CBSE Class 12 Biology Evolution Question Bank

MULTIPLE CHOICE QUESTIONS

Question. Theory of Pangenesis was given by 
(a) Lamarck
(b) Oparin
(c) Darwin
(d) De Vries
Answer. C

Question. The study of homologous structures in mature organisms provides evidence for the evolutionary relationships among certain groups of organisms. Which field of study includes this evidence of evolution? 
(a) Comparative cytology
(b) Biochemistry
(c) Geology
(d) Comparative anatomy
Answer. D

Question. Darwin’s finches were a good example of 
(a) convergent evolution
(b) adaptive radiation
(c) mutation
(d) none of the above
Answer. B

Question. Wings of pigeon, mosquito and bat show
(a) divergent evolution
(b) atavism
(c) convergent evolution
(d) all of these
Answer. C

Question. Which of the following cannot be explained by Lamarckism? 
(a) Absence of lips in snakes
(b) Long neck of giraffe
(c) Degeneration of visual apparatus in cave dwellers
(d) Dull progeny of noble laureate
Answer. D

Question. Thorn of Bougainvillea and tendril of Cucurbita are example of 
(a) analogous organs
(b) homologous organs
(c) vestigial organs
(d) retrogressive evolution
Answer. B

Question. 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
Answer. C

Question. The diagram represents Miller's experiment.
Choose the correct combination of labelling.

(a) A–electrodes, B– NH₃ + H₂ + H₂O + CH₄,C–cold water, D–vacuum, E–U trap
(b) A–electrodes, B–NH₄ + H₂ + CO₂ + CH₃,C–hot water, D–vacuum, E–U trap
(c) A–electrodes, B–NH₃ + H₂O, C–hot water,D–tap, E–U trap
(d) A–electrodes, B–NH₃ + H₂ + H2H₂O + CH₄,C–steam, D– vacuum, E–U trap
Answer. A

Question. Which of the following was most similar to modern man?
(a) Java man
(b) Neanderthal man
(c) Homo habilis
(d) Cro-Magnon man
Answer. D

ASSERTION REASON QUESTIONS

Direction : These questions consist of two statements, each printed as Assertion and Reason. While answering these questions, you are required to choose any one of the following five responses.
(a) If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.
(b) If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.
(c) If the Assertion is correct but Reason is incorrect.
(d) If both the Assertion and Reason are incorrect.
(e) If the Assertion is incorrect but the Reason is correct.

Question. Assertion: We have lost all the direct evidence of origin of life.
Reason: The persons responsible for protecting evidences were not skilled.
Answer. C

Question. Assertion : Ginkgo biloba is a living fossil.
Reason : Organism which have persisted and remain unchanged for the past several million years while their relatives disappeared. 
Answer. A

Question. Assertion : Among the primates, chimpanzee is the closest relative of the present day humans.
Reason : The banding pattern in the autosome numbers 3 and 6 of man and chimpanzee is remarkably similar.
Answer. A

Question. Assertion : From evolutionary point of view, human gestation period is believed to be shortening.
Reason : One major evolutionary trend in humans has been the larger head undergoing relatively faster growth rate in the foetal stage.
Answer. D

Question. Assertion : Coacervates are believed to be the precursors of life.
Reason : Coacervates were self-duplicating aggregates of proteins surrounded by lipid molecules. 
Answer. D

Question. Assertion : Human ancestors never used their tails and so the tail expressing gene has disappeared in them.
Reason : Lamarck's theory of evolution is popularly called theory of continuity of germ plasm. 
Answer. C

Question. Assertion : Comparative biochemistry provides a strong evidence in favour of common ancestory of living beings.
Reason : Genetic code is universal. 
Answer. B

Question. Assertion : Darwin's finches show a variety of beaks suited for eating large seeds, flying insects and cactus seeds.
Reason : Ancestral seed-eating stock of Darwin's finches radiated out from South American mainland to different geographical areas of the Galapagos Islands, where they found competitor-free new habitats.
Answer. A

