Past Entrance Papers

Hint

The correct answer is option (3), because the flippers of the Penguins and Dolphins perform similar function but they are not anatomically similar structures. This is example of analogous structures.
– Option (1) is incorrect as adaptive radiation is the process of evolution of different species in a given geographical area starting from a point and literally radiating to the other areas of geography.
– Option (2) is incorrect as natural selection is a key mechanism of evolution.
– Option (4) is incorrect as divergent evolution results in the formation of homologous structures.

Hint

Answer (1)
Sol. The ribosome consists of structural RNAs and about 80 different proteins.

Hint

Answer (2)
Sol. Option (2) is the correct answer because numbat, spotted cuscus and flying phalanger are Australian marsupials exhibiting adaptive radiation.
Option (3) is incorrect because mole and flying squirrel are placental mammals.
Option (4) is incorrect because lemur and wolf are placental mammals.
Option (1) is incorrect because bobcat is a placental mammal.

Hint

Answer (4)
Sol. Option (4) is the correct answer because flippers of penguins and dolphins are analogous organs as they help in swimming but do not have the same structure.
Option (3), (1) and (2) are true statements and hence cannot be the correct answer.
Homologous organs have the same structure but have different functions according to the needs of the organisms. Hence, homology indicates common ancestry.
Analogous structures have developed for the same function but do not show a similarity in structure.
Hence, they are a result of convergent evolution.
Sweet potato is a root modification for food storage whereas potato is an underground stem modification for storage. Hence they are analogous.

Hint

(a): The random changes in gene frequencies in a population occurring by chance alone rather than by natural selection are called genetic drift or Sewall wright effect. The effects of genetic drift are most marked in very small isolated population, although it occurs in all populations.

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(b) : In a stable population, for a gene with two alleles, ‘A’ (dominant) and ‘a’ (recessive), if the frequency of ‘ \(\mathrm{A}\) ‘ is \(\mathrm{p}\) and the frequency of ‘ \(\mathrm{a}\) ‘ is \(\mathrm{q}\), then the frequencies of the three possible genotypes (AA, Aa and aa) can be expressed by the HardyWeinberg equation:
\(
\begin{aligned}
& p^2+2 p q+q^2=1 \\
& \text { where } p^2=\text { Frequency of AA (homozygous } \\
& \text { dominant) individuals } \\
& q^2=\text { Frequency of aa (homozygous } \\
& \text { recessive) individuals } \\
& 2 p q=\text { Frequency of Aa (heterozygous) } \\
& \text { individuals } \\
&
\end{aligned}
\)

Hint

(b)

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(c)

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(b) : Homologous organs have same fundamental structure but different function. The wing of a bird and flipper of a whale are structurally forelimbs, which consist of humerus, radio-ulna, carpals, metacarpals and digits but they perform different function. The wings of birds help them to fly while flipper helps the whale to swim.

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(d) : The organs which have similar functions but are different in their structural details and origin are called analogous organs. The analogous structures are the result of convergent evolution.

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(a)

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(d) : Analogous organs are the organs which have similar function but are different in their structural details and origin. The analogous structures are the result of convergent evolution. The wings of an insect are analogous to wings of a bird because the basic structure of the wings of the insects is different from the wings of bird. However, their function is similar.

Hint

(d) : Natural selection is the most widely accepted theory concerning the principal causal mechanism of evolutionary change profounded by Charles Darwin and Alfred Russel Wallace. It results from the differential reproduction (some members of a population produce abundant offspring, some only a few and still others none), one phenotype as compared with other phenotypes in the same population. Thisdetermines the relative share of different genotypes which individuals possess and propagate in a population. Industrial melanism supports evolution by natural selection. It is an adaptation where the moths living in the industrial areas developed melanin pigments to match their bodies to the tree trunks.

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(c) : Hardy-Weinberg law states that allele frequencies in a population are stable and remain constant from generation to generation when there is random and non-selective mating. In case of lack of random mating, genetic equilibrium may be disturbed.

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(b): The genetic variations exist due to reshuffling of genes caused by recombinations or by mutations. The recombinations are produced by the routine reshuffling of genes during independent assortment of chromosomes, reciprocal crossing of genes during crossing over and random fertilization of gametes.

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(b) : The brain capacity gradually increased from early human ancestors to modern man. Homo habilis had 650 – 800cc brain capacity which increased around \(900 \mathrm{cc}\) in Homo erectus. The Neanderthal man (Homo neanderthalensis) had \(1400 \mathrm{cc}\) brain capacity which evolved to around \(1450 \mathrm{cc}\) in Homo sapiens.

