NIOS Class 12 Biology Chapter 1 Origin and Evolution of life and Introduction to Classification

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NIOS Class 12 Biology Chapter 1 Origin and Evolution of life and Introduction to Classification

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Also, you can read the NIOS book online in these sections Solutions by Expert Teachers as per National Institute of Open Schooling (NIOS) Book guidelines. These solutions are part of NIOS All Subject Solutions. Here we have given NIOS Class 12 Biology Chapter 1 Origin and Evolution of life and Introduction to Classification Solutions, NIOS Senior Secondary Course Biology Solutions for All Chapter, You can practice these here.

Origin and Evolution of life and Introduction to Classification

Chapter: 1




1. Approximately how many years ago was the earth formed?

Ans. App. 5 billion years ago.

2. Who gave the Chemosynthetic Theory for origin of life?

Ans. I.A. Oparin (1836).

3. Name the four gases present in primitive atmosphere of the earth.

Ans. Ammonia (NH₃), methane (CH₄), CO₂ and water vapours.

4. Name one source of energy which was used for chemical combination in primitive atmosphere.

Ans. UV rays/geothermal energy or lightening. (Write any one)

5. Where did life originate in water or on land?

Ans. In water.

6. What are ‘coacervates’?

Ans. Aggregates of (leaf like) molecules or the precursors of first living beings.

7. In the origin of life, first large molecules were formed from inorganic compounds. Name any two such large molecules.

Ans. (i) Amino acids.

(ii) Fatty acids.

(iii) Sugars, etc. (Write any two)

8. Name the two scientists who experimentally tried to verify Oparin’s hypothesis.

Ans. Miller and Urey.


1. Define organic evolution.

Ans. The slow and gradual change as a result of descent with modification, from a common ancestor is called evolution.

2. Name one fossil animal which forms a connecting link between reptiles and aves.

Ans. Archaeopteryx, the lizard bird.

3. Which organ of man is homologous to the wings of birds?

Ans. Forelimbs of man (arm of a man) is homologous to wings of the birds.

4. Define vestigial organ.

Ans. Vestigial organs are organs, tissues or cells in a body which are no more functional the way they were in their ancestral form of the trait. It is authentication of evolution and hence, were helpful in explaining adaptation. Such a structure can arise due to gene mutation which causes a change in the proteins.

5. Give one example of a connecting link among the living beings.

Ans: Lung fish between fishes and amphibians or prototheria (egg laying mammals between reptilia and mammalia).

6. Give two examples from molecular biology which support organic evolution.

Ans. (i) Plants and some algae possess chlorophyll.

(ii) The human blood proteins are most similar. to those of the chimpanzee among all the apes.


1. Who gave the theory of natural selection?

Ans: Charles Darwin gave theory of natural selection.

 2. What is the modern interpretation of Darwin’s theory called?

Ans: Neo-Darwinism or synthetic theory of evolution.

3. What are the two major contributions of Charles Darwin regarding evolution?

Ans: All organisms are related through ancestry he suggested natural selection as the probable mechanism for evolution.

4. Give two main features of Neo-Darwinism.

Ans. (i) Variation in population forms the basis of evolution.

(ii) Differential reproduction.

5. What do you mean by “differential reproduction”?

Ans. It means “the reproduction of favourable genes is greater.”


1. List the sources of organic variation.

Ans. The sources of organic variation are:

(i) mutation.

(ii) gene flow.

(iii) genetic drift.

(iv) recombination.

2. What is ‘industrial melanism’ about? Answer in one or two sentences.

Ans. Industrial melanism is about evolution of a variety of peppered moth during industrial revolution, through mutation and natural selection”.

3. State one point of difference between

(a) allopatric & sympatric speciation.

(b) Ecological and Ethological Isolation.

Ans. The allopatric speciation leads to differences in population of a species because of the physical isolating barriers. The reproductive barrier separates sympatric species that can live in same geographical area. Both are isolating mechanism. The ecological isolation by barriers of season habital and Ethological Isolation by barriers of behavioural differences.

 4. What is a panmictic population? 

Ans. It is a randomly mating population.

5. According to Hardy Weinberg Principle, (p + q)² = 1. Explain this mathematical expression.

Ans. (q + q)² = 1. It means the frequencies of allelic genes p + q remain same for generation after generation if there is no force of evolution such as variation.


1. Name the scientists who proposed:

(a) Binomial nomenclature.

(b) Five kingdom classification.

Ans. (a) Carolus Linnaeus. and 

(ii) R.H. Whittaker.

2. Which were the first organisms to appear on earth?

Ans. Bacteria.

3. Name the taxonomic category which comes before and after family.

Ans. Genus.

4. Name the categories above order level in a correct sequence.

Ans. These are kingdom, phylum, class and order.

5. Rewrite the following in correct form:

(a) Mangifera Indica.

(b) Homo Sapiens.

(c) Felis leo.

Ans. The correct forms are:

(i) Mangifera indica.

(ii) Homo sapiens.

(iii) Felis leo.

6. Place the following in their respective kingdoms:

(a) Bacteria which curdle milk.

Ans. Bacteria which curdle milk-Monera.

(b) Cow.

Ans. Cow—Animalia.

(c) Grass.

Ans. Grass—Plantae.

(d) Amoeba.

Ans. Amoeba—Protista.

(e) Bread mould.

Ans. Bread mould—Fungi.


