NEET AIPMT Biology Chapter Wise Solutions – Evolution
1. The wings of a bird and the wings of an insect are
(a) phylogenetic structures and represent divergent evolution
(b) homologous structures and represent convergent evolution
(c) homologous structures and represent divergent evolution
(d) analogous structures and represent convergent evolution. (AIPMT 2015)
2. Industrial melanism is an example of
(d) natural selection. (AIPMT 2015)
3. A population will not exist in Hardy-Weinberg equilibrium if
(a) there is no migration
(b) the population is large
(c) individuals mate selectively
(d) there are no mutations. (AIPMT 2015, Cancelled)
4. Which is the most common mechanism of genetic variation in the population of a sexually reproducing organism?
(a) Genetic drift
(d) Chromosomal aberrations (AIPMT 2015, Cancelled)
5. Which of the following had the smallest brain capacity?
(a) Homo neanderthalensis
(b) Homo habilis
(c) Homo erectus
(d) Homo sapiens (AIPMT 2015, Cancelled)
6. In a population of 1000 individuals 360 belong to genotype AA, 480 to Aa and the remaining 160 to aa. Based on this data, the frequency of allele A in the population is
(d) 0.7 (AIPMT 2014)
7. Forelimbs of cat, lizard used in walking; forelimbs of whale used in swimming and forelimbs of bats used in flying are an example of
(a) analogous organs
(b) adaptive radiation
(c) homologous organs
(d) convergent evolution. (AIPMT 2014)
8. Which one of the following are analogous structures?
(a) Wings of bat and wings of pigeon
(b) Gills of prawn and lungs of man
(c) Thorns of Bougainvillea and tendrils of Cucurbita
(d) Flippers of dolphin and legs of horse (AIPMT 2014)
9. According to Darwin, the organic evolution is due to
(a) competition within closely related species
(b) reduced feeding efficiency in one species due to the presence of interfering species
(c) intraspecific competition
(d) interspecific competition. (NEET 2013)
10. The tendency of population to remain in genetic equilibrium may be disturbed by
(a) lack of mutations
(b) lack of random mating
(c) random mating
(d) lack of migration. (NEET 2013)
11. Variation in gene frequencies within populations can occur by chance rather than by natural selection. This is referred to as
(a) random mating
(b) genetic load
(c) genetic flow
(d) genetic drift (NEET 2013)
12. The process by which organisms with different evolutionary history evolve similar phenotypic adaptations in response to a common environmental challenge is called
(a) non-random evolution
(b) adaptive radiation
(c) natural selection
(d) convergent evolution. (NEET 2013)
13. The eye of octopus and eye of cat show different patterns of structure yet they perform similar function. This is an example of
(a) analogous organs that have evolved due to convergent evolution.
(b) analogous organs that have evolved due to divergent evolution.
(c) homologous organs that have evolved due to convergent evolution.
(d) homologous organs that have evolved due to divergent evolution. (NEET 2013)
14. Random unidirectional change in allele frequencies that occurs by chance in all populations and especially in small populations is known as
(b) natural selection
(c) genetic drift
(d) mutation. (Karnataka NEET 2013)
15. Genetic variation in a population arises due to
(a) recombination only
(b) mutation as well as recombination
(c) reproductive isolation and selection
(d) mutations only. (Karnataka NEET 2013)
16. Dinosaurs dominated the world in which of the following geological eras?
(d) Devonian (Karnataka NEET 2013)
17. The finch species of Galapagos islands are grouped according to their food sources. Which of the following is not a finch food?
