NEET Biology Biological Evolution And Mechanism Of Evolution MCQs

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NEET Biology Mcqs Biological Evolution And Mechanism Of Evolution

Question 1. The theory of ‘inheritance of acquired characters was given by

  1. Wallace
  2. Lamarck
  3. Darwin
  4. De Vries

Answer: 2. Lamarck

  • One of the first attempts to explain the mechanism of evolution was made by jean baptiste de Lamarck.
  • His theory was the ‘inheritance of acquired characters’. The theory states that the characteristics acquired during a lifetime are passed on to the progeny and then to subsequent generations and new species are produced.

Read And Learn More: NEET Biology Multiple Choice Question And Answers

Question 2. ‘Philosophie zoologique’ book was written by

  1. Wallace
  2. Charles darwin
  3. Lamarck
  4. Hugo de vries

Answer: 3. Lamarck

Lamarck proposed his theory of inheritance in his book, ‘philosophie zoologique

Question 3. Which of the following theories disagreed with Lamarck’s concept of inheritance of acquired characters?

  1. Mendel’s laws of inheritance
  2. Theory of natural selection
  3. Mutational theory
  4. Theory of continuity of germplasm

Choose the correct combination of the given options to complete the given statement.

  1. 1 and 2
  2. 2 and 3
  3. 1 and 4
  4. 3 and 4

Answer: 3. 1 and 4

Mendel’s laws of inheritance and Weismann’s theory of continuity of germplasm (1892) discarded Lamarck’s concept of inheritance of acquired characters.

Question 4. Weismann cut off tails of mice generation after generation but tails neither disappeared nor shortened showing that

  1. Darwin was correct
  2. The tail is an essential organ
  3. Mutation theory is wrong
  4. Lamarckism was wrong in the inheritance of acquired characters

Answer: 4. Lamarckism was wrong in the inheritance of acquired characters

August Weismann tested Lamarck’s theory in 1904 by cutting off the tails of mice for 22 generations yet he failed to observe a tailless mouse.

On the basis of this test, he put forward the theory of ‘continuity of germplasm’. According to him, the characteristics influencing the germ cells (reproductive) are inherited.

Change in somatic cells is not transmitted to the next generations. Thus, the option is correct.

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NEET Biology Biological Evolution And Mechanism Of Evolution MCQs

Question 5. The key point to Lamarck’s view about organic evolution is that every offspring

  1. Is similar to its parents
  2. Inherits characters acquired by the parental generation
  3. Shows struggle for existence
  4. Repeats phylogeny in its ontogeny

Answer: 2. Inherits characters acquired by the parental generation

According to Lamarck’s theory of inheritance of acquired characteristics, the skills or morphological changes acquired by parental generation during their lifetime are inherited or passed on to the next generation of offspring.

Question 6. Germplasm theory against Lamarck’s principle, was given by

  1. Weismann
  2. Darwin
  3. Lamarck
  4. Hugo de Vries

Answer: 1. Weismann

Mendel’s laws of inheritance and Weismann’s theory of continuity of germplasm (1892) discarded Lamarck’s concept of inheritance of acquired characters.

Question 7. Lamarck’s theory was not accepted because of his statement that

  1. An organ develops because of consistent use by an organism in its lifetime
  2. Organs of the body undergo change and thus show variations because of use or disuse
  3. The influence between the organism and its environment is mutual and
    bilateral
  4. Variations acquired in one’s lifetime pass on to and inherited by the next
    generation

Answer: 4. Variations acquired in one’s lifetime pass on to and inherited by the next generation

Lamarck’s theory was not accepted because of his statement that variations acquired in one’s lifetime pass on to and are inherited by the next generation. But this is not true as only genetic changes are inheritable, not somatic changes.

Question 8. Evidence which does not favour this theory of Lamarck is

  1. Presence of webbed toes in aquatic bird
  2. Absence of limbs in snake
  3. Melanisation in the peppered moth
  4. Lack of pigment in cave-dwelling animals

Answer: 3. Melanisation in the peppered moth

Melanisation in peppered moths favoured the theory of natural selection (not the theory of Lamarck) given by Charles Darwin

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Question 9. ………………… Gave the first theory of evolution.

  1. Charles Darwin
  2. Hugo de Vries
  3. Lamarck
  4. Wallace

Answer: 3. Lamarck

Lamarckism is the first theory of evolution, which was proposed by jean baptiste de Lamarck (1744- 1829), a French biologist. Although the outline of the theory was brought to notice in 1801, his famous book philosophie zoologique was published in 1809, in which he discussed his theory in detail

Question 10. Lamarck in his theory of evolution, explained about

  1. Internal vital force
  2. Effect of environment on an organism
  3. Inheritance of acquired characters
  4. Use and disuse of organs

Choose the option containing the correct factors.

  1. 1 and 2
  2. 2 and 3
  3. 1, 2 and 4
  4. 1, 2, 3 and 4

Answer: 4. 1, 2, 3 and 4

All given factors in question are correct. Thus, the option is correct.

Question 11. Lamarck’s explanation for long-necked giraffes was

  1. Stretching of necks over many generations
  2. Short neck suddenly changed into a long one
  3. Natural selection
  4. Mutation

Answer: 1. Stretching of necks over many generations

Lamarck’s explanation for long-necked giraffes was that they stretched their necks over many generations. This can be explained as the ancestors of giraffes with short necks were incapable of reaching the leaves of trees.

The neck of the giraffe lengthens a little by making efforts to reach the leaves. Offspring with longer necks were produced.

Further, the neck of offspring length increased when the lower branches were consumed. Thus, they had to stretch their neck to reach higher branches of trees.
The very long neck of a giraffe was developed after a number of generations

Question 12. Lamarck noted that the leaves of beech trees present on the sunny side had two layers of palisade cells, whereas leaves that were present in the shade had only one layer. He attributed this to

  1. Environmental reactions
  2. Change of habits
  3. Use and disuse
  4. Inheritance of acquired character

Answer: 1. Environmental reactions

Lamarck believed that environmental reactions play an important role in influencing the form of living organisms.

The influence leads to a change in the activity of an organ or structure. For example, the leaves of the beech tree present on the sunny side had two layers of palisade cells, whereas leaves that were present in the shade had only one layer.

Lamarck from such observations assumed that living organisms react to external conditions and become modified.

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Question 13. Lamarckism fails to explain which of the following phenomenon?

  1. Absence of all four limbs among amphibians
  2. Exceptionally, the long neck of a giraffe
  3. An intellectual having a dull son
  4. Loss of vision in cave-dwelling mammals

Answer: 3. An intellectual having a dull son

Lamarckism failed to explain why an intellectual can have a dull son. Lamarck’s theory was incorrect because he did not know how traits were inherited and that the organism’s behaviour has no effect on inherited characteristics

Question 14. Lamarck’s theory is an evergreen, superstition reported by

  1. C darwin
  2. Cd Darlington
  3. Hugo de Vries
  4. Carson

Answer: 2. Cd Darlington

Lamarckism seems to be able to last indefinitely on the folklore level, but as a serious scientific hypothesis, it has been abandoned. Indeed, as late as 1955 British biologist Cyril Dean Darlington called it an ’evergreen superstition

Question 15. Lamarck’s theory of evolution is also called

  1. Survival of the fittest
  2. Inheritance of acquired characters
  3. Theory of special creation
  4. All of the above

Answer: 2. Inheritance of acquired characters

Lamarck’s theory is the theory of acquired characters. Lamarckism includes the four main factors, i.e. Internal vital force, use and disuse of organs, the effect of environment and new needs and inheritance of acquired characters.

Question 16. Which one of the following scientist’s names are correctly matched with the theory put forth by him?

  1. Weismann – theory of continuity of germplasm
  2. Pasteur– the inheritance of acquired characters
  3. De vries – natural selection
  4. Mendel–theory of pangenesis

Answer: 1. Weismann – theory of continuity of germplasm

Option 1 is a correctly matching pair of scientists and the theory put forth by him.

