Evolution is a process by which species change their characteristics to accommodate themselves to the ever-changing environment. It depends on natural selection. Here are some important questions from evolutionary biology (class 12 biology) that are crucial for NEET 2023 preparations.
- Which of the following was almost nil in the primitive atmosphere?
(a) Ammonia
(b) Methane
(c) Molecular oxygen
(d) Water Vapour
Answer: (c)
Explanation: If molecular oxygen was present in the primitive atmosphere, it would have oxidised everything. Ammonia, methane, carbon dioxide and water vapour were released in abundance from volcanic eruptions. Any oxygen that was present at that time was found in metal oxides. No free oxygen was found in the atmosphere. Because there was no oxygen in the primitive atmosphere, it was reducing in nature unlike today’s atmosphere which is oxidising in nature.
- The evolution from non-cellular forms to the first simple cellular form of life is termed as
(a) Chemical evolution
(b) Biogenesis
(c) Spontaneous generation
(d) Divergent evolution
Answer: (b)
Explanation: Biogenesis is a biological process that shows the evolution of non-cellular forms into cellular forms. It shows how cells evolved from primitive to complex forms.
3. Miller synthesised simple amino acids from
(a) methane, ammonia, oxygen, nitrogen
(b) hydrogen, methane, ammonia, water
(c) ammonia, methane, carbon dioxide, oxygen
(d) hydrogen, oxygen, water, nitrogen
Answer: (b)
Explanation: Haldane and Oparin proposed a theory that life emerged from pre-existing non-living organic molecules such as RNA and protein. To prove this theory, S.L Miller and Urey performed a simulation experiment in 1953 by building an apparatus called a spark discharge apparatus where he created similar conditions as were present on earth millions of years ago. He took CH4, NH3 and H2 in the ratio of 2:1:2 with water vapour circulating through it.
- Which of the following is/are incorrect with respect to the basic concepts of Lamarckism?
1. Internal vital forces
2. Natural selection
3. Effect of environment and new needs
4. Use and disuse of organs
5. Struggle for existence
(a) 1 and 4 only
(b) 2 and 5 only
(c) 3,4 and 5
(d) 1,2 and 3
Answer: (b)
Explanation: J.B Lamarck, a French naturalist proposed the theory of Lamarckism where he explained the inheritance of acquired characters. He postulated three factors:
- Internal vital forces
- Effect of environment and new needs
- Use and disuse of organs
He showed the example of giraffes, who had to elongate their necks over time in an attempt to feed on leaves of plants. This acquired character was passed onto the next generations.
Natural selection and the struggle for existence are factors that were described by Darwin in the theory of natural selection. This theory stated that overproduction leads to a struggle for existence among organisms. This leads to variations among the organisms. Now, the favourable variations were naturally selected by nature to survive and the less favourable ones perished.
- Darwin, in his “Natural Selection Theory”, neglected the role of which one of the following?
(a) Overproduction
(b) Survival of the fittest
(c) Struggle for existence
(d) Discontinuous variations
Answer: (d)
Explanation: Darwin did not take into consideration discontinuous variations in his natural selection theory. Discontinuous variations are large changes that take place suddenly in an organism. He believed that small continuous variations were an innate property of living organisms.
6. In the case of peppered moths, the black coloured form (Biston carbonaria) became dominant over the light-coloured form (Biston betularia) in England after the industrial revolution. This was the result of
(a) deposition of soot on the moths from atmosphere
(b) natural selection whereby the darker forms were selected
(c) appearance of the black coloured individuals due to poor sunlight
(d) protective mimicry
Answer: (b)
Explanation: In the 1850s (pre-industrialisation era), moths were collected and observed in England. It was seen that white coloured moths were dominant in number over the dark-coloured melanised moths. When similar observations were made in the 1920s (post-industrialisation era), it was seen that the scenario had reversed and dark-coloured moths had become dominant over lighter ones.
This can be explained by the theory of natural selection. Due to industrialisation, lichens that used to form thick white coverings on the tree barks used to camouflage the white moths from predators. But the lichens stopped growing due to pollution and hence lighter moths were mostly preyed upon. In this way, the darker moths were naturally selected by the environment.
