Biology Question Bank – 99 MCQs on “Evolution” – Answered!

16Oct 2018 by admin

99 Questions with Answers and Explanations on “Evolution” for Biology Students:

1. Humming birds and Hawk illustrate

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(a) convergent evolution

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(b) homology

(d) parallel evolution.

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Answer and Explanation:

1. (c): Adaptive radiation in evolution was developed by H.F. Osborn in 1898. It is also known as “Divergent evolution” It is development of different functional structures from a common ancestral form. Examples as mentioned in the question.

Whereas development of similar adaptive functional structures in unrelated groups of organism is adaptive convergence = convergent evolution, e.g. wings of insect, bird and bat. When convergent evolution is found in closely related species, it is called “Parallel Evolution”. Example: development of running rabbit in deer (2 toed) and horse (1 toed).

2. Evolution is

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(a) progressive development of a race

(b) history and development of race along with variations

(d) development of race.

Answer and Explanation:

2. (b): The term evolution was coined by Herbert Spencer, an English philosopher which means unrolling or unfolding of nature that brings about an orderly change from one form or condition to another resulting in descendents becoming different from ancestors. Thus, it is history and development of race along with variations.

3. “Continuity of germplasm” theory was given by

(a) De Vries

(b) Weismann

(d) Lamarck.

Answer and Explanation:

3. (b): August Weismann put forward the theory of continuity of germplasm. According to Weismann, the characters influencing the germ cells are only inherited. There is a continuity of germplasm (protoplasm of germ cells) but the somatoplasm (protoplasm of somatic cells) is not transmitted to the next generation hence it does not carry characters to next generation.

Weismann cut off the tails of rats for more than 20 generations and allowed them to breed, but tailless rats were never born. De vries gave mutation theory. Theory of Natural selection was given by Darwin and Lamarck gave the first theory of evolution, Lamarckism.

4. Theory of inheritance of acquired characters was given by

(a) Wallace

(b) Lamarck

(d) De Vries.

Answer and Explanation:

4. (b): One of the first attempts to explain the mechanism of evolution was made by Jean Baptiste de Lamarck. His theory of evolution is known as 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.

5. ‘Origin’ of Species’ was written by

(a) Oparin

(b) Weismann

(d) Darwin.

Answer and Explanation:

5. (d): Darwin published his observations and conclusions regarding evolution in the book “Origin of Species” in 1859. Darwin’s this book became very popular and changed people’s thinking about organic evolution.

6. Parallelism is

(a) adaptive divergence

(b) adaptive divergence of widely separated species

(d) adaptive convergence of closely related groups.

Answer and Explanation:

6. (d): Development of similar adaptive functional structures in unrelated groups of organisms is called adaptive convergence or convergent evolution e.g. wings of insect, bird and bat show marked convergent evolution. When convergent evolution is found in closely related species, it is called “Parallel evolution”. Example: development of running habit in deer (2-toed) and horse (1-toed) with two vestigial splint bones.

7. Basic principles of embryonic development were pronounced by

(a) Von Baer

(b) Weismann

(d) Morgan.

Answer and Explanation:

7. (a): In 1828, Von Baer, the father of modern embryology, proposed Baer’s law which stated that during embryonic development, the generalized features (such as brain, spinal cord, axial skeleton, aortic arches, etc. are common to all vertebrates) appeared earlier than the special features (like hair in mammals only, feathers in birds only, limbs found in quadrupeds only) which distinguish the various members of the group.

Later on this law was modified as the biogenetic law by Ernst Haeckel in 1866. 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 its development. Weisman put forward the theory of continuity of germplasm. Morgan is known as father of modern genetics and worked on Drosophila.

8. Which was absent in the atmosphere at the time of origin of life?

(a) NH3

(b) H2

(d) CH4.

Answer and Explanation:

8. (c): 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. Thus primitive atmosphere was reducing atmosphere (without free oxygen) unlike the present oxidising atmosphere (with free oxygen).

9. Correct order is

(a) palaeozoic —> archaeozoic —> coenozoic

(b) archaeozoic —> palaeozoic —> proterozoic

(d) mesozoic —> archaeozoic —> proterozoic.

Answer and Explanation:

9. (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) —> Mesozoic (era of medieval life) Coenozoic (era of modern life).

10. Study of fossils is

(a) Palaeontology

(b) Herpetology

(d) Organic evolution.

Answer and Explanation:

10. (a): Palaeontology is the study of extinct organisms, including their structure, environment, evolution, and distribution, as reveabled 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.

11. The first organisms were

(a) chemoautotrophs

(b) chemoheterotrophs

(d) eucaryotes.

Answer and Explanation:

11. (b): The first living beings were procaryotic, 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.