Rest options are incorrectly matched and can be corrected as Lamarck – Inheritance of acquired characters Darwin – Natural selection Mendel – Laws of inheritance

Question 17. ‘Fitness’ in terms of Darwin’s explanation referred to

  1. Reproductive fitness
  2. Physiological fitness
  3. Spiritual Fitness
  4. Both 1 and 2

Answer: 1. Reproductive fitness

The option is a correctly matched pair of scientists and the theory put forth by him. Rest options are incorrectly matched and can be corrected as Lamarck – inheritance of acquired characters Darwin – natural selection Mendel – laws of inheritance

Question 18. On the voyage of the beagle, Darwin (1809-1882) found that the flora and fauna of temperate south america are most similar to that of

  1. Tropical south america
  2. Australia
  3. Asia
  4. Europe

Answer: 1. Tropical south america

Darwin observed unique species of plants and animals in south america like finches and iguanas.

He noticed that the temperate south american animals closely resembled the tropical south american animals as compared to temperate European animals.

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Question 19. A co-worker of Darwin was

  1. Wallace
  2. Mendel
  3. Bateson
  4. Lamarck

Answer: 1. Wallace

Alfred russel wallace was the co-discoverer with Darwin in the theory of evolution through natural selection

Question 20. Name of the ship in which charles darwin went for his expedition.

  1. Siboga
  2. Beagle
  3. Seagull
  4. Atlantic

Answer: 2. Beagle

In 1831, Darwin got an opportunity to travel by his beagle for a voyage of world exploration, planned by the British Admiralty. The voyage lasted for five years.

Question 21. Which of the following pieces of evidence is in favour of Darwin

  1. Struggle for existence
  2. Entomophily
  3. Artificial selection
  4. All of the above

Answer: 4. All of the above

All given evidence is in favour of Darwinism. Thus, the option is correct.

Question 22. According to Darwin, evolution is

  1. A sudden but discontinuous process
  2. A slow, gradual and continuous process
  3. A slow, sudden and discontinuous process
  4. A slow and discontinuous process

Answer: 2. A slow, gradual and continuous process

Darwin believed that evolution is a slow, gradual and continuous process which occurs due to the variations of the answers that get accumulated and are heritable.

Question 23. Malay archipelago stands for

  1. A group of islands visited by Wallace
  2. A research paper on evolution written by Wallace
  3. A research paper on ecology written by Wallace
  4. A group of organisms studied by Wallace

Answer: 1. A group of islands visited by Wallace

Malay archipelago is an island group in south-east Asia between Australia and the Asian mainland and it separates the Indian and Pacific oceans.

It includes Indonesia, the Philippines and Malaysia. This island was visited by British naturalist Alfred Russel Wallace for his scientific exploration, during the eight years period from 1854 to 1862.

Question 24. Darwinian fitness can be estimated by

  1. The length of survival of different individuals in a population
  2. Number of offspring produced by different individuals in the population
  3. An individual having a large population size
  4. Recovery of species after the mass extinction

Answer: 2. Number of offspring produced by different individuals in a population

Darwinian fitness can be estimated by the number of offspring produced by different individuals in a population.

The organisms which have favourable variations in accordance with the environment have more offspring than the others which do not have variations in accordance with the environment

Question 25. Consider the following statements.

  1. Darwin could not explain genetic variations.
  2. Genetic variations occur due to sexual selection.

Choose the correct option.

  1. Statement 1 is correct, but 2 is incorrect
  2. Statement 1 is incorrect, but 2 is correct
  3. Both statements 1 and 2 are correct
  4. Both statements 1 and 2 are incorrect

Answer: 3. Both statements 1 and 2 are correct.

Darwin could not explain genetic variations which occur as a result of sexual selection. So, sexual selection in Darwin’s theory was the weakest part

Question 26. ‘Origin’ of Species was written by

  1. Oparin
  2. Weismann
  3. Lamarck
  4. Darwin

Answer: 4. Darwin

The book ‘Origin of Species was written by Darwin

Question 27. Darwin’s theory of pangenesis shows similarity with the theory of inheritance of acquired characters then what shall be correct according to it?

  1. Useful organs become strong and developed, while useless organs become extinct. These organs help in the struggle for survival
  2. The size of organs increases with ageing
  3. The development of organs is due to willpower
  4. There should be some physical basis for inheritance

Answer: 4. There should be some physical basis for inheritance

According to both the theories of Darwin, i.e. the theory of pangenesis and the theory of inheritance, ‘something’ is passed from parent to offspring which causes the development of specific characters, i.e. there should be some physical basis of inheritance.

Question 28. Which one of the following sequences was proposed by Darwin and Wallace for organic evolution?

  1. Variations, natural selection, overproduction, constancy of population size
  2. Overproduction, variations, constancy of population size, natural selection
  3. Variations, constancy of population size, overproduction, natural selection
  4. Overproduction, constancy of population size, variations, natural selection

Answer: 2. Overproduction, variations, constancy of population size, natural selection

The sequences proposed by Darwin and Wallace for organic evolution are overproduction, variations, constancy of population size, natural selection

Question 29. The concept that was not included in Charles Darwin’s theory of natural selection was

  1. Survival of the fittest
  2. Punctuated equilibrium
  3. Overproduction of offspring
  4. None of the above

Answer: 2. Punctuated equilibrium

Punctuated equilibrium is a theory that was formulated after Darwin’s theory and it states that the species remains relatively stable for a long period of time and then, due to some natural catastrophe, changes rapidly in a short period of time. So, it was not included in Charles Darwin’s theory of natural selection

Question 30. What has been added by the study of genetics to Darwin’s theory of
organic evolution?

  1. How variations come about
  2. The role of genes and chromosomes in giving rise to variations
  3. How favourable variations improve in quality and quantity through time
  4. All of the above

Answer: 4. All of the above

The study of genetics helped in modifying the Darwin theory of organic evolution.

Genetics helped to identify how variations come about the role of genes and chromosomes in variations and how variations improve the quality and quantity of a species or a population through time.

Question 31. De Vries discarded the principle of

  1. Darwin
  2. Lamarck
  3. Haeckel
  4. Mendel

Answer: 1. Darwin

Hugo de Vries discarded the principle of Darwin. He said that mutations result in speciation.

He also mentioned that mutations are directionless, while Darwin stated that mutations leading to variations are directional

Question 32. Which one of the following was not explained by Darwinism?

  1. Natural selection
  2. Struggle for existence
  3. The arrival of the fittest
  4. Origin of species

Answer: 3. Arrival of the fittest

Darwinism theory explains the survival of the fittest but is unable to explain the arrival of the fittest.

Question 33. Darwinism explains all the following except

  1. Within each species, there are variations
  2. Organisms tend to produce more offspring than can survive
  3. Offspring with better traits that overcome competition are best suited for the environment
  4. Variations are inherited from parents to offspring through genes

Answer: 4. Variations are inherited from parents to offspring through genes

All given options were explained by Darwin except the concept of variation.

In his book, Darwin had not explained how the environment caused different organisms in the same population to vary in their traits or how offspring inherited those variations from their parents.

Question 34. Darwin proposed that new species evolve from ancestral forms by

  1. The gradual accumulation of adaptations to changing environment
  2. The inheritance of acquired adaptation to the environment
  3. The struggle for limited resources
  4. The accumulation of mutations

Answer: 1. The gradual accumulation of adaptations to changing environment

Darwin said that all living beings on earth today are descendants of modifications of earlier species and that natural selection causes evolution to take place.

Thus, natural selection is a creative process which uses variations and mutations as the raw materials from which better-adapted individuals with more chances of survival are obtained, i.e. The gradual accumulation of adaptations occurs due to changing environment.

Question 35. Lederberg replica experiment explains

  1. Lamarck’s theory
  2. Darwin’s theory
  3. Mutation theory
  4. None of the above

Answer: 2. Darwin’s theory

Joshua Lederberg and Esther Lederberg provided experimental evidence of selection (natural selection as used by Darwin) in bacterium, e. Coli.

They demonstrated it by the replica plating technique.

Question 36. According to Darwin, continuous variations are produced by

  1. Genetic recombinations
  2. Mutations
  3. Changes in the gene pool
  4. Adaptations

Answer: 4. Adaptations

According to Darwin, continuous variations are produced by adaptations.

Question 37. By the statement ‘survival of the fittest, Darwin meant that

  1. The strongest of all species survives
  2. The most intelligent of the species survive
  3. The cleverest of the species survives
  4. The most adaptable of the species to changes survives

Answer: 4. The most adaptable of the species to changes survives

By the statement ‘survival of fittest’, Darwin meant that the most adaptable of the species to changes survive.