(c) Tree buds
(d) Seeds (Karnataka NEET 2013)
18. Evolution of different species in a given area starting from a point and spreading to other geographical areas is known as
(a) adaptive radiation
(b) natural selection
(d) divergent evolution. (Prelims 2012)
19. Which one of the following options gives one correct example each of convergent evolution and divergent evolution?
20. What was the most significant trend in the evolution of modem man (Homo sapiens) from his ancestors?
(a) Shortening of jaws
(b) Binocular vision
(c) Increasing cranial capacity
(d) Upright posture. (Prelims 2012, 2011)
21. The extinct human who lived 1,00,000 to 40,000 years ago, in Europe, Asia and parts of Africa, with short stature, heavy eye brows, retreating fore heads, large jaws with heavy teeth, stocky bodies, a lumbering gait and stooped posture was
(a) Homo habilis
(b) Neanderthal human
(c) Cro-magnon human
(d) Ramapithecus. (Prelims 2012)
22. The idea of mutations was brought forth by
(a) Hugo de Vries who worked on evening primrose
(b) Gregor Mendel who worked on Pisum sativum
(c) Hardy Weinberg who worked on allele frequencies in a population
(d) Charles Darwin who observed a wide variety of organisms during sea voyage. (Mains 2012)
23. Darwin’s finches are a good example of
(a) industrial melanism
(b) connecting link
(c) adaptive radiation
(d) convergent evolution. (Prelims 2010, 2008)
24. Given below are four statements (A-D) each with one or two blanks. Select the option which correctly fills up the blanks in two statements.
25. The most apparent change during the evolutionary history of Homo sapiens is traced in
(a) loss of body hair
(b) walking upright
(c) shortening of the jaws
(d) remarkable increase in the brain size (Mains 2010)
26. Peripatus is a connecting link between
(a) mollusca and echinodermata
(b) annelida and arthropoda
(c) coelenterata and porifera
(d) ctenophora and platyhelminthes (Prelims 2009)
27. In the case of peppered moth (Biston betularia) the black-coloured form became dominant over the light-coloured form in England during industrial revolution. This is an example of
(a) appearance of the darker coloured individuals due to very poor sunlight
(b) protective mimicry
(c) inheritance of darker colour character acquired due to the darker environment
(d) natural selection whereby the darker forms were selected (Prelims 2009)
28. Which one of the following scientist’s name is correctly matched with the theory put forth by him?
(a) De Vries – Natural selection
(b) Mendel – Theory of Pangenesis
(c) Weismann – Theory of continuity of germplasm
(d) Pasteur – Inheritance of acquired characters (Prelims 2008)
29. Which one of the following is incorrect about the characteristics of protobionts (coacervates and microspheres) as envisaged in the abiogenic origin of life?
(a) they were partially isolated from the surroundings
(b) they could maintain an internal environment
(c) they were able to reproduce
(d) they could separate combinations of molecules from the surroundings. (Prelims 2008)
30. Thom of Bougainvillea and tendril of Cucurbita are examples of
(a) vestigial organs
(b) retrogressive evolution
(c) analogous organs
(d) homologous organs. (Prelims 2008)
31. 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
(c) ontogeny repeats phylogeny
(d) stem cells are specialized cells. (2007)
32. 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
(c) possible origin of life by combination of chemicals under suitable environmental conditions .
(d) crystallization of chemicals. (2007)
33. The Finches of Galapagos islands provide an evidence in favour of
(a) evolution due to mutation
(b) retrogressive evolution
(c) biogeographical evolution
(d) special creation. (2007)
34. When two species of different genealogy come to resemble each other as a result of adaptation, the phenomenon is termed
(c) convergent evolution
(d) divergent evolution. (2007)
35. Adaptive radiation refers to
(a) evolution of different species from a common ancestor
(b) migration of members of a species to different geographical areas
(c) power of adaptation in an individual to a variety of environments
(d) adaptations due to geographical isolation. (2007)
36. An important evidence in favour of organic evolution is the occurrence of
(a) homologous and analogous organs
(b) homologous and vestigial organs
(c) analogous and vestigial organs
(d) homologous organs only (2006)
