Human Evolution
Solutions for Biology, Class 10, ICSE
Assertion Reason Type
3 questionsAssertion. Lamarck's theory of inheritance of acquired characters is mainly based on "survival of the fittest".
Reason. Lamarck has explained his principle of 'use and disuse' with the example of Giraffe's neck.
- Both A and R are True.
- Both A and R are False.
- A is True and R is False.
- A is False and R is True.
Answer:
A is False and R is True.
Explanation
"Survival of the fittest" is a concept associated with Darwin's theory of natural selection, not Lamarck's theory. Lamarck's theory is based on the idea that characteristics acquired during an organism's lifetime can be passed on to its offspring.
Lamarck used the example of the giraffe's neck to illustrate his principle of 'use and disuse,' suggesting that giraffes stretched their necks to reach higher leaves, and this trait was then passed on to their offspring.
Assertion. The analogous organ to the vermiform appendix in herbivorous mammals is quite helpful in digesting cellulose. But it is considered a vestigial organ in humans.
Reason. Vermiform appendix is a wide worm-like tubular structure, projecting from the blind part of the colon (a part of large intestine). Its function is the same as that of the colon, i.e., absorption of water and some remnants of digested food.
- Both A and R are True.
- Both A and R are False.
- A is True and R is False.
- A is False and R is True.
Answer:
A is True and R is False.
Explanation
Vermiform appendix is a small and narrow worm-like tubular structure, projecting from the blind part of the colon. It is a vestigial organ in humans having no function.
Assertion. The theory of natural selection, proposed by Charles Darwin, is a fundamental mechanism driving human evolution.
Reason. Natural selection operates through the preservation of favourable variations that enhance an organism's ability to survive and reproduce, leading to the gradual adaptation of populations to their environments over time.
- Both A and R are True.
- Both A and R are False.
- A is True and R is False.
- A is False and R is True.
Answer:
Both A and R are True.
Explanation
Natural selection is the differential survival and reproduction of individuals due to differences in their phenotypes (observable traits). It is a crucial mechanism of evolution, leading to changes in inheritable traits within populations over generations.
Descriptive Type
3 questionsAnswer:
(a) Evolution — Evolution is a slow and continuous process whereby complex forms of life have emerged from simpler forms through millions of years.
(b) Vestigial organs — Vestigial organs are remnants of once-functional structures in the organism's ancestors that have lost their original purpose through evolution in the present-day species.
(c) Speciation — Origin of new species by gradual modification is called 'speciation'.
(d) Bipedalism — Walking straight on hind limbs and freeing of forelimbs from ground is called bipedalism.
(e) Natural selection — Natural selection is the process by which certain heritable traits become more or less common in a population over generations based on their impact on an organism's survival and reproduction in a specific environment.
Answer:
(a) Difference between Australopithecus and Cro-magnon (Chin) —
Australopithecus | Cro-magnon |
---|---|
Lack of chin | Well-developed chin |
(b) Difference between Australopithecus and Modern man (Body hair) —
Australopithecus | Modern man |
---|---|
Body covered with hair | Highly reduced body hair |
(c) Difference between Homo habilis and Homo sapiens (Posture) —
Homo habilis | Homo sapiens |
---|---|
Bent kneed posture | Fully erect posture |
Answer:
Main differences between the theories of Lamarck and Darwin —
Lamarck's Theory | Darwin's Theory |
---|---|
Known as the theory of inheritance of acquired characters | Known as the theory of natural selection |
Believes in the use and disuse of an organ. Parts used or changes acquired get transmitted to the next generation. | Believes that since variations exist in individuals, only the fittest survive in the struggle for existence. |
New species evolve after a long period of time after many generations by acquiring new characters. | New species evolve due to accumulation of favourable variations over a long period of time. |
Multiple Choice Type
10 questionsAnswer:
Smoke
Reason — Earlier the light colour winged moths outnumbered dark winged moths as they could escape the predators but after industrialisation the dark winged moths were able to escape the predators while light colour winged moths were preyed upon. Therefore, the smoke acted as selective agent.
Answer:
Theory of inheritance of acquired characters
Reason — According to the theory of inheritance of acquired characters organisms can pass on traits acquired during their lifetime to their offspring.
Short Answer Type
6 questionsAnswer:
(a) Australopithecus → 450 to 600 cm3
(b) Homo habilis → 680 to 735 cm3
(c) Homo erectus → 800 to 1125 cm3
(d) Cro-magnon → 1450 to 1600 cm3
(e) Homo sapiens sapiens → 1450 to 1600 cm3
Answer:
Lamarck was the first scientist to propose his theory of use and disuse and inheritance of acquired characters to explain evolutionary process.
- Use and disuse — Parts of the body which are used extensively become larger and stronger, while those which are not used deteriorate.
- Inheritance of acquired characters — An organism could pass its modifications to its offspring.
Answer:
(a) The fossil history of humans is fragmentary.
(b) The first remarkable human fossil was that of Homo habilis.
(c) Evolution is an ever continuing process.
Structured Application Skill Type
3 questionsGiven below are two figures (A and B) representing the two stages of evolution of human beings.