The organisms which are provided with favourable variations would survive, because they are fittest to face their surroundings, while the unfitted are eliminated.

Question 38. Darwinism does not explain

  1. Progression
  2. The usefulness of all organs
  3. Retrogression
  4. Presence of vestigial organs

Answer: 4. Presence of vestigial organs

Darwinism does not always explain the presence of vestigial organs found in organisms.

Question 39. Variations caused by mutation, as proposed by Hugo de Vries are

  1. Random and directional
  2. Random and directionless
  3. Small and directional
  4. Small and directionless

Answer: 2. Random and directionless

According to Hugo de Vries, mutations are random and directionless. De Vries believed mutation caused speciation and hence, called saltation (single-step large mutation).

Question 40. According to Hugo de Vries, the mechanism of evolution is

  1. Multiple-step mutations
  2. Minor mutations
  3. Phenotypic variations
  4. Saltation

Answer: 4. Saltation

As permutation theory given by Hugo de Vries, evolution is a discontinuous phenomenon or saltatory phenomenon/ saltation

Question 41. Mutation theory explaining organic evolution was proposed by Hugo de
varies. He worked on

  1. Pisum sativum
  2. Drosophila melanogaster
  3. Oenothera lamarckiana
  4. Althea rosea

Answer: 3. Oenothera lamarckiana

Hugo de Vries (1848-1935) worked on evening primrose (Oenothera lamarckiana) and proposed the ‘mutation theory of evolution in 1901

Question 42. Select the examples which favour the mutational theory of evolution.

  1. Ancon sheep
  2. Hornless cattle
  3. Cicer gigas
  4. Navel oranges
  5. Hairless cat
  6. Double toed cat

Choose the option containing the correct examples.

  1. 1, 2 And 3
  2. 3, 4 And 5
  3. 4, 5 And 6
  4. 1, 2, 3, 4, 5 And 6

Answer: 4. 1, 2, 3, 4, 5 And 6

All given examples favour the mutational theory of evolution. Examples of the mutational theory are as follows

Ancon sheep- it is a short-legged variety that appeared suddenly in Massachusetts in 1791. Hornless cattle -they developed from the horned cattle in 1889.

Single mutation- it can give rise to many varieties even in the species of plants, e.g. Apple, cicer gigas, navel orange.

Hairless cats and double-toed cats–are also the examples of mutational theory of evolution because they originated in a single step and not continuously like natural selection.

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Question 43. Assertion mutations are important for the survival of a species. Reason (r) A living species that would suppress the mutation process might gain a temporary advantage in an unchanged environment.

  1. Both a and r are true and r is the correct explanation of a
  2. Both a and r are true, but r is not the correct explanation of a
  3. A is true, but r is false
  4. Both a and r are false

Answer: 2. Both a and r are true, but r is not the correct explanation of a

Both a and r are true but r is not the correct explanation of a. Mutations are important for the survival of a species as they might help to incorporate beneficial changes and eliminate harmful genes from the gene pool.

By suppressing the event of mutation, an existing species might gain a temporary advantage in an unchanged environment.

Question 44. Evolution is not continuous. It is jerky and a discontinuous process. This is a characteristic of

  1. Natural selection theory of evolution
  2. Theory of acquired character
  3. Mutational theory of evolution
  4. Synthetic theory of evolution

Answer: 3. Mutational theory of evolution

Hugo de Vries (1901) put forward the theory of evolution, called mutation theory.

According to this theory, evolution is a jerky process, where new varieties and species are formed by mutations (discontinuous variations) that functions as the raw materials of evolution.

Question 45. ‘The genetic variations appearing among the members of a population
bring about evolution. This statement defines

  1. Mutation theory
  2. Lamarckism
  3. Darwinism
  4. Neo-Darwinism

Answer: 1. Mutation theory

Accumulation of the variations produces new species. Sometimes a new species is produced from a single mutation. (ie. The genetic variations appearing among the members of a population bring about evolution). This statement is a part of the mutation theory.

Question 46. Neo-Darwinism is

  1. Lamarckism and Darwinism
  2. Lamarckism and mutations
  3. Natural selection and mutations only
  4. Darwinism, natural selection and mutations

Answer: 4. Darwinism, natural selection and mutations

Neo-Darwinism theory of evolution represents a synthesis of Charles Darwin’s theory in terms of Darwinism, natural selection and modern population genetics (mutations).

Question 47. According to neo-Darwinism, evolution is due to

  1. Change in gene frequency
  2. Gene flow
  3. Change in the structure of the gene
  4. Change in size of the gene pool

Answer: 2. Gene flow

According to neo-Darwinism theory, the processes that bring about the changes at the genetic level and are responsible for the origin of new species are mutations, recombinations, gene flow, gene exchange, genetic drift and natural selection

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Question 48. Neo-Darwinians were

  1. Hugo de Vries
  2. Weismann
  3. Aristotle
  4. H. Spencer

Choose the correct option.

  1. 1 And 3
  2. 2 And 3
  3. 3 And 4
  4. 1, 2 And 4

Answer: 4. 1, 2 And 4

A few supporters of neo-Darwinism are romanes, Wallace, fisher, Huxley, ford, haldane, sewall wright, ernst haeckel, august weismann, herbert spencer and hugo de vries, etc. Thus, option 4 is correct.

Question 49. The main basis of neo-Darwinism is

  1. Struggle for existence
  2. Variations
  3. Survival of the fittest
  4. Gene theory

Answer: 2. Variations

Darwinism could not explain the origin of adaptive characters. Neo-Darwinism could explain the sources of variability. So, the main basis of neo-Darwinism is variations.

Question 50. Assertion of the establishment of reproductive isolation is an event of biological significance. Reason (r) In the absence of reproductive isolation, species can merge back into a single population.

  1. Both a and r are true and r is the correct explanation of a
  2. Both a and r are true, but r is not the correct explanation of a
  3. A is true, but r is false
  4. Both a and r are false

Answer: 1. Both a and r are true and r is the correct explanation of a.

Reproductive isolation is the absence of interbreeding between members of different species.

This results in the isolation of the gene pool of a section of the population from the rest
and inhibits gene flow (a spread of genes between populations) and thereby, leading to the formation of new species.

Irrespective of rare frequency, all species exhibit a particular range of genetic recombination among the individual which can lead to the merging of individuals of different species.

Thus, reproductive isolation is mandatory to maintain distinct species and its absence can lead to the merging of different species into one.

Question 51. Why is the advent of reproductive isolation important from an evolutionary standpoint?

  1. Organisms comprising two populations of a species can no longer interbreed
  2. It is not important from an evolutionary standpoint
  3. Reproductive isolation increases the mutational rate
  4. Reproductive isolation may slow down the reproduction

Answer: 1. Organisms comprising two populations of a species can no longer interbreed

Reproductive isolation states the condition when two populations of a species can no longer interbreed. As a result, the flow of genetic material stops between them. This leads to the origin of new species or speciation.

Question 52. The phenomenon in which the members of a species do not interbreed with the members of other species or the same species is

  1. Geographical isolation
  2. Habitat Species
  3. Temporal isolation
  4. Reproductive isolation

Answer: 4. Reproductive isolation

Reproductive isolation states the condition when two populations of a species can no longer interbreed. As a result, the flow of genetic material stops between them. This leads to the origin of new species or speciation.

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Question 53. Which of the following is related to reproductive isolation?

  1. Genetic isolation
  2. Temporal isolation
  3. Behavioural isolation
  4. All of the above

Answer: 4. All of the above

There are many different types of biological incompatibilities that can cause a population to be reproductively isolated from another population, thus dividing these populations into two separate species.

These biological properties of organisms that prevent interbreeding are called reproductive isolating mechanisms.

The pre-zygotic reproductive isolating mechanism includes ecological, temporal, behavioural, mechanical, morphological and genetic isolation.

Question 54. Which is the most important in ‘speciation’?

  1. Geographical isolation
  2. Reproductive isolation
  3. Ecological isolation
  4. Ethological isolation

Answer: 2. Reproductive isolation

Reproductive isolation states the condition when two populations of a species can no longer interbreed. As a result, the flow of genetic material stops between them. This leads to the origin of new species or speciation.

