NCERT Exemplar Solution Class 12 Biology Chapter 7

NCERT Exemplar Solution Class 12 Biology Chapter 7

NCERT Exemplar Solution Class 12 Biology Chapter 7 Evolution all Questions Answer Solution. NCERT Exemplar Class 12 Biology Chapter 7 Solution PDF.

NCERT Exemplar Solution Class 12 Biology Chapter 7: Overview

NCERT Exemplar Solution Class 12 Biology Chapter 7



Exemplar Problem Solution





Chapter Name


NCERT Exemplar Solution Class 12 Biology Chapter 7 Evolution


1) Which of the following is used as an atmospheric pollution indicator?

a.) Lepidoptera

b.) Lichens

c.) Lycopersicon

d.) Lycopodium

Answer: b. Lichen

2.) The theory of spontaneous generation stated that:

a.) Life arose from living forms only

b.) Life can arise from both living and non-living

c.) Life can arise from non-living things only.

d.) Life arises spontaneously, neither from living nor from theNon-living.

Answer: c.Life can arise from non-living things only.

3.) Animal husbandry and plant breeding programmes are the examples of:

a.) Reverse evolution

b.) Artificial selection

c.) Mutation

d.) Natural selection

Answer: b. Artificial selection.

4.) Palaentological evidences for evolution refer to the:

a.) Development of embryo

b.) Homologous organs

c.) Fossils

d.) Analogous organs.

Answer: c. Fossils

5.) The bones of forelimbs of whale, bat, cheetah and man are similar inStructure, because:

a.) One organism has given rise to another

b.) They share a common ancestor

c.) They perform the same function

d.) The have biochemical similarities

Answer:b. They share a common ancestor.

6.) Analogous organs arise due to:

a.) Divergent evolution

b.) Artificial selection

c.) Genetic drift

d.) Convergent evolution

Answer: d. Convergent evolution.

7.) (p+q)2 = p2 + 2pq + q2 = 1 represents an equation used in:

a.) Population genetics

b.) Mendelian genetics

c.) Biometrics

d.) Molecular genetics

Answer: a. Population genetics.

8.) Appearance of antibiotic-resistant bacteria is an example of:

a.) Adaptive radiation

b.) Transduction

c.) Pre-existing variation in the population

d.) Divergent evolution.

Answer: c. Pre-existing variation in the population

9.) Evolution of life shows that life forms had a trend of moving from:

a.) Land to water

b.) Dryland to wet land

c.) Fresh water to sea water

d.) Water to land

Answer: d. Water to land

10.) Viviparity is considered to be more evolved because:

a.) The young ones are left on their own

b.) The young ones are protected by a thick shell

c.) The young ones are protected inside the mother’s body and areLooked after they are born leading to more chances of survival

d.) The embryo takes a long time to develop

Answer: c.The young ones are protected inside the mother’s body and are Looked after they are born leading to more chances of survival

11.) Fossils are generally found in:

a.) Sedimentary rocks

b.) Igneous rocks

c.) Metamorphic rocks

d.) Any type of rock

Answer: a. Sedimentary rocks.

12.) For the MN-blood group system, the frequencies of M and N alleles are0.7 and 0.3, respectively. The expected frequency of MN-blood groupBearing organisms is likely to be

a.) 42%

b.) 49%

c.) 9%

d.) 58%

Answer: a.42%

13.) Which type of selection explains industrial melanism observed in moth,Bistonbitularia:

a.) Stabilising

b.) Directional

c.) Disruptive

d.) Artificial

Answer: b.Directional.

14.) The most accepted line of descent in human evolution is:

a.) Australopithecus –> Ramapithecus –> Homo sapiens –> Homo habilis

b.) Homo erectus –> Homo habilis –> Homo sapiens

c.) Ramapithecus –> Homo habilis –> Homo erectus –> Homo sapiens

d.) Australopithecus –> Ramapithecus –> Homo erectus –>Homo habilis –> Homo sapiens.