37. Which of the following amino-acids was not found to be synthesized in Millers’s experiment?
(c) aspartic acid
(d) glutamic acid (2006)
38. 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
(c) radiation of reptiles and origin of mammal like reptiles
(d) dinosaurs become extinct and angiosperms appear (2006)
39. Praying mantis is a good example of
(b) mullerian mimicry
(c) warning colouration
(d) social insects (2006)
40. 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
(c) microbes appeared from unsterilized organic matter
(d) meat was not spoiled, when heated and kept sealed in a vessel. (2005)
41. De Vries gave his mutation theory on organic evolution while working on
(a) Pisum sativum
(b) Drosophila melanogaster
(c) Oenothera lamarckiana
(d) Althea rosea. (2005)
42. There are two opposing views about origin of modem man. According to one view Homo erectus in Asia were the ancestors of modem man. A study of variation of DNA however suggested African origin of modem 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
(c) similar variation in Africa and Asia
(d) variation only in Asia and no variation in Africa. (2005)
43. 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
(c) prevalence of pesticide resistant insects
(d) development of organs from ‘stem cells’ for organ transplantation. (2005)
44. Which of the following is the relatively most accurate method for dating of fossils?
(a) radio-carbon method
(b) potassium-argon method
(c) electron-spin resonance method
(d) uranium-lead method. (2005)
45. 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?
(d) 0.48. (2005)
46. Which of the following is not tme for a species?
(a) members of a species can interbreed
(b) gene flow does not occur between the populations of a species
(c) each species is reproductively isolated from every other species
(d) variations occur among members of a species. (2005)
47. 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
(c) electron spin resonance (ESR) and fossil DNA
(d) study of carbohydrates / proteins in rocks. (2004)
48. 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
(c) evidence from fossil remains, and the fossil mitochondrial DNA alone
(d) evidence from DNA extracted from sex chromosomes, autosomes. (2004)
49. Which one of the following is a living fossil?
(d) Spirogyra. (2004)
50. According to Oparin, which one of the following was not present in the primitive atmosphere of the earth?
(d) water vapour. (2004)
51. Diversification in plant life appeared
(a) due to long periods of evolutionary changes
(b) due to abrupt mutations
(c) suddenly on earth
(d) by seed dispersal. (2004)
52. Convergent evolution is illustrated by
(a) rat and dog
(b) bacterium and protozoan
(c) starfish and cuttle fish
(d) dogfish and whale (2003)
53. 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
(c) overproduction, constancy of population size, variations, natural selection
(d) variations, natural selection, overproduction, constancy of population size (2003)
54. Random genetic drift in a population probably results from
(a) highly genetically variable individuals
(b) interbreeding within this population
(c) constant low mutation rate
(d) large population size (2003)
55. Industrial melanism is an example of
(a) drug resistance
(b) darkening of skin due to smoke from industries
(c) protective resemblance with the surroundings
(d) defensive adaptation of skin against ultraviolet radiations (2003)
56. In a random mating population in equilibrium, which one of the following brings about a change in gene frequency in a non-directional manner ?
(b) random drift
(d) migration (2003)
57. 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
(c) struggle for existence
(d) discontinuous variations (2003)
58. 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
(c) organs that have no function now,but had an important function in ancestor
(d) organs appearing only in embryonic stage and disappearing later in the adult (2003)
59. Which one of the following is categorised under living fossils ?
(a) Pin us
(d) Metasequoia (2003)
60. Cause of mimicry is
(d) both (b) and (c) (2002)
61. Which of the following is most important for speciation ?
(a) seasonal isolation
(b) reproductive isolation
(c) behavioural isolation
(d) tropical isolation. (2002)
62. Which of the following are homologous organs?
(a) wings of birds and locust
(b) wings of birds and pectoral fins of fish
(c) wings of bat and butterfly
(d) legs of frog and cockroach. (2002)
63. Genetic drift operates in
(a) small isolated population
(b) large isolated population
(c) fast reproductive population
(d) slow reproductive population. (2002)
64. There is no life on moon due to the absence of
(d) temperature. (2002)
65. According to fossils discovered up to present time origin and evolution of man started from
(d) China. (2002)