Question 55. Assertion hybrid breakdown is an example of reproductive isolation. Reason (r) it increases the biotic potential of a species.

  1. Both a and r are true and r is the correct explanation of a
  2. Both a and r are true, but r is not the correct explanation of a
  3. A is true, but r is false
  4. Both a and r are false

Answer: 3. A is true, but r is false.

The hybrid breakdown is an example of a post-mating isolation mechanism, which is the subtype of reproductive isolation.

It is first generation (1) hybrids, which are viable and fertile, but further hybrid generations may be inviable or sterile. Thus, hybrid breakdown does not increase the biotic potential of a species.

Question 56. An example of reproductive isolation

  1. Archaeopteryx
  2. Dinosaurs
  3. Mule
  4. Bonellia

Answer: 3. Mule

Reproductive isolation can occur either by preventing fertilisation or by the creation of a degenerate or sterile hybrid, such as the case with the mule. A mule is an offspring (hybrid) of a male donkey and a female horse

Question 57. Reproductive isolation between segments of a single population is termed as

  1. Sympatry
  2. Allopatry
  3. Population divergence
  4. Disruptive divergence

Answer: 1. Sympatry

Sympatric species are the related species which are not geographically isolated and which could interbreed, but in practice do not, because of differences in behaviour, breeding season, etc.

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Thus, reproductive isolation between segments of a single population is termed sympatry.

Question 58. Darwin in the ‘theory of natural selection states that

  1. Natural selection acts on favourable variations, which appear among individuals of a species
  2. The environment does not play any role in the evolution
  3. Characters acquired during the life of an individual are inherited by its offspring
  4. Heritable variations arise through changes in the gene complex of a species

Answer: 1. Natural selection acts on favourable variations, which appear among individuals of a species

Darwin in the ‘theory of natural selection’ states that natural selection acts on favourable variations, which appear among individuals of a species.

Question 59. Darwin in his ‘natural selection theory’ did not believe in any role of which one of the following in organic evolution?

  1. Discontinuous variations
  2. Parasites and predators as natural enemies
  3. Survival of the fittest
  4. Struggle for existence

Answer: 1. Discontinuous variations

Darwin in his ‘natural selection theory’ did not believe in the role of discontinuous variations in organic evolution. According to this theory, organic evolution is a continuous process.

Question 60. Arrange the following events of Darwin’s concept of evolution sequentially.

  1. Variations and their inheritance
  2. Natural selection
  3. Survival of fittest
  4. Struggle for existence

Choose the correct option.

  1. 1, 2, 3, 4,
  2. 3, 4, 2, 1,
  3. 1, 4, 3, 2,
  4. 4, 1, 2, 3

Answer: 4. 4, 1, 2, 3

The correct sequence of events in Darwin’s concept of evolution is 4, 1, 2, 3

Question 61. Identify the type of natural selection depicted in the given diagram below.

NEET Biology Biological Evolution And Mechanism Of Evolution MCQs Tabilising Directional Disruptive

Type 1 > type 2 > type 3

Choose the correct option.

  1. Disruptive > directional > stabilising
  2. Directional > disruptive > stabilising
  3. Stabilising > directional > disruptive
  4. Stabilising > disruptive > directional

Answer: 3. Stabilising > directional > disruptive

Option 3 is the correct type of natural selection depicted in the given diagram. Stabilising > directional > disruptive

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Question 62. A feature that is true for the stabilising type of natural selection is

  1. Selection of averaged individual
  2. It is bell-shaped
  3. It reduces variation
  4. All of the above

Answer: 4. All of the above

All given features are true for stabilising the type of natural selection. Thus, option 4 is correct

Question 63. The concept of natural selection was introduced in …………. By ………………

  1. 1859, Charles Darwin
  2. 1839, Jb Lamarck
  3. 1864, Herbert Spencer
  4. 1815, T. Malthus

Answer: 1. 1859, Charles Darwin

‘Theory of natural selection was given by Charles Darwin in 1859

Question 64. Which one of the following phenomena supports Darwin’s concept of natural selection in organic evolution?

  1. Development of transgenic animals
  2. Production of ‘dolly’, the sheep by cloning
  3. Prevalence of pesticide-resistant insects
  4. Development of organs from stem cells for organ transplantation

Answer: 3. Prevalence of pesticide-resistant insects

According to Darwinism, some insects in the original population bear resistance genes. In the presence of pesticides, these individuals are selected by nature and thus, these pesticide-resistant insects prevail in nature.

Question 65. ‘Xx’ is a type of selection process in evolution. It promotes population changes in one particular direction, favours small or large-sized individuals and changes the mean size of the population. Identify ‘xx’.

  1. Stabilising selection
  2. Directional selection
  3. Disruptive selection
  4. None of the above

Answer: 2. Directional selection

In directional selection (progressive selection), the population moves towards one particular direction. It means this type of selection favours small or large-sized individuals and more individuals of that type will be present in the new generation.

The mean size of the population changes accordingly.

Question 66. Assertion natural selection is an outcome of the differences in survival and reproduction among individuals that shows variations in one or more traits. Reason (r) adaptive forms of a given trait tend to become more common. Less adaptive ones become less common or disappear.

  1. Both a and r are true and r is the correct explanation of a
  2. Both a and r are true, but r is not the correct explanation of a
  3. A is true, but r is false
  4. Both a and r are false

Answer: 1. Both a and r are true and r is the correct explanation of a

Both a and r are true and r is the correct explanation of a. Darwin believed that the small and useful variations make some species more adapted to the changing environment than others.

Out of a heterogeneous population, nature selects the best adaptative individuals, while less fit or unfit individuals are rejected because the unfit ones fail to survive and reproduce.

Question 67. Which of the following statements are the objections to Darwin’s theory or natural selection?

  1. The type of variations that provide the raw material for natural selection are generally non-inheritable
  2. It fails to explain the role of discontinuous variation
  3. It fails to explain the possible reasons behind over speciation
  4. All of the above

Answer: 4. All of the above

All given statements are objections to Darwin’s theory of natural selection. Thus, option 4 is correct.

Biology MCQ For NEET With Answers

Question 68. Consider the following statements.

  1. Natural selection is essential for evolution.
  2. Natural selection does not include variations.
  3. The concept of natural selection was given by Hugo de Vries.
  4. The mutation is the sudden inheritable change.
  5. Synthetic theory is also called
  6. Neo- Darwinism theory of evolution.

Choose the option containing incorrect statements.

  1. 1, 2 And 3
  2. 1, 3 And 4
  3. 3, 4 And 5
  4. 2 And 3

Answer: 4. 2 And 3

Statements 2 and 3 are incorrect and can be corrected as the theory of natural selection was given by Charles Darwin. This theory states that the variations which are favourable to the environment and inheritable are the major cause of evolution. Rest statements are correct

Question 69. Birds with average-sized wings survived in severe storms but short-winged birds did not. This is an example of

  1. Stabilising selection
  2. Gene flow
  3. Diversifying selection
  4. Founder effect

Answer: 1. Stabilising selection

Stabilising selection (balancing selection) favours average-sized individuals while eliminating small-sized individuals.

It reduces variation and hence, does not promote evolutionary changes. It maintains the mean value from generation to generation. If we draw a graphical curve of the population, it is bell-shaped

Question 70. Resistance to pesticides, antibiotic resistance in bacteria and sickle cell anaemia are examples of

  1. Inverse mutations
  2. Natural selection
  3. Lethal genes
  4. All of the above

Answer: 2. Natural selection

Antibiotic resistance is a consequence of evolution, Natural selection.

The antibiotic action is an environmental pressure and those bacteria which have a mutation allow them to survive, and reproduce further.

They then pass this trait to their offspring, which will be a fully resistant generation. Similarly, resistance to pesticides and sickle-cell anaemia are examples of natural selection.

Question 71. In formulating the theory of evolution by natural selection, Darwin was greatly influenced by the thought offspring

  1. Hugo de vries
  2. Tr malthus
  3. Lamarck
  4. Ai oparin

Answer: 2. Tr malthus

The theory of natural selection was given by Charles robert darwin. He was influenced by reading the work of British geologist sir charles lyell (1797-1875) and the English political economist Thomas R. Malthus (1766-834).

