NCERT Exemplar Class 12 Biology Solutions Chapter 7 Structural Organisation in Animals

NCERT exemplar Class 12 Biology Solutions chapter 7 : Evolution is a process that helps species adapt to their environment over many generations, leading to new kinds of organisms. This chapter talks about the theories of evolution, especially the idea of natural selection, introduced by Charles Darwin, and also the concepts given by Lamarck, along with several examples to give you a clear understanding. Students will learn about how evolution works through genetic changes, mutations, and how the environment influences which species survive in NCERT Exemplar Class 12 Biology Solutions Chapter 7 PDF. Different types of evidences such as fossils, analogous and homologous organs are well-explained.

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1. NCERT Exemplar Class 12 Biology Solutions Chapter 7
2. Explore the NCERT Exemplar Class 12 Biology Solutions Chapter 7 Evolution - Multiple Choice Questions
3. Discover the Very Short Answer Type Questions of NCERT Exemplar Class 12 Science Solutions Chapter 7
4. Get the Short Answer Type Questions of Chapter 7 Evolution
5. Unlock the Long Answer Questions of Evolution NCERT Exemplar Class 12 Biology Solutions Chapter 7
6. Most Important Questions Class 12 Biology Chapter 7
7. Approach to Solve Questions of Class 12 Biology Chapter 7

By studying evolution, students will understand how all living things are connected through common ancestors and how life has changed over millions of years. It is a crucial chapter from an examination point of view. CBSE exams and entrance exams examine the educational skills of the student. Smart work along with hard work is the key to success. The Class 12 Biology NCERT exemplar solutions chapter 7 is a must-have to provide the proper guidance to the students so that they can be mentally prepared for their exams.

NCERT Exemplar Class 12 Biology Solutions Chapter 7

The solved exercises provided below are designed to help students for better understanding of the concepts and techniques covered in the chapter. These exercises include a variety of questions such as multiple-choice, short answer, and long answer questions, which will enable students to apply their knowledge in exams.

Explore the NCERT Exemplar Class 12 Biology Solutions Chapter 7 Evolution - Multiple Choice Questions

Question:1

Which of the following is used as an atmospheric pollution indicator?
a. Lepidoptera
b. Lichens
c. Lycopersicon
d. Lycopodium

Answer:

The answer is option (b) Lichens

Explanation: Lichens are highly sensitive to air pollution, especially sulphur dioxide. In areas with high pollution levels, lichens decline or disappear and thus are used as a reliable indicator of atmospheric pollution.

Question: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 the non-living.

Answer:

The answer is the option (c) life can arise from non-living things only.

Explanation: The theory suggested that organisms like mice and even microorganisms can spontaneously arise from the dead matter and inanimate objects.

Question:3

Animal husbandry and plant breeding programmes are examples of:
a. reverse evolution
b. artificial selection
c. mutation
d. natural selection

Answer:

The answer is the option (b) artificial selection

Explanation: Animal husbandry and plant breeding programmes are example of artificial selection. In these programmes, human with desired traits are selectively breed . It is a artificial selection process are is it is done by human according to their needs.

Question:4

Palaeontological evidences for evolution refer to the:
a. development of embryo
b. homologous organs
c. fossils
d. analogous organs

Answer:

The answer is the option (c) fossils

Explanation: Fossils are the preserved remains or traces of ancient organisms found in sedimentary rocks. In fact, the study of fossils is called palaeontology. The term‚ paleo' is related to old and historical items.

Question:5

The bones of forelimbs of whale, bat, cheetah, and man are similar in structure, 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:

The answer is the option (b) they share a common ancestor

Explanation: These limbs are homologous organs, meaning they have a similar structure and share a common ancestor but perform different functions.

Question:6

Analogous organs arise due to:
a. divergent evolution
b. artificial selection
c. genetic drift
d. convergent evolution

Answer:

The answer is the option (d) convergent evolution

Explanation: Analogous organs have evolved from different ancestors, but all of them show a similar function. Hence, they show convergent evolution.