Hint

(c): According to Hardy Weinberg principle \(\mathrm{p}^2+2 \mathrm{pq}+\mathrm{q}^2=1 ;(\mathrm{p}+\mathrm{q})^2=1\)
(AA) \(\mathrm{p}^2=360\) out of 1000 individual
or \(\mathrm{p}^2=0.36\)
Therefore, \(\mathrm{p}=0.6\)

Hint

(c): The organs which have the same fundamental structure but are different in functions are called homologous organs. These organs follow the same basic plan of organisation during their development. But in the adult condition, these organs are modified to perform different functions as an adaptation to different environments. The fore-limbs of cat, lizard, whale and bat have the same basic structural plan. In each case the fore-limb consists of humerus, radio-ulna, carpals, metacarpals and digits. The skeletal parts of the fore-limbs of all these vertebrates are similar in structure and arrangement. But the fore-limbs of these animals have different shapes and functions. In lizard they are used for walking, in cat for running, in whale for swimming and in bat for flying.

Hint

\((\mathbf{a}, \mathbf{b})\) : The organs which have similar functions but are different in their structural details and originare called analogous organs. The wings of bat are analogous to wings of pigeon. It is due to the fact that the basic structure of the wings of the mammal is different from the wings of bird. However, their function is similar. Similarly, gills of prawn and lungs of man, both are respiratory organs yet they have very different basic structure.

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(c) : Intraspecific competition leads to evolution. Variations arise naturally in a growing population due to crossing over etc. Organisms with variations better suited to their environment are favoured by natural selection, while less fitted ones are eliminated. Gradually this continued process of natural selection leads to evolution. Interspecfic struggle also plays a role in evolution but intraspecific struggle is more intense and prominent one.

Hint

(b): Hardy-Weinberg law states that allele frequencies in a population are stable and remain constant from generation to generation when there is random and non-selective mating. In case of lack of random mating, genetic equilibrium may be disturbed.

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(d) : Genetic drift (Sewall Wright effect) is the random change in the frequency of alleles in a population over successive generations in the gametes. Each new generation differs from its parental generation with regard to allele frequencies simply because of random variation in the distribution of gametes. This process is more rapid in smaller populations, or when the alleles concerned confer no apparent benefit compared to their counterparts.

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(d) : Convergent evolution is the development of superficially similar structures in unrelated organisms, usually because the organisms live in the same kind of environment. Examples are the wings of insects and birds and the streamlined bodies of whales and fish. One can say that it is the similar habitat that has resulted in selection of similar adaptive features in different groups of organisms but toward the same function. An example of convergent evolution is the similar nature of the flight/wings of insects, birds, pteridosaurs, and bats. All four serve the same function and are similar instructure, but each evolved independently. Some species of the lens of eyes also evolved independently in various animals.

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(a)

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(c) : Genetic drift (Sewall Wright effect) is the random change in the frequency of alleles in a population over successive generations in the gametes. Each new generation differs from its parental generation with regard to allele frequencies simply because of random variation in the distribution of gametes. This process is more rapid in smaller populations, or when the alleles concerned confer no apparent benefit compared to their counterparts. 

Hint

(b) : The genetic variations exist due to reshuffling of genes caused by recombinations or by mutations. The recombinations are produced by the routine reshuffling of genes during independent assortment of chromosomes, reciprocal crossing ofgenes during crossing over and random fertilization of gametes. Mutation is the sudden inheritable discontinuous variation which appears in an organism due to permanent changes in its genotype. Mutation can occur at any stage during the development. Mutations are heritable changes, that is, if they appear in somatic cells they are inherited to daughter cells by mitosis but if they appear in gamete cells they are inherited to the offsprings. The former are known as somatic mutations and latter as germ mutations. They bring about a change in the genetic message and cause variation.

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(b) : Dinosaurs dominated in Jurassic period of mesozoic era and were extinct by cretaceous period.

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(a) : Darwin’s finches show adaptive radiation. This radiation occurred in response to various food resources available. These finches feed on insects, tree buds, seeds, cactus etc. Carrion are dead bodies and no finches feed on them.

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(a) : Adaptive radiation (divergent evolution) is the evolution from one species of animals or plants of a number of different forms. As the original population increases in size it spreads out from its centre of origin to exploit new habitats and food sources. In time, this results in a number of populations each adapted to its particular habitat, eventually these populations will differ from each other sufficiently to become new species.

Hint

 (a) : Development of similar adaptive functional structures in unrelated groups of organisms is called convergent evolution. It shows analogy. Examples are wings of butterfly and birds, eye of the octopus and the mammals, flippers of penguins \& dolphins, etc. On the other hand, divergent evolution involves development of different functional structures along different directions due to adaptations to different needs from a common ancestral form. For example, forelimbs of vertebrates (whales, bat, cheetah, human). Though these perform different functions, they have similar anatomical structures.