Malthus recognised that competition between species leads to a struggle for existence. This provided the necessary information to formulate the theory of evolution

Question 72. In a species, the weight of newborns ranges from 2-5 kg. 97% Of the newborn with an average weight between 3-3.3 kg survive whereas 99% of the infants born with a weight from 2-2.5 kg or 4.5-5 kg die. Which type of selection process is taking place?

  1. Directional selection
  2. Stabilising selection
  3. Disruptive selection
  4. Cyclical selection

Answer: 2. Stabilising selection

The given data represent stabilising selection. It eliminates individuals from both ends of a phenotypic distribution hence, maintains the same distribution as an average.

In the given situation, most of the newborns with an average weight of 3-3.3 kg survive. Babies having more or less weight had a low survival rate.

Question 73. The natural selection that preserves existing allelic frequencies is called

  1. Unidirectional
  2. Stabilising
  3. Preserving
  4. Bidirectional

Answer: 2. Stabilising

When more individuals in a population acquire mean character value, the type of natural selection is called stabilising selection.

It preserves existing allelic frequencies and favours the average or normal phenotypes and eliminates the extreme variants’ allelic frequency

Biology MCQ For NEET With Answers

Question 74. Consider the following statements.

  1. Genetic isolation is the key to speciation
  2. In temporal isolation, species breed during different seasons.

Choose the correct option.

  1. Statement 1 is correct, but 2 is incorrect
  2. Statement 1 is incorrect, but 2 is correct
  3. Both statements 1 and 2 are correct
  4. Both statements 1 and 1 are incorrect

Answer: 3. Both statements 1 and 2 are correct

Question 75. The biological concept of species was given by

  1. E Mayer
  2. Darwin
  3. De Vries
  4. Mendel

Answer: 1. E Mayer

The biological concept of species was given by Ernst Mayer

Question 76. One of the important consequences of geographical isolation is cbse

  1. Preventing speciation
  2. Speciation through reproductive isolation
  3. Random creation of new species
  4. No change in the isolated fauna

Answer: 2.  Speciation through reproductive isolation

Speciation takes place, via. reproductive isolation which is the most important consequence of geographical isolation.

The first process in speciation is the formation of geographic barriers between individuals of a population (such as rivers, mountains, etc.)

Due to different adaptability in different environment, the genetic makeup of one individual gets changed

Question 77. The diagram below represents a section of undisturbed layers of sedimentary rock and the location of fossils of closely related species. According to evolutionary theory, which is the most probable assumption about species a, b, c and d?

NEET Biology Biological Evolution And Mechanism Of Evolution MCQs Surface of ground

  1. Species c is more abundant than species a
  2. Species d existed before species b
  3. Species A and b are genetically identical
  4. Species c descended from species a

Answer: 2. Species d existed before species b

Question 78. The role of isolation in evolution is

  1. Differentiation of species
  2. Maintenance of species
  3. Evolutionary divergence
  4. Extermination of species

Answer: 2. Maintenance of species

Isolating mechanisms are intrinsic characteristics of species that reduce or prevent successful reproduction with members of other species viewed genetically, they are characters that act as barriers to the exchange of genes between populations.

Thus, the role of isolation in evolution is the maintenance of species

Biology MCQ For NEET With Answers

Question 79. Assertion the process of speciation occurs in allopatric populations. Reason (r) The sympatric species can arise either due to changes in the chromosome number or due to introgressive hybridisation and polyploidy.

  1. Both a and r are true and r is the correct explanation of a
  2. Both a and r are true, but r is not the correct explanation of a
  3. A is true, but r is false
  4. Both a and r are false

Answer: 2. Both a and r are true, but r is not the correct explanation of a

Both a and r are true, but r is not the correct explanation of a. Reproductive isolation due to geographical isolation from allopatric species.

Genetic drift and natural selection in these two isolated population leads to speciation through allopatry. In contrast, sympatric species are formed due to the instantaneous appearance of mutation, changes in chromosome number, polyploidy, etc.

Due to this, individuals of a population present in the same geographical area are reproductively isolated.

Question 80. Which of the following refers to correct examples (s) of organisms which have evolved due to changes in the environment brought about by anthropogenic action?

  1. Darwin’s finches of Galapagos islands.
  2. Herbicide-resistant weeds.
  3. Drug-resistant eukaryotes.
  4. Man-created breeds of domesticated animals like dogs.

Choose the correct option.

  1. 1 And 2
  2. 2, 3 And 4
  3. Only 4
  4. Only 1

Answer: 2. 2, 3 And 4

Herbicide-resistant weeds, drug-resistant eukaryotes and man-made breeds of domesticated animals are examples of evolution by anthropogenic action. Darwin’s finches are examples of natural selection, adaptive radiation and the founder’s effect.

Question 81. Choose the factors affecting the process of speciation.

  1. Mutation
  2. Recombination
  3. Natural selection
  4. Hybridisation
  5. Genetic drift
  6. Polyploid
  7. Isolation

Choose the option containing the correct factors.

  1. 1, 2, 5, 4 And 6
  2. 2, 3, 4, 5, 6
  3. 2, 3, 4, 5 And 7
  4. 1, 2, 3, 4, 5, 6 And 7

Answer: 4. 1, 2, 3, 4, 5, 6 And 7

All the listed factors affect the process of speciation. Thus, the option is correct. All new species develop from pre-existing species.

The phenomenon of the development of a new species from the pre-existing ones is called speciation

Question 82. When two related populations occupy geographically or spatially separate areas, they are called

  1. Allopatric population
  2. Quantum population
  3. Saltational population
  4. Parapatric population
  5. (E) sympatric population

Answer: 1. Allopatric population

In allopatric speciation, a species separates into two separate groups which are isolated from one another by physical barriers, such as a mountain range or a waterway and makes them impossible to breed with one another.

Each species develops differently, based on the demands of its unique habitat.

Question 83. In the same geographical region, if new species evolve from a single ancestral species then the pattern of speciation is known as

  1. Sympatric speciation
  2. Allopatric speciation
  3. Parapatric speciation
  4. Speciation

Answer: 1. Sympatric speciation

Sympatric speciation is the evolution of a new species from a surviving ancestral species, while both continue to inhabit the same geographic region.

Question 84. Which of the following is the cause of speciation?

  1. Point mutation
  2. Gross mutation
  3. Both 1 and 2
  4. None of the above

Answer: 3. Both 1 and 2

Speciation is the formation of new and distinct species in the course of evolution. It occurs due to both point and gross mutation.

Question 85. A species with several subspecies is called a

  1. Polytypic species
  2. Polytopic species
  3. Super species
  4. Monotypic species

Answer: 1. Polytypic species

A species containing two or more subspecies in the immediately subordinate category is called polytypic species.

Polytopic species are the species occurring in different places as for instance, a subspecies composed of widely separated populations.

Question 86. Overspeciation resulted in the evolution of

  1. Human beings
  2. Birds
  3. Dinosaurs
  4. Amphibians

Answer: 3. Dinosaurs

Dinosaurs evolved into new species with remarkable speed. They evolved rapidly, driven by shifts in the planet’s seas, climates and continents and also the evolution of other dinosaurs and if they did not, they went extinct.

At the end of the Mesozoic era, 66 million years ago, the standing diversity of all the alive dinosaurs, was between 600 and 1,000 species. Thus, over-speciation resulted in the evolution of dinosaurs.

Question 87. The reason for fast speciation in present-day crop plants is due to

  1. Mutation
  2. Isolation
  3. Polyploidy
  4. Sexual reproduction

Answer: 3. Polyploidy

Polyploidy leads to instant speciation by hybridisation and doubling of chromosomes (allopolyploidy).

It has played a very important role in plant evolution. The best example of polyploidy in speciation is the formation of different species of wheat from wild-type diploid (2n = 14) Triticum aegilopoides (wild einkorn)

Question 88. Match the following columns.

NEET Biology Biological Evolution And Mechanism Of Evolution MCQs Question 88 Match the following coloumns

Answer: 2. 1–2, 2–1, 3–4, 4–3

Question 89. Assertion allopatric speciation according to many results due to different variations because of mutations, genetic drift and post-mating and pre-mating reproductive isolation.