- Mutations are _____A_____ while Darwinian variations are _____B______.
(a) A – random and continuous, B – discontinuous
(b) A – minor and directional, B – major and directionless
(c) A – small and directionless, B – random and directional
(d) A – random and directionless, B – small and directional
Answer: (d)
Explanation: Hugo de Vries said that mutations cause evolution and not the minor variations that were described by Darwin. Mutations are random and directionless while Darwinian variations were small and directional.
8. Single step large mutation leading to speciation is termed as ___(i)___ by ____(ii)____.
(a) (i) saltation, (ii) Darwin
(b) (i) saltation, (ii) Hugo de Vries
(c) (i) variation, (ii) Hugo de Vries
(d) (i) natural selection, (ii) Darwin
Answer: (b)
Explanation: Hugo de Vries believed that single, large, random and inheritable mutations in the offspring of an organism can lead to formation of new species in a single generation. He termed this process as saltation.
9. A woman gave birth to a child with a small tail. Which of the following statements is/are correct regarding the child with respect to evolution?
(a) The child shows paleontological evidence of evolution.
(b) The child acts as a connecting link in evolution.
(c) The child shows evidence of evolution by depicting an atavism.
(d) The child shows embryological evidence of evolution.
Answer: (c)
Explanation: Atavism is the phenomenon of sudden appearance of an ancestral trait. This tail will not be functional and can be removed by a simple surgery. Other examples of atavism seen in humans are sharp canines and the ability to move their ear pinna.
10. The eyes of an octopus and a human show different patterns of structure, yet they perform similar functions. This is an example of
(a) Homologous organs that evolved due to divergent evolution.
(b) Analogous organs that have evolved due to convergent evolution.
(c) Analogous organs that have evolved due to divergent evolution.
(d) Homologous organs that have evolved due to convergent evolution.
Answer: (b)
Explanation: Organs that are different structurally but perform similar functions are called analogous organs. These organs evolved as a result of convergent evolution when similar evolutionary pressure resulted in the selection of similar adaptive features in different groups of organisms that perform similar functions.
The eyes of humans and octopuses are very different anatomically. Octopuses do not have a blindspot and the arrangement of nerve fibres and photoreceptor cells is different. This fairly hints that the eyes of both the organisms are different and have evolved separately.
11. Divergent evolution is illustrated by
(a) Wings of insects and birds
(b) Placental mammals and Australian marsupials
(c) Forelimbs of cheetah and wings of bat
(d) Flippers of penguins and dolphins
Answer: (c)
Explanation: When two same structures in the same group of organisms develop in different directions due to different adaptation needs, it is termed as divergent evolution. The structures are known as homologous structures.
12. Which of the following is an example of genetic drift?
(a) Individuals from one population migrate and interbreed with members of a different population.
(b) An allele increases in frequency due to the increase in fitness it provides to the organism.
(c) A massive storm randomly kills many individuals in a population, changing the frequency of alleles in that population.
(d) Occurrence of new genetic combination which is a product of sexual reproduction.
Answer: (c)
Explanation: A sudden change in a population that brings a change in gene frequency is called genetic drift. It can be due to migration or some natural calamity. It is not natural selection that is responsible for changing gene frequency all the time, there are other factors as well, genetic drift being one of them.
13. A living connecting link which provides evidence for organic evolution is _______
(a) Duck-billed platypus between reptiles and mammals.
(b) Sphenodon between reptiles and birds.
(c) Archaeopteryx between reptiles and mammals.
(d) Lungfish between pisces and reptiles.
Answer: (a)
Explanation: Duck-billed platypus are primitive egg laying mammals that are native to eastern Australia. They have mammary glands, hair all over the body, a diaphragm just like mammals and they produce amniotic eggs like reptiles. It is a poisonous organism.
The connecting link between reptiles and birds is Archaeopteryx. Sphenodon is a native of New Zealand that has a highly developed third eye. Lungfishes are connecting links between pisces and amphibians.