Question:7

${(p+q)}^2=p^2+2pq+q^2=1$represents an equation used in:
a. population genetics
b. mendelian genetics
c. biometrics
d. molecular genetics

Answer:

The answer is the option (a) population genetics

Explanation: The above equation is the Hardy-Weinberg equation used in population genetics. This equation helps in studying genetic variation and prediction of allele frequencies in a population.

Question:8

The 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:

The answer is the option (c) pre-existing variation in the population

Explanation: Some bacteria naturally have resistance due to genetic variation. When exposed to antibiotics, the resistant bacteria survive and reproduce, while the non-resistant ones die.

Question:9

Evolution of life shows that life forms had a trend of moving from:
a. land to water
b. dry land to wetland
c. freshwater to seawater
d. water to land

Answer:

The answer is the option (d) water to land

Explanation: Early life starts in water, and over time, some organisms develop adaptations like lungs and limbs to survive on land. This signifies that the evolution of life moved from water to land

Question:10

Viviparity is considered to be more evolved because:
a. the young ones are left on their
b. the young ones are protected by a thick shell
c. the young ones are protected inside the mother's body and are looked after they are born leading to more chances of survival
d. the embryo takes a long time to develop

Answer:

The answer is the option (c) the young ones are protected inside the mother's body and are looked after they are born leading to more chances of survival

Explanation: In viviparous animals, the embryo develops inside the mother's body, receiving protection. It reduces the risk from predators and increasing the chances of their survival.

Question:11

Fossils are generally found in:
a. Sedimentary rocks
b. Igneous rocks
c. Metamorphic rocks
d. Any type of rock

Answer:

The answer is the option (a) Sedimentary rocks

Explanation: Fossil can't be found in Igneous rocks as they are formed from lava. Fossils are generally found in sedimentary rocks. Metamorphic rocks are made from igneous or sedimentary rocks.

Question:12

For the MN-blood group system, the frequencies of M and N alleles are 0.7 and 0.3, respectively. The expected frequency of MN-blood group bearing organisms is likely to be
a. 42%
b. 49%
c. 9%
d. 58%

Answer:

The answer is the option (a) 42%

Explanation: This can be solved by using the binomial expression:

$a^2+b^2+2ab=1$

Here, M=a and N=b

$M^2+N^2+2MN={0.7}^2+{0.3}^2+2\ast 0.7\ast 0.3$

$=0.49+0.09+0.42$

In this equation ; value of 2MN=0.42=42%

Question:13

Which type of selection explains industrial melanism observed in the moth, Boston Bulgaria:
a. Stabilising
b. Directional
c. Disruptive
d. Artificial

Answer:

The answer is the option (b) Directional

Explanation: During the Industrial revolution, darker moths had a survival advantage over the lighter coloured moths. Due to this, the number of dark-coloured moths increased, showing a shift on one side that is directional selection.

Question: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:

The answer is the option(c) Ramapithecus→Homo habilis→Homo erectus→Homo sapiens

Explanation: Ramapithecus→Homo habilis→Homo erectus→Homo sapiens

Question:15

Which of the following is an example for link species?
a. Lobe fish
b. Dodo bird
c. Seaweed
d. Chimpanzee

Answer:

The answer is the option (a) Lobe fish

Explanation: Lobe fish act as a link between aquatic fish and amphibia. They have fleshy, limb-like fins which are considered evolutionary precursors, showing the transition from water to land hence, they are considered as link species.

Question:16

Match the scientists listed under column 'I' with ideas listed column 'II'.

a. A(i); B(iv); C(ii); D(iii)

b. A(iv); B(iii); C(ii); D(i)

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

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

Answer:

The answer is the option (d), A(iv); B(i); C(ii); D(iii)

Explanation: Darwin proposed the theory that evolution happens due to the natural selection. Oparin provided the concept of abiogenesis. Lamarck proposed the use and disuse of organs. The organs that are not in use eventually weaken or disappear, while the organs in use remains. Wagner give the Continental drift theory.

Question:17

In 1953 S. L. Miller created primitive earth conditions in the laboratory and gave experimental evidence for the origin of the first form of life from preexisting non-living organic molecules. The primitive earth conditions created 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 atmosphere containing $C{H}_4$, $N{H}_3$, etc.

Answer:

The answer is the option (d) high temperature, volcanic storms, reducing atmosphere containing $C{H}_4$, $N{H}_3$ etc.