66. In which condition, the gene ratio remains constant for any species population ?
(a) sexual selection
(b) random mating
(d) gene flow. (2002)
67. Sequence of which of the following is used to know the phylogeny?
(d) DNA. (2002)
68. In which era reptiles were dominant ?
(a) coenozoic era
(b) mesozoic era
(c) palaeozoic era
(d) archaeozoic era. (2002)
69. Which statement is correct about centre of origin of plant
(a) more diversity in improved variety
(b) frequency of dominant gene is more
(c) climatic condition more favourable
(d) none of the above. (2001)
70. Half life period of C14 is
(a) 500 years
(b) 5000 years
(c) 50 years
(d) 5 x 104 years. (2001)
71. Most abundant organic compound on earth is
(d) steroids. (2001)
72. Similarities in organism with different genotype indicates
(c) convergent evolution
(d) divergent evolution. (2001)
73. Reason of diversity in living being is
(b) long term evolutionary change
(c) gradual change
(d) short term evolutionary change. (2001)
74. Which of the following is closest relative of man
(d) gibbon. (2001)
75. 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
(c) Peking man, Heidelberg man, Neanderthal man, Cromagnon man
(d) Peking man, Neanderthal man, Homo sapiens, Heidelberg man. (2001)
76. 1st life on earth was
(d) photoautotrophs. (2001)
77. Forthcoming generation are less adaptive than the parental generation due to
(a) natural seleetion
(c) genetic drift
(d) adaptation. (2001)
78. Occurrence of endemic species in South America and Australia is due to
(a) these species has been extinct from other regions
(b) continental separation
(c) there is no terrestrial route to these places
(d) retrogressive evolution. (2001)
79. 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
(c) development of organs is due to will power
(d) there should be some physical basis of inheritance. (2001)
80. Which is not a vestigial organ in man?
(a) third molar
(c) segmental muscles of abdomen
(d) coccyx. (2000)
81. Homo sapiens have evolved in
(d) holocene. (2000)
82. Character which is closely related to human evolution is
(a) disappearance of tail
(b) reduction in size of jaws
(c) binocular vision
(d) flat nails. (2000)
83. Which evidence of evolution is related to Darwin’s finches?
(a) evidences from biogeographical distribution
(b) evidences from comparative anatomy
(c) evidences from embryology
(d) evidences from paleontology. (2000)
84. Who is directly related to man?
(d) orangutan. (2000)
85. 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
(c) synthesis of proteins
(d) none of these. (2000)
86. Phenomenon of ‘Industrial melanism’ demonstrates
(a) geographical isolation
(b) reproductive isolation
(c) natural selection
(d) induced mutation. (1999)
87. Which of the following are homologous organs?
(a) wings of bird and hands of human
(b) nails of human being and claws in animals
(c) wings of bird and wings of insect
(d) wings of bat and wings of cockroach. (1999)
88. 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
(c) Biogenetic law
(d) Hardy-Weinberg law. (1998)
89. The age of the fossil of Dryopithecus on the geological time scale is
(a) 2.5 x 106 years back
(b) 50 x 106years back
(c) 75 x 106 years back
(d) 25 x 106 years back. (1998)
90. Which one of the following statements is correct?
(a) Australopithecus is the real ancestor of modem man
(b) Neanderthal man is the direct ancestor of Homo sapiens
(c) Homo erectus is the ancestor of man
(d) Cro-magnon man s fossil has been found in Ethiopia. (1998)
91. Species occurring in different geographical area are called as
(d) neopatric. (1998)
92. The diversity in the type of beaks of finches adapted to different feeding habits on the Galapagos Islands, as observed by Darwin, provides evidence for
(a) intraspecific competition
(b) interspecific competition
(c) origin of species by natural selection
(d) intraspecific variations. (1998)
93. Genetic drift operates only in
(a) larger populations
(b) Mendelian populations
(c) island populations
(d) smaller populations. (1998)
94. 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
(c) Australopithecus was living in Australia
(d) none of these. (1997)
95. Common origin of man and chimpanzee is best shown by
(a) binocular vision
(b) chromosome number
(c) dental formula
(d) cranial capacity. (1997)