Question. Assertion : The earliest organisms that appeared on the earth were non-green and presumably anaerobes.
Reason : The first autotrophic organisms were the chemoautotrophs that never released oxygen. 
Answer. B

Question. Assertion : The earliest fossil form in the phylogeny of horse is eohippus.
Reason : Eohippus lived during the early pliocene epoch.
Answer. C

Question. Write the hypothetical proposals put forth by Oparin and Haldane.
Answer. Hypothetical proposals given by Oparin and Haldane :
(i) Life originated spontaneously from pre-existing non-living organic molecules.
(ii) Formation of life was preceded by chemical evolution.

Question. Name the scientist who disproved spontaneous generation theory.
Answer. Louis Pasteur disproved spontaneous generation theory and proved biogenesis.

Question. What was proposed by Oparin and Haldane on origin of life? How did S.L. Miller’s experiment support their proposal?
Answer. Oparin of Russia and Haldane of England proposed that the first form of life could have originated from pre-existing non-living organic molecules (e.g. RNA, protein, etc.) and that formation of life was preceded by chemical evolution. i.e., formation of diverse organic molecules from inorganic constituents.
The Oparin-Haldane theory (also called chemical theory or naturalistic theory) was experimentally supported by Stanley Miller. Miller created laboratory conditions similar to primitive earth. Miller used mixture of methane, ammonia, hydrogen and water in an air tight apparatus and passed electrical discharged from electrodes at 800 °C. He passed the mixture through a condenser. He circulated the gases in same way for about a week and then analysed the contents. Formation of simple organic compounds supported chemical evolution of life.

Question. Mention the contribution of S.L. Miller’s experiment on origin of life. 
Answer. Miller’s experiment supported chemical evolution of life. He experimentally showed formation of complex organic molecules from simple inorganic compounds. In a closed flask, he circulated mixture of four gases (H₂, CH₄, NH₄ and water vapour) and passed electric current through it at 800°C. Formation of some amino acids, proved that organic compounds were basis of life.

Question. Write the Oparin and Haldane’s hypothesis about the origin of life on Earth. How does meteorite analysis favour this hypothesis?
Answer. 
Oparin and Haldane proposed that life originates from pre-existing non-living organic molecules, such as RNA, proteins etc. and formation of life was preceded by chemical evolution. Meteroite analysis confirmed presence of similar compounds elsewhere in space, maintaining that, life had reached earth in form of spores from other heavenly bodies.

Question. (a) Explain the theory of biogenesis.
(b) How did Miller demonstrate experimentally the chemical evolution that happened three billion years ago? 
Answer. (a) Louis Pasteur disapproved abiogenesis (spontaneous generation) and put forth the Theory of biogenesis, which states that life originated from pre-existing life. He took broth in a long necked flask and then he bent its neck (swan neck). He boiled the broth in this flask to kill any microorganisms that might be present in it. This flask was kept for months but, no life appeared, as the germ laden dust particles in the air were trapped by the curved neck of the flask that served as filter. If the swan neck was broken off, the broth developed colonies of moulds and bacteria. Thus, he showed that the source of the microorganisms for fermentation or putrefaction was the air and the organisms did not arise from the nutrient media.
(b) Stanley Miller (1953), designed an apparatus for simulating conditions prevalent on earth at the time of abiogenic evolution of organic substances. The apparatus had a spark chamber with two electrodes (for simulation of lightning), a flask for boiling (simulation for evaporation and circulation) and a condenser. A control apparatus was also prepared but without electrodes in the spark chamber. Miller used a mixture of methane, ammonia, hydrogen and water in this apparatus. The mixture was exposed to electric discharges, followed by condensation. It was continued for one week. The experiment was repeated a number of times. The products were extracted and identified through chromatography. He found a large number of simple organic compounds including some amino acids such as alanine, glycine and aspartic aid. Miller proved that organic compounds were basis of life and organic compounds were formed from simple inorganic compounds.