Question:18

Variations during mutations of meiotic recombination are:
a. random and directionless
b. random and directional
c. small and directional
d. random, small and directional

Answer:

The answer is the option (a) random and directionless

Explanation: Mutations occur spontaneously due to errors in DNA replication or external factors. Hence, these changes are random and directionless.

Discover the Very Short Answer Type Questions of NCERT Exemplar Class 12 Science Solutions Chapter 7

Question:1

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

Answer:

Fossilised organisms usually have hard body parts like bones or shells. They were often buried in sediments, preventing decay and after some time undergo mineralization, and turn into fossils.

Question:2

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

Answer:

Yes, aquatic life forms also get fossilised. These fossils are mostly found in sedimentary rocks, especially in seabeds, riverbeds and lake deposits.

Question:3

What are we referring to when we say 'simple organisms' or 'complex organisms'?

Answer:

When we refer to simple or complex organisms, we describe the level of biological organization as simple organisms are having only a few specialized cells but complex organisms are having multiple specialized cells like humans.

Question:4

How do we compute the age of a living tree?

Answer:

Age of a living tree can be determined by measuring the girth of the trunk and comparing the diameter to the average growth factor of that species. Information regarding the average growth factor of a species is historically available.

Question:5

Give an example of convergent evolution and identify the features towards which they are converging.

Answer:

Birds, and bats evolved wings for flight, even though they are not closely related. Their wings are structurally different but both serve the same function, showing adaption to a same environment.

Question:6

How do we compute the age of a fossil?

Answer:

The age of a fossil is determined using carbon dating. The relative presence of radioactive carbon $\left({}^{14}C\right)$, which decays over time, is calculated to compute the age of a fossil.

Question:7

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

Answer:

The most important pre-condition for adaptive radiation is Common ancestry. This means that a single species, when comes in different environments, evolves into multiple species with specialized functions, as seen in Darwin's Finches.

Question:8

How do we compute the age of a rock?

Answer:

Carbon dating is used to find the age of a rock. The relative presence of radioactive carbon $\left({}^{14}C\right)$, which decays over time, is calculated to compute the age of a rock.

Question:9

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

Answer:

Functional macromolecules can evolve into living forms. Through natural selection, they adapt to perform specific functions increasing the survival and processes in an organism.

Question:10

In a certain population, the frequency of three genotypes is as follows:

What is the likely frequency of B and b alleles ?

Answer:

Frequency of B alleles =$BB+\frac{1}{2}Bb={22}^o{/}_o+\frac{1}{2}\ast {62}^o{/}_o={53}^o{/}_o$

Frequency of b alleles = 1-Frequency of B alleles=47%

Question:11

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

Answer:

The other two factors that affect the Hardy- Weinberg equilibrium are Mutation and Natural Selection.

Question:12

What is the founder effect?

Answer:

The Founder effect occurs when a small group of individuals from a larger population moves to a new location and starts a new population. As, they carry only a small portion of the original population, the new population have reduced genetic diversity.

Question:13

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

Answer:

Ramapithecus are the species that resemble more like man.

Question:14

By what Latin name was the first hominid known?

Answer:

First hominid is known by the latin name of Homo habilis.

Question:15

Among Ramapithecus, Australopithecines and Homo habilis -who probably did not eat meat?

Answer:

Homo habilis are the species who probably did not eat meat.

Get the Short Answer Type Questions of Chapter 7 Evolution

Question:1

Louis Pasteur's experiments, if you recall, proved that life can arise from only 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 first forms of life arose? Comment.

Answer:

Louis Pasteur’s experiments proved that life arises only from pre-existing life, and not accepted the idea of spontaneous generation. His work showed that sterile broth remained free of life forms unless it is exposed to pre-existing microorganisms or life. However, this does not explain how the first life forms originated. Scientists believe that abiogenesis meaning life arising from non-living matter under early conditions led to the formation of first organisms, while biogenesis meaning life from life forms explains the continuation of life. Thus, evolution depends on pre-existing life, but the origin of the first life is still an open question in science.

Question:2

The scientists believe that evolution is gradual. But extinction, part of evolutionary story, is 'sudden' and 'abrupt' and also group-specific. Comment whether a natural disaster can be the cause for the extinction of species.