Answer: c. Ramapithecus –> Homo habilis –> Homo erectus –> Homo sapiens

15.) Which of the following is an example for link species?

a.) Lobe fish

b.) Dodo bird

c.) Sea weed

d.) Chimpanzee

Answer: a. Love fish.

16.) Match the scientists listed under column ‘I’ with ideas listed column ‘II’.

Column I. Column II

A.) Darwin i. abiogenesis

B.) Oparin ii. Use and disuse of organs

C.) Lamarck.          iii. Continental drift theory

D.) Mangeriv. Evolution by natural selection

a.) A-I; B-iv; C-ii; D-iii

b.) A-iv; B-I; C-ii; D-iii

c.) A-ii; B-iv; C-iii; D-i

d.) A-iv; B-iii; C-ii; D-i

Answer:b.A-iv; B-I; C-ii; D-iii

17.) In 1953 S. L. Miller created primitive earth conditions in the laboratoryAnd gave experimental evidence for origin of first form of life from pre-Existing non-living organic molecules. The primitive earth conditionsCreated include:

a.) Low temperature, volcanic storms, atmosphere rich in oxygen

b.) Low temperature, volcanic storms, reducing atmosphere

c.) High temperature, volcanic storms, non-reducing atmosphere

d.) High temperature, volcanic storms, reducing atmosphereContaining CH4, NH3 etc.

Answer:d.High temperature, volcanic storms, reducing atmosphere Containing CH4, NH3 etc.

18.) Variations during mutations of meiotic recombinations are:

a.) Random and directionless

b.) Random and directional

c.) Small and directional

d.) Random, small and directional

Answer: a. Random and directionless.


1) What were the characteristics of life forms that had been fossilised?

Answer: Fossils are reamains of the past. The hard tissue cannot decomposed by any microorganisms. So they act as fossils. The fossils of various living beings are not same as in present. The fossils, were too different as compared to present.

2) Did aquatic life forms get fossilised? If, yes where do we come across Such fossils?

Answer: Yes, aquatic life forms , get fossilised ,we come across such as fossils under mountains; because of changes occurs after  a long time in habitat of an organism.

3) What are we referring to? When we say ‘simple organisms’ or ‘complexOrganisms’

Answer: Simple organism can be defined as the organism which have simple morphology, anatomy and functions are called as simple organisms. Complex organism are those which contains complex morphology, anatomy and functions.

4) How do we compute the age of a living tree?

Answer: The age of living tree can be determined  using various parameters such as diameter of trunk height of the tree , and growth factor of tree.

5) Give an example for convergent evolution and identify the features Towards which they are converging.

Answer: Convergent evolution can be defined as when two unrelated species started living in common habitat are called as convergent evolution. Example- wings of insects and birds ; potatoes and sweet potatoes. As wings of insects and birds have different morphology but perform the same function.

6) How do we compute the age of a fossil?

Answer: We can compute age of fossil with the help of radioating. Radioisotope can be used to evaluate the age of fossils. It is significant technique by which are can predict age of fossils.

7) What is the most important pre-condition for adaptive radiation?

Answer: Adaptive radiation in much closer to diversification of life. The organism get migrated to another habitat and became adapted to a particular habitat, based on environmental change.

8.) How do we compute the age of a rock?

Answer: Yes, we can compute the age of rock with the help of technique radioactive isotope half time. The parents to daughter generation, by which the elements life is get halved and age of rock can be determined.

9.) When we talk of functional macromolecules (e.g. proteins as enzymes,Hormones, receptors, antibodies etc), towards what are they evolving?

Answer: Functional macromolecules get evolved from simple to complex process called as progressive evolution. For example- All human being have almost 99.9% similarly in genetic code . All eukaryotes share a common ancestor.

10.) receptorsrtain population, the frequency of three genotypes is as follows: Genotypes: BB Bbbb Frequency: 22% 62% 16%What is the likely frequency of B and b alleles?