12. Evolutionary convergence is development of

(a) common set of characters in group of different ancestry

(b) dissimilar characters in closely related groups

(d) random mating.

Answer and Explanation:

12. (a): 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).

13. Weismann cut off tails of mice generation after generation but tails neither disappeared nor shortened showing that

(a) Darwin was correct

(b) tail is an essential organ

(d) Lamarckism was wrong in inheritance of acquired characters.

Answer and Explanation:

13. (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. August Weismann put forward the theory of continuity of germplasm.

According to this the characters influencing the germ cells are only inherited. There is a continuity of germplasm (protoplasm of germ cells) but the somato-plasm (protoplasm of somatic cells) is not transmitted to the next generation hence it does not carry characters to next generation. Weismann cut off the tails of rats for as many as 22 generations and allowed them to breed, but tailless rats were never born.

14. Theory of Natural Selection dwells on

(a) role of environment in evolution

(b) natural selection acting on favourable variations

(d) none of the above.

Answer and Explanation:

14. (c): Charles Darwin gave the theory of natural selection. The theory is based on five important observations:

(i) All species have great reproductive potential

(ii) Most populations are stable in size

(iii) Natural resources are limited

(iv) Individuals of a population have variations.

(v) Most of the variations are heritable. Species with variations are selected by nature.

15. Genetic drift is change of

(a) gene frequency in same generation

(b) appearance of recessive genes

(d) none of the above.

Answer and Explanation:

15. (d): The random changes in gene frequencies in a population occurring by chance alone rather than by natural selection are called genetic drift. Although genetic drift occurs in all populations, its effects are most marked in very small isolated population.

16. Which one of the following changes involved is irrelevant, in the evolution of man?

(a) perfection of hand for tool making

(b) change of diet from hard nuts and hard roots to soft food

(d) increase in the ability to communicate with others and develop community behaviour.

Answer and Explanation:

16. (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. Loss of tail takes a great role in course of evolution.

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.

17. Which of the following evidences does not favour the Lamarckian concept of inheritance of acquired characters?

(a) lack of pigment in cave-dwelling animals

(b) melanization in peppered moth

(d) presence of webbed toes in aquatic birds.

Answer and Explanation:

17. (b): Melanization in peppered moth is an example in support of the theory of natural selection. Industrial melanism is an adaptation where the moths living in the industrial areas developed melanin pigments to match their body to the soot-covered surroundings. Lamarckism is the first theory of evolution, which was proposed by Jean Baptiste de Lamarck. Lamarckism includes four main factors:

I. Internal vital force. All the living things and their component parts are continually increased due to internal vital force.

II. Effect of Environment and New Needs. A change in environment brings about changes in organisms. It gives rise to new needs. New needs or desires produce new structures and change habits of the organisms.

III. Use and disuse of Organs. If an organ is constantly used it would be better developed whereas disuse of organ results in its degeneration.

IV. Inheritance of Acquired Characters. Whatever an individual acquires (to possess) characters in its life time due to internal vital force, effect of environment, new needs and use and disuse of organs, they are inherited (transmitted) to the next generations. The process continues. After several generations, the variations are accumulated upto such extent that they give rise to new species.

Cave-dwelling animals lack pigment due to absence of light in the caves. As aquatic birds had to go to water due to lack of food etc. they develop web between the toes. Snakes, in order to escape from mammals started living in narrow crevices. So in order to accommodate their bodies they lost limbs (as snakes have been evolved from lizard like ancestors).

18. The earliest fossil form, in the phylogeny of horse, is

(a) Eqiitts

(b) Mesohippus

(d) Merychippus.

Answer and Explanation:

18. (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.

19. Which of the following is a pair of homologous orgarrs?

(a) pectoral fin of rohu and fore-limb of horse

(b) wings of grasshopper and wings of crow

(d) wings of bat and wings of butterfly.

Answer and Explanation:

19. (a): The organs which have the same fundamental structure but different functions are called homologous organs. Pectoral fin of rohu and fore-limb of horse have the same fundamental structure but their functions are different. Pectoral fin is used for swimming by rohu and fore limb is used for walking by horse. Other options show examples of analogous organs. Analogous organs are those organs which have similar functions but different structural details.

20. The process of mating of individuals, which are more closely related than the average of the population to which they belong, is called

(a) heterosis

(b) self breeding

(d) hybridization.

Answer and Explanation:

20. (c): Inbreeding is mating between closely related individuals, the extreme condition being self-fertilization, 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.

21. Which of the following isotopes is most dangerous to Homo sapiens?

(a) phosphorus-32

(b) strontium-90

(d) iodine-131.

Answer and Explanation:

21. (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 (P and y 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.