96. Which of the following is a living fossil?
(a) Mirabilis jalapa
(b) Ginkgo biloba
(c) Pin us longifolia
(d) Dalbergia sissoo. (1997)
97. 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
(c) development of characteristics by random mating
(d) replacement of common characteristics in different groups. (1997)
98. 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
(c) Allen’s Law
(d) Bergamann’s Law. (1996)
99. 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
(c) loss of tail
(d) development of opposable thumb. (1996)
100. Which of the following is the direct ancestor of Homo sapiens?
(b) Homosapiens neanderthals
(d) Homosapiens fossilis. (1996)
101. 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
(c) wisdom tooth, coccyx, body hair and ear muscles
(d) wisdom tooth, body hairs, nictitating membrane and vermiform appendix. (1996)
102. Which of the following is an example of ‘living fossils’?
(d) Ginkgo. (1996)
103. 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
(c) NH3 , protein, carbohydrate and nucleic acid
(d) NH3 , water, nucleic acid and protein. (1996)
104. The first domesticated animal by primitive man was
(d) horse. (1996)
105. Which of the following isotopes is most dangerous to Homo sapiens?
(d) iodine-131. (1995)
106. The change of the lighter-coloured variety of peppered moth (Biston betularia) to its darker variety (Biston carbonaria) is due to
(c) genetic isolation
(d) temporal isolation. (1995)
107.The homologous organs are those that show similarity in
(d) size. (1995)
108.Which period is dubbed as the age of prokaryotic microbes?
(d) proterozoic. (1995)
109.The presence of gill slits, in the embryos of all vertebrates, supports the theory of
(c) organic evolution
(d) recapitulation. (1995)
110. Two zoogeographical regions, separated by high mountain ranges, are
(a) Nearctic and Palaearctic
(b) Neotropical and Ethiopian
(c) Oriental and Australian
(d) Palaearctic and Oriental. (1995)
111. 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
(c) loss of tail
(d) increase in the ability to communicate with others and develop community behaviour. (1994)
112. 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
(c) absence of limbs in snakes
(d) presence of webbed toes in aquatic birds. (1994)
113. The earliest fossil form, in the phylogeny of horse, is
(d) Merychippus. (1994)
114. Which of the following is a pair of homologous organs?
(a) pectoral fin of rohu and fore-limb of horse
(b) wings of grasshopper and wings of crow
(c) lungs of rabbit and gills of rohu
(d) wings of bat and wings of butterfly. (1994)
115. The process of mating of individuals, which are more closely related than the average of the population to which they belong, is called
(b) self breeding
(d) hybridization. (1994)
116. Evolutionary convergence is development of
(a) common set of characters in group of different ancestry
(b) dissimilar characters in closely related groups
(c) common set of characters in closely related groups
(d) random mating. (1993)
117. 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
(c) mutation theory is wrong
(d) lamarckism was wrong in inheritance of acquired characters. (1993)
118. Theory of Natural Selection dwells on
(a) role of environment in evolution
(b) natural selection acting on favourable variations
(c) changes in gene complex resulting in heritable variations
(d) none of the above. (1993)
119. Genetic drift is change of
(a) gene frequency in same generation
(b) appearance of recessive genes
(c) gene frequency from one generation to next
(d) none of the above. (1993)
120. The first organisms were
(d) eucaryotes. (1992)