Total genotype is 100% that means 200 allels are present. B=106;  b=94



            Genotype               Frequency
                BB              22%
                Bb               62%
                bb                16%
        Total genotype            100%

11.)  Among the five factors that are known to affect Hardy-Weinberg Equilibrium, three factorsare gene flow. Genetic drift and genetic recombination. What are the other two factors?

Answer: Along with three factors such as gene flow, genetic drift and genetic recombination ; the two other factors are mutation is the sudden change in genetic makeup of individual and natural selection in selection by nature of the fit candidate.

12.) What is founder effect?

Answer: Founder effect can be defined as migration of small population of individual from a large population and in this new habitat the organism will interbreed and produce a progeny. It is type of genetic drift.

13.) Who among the Dryopithecus and Ramapithecus was more man-like?

Answer: Dryopithecus was a common ancestor between apes and man but it was more ape-like. Ramapithecus was more man-like.

14.) By what Latin name the first hominid was known?

Answer: .It was Homo-habillis ; having brain capacity 650-800cc.

15.) Among Ramapithecus, Australopithecines and Homo habilis – who Probably did not eat meat?

Answer: Out of the three options Homo habilis did not eat meat.


1) Louis Pasteur’s experiments, if you recall, proved that life can arise fromOnly pre-existing life. Can we correct this as life evolves from pre-existent Life or otherwise we will never answer the question as to how the firstForms of life arose? Comment.

Answer: Yes, obviously we can  correct this statement life aise from pre-existing life. The many theories by scientists concluded that inorganic life and same scientist also frame the theory of abiogenesis.

2) The scientists believe that evolution is gradual. But extinction, part of Evolutionary story, are ‘sudden’ and ‘abrupt’ and also group-specific.Comment whether a natural disaster can be the cause for extinction of Species.

Answer: Yes, a natural disaster can cause extinction of species. That is the older population get extinct and after a very long time new population arises but 100% death is not possible.

3) Why is nascent oxygen supported to be toxic to aerobic life forms?

Answer: Yes, the nescent oxygen is harmful to living beings because of it’s reactive nature.  So; that it can be react with any macromolecules such as DNA ,RNA, protein and can disrupt the structure.

4) While creation and presence of variation is directionless, natural selection Is directional as it is in the context of adaptation. Comment.

Answer: The creation and variation are directionless but natural selection is directional.Because in natural selection, nature selects the fit candidate. It is dependent on differential fitness which includes relative reproduction means reproduction more than other and relative survival means survive more than other so, the fit candidate is selected by nature.

5) The evolutionary story of moths in England during industrialization Reveals, that ‘evolution is apparently reversible’. Clarify this statement.

Answer: The evolutionary story of mother was development on industrial mechanism. Before, 1820, in England . These was no pollution; so on a fig tree grow gray coloured lichen and on this lichen  prepared moth called a Bistonbitularia. Which has two species black and gray on gray coloured lichen black colourspecies were visible therefore it was captured by prey and their number decreased. After 1840; industrial revolution period pollution increased; so Black carbon grow on trunk on tree and gray coloured moths where visible therefore their number decreased.

6) Comment on the statement that “evolution and natural selection are End result or consequence of some other processes but themselves are Not processes”.

Answer: Evolution and natural selection are End result because due to evolution we came to know history of life and due to natural selection fit candidate survived . So these are final/ end process.

7) State and explain any three factors affecting allele frequency in Populations.

Answer: They are mutation , non random mating and gene flow.

1.) Mutation- It is sudden change in allele, gene or chromosome.

2.) Non random mating- Mating with other species partner which produces sterile offspring.

3.) Gene flow- It is the movement of alleles.

8) Gene flow occurs through generations. Gene flow can occur acrossLanguage barriers in humans. If we have a technique of measuring specificAllele frequencies in different population of the world, can we not predictHuman migratory patterns in pre-history and history? Do you agree orDisagree? Provide explanation to your answer.