  1. Reason (r) these species are never geographically isolated.
  2. Both a and r are true and r is the correct explanation of a
  3. Both a and r are true, but r is not the correct explanation of a
  4. A is true, but r is false
  5. Both a and r are false

Answer: 3. A is true, but r is false

A is true, but r is false. Reason can be corrected as allopatric speciation involves the geographical isolation of a population

Question 90. Assertion sympatric speciation always occurs due to geographical isolations.

  1. Reason (r) is a single population splitting into two due to reproductive isolation.
  2. Both a and r are true and r is the correct explanation of a
  3. Both a and r are true, but r is not the correct explanation of a
  4. A is true, but r is false
  5. A is false, but r is true

Answer: 4. A is false, but r is true

A is false, but r is true. Assertion can be corrected as in sympatric speciation, reproductive isolation and divergence occur without geographical barriers, e.g. By polyploidy.

Question 91. Which of the following is not true for a species?

  1. Members of a species can interbreed
  2. Variations occur among members of a species
  3. Each species is reproductively isolated from every other species
  4. Gene flow does not occur between the populations of a species

Answer: 4. Gene flow does not occur between the populations of a species

Option 2 is not true and can be corrected as gene flow occurs between populations of a species by gene migration, i.e. Migration and immigration. Rest options are true for a species.

Question 92. Which of the following statements is correct for species?

  1. The members of a species occupy the same habitat
  2. They are morphologically similar
  3. They can interbreed among themselves
  4. They cannot interbreed with members of other species

Answer: 4. They cannot interbreed with members of other species

The statement in option 4 is correct for species. New species arise through a process called speciation.

In speciation, an ancestral species splits into two or more descendant species that are genetically different from one another and can no longer interbreed

Question 93. Sympatric speciation arises due to

  1. The non-overlapping population of the same area
  2. Geographical isolation
  3. Overlapping population of the same area
  4. The non-reproductive population of the same area

Answer: 3. Overlapping population of the same area

Sympatric speciation is the evolution of a new species from a surviving ancestral species, while both continue to inhabit the same geographic region.

Question 94. Which is the most important factor for the continuity of a species from an evolutionary point of view?

  1. Replication of genetic material
  2. Formation of gametes
  3. Synthesis of proteins
  4. None of the above

Answer: 1. Replication of genetic material

Replication of genetic material is the most important factor for the continuity of a species from an evolutionary point of view.

When genetic material replicates, only then it could be transferred from one generation to the next, resulting in the continuity of a species. Other options are explained as asexual animals do not produce gametes, while sexual animals do.

So, the formation of gametes is not an important factor in asexual animals through replication of genetic material takes place in both asexual as well as sexual animals.

The synthesis of proteins does not play any role in the continuity of species.

Question 95. The biologist who has been called the ‘Darwin of the 20th century’, was

  1. Linnaeus
  2. Ernst mayr
  3. Diener
  4. Whittaker

Answer: 2. Ernst mayr

Ernst Walter Mayr was an evolutionary biologist of the 20th century. He made major contributions to ornithology, evolutionary theory and the history and philosophy of biology.

He is best known for his work on speciation. He named 26 new species of birds and 38 orchids.

He wrote many books on the history of evolutionary theory such as ‘the growth of biological thought’, (1982), etc. Therefore, he is renowned as the ‘Darwin of the 20th century’

Question 96. In which type of isolation, two species living in different habitats are prevented from interbreeding?

  1. Temporal
  2. Ecological
  3. Behavioural
  4. All of these

Answer: 4. All of these

The field of biology describes ‘isolation’ as a process by which two species that could otherwise produce hybrid offspring are prevented from doing so.

There are five isolation processes that prevent two species from interbreeding, i.e. Ecological, temporal, behavioural, mechanical/ chemical and geographical

Question 97. Speciation cannot occur unless there is ……… Isolation.

  1. Prezygotic
  2. Genetic
  3. Divergent
  4. Convergent

Answer: 2. Genetic

The process of splitting a genetically homogeneous population into two or more populations that undergo differentiation and eventual reproductive isolation is called speciation. So, speciation cannot occur unless there is genetic isolation.

Question 98. Hardy-Weinberg principle is the

  1. Genetic structure of a non-evolving population
  2. Genetic structure of an evolving population
  3. Phenotypic structure of an evolving population
  4. Phenotypic structure of a non-evolving population

Answer: 1. Genetic structure of a non-evolving population

Hardy-Weinberg principle is the genetic structure or allelic frequency of a non-evolving population under stable conditions

Question 99. The spread of genes from one breeding population to another by migration which may result in a change in gene frequency is

  1. Genetic drift
  2. Gene frequency
  3. Gene flow
  4. None of the above

Answer: 3. Gene flow

In population genetics, gene flow (also known as gene migration or allele flow) is the transfer of genetic variation from one population to another by migration.

If the rate of gene flow is high enough, then two populations are considered to have equivalent allele frequencies and therefore, effectively be a single population.

Question 100. The hardy-weinberg principle cannot operate if

  1. The population is very large
  2. Frequent mutations occur in the population
  3. The population has no chance of interacting with other populations
  4. Free interbreeding, occurs among all members of the population

Answer: 2. Frequent mutations occur in the population

The Hardy-Weinberg principle does not operate in a population if frequent mutation occurs in that population.

Question 101. In the hardy-weinberg principle, the expression of allele frequency is represented by

  1. (Q + p) (q –p)
  2. P2 + 2pq + q 2 =1
  3. (P + q) 2 = 1
  4. Both 2 and 3

Answer: 4. Both 2 and 3

  • In hardy-weinberg law,
  • Homozygous dominant alleles = p2
  • Homozygous recessive alleles = q2
  • Heterozygous alleles = 2pq

[Latex]\text { so, }(p+q)^2=p^2+q^2+2 p q=1[/latex]

Question 102. The gene pool of a population tends to remain stable if certain conditions are met. These conditions include large populations, no mutation, no migration and

  1. Random mating
  2. Natural selection
  3. Reduction of predators
  4. Moderate environmental changes

Answer: 1. Random meeting

A gene pool is the sum total of genes in the reproductive gametes of a population. Gene frequencies are conserved from one generation to the other under certain conditions.

Under these conditions, frequencies of genotypes reach an equilibrium after a single generation of random mating. The conditions include the absence of mutations, selection and migration.

Question 103. A population is in hardy-weinberg equilibrium for a gene with only
two alleles. If the gene frequency of an allele ‘a’ is 0.7 then the genotype frequency of aa is

  1. 0.21
  2. 0.42
  3. 0.360
  4. 0.7

Answer: 2.

According to the HardyWeinberg principle,
p + q = 1
Here, p = A
q = a
Allelic frequency of a = 1–0.7 = 0.3
According to the Hardy-Weinberg equation,
p²+2pq+q²=1
Here, the frequency of heterozygous Aais represented as 2 pq.
Thus, Aa = =2 pq 2 × 0.7 × 0.3 = 0.42

Question 104. In the hardy-weinberg equation, the frequency of heterozygous individual is represented by

  1. P2
  2. 2Pq
  3. Pq
  4. Q2

Answer: 2. 2Pq

In the hardy-weinberg equation, the frequency of heterozygous individual is represented by 2 pq

Question 105. Hardy-weinberg law can be used to predict the inheritance of which of the following types?

  1. Autosomal dominant
  2. Autosomal recessive
  3. X-linked dominant
  4. X-linked recessive

Answer: 2. Autosomal recessive

The hardy-weinberg law makes it possible to determine the frequency of different genotypes in a diploid chromosomal complement (i.e. Where two separate copies of a certain gene exist).

In clinical genetics, it is mainly used for determining the frequency of heterozygosity in autosomal recessive heritable disorders when only the disease frequency is known

Question 106. In a population at hardy-weinberg equilibrium, the allele frequency of ‘a’ is 0.3, and the expected frequency of ‘aa’ individuals is

  1. 0.21
  2. 0.42
  3. 0.63
  4. 0.18

Answer: 2. 0.42

According to hardy-weinberg law,

P q+ = 1
A+ a = 1
We have a = 0.3
0.3 + a=1
A = −1 0.3 = 0.7
2Pq=aa=2×0.3×0.7 =0.42

Question 107. Find out the frequency of the ‘b’ allele and heterozygous genotype in a random mating population at equilibrium given that the frequency of the ‘a’ allele is 0.4.

