Extra Questions for Class 12 Biology Chapter 7 Evolution
Q.1. What is fossil?
Ans. Fossils are the remains or impressions of ancient organisms preserved in sedimentary rocks or other media.
Q.2. Life originated from earth’s inorganic atmosphere in past but not today. Suggest two reason.
Ans. (i) Presence of free oxygen in present day atmosphere.
(ii) Very high temperatures.
Q.3. How do we compute the age of a fossil?
Ans. By radiocarbon dating.
Q.4. When does a species become founders to cause founder effect?
Ans. When the change in the alleles frequency is so different in the new sample of population that they become a different species, the original drifted population becomes founder.
Q.5. Name the scientist who disproved spontaneous generation theory.
Ans. Louis Pasteur disproved the theory of spontaneous generation.
Q.6. What did Louis Pasteur’s experiment on ‘killed yeast’ demonstrate? Name the theory that got disproved on the basis of his experiment.
Ans. Louis Pasteur demonstrated that life comes only from pre-existing life. The theory of spontaneous generation was disproved on the basis of his experiment.
Q. 7. Identity the examples of convergent evolution from the following:
(i) Flippers of penguins and dolphins
(ii) Eyes of octopus and mammals
(iii) Vertebrate brains
Ans. (i) Flippers of penguins and dolphins
(ii) Eyes of octopus and mammals
Q.8. Write the hypothetical proposals put forth by Oparin and Haldane.
OR
State two postulates of Oparin and Haldane with reference to origin of life.
Ans. Oparin and Haldane proposed that life originated from pre-existing non-organic molecules
and the diverse organic molecules were formed from these inorganic constituents by chemical
evolution i.e., formation of life was preceded by chemical evolution.
Q.9. According to Hardy-Weinberg’s principle, the allele frequency of a population remains constant. How do you interpret the change of frequency of alleles in a population?
Ans. Change of frequency of alleles in a population will result in natural selection leading to the
evolution.
Q.10. How can you suggest that biochemistry gives evidence for organic evolution?
Ans. In the same species or group of organisms, similar type of proteins are found, thus supporting organic evolution.
Q.11. Mention one example each from plants and animals exhibiting divergent evolution.
Ans. Thorn of Bougainvillea and tendrils of Cucurbita, forelimbs of whales, bats, cheetah and humans (all mammals)/vertebrate hearts/vertebrates brains. (Any one)
Q.12. Write the names of the following:
(a) A 15 mya primate that was ape-like (b) A 2 mya primate that lived in East African grasslands
Ans. (a) Dryopithecus
(b) Australopithecine/Homo habilis.
Q.13. State the significance of the study of fossils in evolution.
Ans. Fossils represent extinct organisms. They show life forms restricted to certain geological time spans existing in the past. Show ancestry of present day organisms are connecting links between two groups of organisms. (Any one)
Q.14. Identify the examples of homologous structures from the following:
(i) Vertebrate hearts
(ii) Thorns in Bougainvillea and tendrils of Cucurbita.
(iii) Food storage organs in sweet potato and potato.
Ans. (i) Vertebrate hearts
(ii) Thorns in Bougainvillea and tendrils of Cucurbita.
Q.15. “Sweet potato tubers and potato tubers are the result of convergent evolution.” Justify the statement.
Ans. Sweet potato tuber is a modified root whereas potato tuber is a modified stem. These are
anatomically different structures but perform the same function of food storage. Therefore, they
are the result of convergent evolution.
Q.16. 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.
Ans. Natural selection or survival of fittest as nature selected the moths which could match with black surroundings due to soot deposition.
Q.17. 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?
Ans. They are similar in function. Thus we infer that these organs are analogous which has resulted in convergent evolution.
Q.18. Why are analogous structures a result of convergent evolution?
Ans. Analogous structures are not anatomically similar, i.e., they do not have common ancestors and evolve for similar function in the same habitat. Therefore, they are said to be a result of convergent evolution.
Q.19. Rearrange the human activities mentioned below as per the order in which they developed after the modern Homo sapiens came into existence during ice age:
(i) Human settlement
(ii) Prehistoric cave art
(iii) Agriculture
Ans. The order of activities is as follows:
(i) Pre-historic cave art
(ii) Agriculture
(iii) Human Settlement
Q.20. Comment on the similarity between the flippers of dolphins and penguins, with reference to evolution.
Ans. Similarity between the flippers of dolphins and penguins is that they perform similar functions though structurally different. Thus, they are analogous organs. These are the result of convergent evolution.
Q.21. Mention the type of evolution that has brought the similarity as seen in potato tuber and sweet potato.
Ans. Convergent evolution
Q.22. Coelacanth was caught in South Africa. State the significance of discovery of Coelacanth in the evolutionary history of vertebrates.
Ans. Coelacanth evolved as first amphibian (lived on both land and water). It is an ancestor of modern day frogs and salamanders.
Q.23. When we say “survival of the fittest”, does it mean that
(a) those which are fit only survive, or
(b) those that survive are called fit.
Comment.
Ans. Those individuals which survive and reproduce in their respective environment are called fit.
Q.24. 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?
Ans. Wings of a bird and a bat perform the same function of flying despite their structural dissimilarity. This infers that they are analogous organs. It can be inferred that it is of convergent evolution.
Q.25. What does Hardy-Weinberg equation p2 + 2pq + q2 = 1 convey?
Ans. Hardy–Weinberg equation conveys genetic equilibrium, i.e., sum total of all allelic frequencies is 1.
Q.26. What is founder effect?
Ans. Sometimes the change in allele frequency is so different in the new sample of population that they become a different species. The original drifted population becomes founder and the effect is called founder effect.
Q.27. By what Latin name the first hominid was known?
Ans. Homo habilis
Q.28. Among Ramapithecus, Australopithecous and Homo habilis, who probably did not eat meat?
Ans. Homo habilis
Q.29. Name the common ancestor of the great apes and man.
Ans. Dryopithecus/Ramapithecus
Q.30. State the significance of biochemical similarities amongst diverse organism in evolution.
Ans. Biochemical similarities indicate evolution from common or shared ancestry.
Q.31. If the frequency of one allele is ‘p’ and for another, it is ‘q’ for one gene, what will be the formula to calculate allele frequency in future generations according to Hardy–Weinberg genetic equilibrium?
Ans. (p+q)2 = p2 + 2pq + q2 = 1
Q.32. Write the probable differences in eating habits of Homo habilis and Homo erectus.
Ans. Homo habilis did not eat meat. They were vegetarian.
Homo erectus ate meat. They were meat eater.
Q.33. According to de Vries what is saltation?
Ans. According to de Vries, saltation is single step (large) mutation.
Q.34. State the significance of Coelacanth in evolution.
Ans. It is an ancestor of amphibians.