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(c) : Binocular vision, smaller jaw and upright posture are the main adaptations that led to evolution of man from its ancestors. But, during human evolution major and most significant changes occurred in the cranial capacity of man. In living modern man it is about \(1450 \mathrm{cc}\) compared to \(500 \mathrm{cc}\) in Australopithecus. Increased cranial capacity accommodates larger brain and forms the basis of social, cultural and educational evolution of modern man.

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(b)

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(a) : The term mutation was coined by Hugo de Vries (1901) for large spontaneous inheritable changes which occur suddenly in naturally reproducing population. He also proposed mutation theory of evolution in his book “The Mutation Theory” published in 1903 in which he put forth that evolution occurred due to large discontinuous variations. He worked on Oenothera lamarckiana or evening primrose. During his experiments he found 834 mutations in a population of 54343 plants. It was later on found that the mutations observed by Hugo de Vries were actually chromosomal aberrations.

Hint

(c):

Darwin’s finches show adaptive radiation.

This radiation occurred in response to various food resources available. These finches feed on insects, tree buds, seeds, cactus etc. Carrion are dead bodies and no finches feed on them.

Hint

(a) : Binocular vision, smaller jaw and upright posture are the main adaptations that led to evolution of man from its ancestors. But, during human evolution major and most significant changes occurred in the cranial capacity of man. In living modern man it is about \(1450 \mathrm{cc}\) compared to \(500 \mathrm{cc}\) in Australopithecus. Increased cranial capacity accommodates larger brain and forms the basis of social, cultural and educational evolution of modern man.

Hint

(b) : Peripatus belongs to phylum onychophora. It shows characters of annelids as well as arthropods. Owing to its resemblance with two different phyla, Peripatus is often referred to as connecting link between them. This shows an important morphological and anatomical evidence of evolution.

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(d) : During post industrialisation period the tree trunk became dark due to industrial smoke and soots. White winged moths did not survive due to predators and dark winged moths survived because they were less easily seen by them against a dark background. Thus industrial melanism supports evolution by natural selection that favours the establishment of one particular advantageous mutation within a population.

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(d) : The most apparent change during evolutionary history of modern man (Homo sapiens) is the increase in the brain size. The brain capacity gradually increased from early human ancestors. Homo habilis had \(650-800\) c.c. brain capacity which increased to 900 c.c. in Homo erectus. The true men including the living modern man also displayed the gradual increase in cranial size. The neanderthal man had \(1400 \mathrm{cc}\) brain capacity which evolved to around 1450 c.c. \((1300-1600\) c.c.) in living modern man (Homo sapiens sapiens).

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(c) : Theory of continuity of germplasm was put forward by August Weismann. According to this, the characters influencing the germ cells are only inherited. There is a continuity of germ plasm but the somataplasm is not transmitted to the next generation hence it doesn’t carry characters to next generation.

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(c): The condition for origin of life, partial isolation, has been attained within aggregates of artificially formed prebiotic molecules. These aggregates are called protobionts which can separate combinations of molecules from the surroundings. They maintain an internal environment but are unable to reproduce. Two important protobionts are coacervates and microspheres.

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(d) : The organs which have the same fundamental structure but are different in function are called homologous organs. Thorn of Bougainvillea and tendril of Cucurbita both arises in the axillary position, but have different functions.

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(c) : Haeckel (1810) proposed that developing animal embryo passes through stages resembling adult forms of its ancestors. Earnst Haeckel \((1868,1874)\) formulated biogenetic law or racapitulation theory which states that ontogeny (developmental history of an individual) repeats phylogeny (development history of races).

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(c) : Chemical evolution has two meanings and uses. The first refers to the theories of evolution of the chemical elements in the universe through nucleosynthesis. The second use of chemical evolution or chemosynthesis is as a hypothesis to explain how life might possibly have developed or evolved from non-life.

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(c) : Biogeographical evolution is a process in which gene pool of a population gradually changes in response to environmental pressures, natural selection and genetic mutations.

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(c):

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(a):

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(b) : Homologous organ and vestigial organs provide an important evidence in favour of organic evolution (process by which changes in the genetic composition of populations of organisms occur in response to environmental changes). For example, human appendix is a developmental derivative and evolutionary vestige of the end of the much larger herbivorous caecum found in our primate ancestors. They both are structurally homologous and have different functions. In most vertebrates, the caecum is a large, complex gastrointestinal organ, enriched in mucosal lymphatic tissue and specialized for digestion of plants. The caecum varies in size among species, but in general the size of the caecum is proportional to the amount of plant matter in a given organism’s diet. It is largest in obligate herbivores, animals whose diets consist entirely of plant matter. However, even though humans are herbivorous, the small human caecum does not house cellulosedigesting bacteria, and lost an essential function of cellulose digestion. This shows the close evolutionary relationships between homologous and vestigial organs.