  1. 0.6 and 0.24
  2. 0.6 and 0.96
  3. 0.6 and 0.48
  4. 0.6 and 0.50

Answer: 3. 0.6 and 0.48

In the hardy-weinberg principle,

P + q =1
P²+ 2pq + q² =1

Here, p = a and q = b
allele frequency of b = 1– 0.4 = 0.6
allele frequency of heterozygous is
= 2 × 0.6 × 0.4 = 0.48

Question 108. Hardy-Weinberg law is applicable to

  1. Genetic equilibrium
  2. Small population
  3. Non-random mating
  4. None of the above

Answer: 1. Genetic equilibrium

The hardy-weinberg equilibrium is a principle stating that the genetic variation in a population remains constant from one generation to the next in the absence of disturbing factors. Thus, it is applicable to genetic equilibrium.

Question 109. Which of the following basic processes affect the hardy-weinberg equilibrium?

  1. Mutation and recombination
  2. Gene migration and genetic drift
  3. Natural selection
  4. All of the above

Answer: 4. All of the above

All given basic processes affect the hardy-weinberg equilibrium. These include mutations, natural selection, non-random mating, genetic drift and gene flow.

For instance, recombination mutations disrupt the equilibrium of allele frequencies by introducing new alleles into a population

Question 110. A population containing a gene ‘x’ with two alleles ‘aa’. In Hardy -Weinberg equilibrium for gene ‘x’, if the gene frequency of allele ‘a’ is 0.2 allele frequency of ‘a’ is

  1. 0.2
  2. 0.42
  3. 0.8
  4. 1

Answer: 3. 0.8

Allelic /gene frequency of ‘a’ = 0.2 For, allelic frequency a + a=1 so, allelic frequency of ‘a’ =1 – 0.2 = 0.8

Question 111. Assertion According to hardy-weinberg equilibrium, the frequency of an allele remains the same generation after generation. Reason (r) the only way to bring about a change is by natural selection.

  1. Both a and r are true and r is the correct explanation of a
  2. Both a and r are true, but r is not the correct explanation of a
  3. A is true, but r is false
  4. Both a and r are false

Answer: 3. A is true, but r is false

A is true, but r is false. Reason can be corrected as besides natural selection, many other factors can bring changes in allele frequencies, e.g. Mutations, genetic drift, etc.

Question 112. At a particular locus, the frequency of an 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?

  1. 0.36
  2. 0.16
  3. 0.24
  4. 0.48

Answer: 4. 0.48

In 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 as p2+ 2pq + q 2 =1 where, p = frequency of aa (homozygous dominant) individuals, 2pq = frequency of aa (heterozygous) individuals and q2 = frequency of aa(homozygous recessive) individuals.

So, p = 0.6 and q = 0.4(given) 2pq (frequency of heterozygote) = 2 × 0.6 × 0.4 = 0.48

Question 113. A population exhibiting Hardy-Weinberg equilibrium possesses 25% recessive traits. Then, the frequency of recessive alleles in the gene pool of the same population will be

  1. 0.5
  2. 0.42
  3. 0.3
  4. None of these

Answer: 1. 0.5

Presence of recessive traits,

[Latex]\begin{aligned}
q^2 & =25 \% \\
q & =\sqrt{0.25} \\
q & =0.5
\end{aligned}[/latex]

Question 114. A gene locus has two alleles, i.e. A, a. If the frequency of dominant allele a is 0.4, then what will be the frequency of homozygous dominant, heterozygous and homozygous recessive individuals in the population?

  1. 0.36(aa), 0.48(aa), 0.16(aa)
  2. 0.16(aa), 0.24(aa), 0.36(aa)
  3. 0.16(aa), 0.48(aa), 0.36(aa)
  4. 0.16(aa), 0.36(aa), 0.48(aa)

Answer: 3. 0.16(aa), 0.48(aa), 0.36(aa)

  • Frequency of dominant allele (say) = 0.4
  • Frequency of recessive allele (say q) = 1 – 0.4 = 0.6
  • Frequency of homozygous dominant individuals (aa)= p2= (0.4) 2 = 0.16
  • Frequency of heterozygous individuals (aa) = 2pq = 2(0.4)(0.6) = 0.48
  • Frequency of homozygous recessive individuals (aa)= q2= (0.6) 2 = 0.36

Question 115. Most recent knowledge of Darwinism says that

  1. Mutations add new genes with their alleles in the population
  2. Evolution disturbs the Hardy-Weinberg equilibrium
  3. Relative frequencies of genes do not change in different species
  4. The individual is only the unit of evolution

Answer: 2. Evolution disturbs the Hardy-Weinberg equilibrium

Darwin’s theory of natural selection says that those individuals with heritable traits better suited to the environment will survive.

Hardy-weinberg law predicts how gene frequencies are transmitted from one generation to another under a specific set of assumptions.

These include infinitely large, random mating populations, free from outside evolutionary forces, mutation, migration and natural selection.

Under the listed conditions, the gene frequencies do not change over time. However, evolution disturbs hardy-weinberg law as this law has been stated by considering the genotypic and allelic frequencies as constant from generation to generation.

Question 116. Genetic drift is a change of

  1. Gene frequency in the same generation
  2. Appearance of recessive genes
  3. Gene frequency from one generation to next
  4. None of the above

Answer: 3. Gene frequency from one generation to next

Genetic drift is also known as the Sewall-Wright effect. It refers to the random changes in gene frequencies in a population by chance, either due to intensive inbreeding or the death of a small section of the population by natural calamity. Its effect is more marked in a small isolated population

Question 117. The theory of random genetic drift was proposed by

  1. Sewall wright
  2. Hardy-Weinberg
  3. Mayer
  4. Ra fisher

Answer: 1. Sewall Wright

The theory of random genetic drift was proposed by sewall wright. The term genetic drift (sewall wright effect) refers to the elimination of certain traits when a section of the population migrates or dies of natural calamity.

Question 118. The genetic diversity in a population is most likely to decrease by which factor?

  1. Genetic recombination
  2. Stabilising natural selection
  3. Genetic drift
  4. Both 1 and 2

Answer: 2. Stabilising natural selection

Stabilising natural selection is a condition in which the conditions of natural selection become static.

Due to static conditions, there is no origin of variation. That is why, genetic diversity decreases in the stabilising natural selection.

Question 119. Genetic drift operates in

  1. Small isolated population
  2. Large isolated population
  3. Non-reproductive population
  4. Slow reproductive population

Answer: 1. Small isolated population

Genetic drifts occur only in small isolated populations. Random genetic drift in a population probably results from a small interbreeding population size. Random fluctuation in allele frequencies occurs in interbreeding populations.

The changes in the gene frequencies can be brought about without the existence of any directional force, i.e. Mutation, selection or migration and this change in gene frequency has been called random genetic drift.

Question 120. The phenomenon in which genetic drift gives rise to a new sample of the population is known as

  1. Founder’s effect
  2. Divergent evolution
  3. Both 1 and 2
  4. Stabilising selection

Answer: 1. Founder’s effect

The founder effect is the process by which genetic drift leads to the establishment of a new population that contains a very small number of individuals called founders. Sometimes, they form a new species.

The population in a new settlement may have different genotype frequencies from that of the parent population.

Question 121. Assertion genetic drift refers to a change in allelic frequencies of a gene pool due to chance and occurs both in large and small populations. Reason (r) Small populations suffer more than larger ones due to genetic drift.

  1. Both a and r are true and r is the correct explanation of a
  2. Both a and r are true, but r is not the correct explanation of a
  3. A is true, but r is false
  4. Both a and r are false

Answer: 2. Both a and r are true, but r is not the correct explanation of a

Both a and r are true, but r is not the correct explanation of a Genetic drift that occurs in populations of all sizes but its effects tend to be stronger in small populations.

Low probability random events have much less impact on genetic diversity when the population size is large. However, this impact can be profound in small populations.

Question 122. Consider the following statements.

  1. Cheetah is an example of the bottleneck effect.
  2. The bottleneck effect is when the population is subjected to near extinction by a natural disaster or slaughter by humans.

Choose the correct option.