22. The change of the lighter-coloured variety of peppered moth (Biston betularia) to its darker variety (Biston carbonaria) is due to

(a) mutation

(b) regeneration

(d) temporal isolation.

Answer and Explanation:

22. (a): Industrial melanism is an example of natural selection where the moths living in the industrial areas developed melanin pigments to match their body to the soot-covered surrounding. This phenomenon provides an excellent instance of operation of selection in natural conditions. It has occurred in several species of moths. Of these, peppered moth (Biston betularia) is the most intensely studied one.

The first melanic form (entirely black form) of peppered moth has been observed in 1845, and till that period all known moths were light coloured. 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. This melanisation helps the black moths to escape from being picked up by birds which otherwise picked white moths (which were easily noticeable on the root covered trees).

23. The homologous organs are those that show similarity in

(a) appearance

(b) function

(d) size.

Answer and Explanation:

23. (c): Homologous organs have the same fundamental structure which they inherit from common ancestors thus their origin is common but they are different in functions e.g. the fore-limbs of frog, lizard, pigeon and whale have the same basic structural plan. In each case the fore-limb consists of an upper arm, fore-arm, wrist, palm and fingers. The upper arm is always made up of humerus, the forearm composed of radio-ulna, the wrist consists of carpals, and the palm containing 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 frog, they are used for leaping, in lizard for creeping, in pigeon for flying and in whale for swimming.

24. Which period is dubbed as the age of prokaryotic microbes?

(a) precambrian

(b) phanerozoic

(d) proterozoic.

Answer and Explanation:

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

25. The presence of gill slits, in the embryos of all vertebrates, supports the theory of

(a) metamorphosis

(b) biogenesis

(d) recapitulation.

Answer and Explanation:

25. (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.)

26. Two zoogeographical regions, separated by high mountain ranges, are

(a) Nearctic and Palaearctic

(b) Neotropical and Ethiopian

(d) Palaearctic and Oriental.

Answer and Explanation:

26. (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, and Malayan Islands. The Palaerctic and Oriental regions are separated by Himalayan range.

27. The animals of cold countries have relatively shorter and poorly developed ears, eyes, hairs and other phenotypic characters. This is known by which law?

(a) Cope’s Law

(b) Dollo’s Law

(d) Bergamann’s Law.

Answer and Explanation:

27. (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.

28. Which of the following changes for man in the course of evolution is probably useless?

(a) development of being erect

(b) development of cranial capacity

(d) development of opposable thumb.

Answer and Explanation:

28. (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 accomodate 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 of the hand for better grasping power.

29. Which of the following is the direct ancestor of Homo sapiens?

(a) Australopithecus

(b) H. sapiens neanderthals

(d) Homosapiens fossilis.

Answer and Explanation:

29. (d): Homo sapiens fossilis is also known by the name of Cro-magnon man. He was the direct ancestor of modern man (Homosapiens). Cro-Magnon man emerged about 34000 years ago in Holocene epoch. Thus, it is regarded as most recent ancestor of today’s man.

Its face was perfectly orthognathous with an arrow, elevated nose, broad and arched forehead, moderate brow-ridges, strong jaws with man-like dentition, and a well developed chin. Its cranial capacity was, however, somewhat more than ours, being about 1650 cc. It became extinct about 10000- 11000 years ago.

30. Which of the following is the correct group of vestigial organs in man?

(a) nictitating membrane, ear muscles, eyelids and coccyx

(b) appendix, coccyx, ear muscles and elbow joint

(d) wisdom tooth, body hairs, nictitating membrane and vermiform appendix.

Answer and Explanation:

30. (d): The organs which are present in reduced form and do not perform any function in the body but correspond to the fully developed functional organs of related animals are called vestigial organs. They are believed to be remnants of organs which were complete and functional in their ancestors.

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.

31. Which of the following is an example of ‘living fossils’?

(a) Pinus

(b) Riccia

(d) Ginkgo.

Answer and Explanation:

31. (d): Living fossils are those plants and animals which have become extinct excepting one or two representatives. The living species Ginkgo biloba originated in the triassic period of the mesozoic era and since then it has continued to live unchanged and unaltered by the innumerable environmental hazards, concealing in its steady stature.

32. The correct sequence for the manufacture of molecules/organic compounds on the primitive earth is

(a) NH3, nucleic acid, protein and carbohydrate

(b) protein, carbohydrate, water and nucleic acid

(d) NH3, water, nucleic acid and protein.

Answer and Explanation:

32. (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 (NH3). So water and ammonia were probably the first compound molecules of primitive earth. Later methane, water and NH3 join to form amino acid which gets converted into proteins while hydrogen bases, sugars and phosphates combine to form nucleic acids.

33. The first domesticated animal by primitive man was

(a) cat

(b) cow

(d) horse.