14. Archaeopteryx is a transitional fossil between
(a) birds and mammals
(b) mammals and reptiles
(c) reptiles and birds
(d) reptiles and amphibians
Answer: (c)
Explanation: Organisms or fossils that show intermediate characteristics between their ancestral forms and corresponding descendants are known as transitional fossils. Archaeopteryx is considered as a link between reptiles and birds because it showed characters common to both the classes such as toothed beak, winged claws, long tail with many vertebrae and airfoil wings with contour feathers.
15. The Mesozoic era is also called the golden age of the ____________
(a) fishes
(b) reptiles
(c) mammals
(d) both b and c
Answer: (b)
Explanation: The span of Earth’s evolutionary history is divided into eras such as Paleozoic → Mesozoic → Cenozoic eras. The Mesozoic era is also known as the golden age of reptiles. Dinosaurs which were giant reptiles were highly dominant at this time. The Cenozoic era or the current era we are living in, is the age of mammals. The Devonian period of the Paleozoic era was considered as the age of fishes.
16. According to Darwin, the finches of Galapagos Islands provide an evidence in favour of __________
(a) special creation
(b) evolution due to mutation
(c) theory of abiogenesis
(d) adaptive radiation
Answer: (d)
Explanation: Adaptive radiation is the process of evolution of different species in a geographical area from a common ancestor, adapted to new ways and habitats of life. In the Galapagos islands, the finches became geographically separated from each other and hence evolved different beaks and became different insectivorous tree dwelling finches, vegetarian finches, seed eating finches and many more.
Originally, the finches belonged to South America but they reached Galapagos island probably due to some calamity or unknown reasons.
17. A population will not remain in Hardy-Weinberg equilibrium if
(a) the size of the population is large
(b) there are no mutations
(c) there is no gene flow/gene migration
(d) natural selection is operating in the population
Answer: (d)
Explanation: Hardy-Weinberg equilibrium takes into consideration the following factors –
- The population should be very large.
- No mutations should take place in the population.
- No gene migration or gene flow.
- No genetic drift
- No natural selection in the population.
18. In a population, at Hardy-Weinberg equilibrium, the frequency of two alleles studied are 0.6 and 0.4. What will be the genotypic frequency of heterozygotes?
(a) 0.46
(b) 0.80
(c) 0.48
(d) 0.08
Answer: (c)
Explanation: The Hardy-Weinberg equilibrium is represented by the following mathematical expression –
| (p+q)2 = p2 + q2 + 2pq = 1 |
|---|
Here, p2 is frequency of homozygous dominant,
q2 is frequency of homozygous recessive. And
2pq is the frequency of heterozygous dominant.
Now, given p=0.6 and q=0.4
The condition for heterozygotes is 2pq according to above mentioned expression,
Therefore, 2pq = 2*0.6*0.4 = 0.48
19. In stabilising selection
(a) individuals with the mean value of the trait are favoured.
(b) individuals with the extreme value of the trait are favoured.
(c) individuals with the mean value of the trait are eliminated.
(d) individuals with the extreme value of the trait are unaffected.
Answer: (a)
Explanation: The operation of natural selection in such a way that mean values of the trait are favoured is known as stabilising selection. Stabilising selection means eliminating extreme phenotypes and favouring intermediate phenotypes.
- Match column I with column II and select the correct option.
| Column I | Column II |
|---|---|
| i) Dryopithecus | P. Handyman |
| ii) Australopithecines | Q. Ate meat |
| iii) Homo habilis | R. Ate fruits |
| iv) Homo erectus | S. Ape-like primates |
(a) i)-Q, ii)-R, iii)-S, iv)-P
(b) i)-R, ii)-S, iii)-Q, iv)-P
(c) i)-P, ii)-R, iii)-Q, iv)-S
(d) i) S, ii)-R, iii)-P, iv)-Q
Answer: (d)
Explanation: Dryopithecus were the most primitive human ancestors that were ape-like and lived 15 million years ago. Australopithecine were human ancestors living in African grasslands about 2 million years ago and ate fruits. Homo habilis were handymen that mastered the art of making tools from stones. Homo erectus lived 1.5 million years ago and probably ate meat.
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