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(d) : Stanley Miller in 1953 , who was then a graduate student of Harold Urey at the University of Chicago, circulated four gases – methane, ammonia, hydrogen and water vapour in an air tight apparatus and passed electrical discharges from electrodes. He passed the mixture through a condenser. He circulated the gases continuously in this way for one week and then analysed the chemical composition of the liquid inside the apparatus. He found a large number of simple organic compounds including some amino acid such as alanine, glycine and aspartic acid. Glutamic acid was not found.

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(b) : Jurassic period of mesozoic era is characterised by gymnosperms as dominant plant and the appearance of first toothed bird. Conifers, cycads and ferns were widespread.

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(a): Praying mantis shows the phenomenon of camouflage by blending itself into the background. This enables it to elude predators.

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(d) : Microbes were killed by heating the meat and the sealed vessel formed a closed system wherein the new microbes could not come in contact with the nutrient medium and hence no spoilage of meat.

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(c) :

Hint

(b) \(\square\)

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(c) : According to Darwin’s theory of survival of the fittest (Natural selection), the organisms which are provided with favourable variations would survive, because they are the fittest to face their surroundings, while the unfit are destroyed. Darwin considered that useful variations are transmitted to the offspring and appear more prominently in succeeding generations. After some generations these continuous and gradual variations in the possessor would be so distinct that they form a new species. This is proved by, the pesticide resistant insects that have the ability to survive as they have resistance genes and so they are selected by nature. Other insects lacking these genes will be killed by pesticides.

Hint

(c) : Electron spin resonance (ESR) measures the number of charges occupying deep traps in the crystal bandgap. By measuring the change in absorption of microwave energy within a continuously varying strong magnetic field, this method detects the number of “unpaired spins” of electronic charges trapped at various defects in the mineral lattice.
The principle of ESR dating is that radiation damage occurs in minerals as a result of uranium uptake, and external effects. This damage is usually repaired in living tissue, but in dead tissue it accumulates. If themethod of uptake can be judged, then the approximate age of the tissue can be deduced from the extent of the radiation damage.

Hint

(d) : In a stable population, for a gene with two alleles, \(A\) (dominant) and \(a\) (recessive), if the frequency of \(A\) is \(p\) and the frequency of \(a\) is \(q\), then the frequencies of the three possible genotypes ( \(A A\), \(A a\), and \(a a\) ) can be expressed by the given HardyWeinberg equation :
\(
p^2+2 p q+q^2=1 \text {. }
\)
where \(p^2=\) frequency of \(A A\) (homozygous dominant) individuals, \(2 p q=\) frequency of \(\mathrm{Aa}\) (heterozygous) individuals, and \(q^2=\) frequency of \(a a\) (homozygous recessive) individuals. The equation can be used to calculate allele frequencies if the numbers of homozygous recessive individuals in the population is known. The equation and the equilibrium are named after British mathematician G.H. Hardy and German physician W. Weinberg.
So \(p=0.6\) and \(q=0.4\) (given)
\(\therefore 2 p q\) (frequency of heterozygote)
\(
=2 \times 0.6 \times 0.4=0.48
\)

Hint

(b) : Species may be defined as an uniform interbreeding population or group of individuals which freely interbreed among themselves. Gene flow occurs between populations of a species by gene migration i.e., emigration and immigration.

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(c):

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(d): Apes are the members of the hominoidea superfamily of primates, which includes humans. Under the current classification system there are two families of hominoids:
– The family hylobatidae consists of 4 genera and 13 species of gibbons, including the Lar Gibbon and the Siamang, collectively known as the “lesser apes”
– The family hominidae consisting of orangutans, gorillas, chimpanzees, and humans, collectively known as the “great apes”.

Within the superfamily Hominoidea, gibbons are the outgroup: this means that the rest of the hominoids are more closely related to each other than any of them are to gibbons.
Investigation showed orangutans to be the outgroup, but comparing humans to all three other hominid genera showed that African apes (chimpanzees and gorillas) and humans are more closely related to each other than any of them are to orangutans.
However, DNA comparisons from sex chromosomes and autosomes provide convincing evidence that within the subfamily homininae, gorillas are the outgroup. This suggests that chimpanzees should be in hominini along with humans.

Hint

(a) : Cycas and Ginkgo are often considered as the living fossil because they are one of the few representative of once a large group of plants (which was once a well flourished group) and possess traits of extinct pteridosperms and other gymnosperms.

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(b) : The first scientific explanation of origin of life was put forward by a Russian Scientist, A.I. Oparin in 1923. J.B.S. Haldane (1928), England-born Indian Scientist, also made similar observations regarding the origin of life. According to them primitive atmosphere was reducing atmosphere because hydrogen atoms (most numerous and most reactive) combined with all available oxygen atoms to form water and leaving no free oxygen.

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(a) : Diversification in plant life appeared due to long periods of evolutionary changes. Initially plants were thalloid. There were no differentiation among root, stem and leaves. Vascular tissues were absent.

