocyte              b) monocyte                c) neutophil                 d) lymphocyte             e) platelet

4.        Name the main constituent of food in the absence of which one cannot live 

a) Carbohydrates      b) Mineral salts        c)  Proteins                d) Vitamins               e) Fat

5.        Stomach is protected from HCI and gastric juice because

a)  The two are dilute          

b) Wall has neutralizing agents 

c) Epithelial lining is resistant to them 

d) Mucous lining is covered by mucus 

e) HCL is weak  

6.        The human intestine is long because

a) Bacteria in food can be killed gradually

b) It provides more space for food storage

c) It increases surface area for absorption of food

d) retain food for a long time  

e) None of these  

7.         Secretion of gastric juce is stopped

            a) gastrin                                  b) pancryozymin                                 c) cholecytokinin        

d) enterogastrone                     e) villikinin

8.         Sphincter of oddi occurs between

a) pylorus and duodenum                                b) oesophagus and stomach            

c)large intestine and small intest                      d) ampulla of vater and duodenum     

e) none of these

9.         Adam’s apple corresponds to

a) epiglottis                  b) trachea                     c) larynx                      d) thyroid                     e) thymus

10.     In lungs air is separated from venous blood by

            a)   squamous epithelium and tunica exerna of blood vessel

b)      squamous epithelium and endothelium of blood vessel

c)      transitional epithelium and tunica media of blood vessel

d)      columnar epithelium and 3layered wall of blood vessel

e)none of these

11.     During Rigor mortis there is

a) permanent irreversible contraction              

b) establishment of permanent link between actin and myosin           

c) loss of ATP                         d) Stiffness of muscles             e) all the above

12.     Castle’s intrinsic factor is necessary for the intestinal absorption of

            a) Vitamin K               b) Vitamin D               c) Vitamin C   

d) Vitamin B12           e) Vitamin B1

13.     In expiration diaphragm becomes

            a) arched          b) relaxed        c) flattened       d) remain in the same position     e) None of the above

14.     Crypts of Lieberkuhn are

a) Intestinal glands                   b) In appendix                         c) Gastric glands         

d) salivary glands                    e) lacteals

15.     The CO₂ transport, HCO₃^–  diffuses from RBC to plasma and inturn to keep the ionic balance an equal number of Cl ^– ions pass into the RBC. This process in known as

a) Hamburger phenomenon     b) Bicarbonate Shift                c) Transport rate   

d) Carbonation                        e) Carbo-chlorosis

16.     In heavy smokers the alveoli of the lungs are enlarged and damaged which reduces the surface area for the exchange of  respiratory gases. This condition is called

a) Asthma        b) Silicosis       c) Emphysema             d) Anosmnia       

e) Bronchitis

17.     Coagulation of blood can be prevented by

            a) heparin        b) calcium removal      c) oxalate solution       d) hirudin

            e) all

18.     Hepatic portal system starts from

            a) digestive system to liver      b) kidney to liver         c) liver to heart

            d) liver to kidney

19.     The chief difference between erythrocytes of man and frog is

            a) Human erythrocytes have more nuclei       

b) Human erythrocytes have two nuclei

c) Human erythrocytes have no nuclei

d) Human erythrocytes have more haemoglobin

e) Human erythrocytes have three nuclei

20.     The pH of blood is maintained in balance by ration of

a) CO₂ and H₂O                                  b) Pyruvic acid and H₂CO₃    

c) Lactic acid and pyruvic acid            d) NaHCO₃ and H₂CO₃         

e) CO₂ and H₂CO₃

21.     Human blood is isotonic to

            a) 6% starch solution   b) 0.9% sodium chloride        

c) 1.0% potassium sulphate                 d) sea water                

e) 10% sodium chloride

22.     Right auricle of human heart receives

a) pulmonary veins and vena cavae     b) Coronary vein and pulmonary veins

c) coronary vein and vena cavae        

d) superior vena cavae, inferior vena cavae and coronary vein                      

e) coronary artery and vena cavae

23.     Squeezing out of leucoctyes from the endothelium of capillaries to the tissue is called

            a) haemolysis               b) haemopioiesis          c) phagocytosis           

d) diapediesis               e) filtration

24.     Payers patches are

a) lymph nodules in intestine   b) mucus cells of gastric gland           

c) gastric pits of stomach         d) milk glands              e) none of these

25.     Areolar connective tissue joins

            a) bones with bones     b) fat body with muscles        

c) integuments with muscle                 d) bone with muscles   e) bone to CNS

e) eye to orbit

26.     Lining of nasal chamber is sensitive to smell and also known as

            a) Schneiderian membrane      b) Circulating membrane        

c) Storage membrane               d) Reisnners membrane          

e) Basilar membrane

27.     Surgical removal of gall bladder in man would lead to

            a) impairments of digestion     b) jaundice      c) increased acidity     

            d) marasmus                e) kwashiorkor

28.     Erythroblastosis foetalis can occur in the case of

            a) Man Rh+ and Woman Rh+             b) Man Rh- and Woman Rh-

            c) Man Rh+ and Woman Rh-              d) All the above           e) None

29.     In mammals the opening of post caval in the right auricle is guarded by

            a) mitral vlave              b) eustachius valve                  c) sino-auricular valve             d) tricuspid valve         e) thebesius valve

30.     The wall of the left ventricle are relatively thick because

            a) it contains oxygenated blood                       b) it pumps blood to the entire body               

c) it is bigger than the right ventricle               d) aorta arises from it

            e) all the above