Answer and Explanation:

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

34. Which of the following statements is correct regarding evolution of mankind?

(a) Homo erectus is preceded by Homo habilis

(b) neanderthal man and cro-magnon man were living at the same time

(d) none of these.

Answer and Explanation:

34. (a): Homo habilis lived during Pleistocene. 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.

35. Common origin of man and chimpanzee is best shown by

(a) binocular vision

(b) chromosome number

(d) cranial capacity.

Answer and Explanation:

35. (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 cc. Cranial capacity of man is 1350 to 1600 cc.

36. Which of the following is a living fossil?

(a) Mirabilis jalapa

(b) Ginkgo bilpba

(d) Dalbergia sissoo.

Answer and Explanation:

36. (b): Refer answer 31.

37. Evolutionary convergence is characterized by

(a) development of dissimilar characteristics in closely related groups

(b) development of a common set of characteristics in groups of different ancestry

(d) replacement of common characteristics in different groups.

Answer and Explanation:

37. (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).

38. In the developmental history of mammalian heart, it is observed that it passes through a two chambered fish like heart, three chambered frog like heart and finally four chambered stage. To which hypothesis can this above cited statement be approximated?

(a) Lamarck’s principle

(b) Mendalian principles

(d) Hardy Weinberg law.

Answer and Explanation:

38. (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.

39. The age of the fossil of Dryopithecus on the geological time scale is

(a) 2.5 x 106 years back

(b) 50 x 106 years back

(d) 25 x 106 years back.

Answer and Explanation:

39. (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 ape-like but had arms and legs of the same length. Heels in its feet indicate its semi erect posture. It had large brain, a large muzzle and large canines. It was without brow ridges. It was arboreal, knuckel-waiker and ate soft fruits and leaves. Dryolpithecus africanus is regarded a common ancestor of man and apes (gibons, organgutan, chimpanzee and gorilla).

40. Which one of the following statements is correct?

(a) Australopithecus is the real ancestor of modern man

(b) Neanderthal man is the direct ancestor of Homo sapiens

(d) Cro-magnon man’s fossil has been found in Ethiopia.

Answer and Explanation:

40. (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 Cro-magnon 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.

41. Species occurring in different geographical area are called as

(a) sympatric

(b) allopatric

(d) neopatric.

Answer and Explanation:

41. (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.

42. The diversity in the type of beaks of finches adapted to different feeding habits on the Galapages Islands, as observed by Darwin, provides evidence for

(a) intraspecific competition

(b) interspecific competition

(d) intraspecific variations.

Answer and Explanation:

42. (c): Charles Darwin (1809-1882) was an English naturalist. In 1831, Darwin got an opportunity to travel on H.M.S. Beagle (a ship in which Charles Darwin sailed around the world) for a voyage of world exploration. During that period Darwin explored the fauna and flora of a number of continents and islands. Later Beagle was sailed to the Galapagos Islands where Darwin observed great variations among the organisms that lived on these 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. Competition occurring between members of a species is known as intraspecific competition and that occurring between different species is known as interspecific competition.

43. Genetic drift operates only in

(a) larger populations

(b) Mendelian populations

(d) smaller populations.

Answer and Explanation:

43. (d): Genetic drift is the random change in the frequency of alleles in a population over successive generations due to sampling error 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.

Over time, this may lead to certain alleles becoming fixed and others being lost altogether. This process is more rapid in smaller populations, or when the alleles concerned confer no apparent benefit compared to their counterparts. Hence, genetic drift can ultimately cause loss of genetic diversity if there are no counteracting factors.

44. Phenomenon of Industrial melanism’ demonstrates

(a) geographical isolation

(b) reproductive isolation

(d) induced mutation.

Answer and Explanation:

44. (c): Refer answer 22.

45. Which of the following are homologous organs?

(a) wings of bird and hands of human

(b) nails of human being and claws in animals

(d) wings of bat and wings o~ cockroach.

Answer and Explanation:

45. (a): The organs which have the same fundamental structure but different functions are called homologous organs. 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.

46. Which is not a vestigial organ in man?

(a) third molar

(b) nails

(d) coccyx.

Answer and Explanation:

46. (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.

47. Homo sapiens have evolved in

(a) palaeocene

(b) pleistocene

(d) holocene.

Answer and Explanation:

47. (d): Homo 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.

48. Character which is closely related to human evolution is

(a) disappearance of tail

(b) reduction in size of jaws

(d) flat nails.

Answer and Explanation:

48. (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.

49. Which evidence of evolution is related to Darwin’s finches?

(a) evidences from biogeographical distribution j

(b) evidences from comparative anatomy

(d) evidences from paleontology.