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(d) : Convergent evolution is the formation of similar traits by unrelated groups of organisms. Dogfish and whale are the interesting examples of convergent evolution in animals as both of them have more or less similar body organization.

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(c) : The gist (in brief) of Darwin – Wallace theory is as follows.
(i) Individuals within species show considerable but continuous variation in the form and physiology.
(ii) This variation arises in a random fashion and is heritable.
(iii) The potential for increase within population of animals and plants is considerable.
(iv) Since resources are limited, so individuals in a population struggle for their own existence.
(v) Only some survive and leave offsprings with the same trait – through this natural selection of the fittest species become represented by individuals which are better adapted.

Hint

(b):

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(c) : Industrial melanism is an adaptation where the moths living in the industrial areas developed melanin pigments to match their body to the sootcovered surroundings. These melanic forms are mainly distributed in and around large industrial cities, where the environment has been altered by the pollution of the atmosphere; and is manifested by the appearance of dark colour of lichen-covered tree trunks, on which the moths rest during the day time. The peppered moth exists in two strains (forms) : light coloured (white) and melanic (black). In the past, bark of trees was covered by whitish lichens, so white moths escaped unnoticed from predatory birds. After industrialization barks got covered by smoke, so the white moths were selectively picked up by birds. But black moths escaped unnoticed so they managed to survive resulting in more population of black moths and less population of white moths

Hint

(b) : In a random mating population in equilibrium, random drift brings about a change in gene frequency in a non-directional manner. Random drift is a non-directional factor. In actual practice, the gene frequencies due to random drift may approach to limits, i.e., 0 and 1 . This would be possible only when new population arises due to a very small sample leading to the fixation of one allele at the cost of other. In this manner the changes in the gene frequency can be brought about without the existence of any directional force i.e. mutation, selection and migration and this change in gene frequency has been called random genetic drift.

Hint

(d) : The theory of natural selection is based on the following factors :
(i) Rapid multiplication and limited food and space which leads to struggle for existence.
(ii) Struggle for existence and variations which leads to natural selection or survival of the fittest.
(iii) Natural selection and inheritance of useful variation over many generation which leads to formation of new species.

Darwin in his “Natural Selection Theory” did not believe in the role of discontinuous variation in natural selection. Darwin always believed in the universal occurrence of variation. In his opinion, variation is continuous in nature. Darwin did not understand the cause of variation and assumed it was one of the innate properties of living things. Now it is known that variation is due to mutation and thus it may be discontinuous.

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(a):

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(b) :

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(d) : Mimicry is specially evolved primarily for concealment and protection. Concealment itself may prove to be defensive and may also help in offence. Mimicry is defined as the resemblance of one organism to another or to any natural object.

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(b) : The phenomenon of development of a new species from pre-existing one is called speciation.Reproductive isolation is the prevention of interbreeding between the populations of two different species. It maintains the characters of the species but can lead to the origin of new species.

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(b)

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(a):

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(b) : Water is the most essential material to survive. One can thrive without \(\mathrm{O}_2\) (anaerobic bacteria) and light and in a wide range of temperature but one cannot live without water which is the most important component of the body (about \(90 \%\) of plasma consists of water) and life was originated from abiogenetic materials in water.

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(c) : The common ancestor of both ape and man is Dryopithecus – a 20 million years old fossil discovered from Africa. Austroalopithecus also lived in Africa between 6 million to 1 million years ago. The genus Homo evolved 2 million years ago from one of such Australopithecines in Africa and then only moved out of the continent.
The first such Homo lived throughout Asia, some parts of Europe and Africa. But obviously its evolution took place in Africa.

Hint

(b) : Allele frequency in a population can remain constant only if individuals of the population randomly interbreed. Generally it never happens in nature and species populations exist in small groups of randomly breeding subpopulations. Thus allele frequency between two subpopulations may differ but allele frequency within the subpopulation will remain constant. Such subpopulations are termed Mendelian populations or deme. Exchange of genes between demes takes place occasionally. Mutation, gene flow (due to migration), etc. may tend to change the allele frequency of the subpopulation.

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(b) : Carl Woese came up with the theory of life based on his discovery that the genes encoding ribosomal RNA are ancient and distributed over all lineages of life with little or no gene transfer. Therefore, \(r\) RNA are commonly recommended as molecular clocks to the phylogeny.

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(b) : Mesozoic era is the era during which reptiles were dominant. It includes three periods : Triassic ( 240 million years ago), Jurassic ( 195 million years ago) and Cretaceous ( 135 million years ago). Origin of dinosaurs occurred during triassic period. During Jurassic period, lizards, crocodiles and alligators originated. Dinosaurs became large and reptiles were dominant during this period. During cretaceous period, dinosaurs got extinct.

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(a) : The two criteria on basis of which Nikolai Ivanwitch Vavilov proposed different centre of origin were (a) occurrence of maximum variation in the crop and (b) occurrence of wild relatives.