  1. Statement 1 is correct, but 2 is incorrect
  2. Statement 1 is incorrect, but 2 is correct
  3. Both statements 1 and 2 are correct
  4. Both statements 1 and 2 are incorrect

Answer: 3. Both statements 1 and 2 are correct

Both statements 1 and 2 are correct. A population bottleneck is a sharp reduction in the population size which leads to reduced variations in the gene pool of that population.

Thus, a small population with less genetic diversity may continue to breed but get subjected to near extinction. One such situation is observed in the case of the cheetah population.

Question 123. What is the exact process of organic evolution?

  1. Over reproduction
  2. Discontinuous genetic variations
  3. Inheritance of acquired characters
  4. Continuous genetic variations

Answer: 4. Continuous genetic variations

Organic evolution provided paleontological evidence which was the result of continuous genetic variations.

Question 124. Chromosomal incompatibility leads to

  1. Genetic isolation
  2. Ethological isolation
  3. Mechanical isolation
  4. Temporal isolation

Answer: 1. Genetic isolation

Without genetic isolation in evolution, mating will bring about the exchange of genes between the populations and minimise the differences between them so, they do not diverge.

So, chromosomal incompatibility leads to genetic isolation

Question 125. A mutation is most likely to have a selective advantage in evolution if

  1. It affects dominant genes
  2. It affects recessive genes
  3. It affects whole chromosomes
  4. The environment remains stable

Answer: 2. It affects recessive genes

The mutation is more common when it is present in the dominant condition because the dominant mutant gene can express in both homozygous and heterozygous conditions, while the recessive gene can express only in homozygous conditions.

Thus, recessive genes are often masked due to which mutation in these genes have a selective advantage

Question 126. Mutation can be considered essential for evolution because it

  1. Stops struggle for existence
  2. Produces new variations
  3. Brings balance to an environment
  4. Causes recombination

Answer: 2. Produces new variations

A mutation is a change in dna, the hereditary material of life. So, a change in an organism’s dna can cause changes in all aspects of its life.

Mutations are essential to evolution and they are the raw material of genetic variation.

Without mutation, evolution could not occur. So, mutation can be considered essential for evolution because it produces new variations.

Question 127. Mutations

  1. Take place gradually and in small steps
  2. Are all heritable and give rise to new species
  3. Are subject to natural selection
  4. Are random changes in the base sequence of RNA

Answer: 3. Are subject to natural selection

Mutations are subject to natural selection, as it is expressed in the phenotypes of individuals. Even mutations that have a neutral effect can become advantageous or harmful if the environment changes to select or eliminate them

Question 128. Which are the necessary conditions for modern population genetics or evolution called Hardy-Weinberg law?

  1. Selective mating and a small population
  2. A high mutation rate and random mating
  3. A low mutation rate and a small population
  4. Random mating and a large population

Answer: 4. Random mating and large population

The conditions to maintain the hardy-weinberg equilibrium includes no mutation, no gene flow, infinite population size, random mating and no natural selection.

The hardy- weinberg equilibrium can be disrupted by deviations from any of its five main underlying conditions. So, random mating and a large population are the necessary conditions for modern population genetics or evolution

Question 129. Certain mutations are not eliminated from the gene pool because they are carried by

  1. Homozygous individuals
  2. Recessive homozygous individuals
  3. Heterozygous individuals
  4. Dominant heterozygous individuals

Answer: 3. Heterozygous individuals

Harmful mutation does not get eliminated from the gene pool because most of the harmful mutations are recessive and they are carried in heterozygous conditions in the individual.

If they (mutation) are dominant then they easily get eliminated by the death of an organism.

Question 130. In a gene pool, mutations that are beneficial as well as detrimental to an individual occur. They are irreversible since

  1. Once a mutation occurs no chance of survival of the individual.
  2. They are acquired traits.
  3. They are recessive and carried by heterozygous individuals only.
  4. They show genetic drift.

Choose the option containing incorrect statements.

  1. 1 And 3
  2. 1 And 2
  3. 2 And 4
  4. Only 3

Answer: 4. Only 3

Harmful mutation does not get eliminated from the gene pool because mostly harmful mutations are recessive and carried by heterozygous individuals. Rest all statements are correct.

Question 131. Which of the following statements about mutation are true?

  1. Mutations are the source of new alleles for genes.
  2. Organisms are able to create mutations to meet their specific needs.
  3. Mutations are random events and can happen in any cell at any time.
  4. Most mutations tend to be harmful or have no effect on an organism.

Choose the correct option.

  1. 1, 2 And 3
  2. 1, 4, 3 And 4
  3. 1, 3 And 4
  4. 1 And 3

Answer: 3. 1, 3 And 4

All given statements are true about mutation except statement 2. The incorrect statement can be corrected as mutation occurs by itself. It is a spontaneous phenomenon.

Question 132. Identify the incorrect statement about mutation.

  1. Mutation is predestined
  2. A major source of evaluation
  3. Usually deleterious and recessive
  4. None of the above

Answer: 1. Mutation is predestined

The statement in option 1 is not incorrect and can be corrected mutations are the ultimate source of all genetic variations and without which all the genes could exist in only one form. These are not predestined but spontaneous in nature. Rest statements are true about mutations.

Question 133. Gene flow occurs by

  1. Interbreeding between one population and another
  2. Interbreeding between one population only
  3. Interbreeding between one population to another
  4. Interbreeding between one population only

Answer: 3. Interbreeding between one population to another

Gene flow takes place when one population interbreed with another population and gives rise to new individuals. It also refers to the changes in the alleles of a population’s gene pool. It upsets the hardy-weinberg principle.

Question 134. Hawaiian honeycreepers (birds) are an example of

  1. Genetic drift
  2. Founder effect
  3. Both 1 and 2
  4. Phyletic speciation

Answer: 3. Both 1 and 2

Many ornithologists tout the Hawaiian honeycreepers as the most spectacular avian example of adaptive radiation.

From a single ancestor, this group evolved into more than 50 honeycreeper species, spanning an incredible variety of bill shapes and feeding behaviours. Thus, these are examples of genetic drift and founder effect. Thus, option 3 is correct.

Question 135. Genetic variation arises by

  1. Recombination
  2. Nucleolus
  3. Mutation
  4. Both 1 and 3

Answer: 4. Both 1 and 3

Genetic variation occurs by recombination and mutation. These are heritable variations and these arise due to changes in genetic material.

Only these variations have evolutionary significance. The new combination of alleles produced by crossing over and recombination may prove beneficial and may be proved by natural selection.

Question 136. The process of genetic mutation is

  1. Reversible
  2. Irreversible
  3. Partially reversible
  4. Continuous

Answer: 2. Irreversible

Mutations alter the configuration and position of nucleotides which is an irreversible process except in the case of reverse or back mutation.

Question 137. Which mechanism of evolution affects the genetic makeup of a population?

  1. Natural selection
  2. Adaptation
  3. Genetic drift
  4. Gene mutation

Answer: 4. Gene mutation

Gene mutations refer to changes in gene structure and expression due to addition, deletion, substitution or inversion of nucleotides. The frequency of gene mutations varies from gene to gene.

Mutated genes add new alleles to the gene pool and hence, alter the genetic makeup of a population. The accumulation of many mutations may add up to large-scale changes, which finally lead to the formation of new species.

Question 138. What is not true about mutations?

  1. They spring up suddenly and spontaneously
  2. They are sporadic and random
  3. They are chiefly recessive in nature
  4. They do not breed true

Answer: 4. They do not breed true

Mutations exhibit the characters listed in options 1, and but not 2. Mutations, once occurred, pass on to the next generations without undergoing, immediate changes, i.e. Mutations breed true.

Question 139. In order to determine whether variations of a character in a population were genetically controlled, the most appropriate procedure will be to

  1. Count chromosomes and find out the variations in number in the population
  2. Examine dna and see if the population shows any variation
  3. Measure the variations and see if they are continuous or discontinuous
  4. Cross individuals of both extremes and see if the offspring and parents show a range of variations

Answer: 4. Cross individuals of both extremes and see if the offspring and parents show a range of variations

If the variations are genetic, they are expected to appear in a cross involving different genes, i.e. Cross individuals of both extremes and see if the offspring and parents show the range of variations.

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