Answer and Explanation:

49. (a): Galapagos Islands are a chain of 14 islands in the pacific ocean on the west coast of South America. Charles Darwin visited these islands during his famous voyage on HMS Beagle (name of his ship) in 1835. The flora and fauna of these islands resemble with those of the South American mainland with which the Galapagos Islands were once connected.

However, Darwin’s finches (birds of Galapagos Islands) influenced Darwin to think about the evolutionary change. These birds designated as Darwins’ finches by Dr. David Lack (1947) do not resemble the birds of the South American species. These finches were the first to reach the Galapagos Islands as migrants from the mainland (South America). When they reached the islands, they faced many problems for obtaining food. They had to change their feeding habits.

50. Who is directly related to man?

(a) gorilla

(b) rhesus

(d) orangutan.

Answer and Explanation:

50. (a): 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 super family Hominoidea, gibbons are the out group: 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 out group, 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 provide convincing evidence that within the subfamily homininae, gorillas are the out group. This suggests that chimpanzees should be in hominini along with humans.

51. Which is the most important factor for continuity of a species from evolutionary point of view?

(a) replication of genetic material

(b) formation of gametes

(d) none of these.

Answer and Explanation:

51. (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.

52. Which statement is correct about centre of origin of plant?

(a) more diversity in improved variety

(b) frequency of dominant gene is more

(d) none of the above.

Answer and Explanation:

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

53. Half life period of C14 is

(a) 500 years

(b) 5000 years

(d) 5 x 104 years.

Answer and Explanation:

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

54. Most abundant organic compound on earth is

(a) protein

(b) cellulose

(d) steroids.

Answer and Explanation:

54. (b): Cellulose is the most abundant organic compound, most abundant biopolymer and most abundant ; polysaccharide found on earth. It forms the main constituent of cell wall of plants, most algae and some fungi and also the food for ruminant mammals, termites possessing bacteria that secrete cellulose digesting enzymes.

55. Similarities in organism with different genotype indicates

(a) microevolution

(b) macroevolution

(d) divergent evolution.

Answer and Explanation:

55. (c): 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 convergene). Development of different functional structures from a common ancestral form is called divergent evolution. Microevolution produces minute changes below the species level. Macroevolution involves the evolution of species and genera or differentiation of group of animals by adaptive radiation.

56. Reason of diversity in living being is

(a) mutation

(b) long term evolutionary change

(d) short term evolutionary change.

Answer and Explanation:

56. (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.

57. Which of the following is closest relative of man?

(a) chimpanzee

(b) gorilla

(d) gibbon.

Answer and Explanation:

57. (a): Chimpanzees are human’s closest relative. This relationship is supported by immunological, DNA-DNA hybridization and DNA sequence data and by chromosomal analyses and protein sequences.

58. Which of the following is correct order of the evolutionary history of man?

(a) Peking man homo sapiens, Neanderthal man, Cromagnon man

(b) Peking man, Heidelberg man. Neanderthal man, Cromagnon man

(d) Peking man, Neanderthal man. Homo sapiens, Heidelberg man.

Answer and Explanation:

58. (c): The Pleistocene rocks from which fossils of Peking man were excavated are about 6 lakh years old. The Peking man was omnivorous and cannibal. There is a clear evidence of use of fire by it. It has been confirmed that Peking men used to live in caves in small groups or tribes. The tools of Peking man were relatively more sophisticated. Heidelberg man had lower jaw with all the teeth. He used the tools and fire.

The cranial capacity is believed to be about 1300 cc. Neanderthal man had slightly prognathous face. Neanderthals walked upright, as we do, and had low brows, receding jaws, and high domed heads. Their cranial capacity was 1300 to 1600 cubic centimetres. They became extinct 30000 years ago. Cro-Magnon man emerged about 34000 years ago in Holocene epoch.

Thus, it is regarded as most recent ancestor of today’s man. Its face was perfectly orthognathous with an arrow, elevated nose, broad and arched forehead, moderate brow-ridges, strong jaws with man-like dentition, and a well developed chin. Its cranial capacity was, however, somewhat more than ours, being about 1650 cc. It became extinct about 10000-11000 years age.

59. 1st life on earth was

(a) cyanobacteria

(b) chemohetrotrophs

(d) photoautotrophs.

Answer and Explanation:

59. (b): The first living beings were procaryotic, 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.

60. Forthcoming generation are less adaptive than the parental generation due to

(a) natural selection

(b) mutation

(d) adaptation.

Answer and Explanation:

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

61. Occurrence of endemic species in South America and Australia is due to

(a) these species has been extinct from other regions

(b) continental separation

(d) retrogressive evolution.

Answer and Explanation:

61. (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.