Answer:

Scientists believe evolution is mostly gradual, but some events, like mass extinctions, cause sudden and abrupt changes affecting specific groups. Most scientists agree on the theory of dinosaur's extinction, claiming that a meteor strike led to the dinosaur's large scale destruction and eventual extinction. This theory suggests that a natural disaster can, in fact, be the cause for the extinction of species.

Question:3

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

Answer:

Nascent oxygen(O) is toxic to aerobic life forms because it is highly reactive and unstable. Due to this, there is a possibility that they react with many molecules such as DNA, proteins, and lipids.Sci Nascent oxygen is threatening to life forms as this can potentially result in unwanted mutations.

Question:4

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

Answer:

Mutation and recombination create random genetic changes, but natural selection acts on these variation in a specific direction, favoring the traits that improve survival and reproduction. Over time, this leads to adaptations, that are best suited to environment. Hence, creation and presence of variation are directionless, but natural selection and adaptation are directional.

Question:5

The evolutionary story of moths in England during industrialization reveals, that 'evolution is reversible'. Clarify this statement.

Answer:

Before industrialization, light-coloured moths were common, blending with clean tree bark. Post industrialization, tree trunks turned dark due to pollution leading to a drop in the population of white-winged moths. In this scenario, dark-winged moths reappeared and survived. Later, when pollution decreased light coloured moths again become dominant.Thus, the evolution of white wings was reversed because of pollution. This shows that evolution is apparently reversible.

Question:6

Comment on the statement that "evolution and natural selections are result or consequence of some other processes but themselves are not processed".

Answer:

Evolution and natural selection are result of other biological processes, not themselves because they result from genetic mutations, variations, environmental pressures, and reproduction. Natural selection filters these variations leading to evolution over generations.

Question:7

State and explain any three factors affecting allele frequency in populations.

Answer:

Factors which affect allele frequency in populations:

1. Genetic Drift: Due to random sampling, there are changes in the frequency of a gene variant. Genetic drift may cause a gene variant to disappear completely and result in reduced genetic variation.

2. Genetic Recombination: When offspring with traits different from parents are produced, it is called genetic recombination.

3. Natural Selection: The nature selects only the traits which help an organism to survive in the changed conditions. Natural selection leads to survival of the fittest. Traits that are unfit to survive, perish in the long run, which paves the way for the evolution of a new species.

Question:8

Gene flow occurs through generations. Gene flow can occur across language barriers in humans. If we have a technique of measuring specific allele frequencies in a different population of the world, can we not predict human migratory patterns in pre-history and history? Do you agree or disagree? Explain your answer.

Answer:

Yes, it is possible to understand gene flow in different populations of the world with the human genome project, which is now turning into a reality. This can help us in assessing and predicting human migratory patterns in pre-history and history.

Question:9

How do you express the meaning of words like race, breed, cultivars or variety?

Answer:

Race: A group within a species that has unique features, usually based on location or adaptation. Members from different races of the same species can interbreed.

Breed: A type of animal with special traits, created by humans through selective breeding and are homogenous in appearance, example- labrador dogs.

Cultivar: A special type of plant grown by farmers for specific qualities through vegetative propagation, example- seedless grapes.

Variety: Different types of the same plant species, either naturally or bred, example- different kinds of mangoes.

Question:10

When we say, "survival of the fittest", does it mean that
a. those who are fit only survive, or
b. those that survive are called fit? Comment.

Answer:

Survival of fittest means that organisms which are best adapted to their environment are more likely to survive ,and reproduce. Organisms that survive and pass on their genes are called fit.

Question:11

Enumerate three most characteristic criteria for designating a Mendelian population.

Answer:

The three most important criteria for designating a Mendelian population are as follows:

• The population must be sufficiently large.

• Free flow of genetic materials is ensured through sexual reproduction.

• There should be negligible or nil migration in the population.

Question:12

"Migration may enhance or blur the effects of selection". Comment.

Answer:

Migration may enhance or block the effects of selection by changing genetic variation in a population. If new individuals bring advantage, natural selection may enhance it. However, if individuals introducing harmful genes, they can be slow down or block by natural selection, hence blur the effects.