121. Which was absent in the atmosphere at the time of origin of life?
(d) CH4. (1991)
122. Correct order is
(a) palaeozoic —> archaeozoic —> coenozoic
(b) archaeozoic —> palaeozoic —> proterozoic
(c) palaeozoic —> mesozoic —> coenozoic
(d) mesozoic —> archaeozoic —> proterozoic. (1991)
123.Study of fossils is
(d) Organic evolution. (1991)
124. Parallelism is
(a) adaptive divergence
(b) adaptive divergence of widely separated species
(c) adaptive convergence of widely different species
(d) adaptive convergence of closely related groups. (1990)
125. Basic principles of embryonic development were pronounced by
(a) von Baer
(d) Morgan. (1990)
126. Evolution is
(a) progressive development of a race
(b) history and development of race alongwith variations
(c) history of race
(d) development of race. (1989)
127. “Continuity of germplasm” theory was given by
(a) De Vries
(d) Lamarck. (1989)
128. Theory of inheritance of acquired characters was given by
(d) DeVries. (1989)
129. ‘Origin of Species’ was written by
(d) Darwin. (1989)
130. Humming birds and Hawk illustrate
(a) convergent evolution
(c) adaptive radiation
(d) parallel evolution. (1988)
1. (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.
2. (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. This
determines 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.
3. (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.
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.
5. (b) :
The brain capacity gradually increased from early human ancestors to modern man. Homo habilis had 650 – 800cc brain capacity which increased around 900cc in Homo erectus. The Neanderthal man (Homo neanderthalensis) had 1400cc brain capacity which evolved to around 1450cc in Homo sapiens.
According to Hardy Weinberg principle.
p2 + 2pq + q2 = 1; (p + q)2 = 1
(AA) p2 = 360 out of 1000 individual or p2= 0.36
Therefore, p = 0.6.
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.
8. (a & b) :
The organs which have similar functions but are different in their structural details and origin are 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.
9. (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.
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.
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.
12. (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.
14. (c) :
Refer answer 11.
15. (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. 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 i 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.
16. (b) :
Dinosaurs dominated in Jurassic period of jmesozoic era and were extinct by cretaceous period.
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.
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.
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.
20. (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 modem man it is about 1450 cc compared to 500 cc in Australopithecus. Increased cranial capacity accommodates larger brain and forms the basis of social, cultural and educational evolution of modem man.
22. (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 y/as later on found that the mutations observed by Hugo de Vries were actually chromosomal aberrations.
23. (c) :
Refer answer 17.
The most apparent change during evolutionary history of modem 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 modem man also displayed the gradual increase in cranial size. The neanderthal man had 1400 cc brain capacity which evolved to around 1450 c.c. (1300 – 1600 c.c.) in living modem man (Homo sapiens sapiens).
26. (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.
27. (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.
28. (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.
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.
30. (d) :
The organs which have the same fundamental structure but are different in function are called homologous organs. Thom of Bougainvillea and tendril of Cucurbita both arises in the axillary position, but have different functions.
Haeckel (1810) proposed that developing animal embryo passes through stages resembling adult forms of its ancestors. Eamst Haeckel (1868, 1874) formulated biogenetic law or recapitulation theory which states that ontogeny (developmental history of an individual) repeats phylogeny (development history of races).
32. (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.
33. (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.
Refer answer 12.
35. (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.
36. (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 an important evidence in fayour 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 can not be said for analogous organ (that have similar functions in different organisms and do not share a common evolutionary origin).
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), and 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 have synthesized a great variety of organic compounds including purines, pyrimidines and simple sugars, etc. It is considered that the essential building blocks’ such as nucleotides, amino acids, etc. of living organisms could thus have formed on the primitive earth.
38. (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.
39. (a) :
Praying mantis shows the phenomenon of camouflage by blending itself into the background. This enables it to elude predators.
40. (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.
41. (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.
43. (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.
44. (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 the method of uptake can be judged, then the approximate age of the tissue can be deduced from the extent of the radiation damage.
45. (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 :
p2 + 2pq + q2 = 1.
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 GH. Hardy and German physician W. Weinberg.
So p = 0.6 and q = 0.4 (given)
2pq (frequency of heterozygote)
= 2 x 0.6 x 0.4 = 0.48
46. (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.
Refer answer 44.
48. (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.
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.
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.
51. (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.
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.
The gist (in brief) of Darwin – Wallace theory is as follows.