62. Darwin’s theory of pangenesis shows similarity with theory of inheritance of acquired characters then what shall be correct according to it

(a) useful organs becomes strong and developed while useless organs become extinct

(b) size of organs increase with aging

(d) there should be some physical basis of inheritance.

Answer and Explanation:

62. (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.

63. Cause of mimicry is

(a) concealment

(b) offence

(d) both (b) and (c)

Answer and Explanation:

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

64. Which of the following is most important for speciation ?

(a) seasonal isolation

(b) reproductive isolation

(d) tropical isolation.

Answer and Explanation:

64. (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.

65. Which of the following are homologous organs?

(a) wings of birds and locust

(b) wings of birds and pectoral fins of fish

(d) legs of frog and cockroach.

Answer and Explanation:

65. (b): The organs which have the same fundamental | structure but different functions are called homologous organs. Wings of birds and pectoral fins of fish have the same fundamental structure but their functions are different. Wings are used for flying by birds and pectoral fins are used for swimming by fish. Other options show examples of analogous organs. Analogous organs are those organs which have similar functions but different structural details.

66. Genetic drift operates in

(a) small isolated population

(b) large isolated population

(d) slow reproductive population.

Answer and Explanation:

66. (a): Refer answer 43.

67. There is no life on moon due to the absence of

(a) O2

(b) water

(d) temperature.

Answer and Explanation:

67. (b): Water is the most essential material to survive. One can thrive without 02 (anaerobic bacteria) and light and in a wide range of temperatue 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 a biogenetic materials in water.

68. According to fossils discovered up to present time origin and evolution of man started from

(a) France

(b) Java

(d) China.

Answer and Explanation:

68. (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.

69. In which condition, the gene ratio remains constant for any species population?

(a) sexual selection

(b) random mating

(d) gene flow.

Answer and Explanation:

69. (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 denies takes place occasionally. Mutation, gene flow (due to migration), etc may tend to change the allele frequency of the subpopulation.

70. Sequence of which of the following is used to know the phylogeny?

(a) m-RNA

(b) r-RNA

(d) DNA.

Answer and Explanation:

70. (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 as we do, and had low brows, receding jaws, and high domed heads. Their cranial capacity was 1300 to 1600 cubic centimetres.

They became extinct 30000 years ago. Cro-Magnon man emerged about 34000 years ago in Holocene epoch. Thus, it is regarded as most recent ancestor of today’s man. Its face was perfectly orthognathous with an arrow, elevated nose, broad and arched forehead, moderate brow-ridges, strong jaws with man-like dentition, and a well developed chin.

Its cranial capacity was, however, somewhat more than ours, being about 1650 cc. It became extinct about 10000-11000 years.

71. In which era reptiles were dominant?

(a) coenozoic era

(b) mesozoic era

(d) archaeozoic era.

Answer and Explanation:

71. (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 occured 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.

72. Convergent evolution is illustrated by

(a) rat and dog

(b) bacterium and protozoan

(d) dogfish and whale

Answer and Explanation:

72. (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.

73. Which one of the following sequences was proposed by Darwin and Wallace for organic evolution?

(a) overproduction, variations, constancy of population size, natural selection

(b) variations, constancy of population size, overproduction, natural selection

(d) variations, natural selection, overproduction, constancy of population size (2003)

Answer and Explanation:

73. (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 off springs with the same trait – through this natural selection of the fittest species become represented by individuals which are better adapted.

74. Random genetic drift in a population probably results from

(a) highly genetically variable individuals

(b) interbreeding within this population

(d) large population size

Answer and Explanation:

74. (b): Genetic drift is the change in number and frequency of genes in small isolated population due to intensive inbreeding causing permanent fixation of some alleles, disappearance of a number of alleles and change in frequency of others.

75. Industrial melanism is an example of

(a) drug resistance

(b) darkening of skin due to smoke from industries

(d) defensive adaptation of skin against ultraviolet radiations.

Answer and Explanation:

75. (c): Industrial melanism is an adaptation where the moths living in the industrial areas developed melanin pigments to match their body to the soot-covered 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.

76. In a random mating population in equilibrium, which one of the following brings about a change in gene frequency in a non-directional manner?

(a) mutations

(b) random drift

(d) migration

Answer and Explanation:

76. (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.

77. Darwin in his “Natural Selection Theory” did not believe in any role of which one of the following in organic evolution?

(a) parasites and predators as natural enemies

(b) survival of the fittest

(d) discontinuous variations

Answer and Explanation:

77. (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.

78. Which one of the following describes correctly the homologous structures?

(a) organs with anatomical similarities, but performing different functions

(b) organs with anatomical dissimilarities, but performing same function

(d) organs appearing only in embryonic stage and disappearing later in the adult

Answer and Explanation:

78. (a): Refer answer 23.