Unlock the Long Answer Questions of Evolution NCERT Exemplar Class 12 Biology Solutions Chapter 7

Question:1

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

Answer:

Hardy Weinberg Principle states that the sum of allelic frequencies in a population remains the same through generations. The total of allelic frequencies in a population is 1.

Frequency of allele A=p

Frequency of allele a=q

$p+q=1$

In a diploid individual,

Frequency of allele $AA=p^2$

Frequency of allele $aa=p^2$

Frequency of allele $Aa=2pq$

This can be shown by the following equation which is derived from the algebraic identity

${(P+q)}^2=p^2+q^2+2pq=1$

The extent of evolutionary change can be evaluated by measuring the difference between the measured values of these values from the expected value.

Following five factors influence these values:

1. Gene migration or gene flow

2. Genetic drift

3. Genetic recombination

4. Mutation

5. Natural selection

Question:2

Explain divergent evolution in detail. What is the driving force behind it?

Answer:

Divergent evolution is a process in which two or more related species develop different traits and adaptations over time due to different environmental pressures or niches. It occurs when a common ancestor gives rise to multiple species with distinct characters, leading to increased diversity. A classic example of divergent evolution is Darwin's Finches on the Galapagos Islands.

The main driving force behind divergent evolution is natural selection, along with mutation, genetic drift, and adaptation to different environments. The homologous organs are result of divergent evolution. Forelimbs of mammals and birds are good examples of divergent evolution. While mammals use their forelimbs for walking, running and other chores, birds use forelimbs (modified into wings) for flight adaptations. In both cases, forelimbs are supported by humerus, radio -ulna, carpals, and metacarpals. This may indicate common ancestry.

Question: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:

The story of moths in England during industrialization is a classic example of natural selection. Before industrialization in England, the population of black-winged moths was less than the population of white-winged moth. Due to the industrial revolution, tree trunks became darker because of the accumulation of industrial smoke or soot and reduction in the population of lichens. This provided camouflaging advantage to black-winged moths, and thus, the population of black-winged moth gradually started to increase.

If the industry had been removed, pollution levels decreased, and the tree bark would have returned to its orginal light colour. In this case, light colored moths will gonna increase rather than dark coloured moths.

This showed that evolution is apparently reversible.

Question:4

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

Answer:

The two prominent concepts in the evolutionary theory of Darwin are natural selection and branching descent.

Natural Selection: All living beings adapt to changing environmental conditions by developing useful adaptations. Organisms, which can survive the changes, will produce more progenies and thereby maintain their lineage. Nature selects only those who are fit to survive, leaving behind the rest to perish. Therefore, we can conclude that natural selection plays an important role in evolution.

Branching Descent: Branching descent follows the popular premise that all life forms are branched from a common origin. This is often referred to as the "Tree of Life" illustrated in the following diagram.

Fishes and Amphibians have a common ancestor. Amphibians have been considered as ancestors to other land animals such as reptiles, mammals and even birds.Darwin used various proofs to show that living beings have evolved from a common ancestor through branching.

Question:5

Two organisms occupying a particular geographical area (say desert) show similar adaptive strategies. Taking examples describe the phenomenon.

Answer:

Two organisms found in the same geographical area often have similar adaptations, and this is called convergent evolution. It is commonly observed in desert plants, although not all of them are closely related.

For example, kangaroo rats(a mammal) and desert lizards(a reptile) both use water conserving strategies. Kangaroo rats produce fewer offspring with high survival rates, avoiding water loss by staying in burrows and having efficient-kidneys. Similarly, desert lizards lay tough-shelled eggs that reduce water loss, and some species even give birth to live young, making sure the better survival in dry conditions.

Question:6

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

Answer:

Yes, Humans are still evolving, as evolution is a continuous process that affects all living organism, including us. Evolution occurs through mechanisms such as natural selection, genetic drift, mutations and gene flow, all of which continue to shape the human species over time. Some scientists have studied human evolution and have shared following observations that suggest modern humans are also evolving. Since the discovery of farming about 10,000 years ago human evolution has worked at lightning speed as scientists have observed multiple genetic difference between hunter gatherers and current humans.