Question. How does ‘fitness’ of a population help in evolution?
Answer. The fittest organisms, i.e., the organism with beneficial variations, survives and adapts to ever changing harsh environmental condition. Therefore, fit bettter in an environment, produce more progeny and therefore will survive and hence are selected by the nature.

Question. State a reason for the increased population of dark coloured moths coinciding with the loss of lichens (on tree barks) during industrialisation period in England.
Answer. During industrialisation period in England, in the industrial areas, sulphur dioxide pollution from the burning of coal killed the lichens growing on the trees, exposing the darker bark which was further darkened by falling smoke particles. So, white moths were selectively picked up by birds and black moths escaped unnoticed and managed to survive resulting in more population of black moth than white moth.

Question. Why are analogous structures a result of convergent evolution?
Answer. Analogous organs are a result of convergent evolution. Convergent evolution is development of similar adaptive functional structures in unrelated group of organisms. e.g., wings of an insect and wings of bird show convergent evolution, both have similar function but different basic structure.

Question. Identify the examples of convergent evolution from the following :
(a) Flippers of penguins and dolphins
(b) Eyes of octopus and mammals
(c) Vertebrate brains 
Answer. (a) Flippers of penguins and dolphins and (b) eyes of octopus and mammals are analogous organs showing convergent evolution

Question. “Sweet potato tubers and potato tubers are the result of convergent evolution.” Justify the statement. 
Answer. Sweet potato tubers (root modification) and potato tubers (stem modification) shows convergent evolution as both have different structure but perform similar function of storing food. Thus, these structures are analogous.

Question. Identify the examples of homologous structures from the following.
(a) Vertebrate hearts
(b) Thorns in Bougainvillea and tendrils of Cucurbita.
(c) Food storage organs in sweet potato and potato. 
Answer. (a) Vertebrate hearts and (b) thorns of Bougainvillea and tendrils of Cucurbita are homologous organs, indicating common ancestry.

Question. Write the similarity between the wing of a butterfly and the wing of a bat. What do you infer from the above with reference to evolution?
Answer. Wing of butterfly and wing of bat are analogous organs as they perform similar function of flying but have different origin and structures. Wings of butterfly are composed to chitinous membranes while wings of bat are composed of bony skeleton. This infer that they represent convergent evolution.

Question. State the significance of the study of fossils in evolution. 
Answer. Fossils are remains of organisms of the past buried in different strata of the earth. The study of fossils helps in understanding about the past life.
(i) The fossil records have helped in reconstructing the phylogeny of many organisms e.g., of horse, elephant and man.
(ii) Fossils also indicate the connecting links between two groups of organisms e.g. Archaeopteryx shows features of both reptiles and birds.

Question. State the significance of biochemical similarities amongst diverse organism in evolution.
Answer. Similarities in proteins and genes performing a given function among diverse organisms give clues to common ancestry. Biochemical similarities point to the same shared ancestry as structural similarities among diverse organisms and hence show common ancestry and evolution of different groups of organisms.

Question. Comment on the similarity between the wing of a cockroach and the wing of a bird. What do you infer from the above, with reference to evolution? 
Answer. Wing of a cockroach and wing of bird are analogous organs as they have different basic structure but perform same function, and thus show convergent evolution.

Question. Explain convergent and divergent evolution with the help of one example of each.
Answer. Divergent evolution is development of different functional structures from a common ancestral form. It represents adaptive radiation. Homologous organs show adaptive radiation or divergent evolution E.g., Darwin’s finches of the Galapagos islands. They had common ancestors but now have different types of modified beaks according to their food habits. Convergent evolution is development of similar adaptive functional structures in unrelated groups of organisms. It is called adaptive convergence or convergent evolution. E.g., wings of insect, bird and bat.

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