79. Which one of the following is categorized under living fossils?

(a) Pinus

(b) Cycas

(d) Metasequoia

Answer and Explanation:

79. (b): Cycas and Ginkgo are often considered as the living fossil because they are lone/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.

80. Age of fossils in the past was generally determined by radio-carbon method and other methods involve radioactive elements found in the rocks. More precise methods, which were used recently and led to the revision of the evolutionary periods for different groups of organisms, includes

(a) study of carbohydrates/proteins in fossils

(b) study of the conditions of fossilization

(d) study of carbohydrates / proteins in rocks.

Answer and Explanation:

80. (c): Electron spin resonance (ESR) measures the number of charges occupying deep traps in the crystals bandgap. By measuring the change in absorption of microwave energy within a continuously varying strong genetic field, this method detects the number of unpaired INS of electronic charges trapped at various defects in the mineral lattice. The basic principle of ESR is the same as those described for luminescence i.e. electrons become trapped and stored as a result of ionising radiation. Egs, of ESR dating are – dating of coral reefs (eg. Pleistocene liaised coral reefs of Barbados) and dating of tooth enamel.

81. What kind of evidence suggested that man is more closely related with chimpanzee than with other hominoid apes?

(a) evidence from DNA extracted from sex chromosomes only

(b) comparison of chromosomes morphology only

(d) evidence from DNA extracted from sex chromosomes, autosomes.

Answer and Explanation:

81. (d): Refer answer 50.

82. Which one of the following is a living fossil?

(a) Cycas

(b) Moss

(d) Spirogyra

Answer and Explanation:

82. (a): Refer answer 79.

83. According to Oparin, which one of the following was not present in the primitive atmosphere of the earth?

(a) methane

(b) oxygen

(d) water vapour.

Answer and Explanation:

83. (b): The first scientific explanation of origin of life | was put forward by a Russian Scientist, A.I. Oparin in Il923. J.B.S. Haldane (1928), England-born Indian I Scientist, also made similar observations regarding the t 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.

84. Diversification in plant life appeared

(a) due to long periods of evolutionary changes

(b) due to abrupt mutations

(d) by seed dispersal.

Answer and Explanation:

84. (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.

85. Which one of the following experiments suggests that simplest living organisms could not have originated spontaneously from non-living matter?

(a) larvae could appear in decaying organic matter

(b) microbes did not appear in stored meat

(d) meat was not spoiled, when heated and kept sealed in a vessel.

Answer and Explanation:

85. (d): Microbes were killed by heating the meat and i 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.

86. De Vries gave his mutation theory on organic evolution while working on

(a) Pisum sativum

(b) Drosophila melanogaster

(d) Althea rosea.

Answer and Explanation:

86. (c): Hugo de Vries, a Dutch botanist, one of the independent rediscoverers of Mendelism, put forward his views regarding the formation of new species in 1901. According to him, new species are not formed by continuous variations but by sudden appearance of variations, which he named as mutations. Hugo de Vries stated that mutations are heritable and persist in successive generations. He conducted his experiments on Oenothera lamarckiana (evening primrose). Mendel worked on Pisum sativum and gave principal of inheritance. T.H. Morgan worked on Drosophila and gave linkage theory.

87. There are two opposing views about origin of modern man. According to one view Homo erectus in Asia were the ancestors of modern man. A study of variation of DNA however suggested African origin of modern man. What kind of observation on DNA variation could suggest this?

(a) greater variation in Asia than in Africa

(b) greater variation in Africa than in Asia

(d) variation only in Asia and no variation in Africa.

Answer and Explanation:

87. (b): The more the genetic variations the more is the age of mankind.

88. Which one of the following phenomena supports Darwin’s concept of natural selection in organic evolution?

(a) development of transgenic animals

(b) production of ‘Dolly’, the sheep by cloning

(d) development of organs from ‘stem cells’ for organ transplantation.

Answer and Explanation:

88. (c): One of the features of Darwin’s theory is survival of the fittest (Natural selection). According to this 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. So, the pesticide resistant insects 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.

89. Which of the following is the relatively most accurate method for dating of fossils?

(a) radio-carbon method

(b) potassium-argon method

(d) uranium-lead method.

Answer and Explanation:

89. (c): Electron spin resonance (ESR) measures the number of charges occupying deep traps in the crystal band gap. 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 the method of uptake can be judged, then the approximate age of the tissue can be deduced from the extent of the radiation damage.

90. At a particular locus, frequency of A allele is 0.6 and that of a is 0.4. What would be the frequency of heterozygotes in a random mating population at equilibrium?

(a) 0.36

(b) 0.16

(d) 0.48.

