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):
|
Australopithecus |
Cro-magnon |
|
Lack of chin |
Well-developed chin |
(b) Differences between Australopithecus and Modern man (Body hair):
|
Australopithecus |
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:
|
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
(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.
(d)
(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.