Answer:  Yes, we agree to this statement that gene flow is present due to migratory habits. Therefore the frequency of allels, changes into population.

9) How do you express the meaning of words like race, breed, cultivars or Variety?

Answer: Race can be defined as classification of human on the basis of geographical area, anatomy and morphology.

Breed- Breed can be termed as a group of animals having similar characristics such as behaviour and appearance. Cultivars as the name of suggest they are selected for a particular propagation.

Variaty- Difference among individuals and species called as variations.

10) 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.

Answer: Yes, both the statement are correct according to struggle of the existence. Nature will select fit candidate and the candidate selected by nature are only surviving.

11) Enumerate three most characteristic criteria for designating a Mendelian Population.

Answer: Criterias are

1.) The population must be large.

2.) Have ability of sexual reproduction .

3.) These should be no migration.

12) “Migration may enhance or blurr the effects of selection”. Comment.

Answer:  The migration that is the movement of population from one space to another.  The migration can be outside the habitat called emigration or within the habitat called immigration . Emigration can be lead to removal of some characters and immigration leads to introduction of new character.


1) Name the law that states that the sum of allelic frequencies in a populationRemains constant. What are the five factors that influence these values?

Answer: According to Hardy and Weinberg, gene and genotype frequencies in a population reamains the same generation  after generation if the population follows following conditions:-

1.) Random mating( no mate choice) ( A can maye with any should no choice)

2.) Large population size  (Panmictimpopulation / Effectively infinite size)  ( as large as which can have random mating)

3.)  No selection pressure.

4.) No genetic drift.( No random death)

5.) No mutation.

6.) No migration.

7.) Biparental mode of reproduction.

So practically this condition is not possible but technologically in human population it is possible.

2) Explain divergent evolution in detail. What is the driving forceBehind it?

Answer: Divergent evolution can be defined as the members of one group get diversified for some reason and now they are called as two different populations. Homologous organs are results of divergent evolution. Homologous organs are those organs which have same origin but different function. For example forelimb of mammals, Thorns in bounganvillea and tendrils in cucumber. It is at type of speciation (formation of new species)  When competition occurs in parental population; the members of a group migrate to different habitat called as divergent evolution.

3) You have studied the story of Pepper moths in England. Had the Industries been removed, what impact could it have on the moth Population? Discuss.

Answer: In 1820, in England industrial melanism story was occurred. The fig tree is present and lichen was grown on the fig tree. The lichen was gray coloured. At such time the population of two insect was more. The name of the insect was Bistonbitularia has two types gray colouredmoth. (Topics form) and black coloured moth (carbonifera form) . Before industrial revolution the number of black coloured moth was decreased due to visualisation on gray lichen. After industrialisation, black colouredcarbon grow on trunk of fig tree and therefore the number of graycoloured moths were decreased.

4) What are the key concepts in the evolution theory of Darwin?


5) Two organisms occupying a particular geographical area (say desert) Show similar adaptive strategies. Taking examples, describe the Phenomenon.

Answer: It is the example of convergent evolution; two members of different groups started living in one habitat called as convergent evolution. It is results to analogous organs. The analogous organs can be defined as having different origin but same in function. For example- Wings of insects and wings of birds.

6) We are told that evolution is a continuing phenomenon for all living Things. Are humans also evolving? Justify your answer.

Answer: Yes, human continue to evolve due to industrialisation or modern habits. Such as wisdom teeth were present in ancestor but not in modern man.The secondly rudimentary tail, next is vermiform appendix, and latest lactose inflorescence because infant did not get mother’s milk regularly, so ability is getting lost day by day.

7) Had Darwin been aware of Mendel’s work, would he been able to explainThe origin of variations. Discuss.

Answer: Yes, Darwin was aware of Mendel’s work therefore, both were working criterias but their explanation were the concept of Neo Darwinism was carried out.

Updated: July 14, 2021 — 3:20 pm

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