- Individuals within species show considerable but continuous variation in the form and physiology.
- This variation arises in a random fashion and is heritable.
- The potential for increase within population of animals and plants is considerable.
- Since resources are limited, so individuals in a population struggle for their own existence.
- 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.
Refer answer 11.
55. (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.
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.
The theory of natural selection is based on the following factors :
- Rapid multiplication and limited food and space which leads to struggle for existence.
- Stmggle for existence and variations which leads to natural selection or survival of the fittest.
- 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.
58. (a) :
Refer answer 36.
Refer answer 49.
60. (b) :
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.
61. (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.
63. (a) :
Refer answer 11.
64. (b) :
Water is the most essential material to survive. One can thrive without O2 (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.
65. (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.
66. (b) :
Allele frequency in a population can remain constant only if individuals of the population randomly interbreed. Generally it never happens in nature and i 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.
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, rRNA are commonly recommended as molecular clocks to the phylogeny.
68. (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.
69. (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.
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 j in the atmosphere. From the amount of 14C in the dead sample, the age of the organism can be determined.
71. (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.
72. (c) :
Refer answer 12.
73. (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.
74. (a) :
Refer answer 48.
75. (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.
76. (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.
Mutation is any hereditary change in the make up of an individual other than Inal which may be caused by the simple recombination of genes. Mutations may occur in any direction.
78. (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.
79. (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.
80. (b) :
The vestigial organs are the useless remnants I 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.
81. (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.
82. (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.
Galapagos Islands are a chain of 14 islands in j 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 Darwin’s 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. The had to change their feeding habits.
Refer answer 48.
85. (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.
86. (c) :
Refer answer 55.
87. (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.
88. (c) :
Haeckel’s biogenetic law states that “Ontogeny repeats phytogeny”. 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.
89. (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 semierect posture. It had large brain, a large muzzle and large canines. It was without browridges. It was arboreal, knuckel-walker and ate soft fruits and leaves. Dryolpithecus africanus is regarded a common ancestor of man and apes (gibons, organgutan, chimpanzee and gorilla).
90. (c) :
Homo erectus is the ancestor of man (not the direct ancestor of modem 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.
91. (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.
92. (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.
Refer answer 11.
94. (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.
95. (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 ofman is 1350 to 1600 cc.
96. (b) :
Refer answer 49.
97. (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).
98. (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.
99. (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 modem 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.
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 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.
101. (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.
102. (d) :
Refer answer 49.
103. (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 acids which gets converted into proteins while hydrogen bases, sugars and phosphates combine to form nucleic acids.
104. (c) :
The first domesticated animal by primitive man was dog. Cro-magnon man used to carry domesticated dogs while going for hunting.
105. (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 (b and g 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.
106. (a) :
Refer answer 55.
107. (c) :
Refer answer 36.
108. (a) :
Pre – cambrian 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.
109. (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.)
110. (d) :
Sclatter in 1857 recognised six zoogeographical regions on the basis of the distribution of terrestrial vertebrates, chiefly mammals.
- The Palaearctic region
- The Ethiopian region
- The Indian region (Oriental)
- The Australian region
- The Neotropical region
- 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 Palaerctic and Oriental regions are separated by Himalayan range.
111. (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 irrelevent change in the evolution of man.
112. (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:
- Internal vital force. All the living things and their component parts are continually increased due to internal vital force.
- 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.
- Use and disuse of Organs. If an organ is constantly used it would be better developed whereas disuse of organ results in its degeneration.
- 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 accomodate their bodies they lost limbs (as snakes have been evolved from lizard like ancestors).
113. (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.
114. (a) :
Refer answer 36.
115. (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.
Refer answer 12.
117. (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 bom.
118. (c) :
Refer answer 57.
Refer answer 11.
Refer answer 76.
122. (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 modem 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 modem life).
123. (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.
124. (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.
126. (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 alongwith variations.
128. (b) :
Refer answer 112.
129. (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.
130. (c) :
Refer answer 17.