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(b) : \({ }^{14} \mathrm{C}\) has a half life of 5570 years and is used in radio carbon dating. Carbon in living things contains a uniform amount of radioactive \({ }^{14} \mathrm{C}\) produced constantly in the atmosphere. From the amount of \({ }^{14} \mathrm{C}\) in the dead sample, the age of the organism can be determined.

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(b)

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(c) :

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(b): The organisms which are provided with favourable variations would survive, because they are the fittest to face their surroundings, while the unfit are destroyed. Darwin considered that useful variations are transmitted to the offspring and appear more prominently in succeeding generations. After some generations these continuous and gradual variations in the possessor would be so distinct that they form a new species.

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(a):

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(c)

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(b) : The first living beings were prokaryotic, like bacteria. They were single-celled. Nucleic acid core consisted of naked DNA. These living beings were present in the environment of soupy sea having abundant organic molecules. Nutritionally they were chemoheterotrophs. They absorbed the organic materials from outside both for body building and liberation of energy. Respiration was anaerobic since free oxygen was absent in the environment.

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(b) : Mutation is any hereditary change in the make up of an individual other than that which may be caused by the simple recombination of genes. Mutations may occur in any direction.

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(b) : Occurrence of endemic species in South America and Australia is due to geographic isolation (continental separation). Animals occupy all diverse habitats. The distribution, continuous or discontinuous of a species or a group of organisms depends on many factors like evolutionary, climatic, physical or biological barriers etc.

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(d) : According to theory of pangenesis Darwin thought that every somatic cell of the body produces a tiny particle called gemmule or pangene which contains both the parental and acquired characters. All gemmules or pangenes of the body cells collect in the gametes and are passed on to the zygote where they guide the growth of different parts of the embryo.

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(b): The vestigial organs are the useless remnants of structures or organs which might have been large and functional in the ancestors. Segmental muscles in abdomen, coccyx, third molar (wisdom teeth) of human are vestigial organs. Nail is not a vestigial organ of human.

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(d) : Homo sapiens sapiens appeared about 25000 years ago in holocene epoch and started spreading all over the world about 10000 years ago. It is believed that the man of today first appeared about 11000 or 10000 years ago in the region around Caspean and Mediterraneasn Seas. From there, its members migrated westwards, eastwards and southwards, respectively changing into the present day white or Caucasoid, Mongoloid and black or Negroid races.

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(a) : Humans differ from most primates in that they lack a tail. The lower primates have tails, and the apes, which are believed by many to be our closest relatives, likewise are tailless.

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(a): Galapagos Islands are a chain of 14 island in the Pacific ocean on the west coast of Sout America. Charles Darwin visited these islands durin his famous voyage on HMS Beagle (name of his ship in 1835. The flora and fauna of these islands resembl with those of the South American mainland wit which the Galapagos Islands were once connected However, Darwin’s finches (birds of Galapago Islands) influenced Darwin to think about th evolutionary change. These birds designated a Darwins’ finches by Dr. David Lack (1947) do no resemble the birds of the South American species These finches were the first to reach the Galapago Islands as migrants from the mainland (Sout America). When they reached the islands, they face many problems for obtaining food. Thus, they had \(t\)

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(a):

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(a): Replication of genetic material is the most important factor for continuity of a species from evolutionary point of view. When genetic material replicates, only then it could be transferred from one generation to next resulting in continuity of a species. Asexual animals do not produce gametes while sexual animals do. So, formation of gametes is not an important factor in asexual animals though replication of genetic material takes place in both asexual as well as sexual animals. Synthesis of proteins does not play any role in continuity of species.

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(c):

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(a) : Wings of birds and hands of human have the same structure but different functions. Birds use their wings for flying while humans use their hands for grasping. Other options show examples of analogous organs. Analogous organs are those organs which have similar functions but different structural details.

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(c) : Haeckel’s biogenetic law states that “Ontogeny repeats phylogeny”. Ontogeny is the life history of an organism while phylogeny is the evolutionary history of the race of that organism. In other words an organism repeats its ancestral history during development. Therefore, during embryonic development the mammalian heart first takes the form of fish, then frog and at last mammal.

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(a): The fossil of Dryopithecus africanus was discovered from Miocene rocks of Africa and Europe. It lived about \(20-25\) million years ago. It was apelike but had arms and legs of the same length. Heels in its feet indicate its semi-erect Dryopithecus africanus is regarded a common ancestor of man and apes (gibons, organgutan, chimpanzee and gorilla).

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(c): Homo erectus is the ancestor of man (not the direct ancestor of modern man). It includes three fossils: Java Ape-man, Peking man and Heidelberg man. Neanderthal man is the direct ancestor of Cromagnon man which in turn is the direct anceston of modern man. Fossils of Cro-magnon were discovered from France. Australopithecus is the first ape man.