1. With reference to viruses fill in the blanks (1, 2 and 3) in the following table:


1. ________TobaccoTobacco Mosaic Disease
HIV2. _______AIDS
HerpesHuman3. _________
Tobacco Mosaic Virus (1)TobaccoTobacco Mosaic Disease
HIVHumans (2)AIDS
HerpesHumanHerpes Virus (3)

2. Give one feature because of which viruses are considered non-living.

Ans. (i) Viruses cannot reproduce on their own. 

(ii) They can be crystallised.

3. Name one chemical common to viruses and all other organisms.

Ans. Either nucleic acid or the protein. 

4. Complete the following:

(a) Core particle of virus contains.

Ans. DNA & RNA. 

(b) Coat of virus is made of.

Ans. Protein.

5. In what way is viroid structurally different from a virus?

Ans. A virus possesses a DNA & RNA molecule enclosed by a protein coat. A viroid is only an RNA molecule.

6. Why are viroids considered a menace for plants that they attack?

Ans. The viroids infect plants but when inside the plant cells. They use host plants’ enzymes to replicate as well as to increase in number causing stunted & abnormal growth of the plant.


1. Explain the most valid theory about origin of life on earth. How did Miller and Urey verify the chemosynthesis theory of evolution?

Ans. The most valid theory about the origin of life on earth is chemosynthetic theory.

The earth is said to have originated app. 5 billion years ago. The earth was made up of hot gases as well as the vapours of various chemicals. Slowly the earth cooled down and a solid crust was formed.

The early atmosphere of earth had ammonia, water vapour (H₂O), hydrogen (H₂) and methane (CH₄). Free oxygen was absent then. This kind of atmosphere is still found on Jupiter and Saturn.

Fig. 1.11. Primitive conditions on the earth.

The heavy rains fell on the hot surface of earth. After a long period water bodies appeared which still contained hot water. CH4 and NH3 from the atmosphere dissolved in the water of the seas and chemical reactions took place there and produced amino acids nitrogenous bases, sugars and fatty acids, etc. These further reacted and combined and produced big molecules of life like the proteins and the nucleic acids.

Miller and Urey experimentally proved it by recreating in the laboratory the probable conditions of primitive earth. They made an apparatus of glass tubes plus flasks and provided energy by heating and electric sparks through electrodes. In the flask water vapours, H₂, CH₄ and NH₃ was kept. Various kinds of amino acids and sugars were formed after the electric spark.

Fig. 1.12. Apparatus used by Miller and Urey to show abiotic origin of life in the stimulated primeval atmosphere.

2. Differentiate between Darwinism and Neo-Darwinism.

Ans. Differences between Darwinism and Neo-Darwinism:

1. No role of reproductive isolation. Reproductive isolation plays key role.
2. Causes of variations are changed in the environment and struggle for existence.Variations occur due to small changes in genes or chromosome mutations. 
3. New adaptations are inherited.Change in genetic make up of a population leads to new species.

3. Explain the synthetic theory of evolution.

Ans. Neo-Darwinism/Modern Synthetic Theory: Main points are:

(i) Unit of evolution is ‘population’. It possesses its own gene pool (group of all different genes of a population).

(ii) Heritable genetic changes appear in the individuals of a population. These form basis of evolution.

(ii) Heritable changes/variations take place by small mutations in genes or chromosomes as well as their recombinations.

(iv) Natural selection occurs and it selects variations that are helpful to adapt to the environment.

(v) A change in the genetic constitution of a population that was selected by natural selection is responsible for formation of a new species or speciation.

(vi) Much more offsprings with favourable genetic changes are born. It is known as ‘differential reproduction’.

(vii) The reproduction isolation is helpful to keep species distinct.

5. Substantiate the idea of evolution through molecular evidence.

Ans. Molecular Evidence of Evolution: It considers the various points like all the organisms are made of cell or cells. Cell is the “basic unit of life”. It is composed bio-molecules common to all organisms. The ribosomes are of universal occurrence in organisms. The DNA is the hereditary or genetic material of all the organisms. ATP is a molecule that stores as well as releases energy for all the biological phenomena. The genetic code is universal and same 22 amino acids form the constituents of proteins of app. all the organisms.

Moreover the central dogma is same as well as the basic steps in protein synthesis are same to all the organisms Nucleotide sequence in Tata Box is same to all organisms.

6. Classify the following animals: earthworm, roundworm, frog and human beings. 

Ans. Classification of Earthworm, Roundworm, Frog and Human beings:

S. NoEarthwormRoundwormFrogHuman beings

7. Write the scientific names of:

(i) Mango.

Ans. Mango—Mangifera indica.

(ii) Man.

Ans. Human—Homo sapiens. 

(iii) Cat.

Ans. Cat—Felis domestica 

(iv) Tiger.

Ans. Tiger—Panthera tigris.

8. How does a virus increase in number? Show only by explanatory diagrams.

Ans. A virus multiplies only in a living cell or living host cell. After infection it enters the living cell. It leaves the protection coat behind. DNA of virus using machinery of host replicates and synthesises new capsids (protein coats). One DNA core enters in each capsid. These viruses come out by lysing the cell walls of the host.

Fig. 1.13. Multiplication of Virus.

9. Give a schematic diagram of the five kingdom classification.


Fig. 1.14. Five kingdoms of life.

10. State the criteria on which the five kingdom classification is based.

Ans. Criteria for five kingdom classification of organisms:

(i) Presence or absence of nucleus. 

(ii) Unicells or multicells. 

(iii) The mode of nutrition.

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