One clear example of human evolution is lactose tolerance. As young ones stop consuming milk after a certain age, they become lactose intolerance. But, human beings consume milk throughout their life as they get it from domesticated animals. Humans have also developed resistance to many infectious diseases. This is another sign of evolution. While evolution in humans may not be visible or rapid, as in other species, it is continuously happening.

Question:7

Had Darwin been aware of Mendel's work, would he be able to explain the origin of variations? Discuss.

Answer:

If Darwin had been aware of Mendel's work, he would have given a clear understanding of the origin of variations in species. Darwin's theory of Natural Selection was based on the idea that organisms in a population show variations, and those having beneficial traits survive and reproduce. Mendel observed reproduction in pea plants to come up with his theories on variations. Through these experiments, Mendel could attribute the origin of variations to some factors.

Mendel's discoveries laid the foundation for modern genetics, which later merged with Darwin's Theory in the modern synthesis of evolution. Darwin was from the same era as Mendel and would have had access to the same technology and information as Mendel had. Darwin was out on an exploration, and it would not have been possible to experiment similarly to the one conducted by Mendel. The goals and focus of their experiments were quite different from each other. Because of these factors, it seems highly unlikely that Darwin would have been able to explain the origin of variations.

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NCERT Exemplar Class 12 Biology Solutions Chapter 7 Evolution- Learning Outcome

In Class 12 Biology NCERT exemplar solutions chapter 7, the students will learn about the different topics that one needs to know to understand the origin of life on Earth and the evolution of life forms by various factors. It includes the various aspects of evolutionary biology like the origin and evolution of life forms, the evidence of evolution, theories and principles given by various scientists on the evolutionary mechanism. The work of Darwin, Lamarck, and other scientists who have played an important role in explaining evolution is thoroughly explained in the NCERT exemplar class 12 Biology chapter 7 solutions by our subject experts. Along with different topics, it also includes extra questions like MCQS, short and Long answers for providing in-depth knowledge.

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Important Topics in NCERT Exemplar Class 12 Biology Solutions Chapter 7

● The NCERT exemplar Class 12 Biology chapter 7 solutions bring out the details on the origin of life on earth and the various theories proposed by different scientists, like the theory of biogenesis, unique creation, chemical evolution, etc.

● The work of Charles Darwin, Lamarck, Hardy-Weinberg principle or the theories of Hugo deVries are detailed in the NCERT exemplar solutions for Class 12 Biology chapter 7, along with their different examples to explain clearly the concept.

● NCERT exemplar Class 12 Biology solutions chapter 7 also talks about the origin and development of homo sapiens that is the humankind, the different factors that lead to their evolution, and the concepts of adaptation.

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NCERT Exemplar Class 12 Biology Chapter Wise Links

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Most Important Questions Class 12 Biology Chapter 7

Evolution is an important chapter for NEET and board exams that explains how life has evolved and diversified over millions of years. It deals with very crucial points like the origin of life, evolution theories, evidence for evolution, adaptive radiation, and human evolution. If one gets this chapter, it is possible to encounter questions about natural selection, genetic drift, speciation, and human ancestry, and hence, conceptual understanding as well as getting good marks becomes compulsory.

Question: What is evolution?

Answer: Evolution is the process by which living things develop and become diversified from previous forms throughout Earth's history.

Question: Who is called the Father of Evolution and why?

Answer: Charles Darwin is referred to as the Father of Evolution since he formulated the Theory of Natural Selection, describing how species change through time through survival and reproduction.

Question: Define natural selection.

Answer: Natural selection is the mechanism by which organisms with characteristics more suited to their surroundings survive and reproduce, transferring those beneficial characteristics to their offspring.

Question: Briefly state Darwin's theory of natural selection.

Answer: Darwin's theory is that populations contain variations, there is competition for resources, and individuals with beneficial variations survive, reproduce, and transfer their characteristics, resulting in gradual evolution.

Question: Match the following:

A. Adaptive radiation – i. Different species from a common ancestor

B. Homologous organs – ii. Same structure, different function

C. Analogous organs – iii. Different structure, same function

Options:

1. A-i, B-ii, C-iii
2. A-ii, B-i, C-iii
3. A-iii, B-ii, C-i
4. A-i, B-iii, C-ii

Answer: Option 1: A-i, B-ii, C-iii

Question: What are homologous and analogous organs? Give examples.