Answer the following:
(a) Mention any two contrasting characters between the two stages.
(b) Write all the stages of human evolution in their correct sequence.
(c) State any two characteristic features of stage B.
Answer:
Stage A → Australopithecus
Stage B → Homo sapiens sapiens (modern man)
(a) Contrasting characters between Australopithecus and Homo sapiens sapiens :
Characters | Australopithecus | Homo sapiens sapiens |
---|---|---|
Cranial capacity | 450 to 600 cm3 | 1450 to 1600 cm3 |
Development of chin | Lack of chin, prognathous face | Prominent chin, snout disappeared |
(b) Stages of human evolution in their correct sequence:
Australopithecus → Homo habilis → Homo erectus → Neanderthal man → Cro-Magnon man → Homo sapiens sapiens (modern man)
(c) Characteristic features of stage B (Homo sapiens sapiens):
- Bipedal locomotion with four reversed curves in the spine.
- Thoracic region flattened into a broad chest by flattening of sternum.
Given below are two figures (A and B) showing a phenomenon that was first observed in Manchester before and after the year 1850.

Answer the following.
(a) What name has been given to this phenomenon?
(b) Give the common name and the scientific name of the insect involved in this phenomenon.
(c) Briefly mention why the changes shown in the two figures appeared.
(d) The following phenomenon provides a classical explanation of a scientific theory given by a certain scientist.
(i) Name and explain the said theory.
(ii) Give the name of the scientist who gave this theory.
Answer:
(a) Industrial Melanism
(b) Common name — Peppered moth
Scientific name — Biston betularia
(c) Biston betularia, this moth with its light coloured wings dotted with spots blended well with the lichens growing on the houses and tree trunks on which it rested. After the Industrial Revolution, pollution resulted in a decline in the growth of lichens. The tree bark got exposed due to the absence of lichens. As a result, dark-coloured moths now got an advantage of a dark background, were camouflaged and survived, while the light-coloured moths were easily picked by predators. This showed that in a mixed population, those moths which could adapt to the changing environment after the Industrial Revolution survived and increased in number, while the ones which could not adapt were slowly wiped out from the population.
(d) The theory explaining Industrial Melanism and the name of the scientist who gave it is given below:
- Natural selection — During the struggle for existence, only those individuals which have advantageous variations survive while the ones which lack these variations are wiped out. Nature selects only those variations which are suitable for existence. This process is called natural selection.
- Charles Darwin
Observe the figure given below and answer the questions that follow:

(a) What is the figure depicting ?
(b) What was the reason that the giraffe stretched their neck and forelimbs ?
(c) What is the name of the theory that is being depicted in the figure ?
(d) Who explained the theory ?
(e) What is the conclusion of this theory ?
Answer:
(a) The figure depicts evolution in Giraffe due to extensive use of neck and forelimbs.
(b) The area where giraffe fed on grasses, fell short of its ground level vegetation and therefore they had to stretch their neck and forelimbs to reach leaves of trees.
(c) Lamarck's theory of inheritance of acquired characters
(d) Lamarck
(e) According to this theory, variations are seen in organisms due to less or overuse of organs. These variations are passed on to the offsprings. After many generation these variations become permanent feature of the organism.