Answer and Explanation:

90. (d): Hardy-Weinberg equilibrium states that there is balance in the relative numbers of alleles that is maintained within a large population over a period of time assuming that: (i) mating is random; (ii) there is no natural selection; (iii) there is no migration; (iv) there is no mutation. In such 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 (AA, Aa, and aa) can be expressed by the Hardy-Weinberg equation:

Where p2 = frequency of AA (homozygous dominant) individuals, 2pq = frequency of Aa (heterozygous) individuals, and q2 = frequency of aa (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.

91. An important evidence in favour of organic evolution is the occurrence of

(a) homologous and analogous organs

(b) homologous and vestigial organs

(d) homologous organs only

Answer and Explanation:

91. (b): Homologous structures have the same embryonic origin and basic structure, though they may or may not perform the same function. Homologous structures shows that the animal which possess them have common ancestory and show evolution by divergence from the ancestral type. Vestigial organs are those which have ceased to be any use to their possessor but still persist generation after generation in a reduced form. They are retrogressive organs but were well developed and functional in the ancestors.

Homologous organ and vestigial organs provide 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.

In many herbivorous mammals the caecum is as large as the rest of the intestines, and it may even be coiled and longer than the length of the entire organism (as in the koala). In herbivorous mammals, the caecum is essential for digestion of cellulose, a common plant molecule. The caecum houses specialized, symbiotic bacteria that secrete cellulase, an enzyme that digests cellulose. Otherwise cellulose is impossible for mammals to digest.

However, even though humans are herbivorous, the small human caecum does not house cellulose- digesting bacteria, and lost an essential function of cellulose digestion. This shows the close evolutionary relationships between homologous and vestigial organs. The same cannot be said for analogous organ (that have similar functions in different organisms and do not share a common evolutionary origin).

92. Which of the following amino-acids was not found to be synthesized in Millers’s experiment?

(a) alanine

(b) glycine

(d) glutamic acid

Answer and Explanation:

92. (d): Stanley Miller in 1953, who was then a graduate student of Harold Urey at the University of Chicago, demonstrated it clearly that ultra-violet radiation or electrical discharges or heat or a combination of these can produce complex organic compounds from a mixture of methane, ammonia, water (stream of water), ant hydrogen.

Miller 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 In another experiment Miller circulated the mixture of the gases in the same way but he did not pass the electric discharge.

He could not get the significant yield of the organic compounds. Later on many investigators haw synthesized a great variety of organic compound including purines, pyrimidines and simple sugars, etc. is considered that the essential building blocks’ such as nucleotides, amino acids, etc. of living organisms could thus have formed on the primitive earth.

93. Jurassic period of the mesozoic era is characterised by

(a) flowering plants and first dinosaurs appear

(b) gymnosperms are dominant plants and first birds appear

(d) dinosaurs become extinct and angiosperms appear (2006)

Answer and Explanation:

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

94. Praying mantis is a good example of

(a) camouflage

(b) mullerian mimicry

(d) social insects

Answer and Explanation:

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

95. Which one of the following statements is correct?

(a) there is no evidence of the existence of gills during embryogenesis of mammals

(b) all plant and animal cells are totipotent

(d) stem cells are specialized cells.

Answer and Explanation:

95. (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 recapitulation theory which states that ontogeny (developmental history of an individual) repeals phylogeny (development history of races).

96. The concept of chemical evolution is based on

(a) interaction of water, air and clay under intense heat

(b) effect of solar radiation on chemicals

(d) crystallization of chemicals.

Answer and Explanation:

96. (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.

97. The Finches of Galapagos Islands provide evidence in favour of

(a) evolution due to mutation

(b) retrogressive evolution

(d) special creation.

Answer and Explanation:

97. (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.

98. When two species of different genealogy come to resemble each other as a result of adaptation, the phenomenon is termed

(a) microevolution

(b) co-evolution

(d) divergent evolution.

Answer and Explanation:

98. (c): Convergent evolution is the process whereby organisms not closely related, independently evolve similar traits as a result of having to adapt to similar environment or ecological niches. On a molecular level, this can happen due to random mutation unrelated to an adaptive change.

In Cultural Revolution, convergent evolution is the development of similar cultural adaptations to similar environmental conditions by different people switch different ancestral cultures. 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 in structure, but each evolved independently. Some species of the lens of eyes also evolved independently in various animals.

99. Adaptive radiation refers to

(a) evolution of different species from a common ancestor

(b) migration of members of a species to different geographical areas

(d) adaptations due to geographical isolation.

Answer and Explanation:

99. (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.

A good example of this process is the evolution of the Australian marsupials into species adapted as carnivores, herbivores, burrowers, fliers, etc. On a smaller scale, the adaptive radiation of the Galapagos finches provided Darwin with crucial evidence for his theory of evolution.

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