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(b) : Allopatric species are those that could interbreed but do not because they are geographically isolated. Sympatric are groups of similar organisms that, although in close proximity and theoretically capable of interbreeding, do not interbreed because of differences in behaviour, flowering time, etc. Siblings are offspring of the same parents.

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(c) : Darwin observed great variations among the organisms that lived on Galapagos islands. The common birds of Galapagos islands, the finches were markedly different from the finches of main land. In fact Darwin took idea from the finches found on the Galapagos Islands for his theory of natural selection.

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(d)

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(a): Homo habilis lived during Pleistocene. \(\mathrm{He}\) lived in Africa about 2 million years ago. He was about 1.2 to 1.5 metres tall. He had bipedal locomotion, moved erect and was omnivorous. Homo habilis (habilis \(\)=\(\) mentally able or skilful) was the first tool maker and used tools of chipped stones extensively. Homo erectus appeared about 1.7 million years ago in middle Pleistocene. H. erectus evolved from Homo habilis. He had erect posture, protruding jaws, projecting brow ridges and small canines and large molar teeth. He was omnivorous. He made more elaborate tools of stones and bones, hunted big game and perhaps knew use of fire.

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(d) : A close relationship of apes with man is revealed by their relatively larger brain and cranial capacity, efficient memory. Cranial capacity of apes is under \(650 \mathrm{cc}\). Cranial capacity of man is 1350 to \(1600 \mathrm{cc}\).

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(b):

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(b): Development of similar adaptive functional structures in unrelated groups of organisms is called convergent evolution. Example : wings of insect, bird and bat. Thus analogous organs show convergent evolution (adaptive convergence).

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(c): Allen’s law states, animals that live in very cold climates, their extremities such as ears, tails etc. become progressively smaller. Cope’s law states that there is a tendency for animals to increase in size during the long course of evolution. Dollo’s law states that evolution is irreversible. Bergman’s law states that warm blooded animals become larger in the northern and colder parts of their range.

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(c): Loss of tail is probably the useless change for the man in the course of evolution. The volume of cranial cavity and size of skull also increased in order to accommodate the large and complex brain. The modern man excels all other animals in intelligence. Erect posture of human beings is due to major changes in the muscle skeletal system. During the course of evolution of man, thumb (pollex) has been brought opposite to the fingers thus enabling the hand for better grasping power.

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(d): Homo sapiens fossilis is also known by the name of Cro-magnon man. He was the direct ancestor of modem man (Homo sapiens). Cro-Magnon man emerged about 34000 years ago in Holocene epoch. Thus, it is regarded as most recent ancestor of today’s man. Its cranial capacitywas, however, somewhat more than ours, being about \(1650 \mathrm{cc}\). It became extinct about \(10000-11000\) years ago.

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(d): Human body has been described to possess about 90 vestigial organs. Some of these are nictitating membrane, muscles of pinna (part of external ear), vermiform appendix, caudal vertebrae (also called coccyx or tail bone), third molars (wisdom teeth), hair on body, and nipples in male.

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(d):

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(d) : Hydrogen atoms were most numerous and most reactive in primitive atmosphere. First hydrogen atoms combined with all oxygen atoms to form water and leaving no free oxygen. Hydrogen atoms also combined with nitrogen, forming ammonia \(\left(\mathrm{NH}_3\right)\). So water and ammonia were probably the first compound molecules of primitive earth. Later methane, water and \(\mathrm{NH}_3\) join to form amino acids which gets converted into proteins while hydrogen bases, sugars and phosphates combine to form nucleic acids.

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(c) : The first domesticated animal by primitive man was dog. Cro-magnon man used to carry domesticated dogs while going for hunting.

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(b) : The radioactive strontium – 90 can lead to various bone disorders and diseases, including bone cancer. It emits high energy beta radiations. Phosphorus – 32 also emit high energy beta radiations but they cannot penetrate human skin. Caesium – 137 (beta emitter) and iodine -131 ( \(\beta\) and \(\gamma\) emitter) also pose danger to human health but not as much as strontium – 90 which is a long-lived radioactive element and tends to cycle like calcium.

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(a): Industrial melanism is an adaptation where the moths living in the industrial areas developed melanin pigments to match their body to the sootcovered surroundings. These melanic forms are mainly distributed in and around large industrial cities, where the environment has been altered by the pollution of the atmosphere; and is manifested by the appearance of dark colour of lichen-covered tree trunks, on which the moths rest during the day time. The peppered moth exists in two strains (forms) : light coloured (white) and melanic (black). In the past, bark of trees was covered by whitish lichens, so white moths escaped unnoticed from predatory birds. After industrialization barks got covered by smoke, so the white moths were selectively picked up by birds. But black moths escaped unnoticed so they managed to survive resulting in more population of black moths and less population of white moths. 

