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Class 10 SELINA Solutions Biology Chapter 14 - Human Evolution

Human Evolution Exercise Ex. 1

Solution A.1

(b) Caecum

Solution A.2

(a) Lichens

Solution A.3

(a) Darwin

Solution A.4

(c) Theory of inheritance of acquired characters 

Solution A.5

(b) Natural selection 

Solution A.6

(c) Use and disuse 

Solution A.7

(a) Cro-magnon

Solution A.8

(c) Darwin

Solution A.9

(c) Peppered moth

Solution A.10

(b) Darwin

Solution B.1

Four main postulates of Darwin's theory:

1. Overproduction

2. Struggle for existence

3. Variation

4. Survival of the fittest

Solution B.2

Ancestral forms

Cranial capacities

(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


Solution B.3

(a) Use and disuse:

Parts of the body which are used extensively become larger and stronger, while those which are not used deteriorate.


(b) Inheritance of acquired characters:

An organism could pass its modifications to its offspring.

Solution B.4

Three vestigial organs found in humans are wisdom teeth, vermiform appendix and pinna.

Solution B.5

Biston betularia is a classical example of 'natural selection'.

Solution B.6

(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. 

Solution C.1

(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 those organs that have ceased to be of any use to the possessor but still persist generation after generation in a reduced form.

(c) Speciation: Origin of new species by gradual modification is called speciation.

(d) Bipedalism: Bipedalism is the movement of an animal or a human being with two legs, thereby freeing up the forelimbs from the ground.

(e) Natural selection: During struggle for existence, nature selects only those individuals with advantageous adaptations or variations over those individuals which lack these variations. This process is called natural selection.

Solution C.2

(a) Differences between Australopithecus and Cro-magnon (Chin):



Lack of chin

Well-developed chin


(b) Differences between Australopithecus and Modern man (Body hair):


Modern man

Body covered with hair

Highly reduced body hair


(c) Differences between Homo habilis and Homo sapiens (Posture):

Homo habilis

Homo sapiens

Bent kneed posture

Fully erect posture


Solution C.3

Differences between Lamarck's Theory and Darwin's Theory:

Lamarck's Theory

Darwin's Theory

1. Known as the theory of inheritance of acquired characters

1. Known as the theory of natural selection

2. Believes in the use and disuse of an organ. Parts used or changes acquired get transmitted to the next generation.

2. Believes that since variations exist in individuals, only the fittest survive in the struggle for existence.

3. New species evolve after a long period of time after several generations by acquiring new characters.

3. New species evolve due to accumulation of favourable variations over a long period of time.


Solution D.1

Stage A: Australopithecus

Stage B: Homo sapiens sapiens

(a) Contrasting characters between Australopithecus and Homo sapiens sapiens:



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


(c) Characteristic features of stage B (Homo sapiens sapiens):

 Bipedal locomotion with four reversed curves in the spine

 Forehead steep, reduced brow ridges

Solution D.2

(a) Industrial melanism


(b) Common name: Peppered moth

Scientific name: Biston betularia


(c) Reasons for changes in the two figures:

  • Before the Industrial Revolution, a thick growth of white-coloured lichen covered the trees. As a result, the light-coloured moths were camouflaged and survived under this cover, while the dark-coloured moths were easily spotted by predators.
  • 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.


(i) 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.

(ii) Charles Darwin

Solution D.3

(a) The figure depicts the evolution of long, muscular neck and forelimbs in giraffe.

(b) Primarily, the giraffe fed on grasslands which were later replaced by tall trees. As the ground-level vegetation became scarce, the giraffe took to feeding on tall trees. To reach the higher foliage leaves, the giraffe had to continuously stretch their neck and forelimbs. As a result, over generations, these structures became longer and stronger.

(c) The figure depicts the theory of inheritance of acquired characters.

(d) The theory was explained by Jean Baptist de Lamarck.

(e) From the theory of inheritance of acquired characters, it can be concluded that the organisms change physically as they struggle to meet the demands of their changing environment and whatever may be the modifications, they would pass on to the offspring generation after generation.

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