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Biology [5 Mark Question Answer]

Human Evolution · ICSE STD 10 (ICSE - English Medium). 3 questions.

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[5 Mark Question Answer]

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Question 15 Marks
Why Neanderthal man and modern man belong to two distinct species?
Answer
Neanderthal man and modern man exhibit different characteristics, and hence, they are considered two distinct species. Below are the characteristic differences between Neanderthal man and modern man:
Characteristics Neanderthal man Modern man
Locomotion Absolute bipedalism Bipedal locomotion
Head and forehead Large head, broad, flat and sloping forehead Upright head, skull on the top of the vertebral column, steep forehead
Brow ridges Prominent brow ridges Reduced brow ridges
Chin No chin Well developed and prominent chin
Hair on body Less hair on the body Prominent hair on limbs
Cranial capacity $1450 cm^3$​​​​​​​ $1450$ to $1600 cm^3​​​​​​​$​​​​​​​
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Question 25 Marks
Briefly discuss Lamarckian Theory of Inheritance citing an appropriate example.
Answer
  • According to the theory of inheritance of acquired characters, 'the changes in structure or function of any organ acquired during the life-time of an individual in response to changes in the surrounding environment are inherited by offspring and keep on adding over a period of time'.
  • This theory states that characters are acquired by animals in two ways:

    • - Effects of environment
    - Use and disuse of body parts
  • For example, the long neck of giraffe is explained by Lamarck on the same principle. Giraffe, which lived in the dry and arid deserts of Africa, tried to reach the foliage high up on the trees to eat them as there was no vegetation on the ground. In the process, its neck and forelegs got stretched a bit and this was inherited by the next generation. Then, in the next generation, the same efforts continued. Gradually, through many successive generations, we got a giraffe having a long neck and long forelegs.
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    Question 35 Marks
    Briefly discuss the Theory of Natural Selection as given by Darwin.
    Answer
    Charles Darwin proposed the idea of natural selection. Darwinism or Theory of Natural Selection is based on some facts: (i) Overproduction:
    • All organisms have the capacity to reproduce at a very high rate.
    • However, organisms cannot survive by reproduction alone.
    • Due to lack of food and space, offspring soon begin to die.
    • Some are eaten by predators, while some get destroyed due to adverse environmental conditions.
    (ii) Struggle for existence:
    • Overproduction of organisms results in a struggle for existence among organisms.
    • The struggle is to obtain food, space and mate.
    (iii) Variation:
    • Progeny of the same parents are not exactly alike. Such differences are known as variations. The variations may be harmful or advantageous.
    (iv) Survival of fittest:
    • In the struggle for existence, organisms that develop new favourable characteristics will survive in the long run. This idea is called 'Survival of the fittest'.
    • Organisms which survive will transmit favourable characters to their offspring.
    • These characters get accumulated and give rise to new species.
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