Chapter 9: Heredity and Evolution- Exercise- 3

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Chapter 9: Heredity and Evolution

Class: X

Exercise number 3

Question 1

What are the different ways in which individuals with a particular trait may increase in a population?

Answer 1

• Natural selection: Those variations in traits which give survival advantage to an organism, are selected in nature resulting in increase of population.
• Genetic drift: There’s change in gene frequency, when particular type of genes accumulates. This causes genetic drift.
• Geographical isolation: It results in change of gene frequency which leads to expression of one type of traits in a geographically isolated population.
• Migration: Migration results in the flow of a particular type of gene in a specified population.

 

Question 2

Why are traits acquired during the life-time of an individual not inherited?

 

Answer 2

Acquired traits during the life time of an individual can’t be inherited because, acquired traits are due to changes in the life style, injury, loss of body parts. These are the traits which occur in the somatic cells. Any changes in the somatic cells are not passed on to the offspring belonging to next generation. For example: - if a person has amputated legs, it won’t be passed to the next generation.

Question 3

Why are the small numbers of surviving tigers a cause of worry from the point of view of

genetics?

 

Answer 3

 

The tiger population is decreasing sharply, along with the decrease in genetic pool of the tigers. The entire gene pool of these tigers has the alleles of surviving members. This leads to a limitation on the variations which can be introduced in the genetic makeup of the tigers. This might have serious consequences, because a small population leads to the accumulation of "bad" alleles, resulting in lot of inbreeding. This might even put tigers at the verge of extinction.