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(c): Homologous organ and vestigial organs provide an important evidence in favour of organic evolution (process by which changes in the genetic composition of populations of organisms occur in response to environmental changes). For example, human appendix is a developmental derivative and evolutionary vestige of the end of the much larger herbivorous caecum found in our primate ancestors. They both are structurally homologous and have different functions. In most vertebrates, the caecum is a large, complex gastrointestinal organ, enriched in mucosal lymphatic tissue and specialized for digestion of plants. The caecum varies in size among species, but in general the size of the caecum is proportional to the amount of plant matter in a given organism’s diet. It is largest in obligate herbivores, animals whose diets consist entirely of plant matter. However, even though humans are herbivorous, the small human caecum does not house cellulosedigesting bacteria, and lost an essential function of cellulose digestion. This shows the close evolutionary relationships between homologous and vestigial organs. 

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(a): Precambrian period extends from 2300 to 3800 million years ago, which is considered as period of early life. During this period prokaryotes (monera) and eukaryotes (protista) originate.

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(d): In the embryos of all vertebrates, the presence of gill slits support the theory of recapitulation (repeating the early stages of embryogenesis in earlier evolved animals.)

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(d): Sclatter in 1857 recognised six zoogeographical regions on the basis of the distribution of terrestrial vertebrates, chiefly mammals.
(i) The Palaearctic region
(ii) The Ethiopian region
(iii) The Indian region (Oriental)
(iv) The Australian region
(v) The Neotropical region
(vi) The Neoarctic region

The Palaearctic region includes the whole northern part of the Old World, i.e. whole of Europe, northern part of Africa and Asia, North of the Himalayas. Oriental region includes the whole of India, Ceylon, South China, Burma, Thailand, Malaya of Peninsula, Malayan Islands. The Palaearctic and Oriental regions are separated by Himalayan range.

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(b) : In ancient period hands were used to collect food and to save themselves. Gradually men learnt to cook food, to make tools for their own purpose, this change in habit brings perfection in their hand. Similarly, there is an increase in the ability to communicate with others and develop community behaviour. But as in ancient period, men still eat hard nuts and hard roots (though they often take soft food also). Thus change in diet is the most irrelevant change in the evolution of man.

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(b) : Melanization in peppered moth is an example in support of the theory of natural selection. Lamarckism is the first theory of evolution, which was proposed by Jean Baptiste de Lamarck. Its theory of inhertance of acquired characters cannot be explained by melanization in peppered moth.

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(c) : The first fossil of the horse was found in north America. It was named Eohippus. This horse was about the size of a fox having short head and neck. The fore feet were with four complete fingers and one splint of first finger and the hind feet with three functional toes and one splint of fifth toe. Other stages in the evolution of horse were mesohippus, merychippus, pliohippus and equus.

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(a)

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(c) : Inbreeding is mating between closely related individuals, the extreme condition being selffertilization, which occurs in many plants and some primitive animals. Heterosis is also known as hybrid vigour which is the increased vigour displayed by the offspring from a cross between genetically different parents. Hybridization is the production of one or more hybrid organisms by the mating of genetically different parents. In self-breeding the male and female gametes are derived from the same individual.

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(a):

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(d) : Lamarck gave theory of Lamarckism in which he explained inheritance of acquired characters which states that whatever an individual acquires characters in its life time due to internal vital force, effect of environment, new needs and use and disuse of organs, they are inherited to the next generations. The process continues. After several generations, the variations are accumulated upto such extent that they give rise to new species. This theory was proved wrong by August Weismann. Weismann cut off the tails of rats for as many as 22 generations and allowed them to breed, but tailless rats were never born.

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(c)

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(d)

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(b) :  The first living beings were prokaryotic, like bacteria. They were single-celled. Nucleic acid core consisted of naked DNA. These living beings were present in the environment of soupy sea having abundant organic molecules. Nutritionally they were chemoheterotrophs. They absorbed the organic materials from outside both for body building and liberation of energy. Respiration was anaerobic since free oxygen was absent in the environment. 

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(c): The primitive atmosphere was reducing atmosphere i.e., without free oxygen.

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(c) : The first geological time scale was developed by Giovanni Avduina, Italian scientist in 1760. The history of the earth has been divided into a number of major divisions called eras. The eras are sub-divided into periods. The modern periods are further divided into epochs. There are four eras. The correct sequence is Precambrian Palaeozoic (era of ancient life) \(\rightarrow\) Mesozoic (era of medieval life) \(\rightarrow\) Coenozoic (era of modern life).

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(a) : Palaeontology is the study of extinct organisms, including their structure, environment, evolution, and distribution, as revealed by their fossil remains. Herpetology is the study of reptiles and amphibians. Saurology is the study of snakes. Organic evolution deals with study of origin of life and origin of new species.