Answer: Homologous organs possess the same basic structure but different functions (e.g., forelimbs of whales, bats, and humans). Similar structures but different functions have analogous organs (e.g., insect wings and bird wings).

Question: Differ between convergent and divergent evolution?

Answer: The major difference between convergent and divergent evolution is:

• Convergent Evolution: Different species evolve the same characteristics independently as a response to similar environments. (Example: Bird and bat wings)

• Divergent Evolution: Similar organisms develop different characteristics to respond to different environments. (Example: Darwin's finches)

Question: Define adaptive radiation. Provide an example.

Answer: Adaptive radiation is the process of evolution of various species from a single ancestor, each suited to a different environment. For Example, Darwin's finches on the Galápagos Islands evolved various beak types according to their diet.

Question: What are fossils? How do they support evidence for evolution?

Answer: Fossils are ancient remains or traces of organisms. They attest to evolution through gradual changes in species over geological time and record the emergence of new features.

Question: Describe any two pieces of evidence for evolution.

Answer: The Fossil Record indicates chronological changes in species over geological time. At the same time, comparative anatomy indicates similarity in the structure of different organisms for common ancestry.

Question 2: Describe other theories of organic evolution apart from Darwin's theory with examples.

Answer: Apart from Darwin's natural selection, there have been several other theories suggested to account for organic evolution:

Lamarck's Theory (Inheritance of Acquired Characters):

Lamarck suggested that acquired characters in an organism's lifetime may be inherited by offspring. For Example, Giraffes developed long necks by stretching to eat higher leaves.

Mutation Theory (Hugo de Vries):

Hugo de Vries proposed that sudden mutations (large changes) instead of small variations are the raw material for evolution. For Example,a Mutation in plants that creates new flower colours.

Modern Theory of Evolution:

This theory integrates Darwin's natural selection with contemporary genetics and focuses on the fact that evolution is powered by genetic variations (mutation, recombination), natural selection, genetic drift, and gene flow.

Hardy-Weinberg Principle:

It explains the genetic equilibrium of a population if there are no forces of evolution. According to it, evolution is said to take place when the frequencies of genes change.

These theories highlight that evolution is a dynamic process influenced by a combination of natural forces, genetics, mutations, and environmental interactions.

Approach to Solve Questions of Class 12 Biology Chapter 7

This chapter consists of a mix of direct, conceptual, and application-type questions. To prepare well:

• Read NCERT and Exemplar in depth for knowing the origin of life, evolutionary theories (Lamarckism, Darwinism, Mutation Theory), evidence for evolution (fossils, comparative anatomy, embryology), and human evolution.
• Practice drawing and labelling diagrams like evolutionary trees, homologous and analogous structures, adaptive radiation patterns, and human evolutionary stages.
• Memorise the order of evolutionary phases, and key terms like natural selection, genetic drift, gene flow, mutation, adaptive radiation, homologous organs, and analogous organs.
• Complete all Exemplar questions, highlighting differences between homologous and analogous organs, convergent and divergent evolution, the Hardy-Weinberg principle, and examples of adaptive radiation.
• Rewrite the work of scientists like Charles Darwin (natural selection), Hugo de Vries (mutation theory), and others who participated in the contemporary synthetic theory, and gain a clear understanding of experiments and concepts that verify evolutionary evidence.

Must Read NCERT Notes subject-wise

• NCERT Notes for Class 12 Physics
• NCERT Notes for Class 12 Chemistry
• NCERT Notes for Class 12 Maths
• NCERT Notes for Class 12 Biology

These Class 12 Biology NCERT Exemplar chapter 7 solutions provide the basic understanding of how life evolved on the Earth and what evidence of evolution. It also provides the knowledge of Darwin and Lamarck's Theory that laid the foundation of the explanation of Evolution, and also about the origin and evolution of humans. Solved exercises will give clarity on the question patterns and help gain confidence in answering the questions effectively. The learning of this chapter will be very useful in higher classes of CBSE and in competitive exams like NEET.