NCERT Solution for Class 10 Science Chapter 9
Heredity and Evolution
NCERT Books for Session 2022-2023
CBSE Board and UP Board
Exercises Questions
Page No-159
Questions No-12
Only variations that confer an advantage to an individual organism will survive in a population. Do you agree with this statement? Why or why not?
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In species, variations that offer survival advantages are naturally selected. Individuals
adjust to their environments with the help of these selected variations and consequently
these variations are passed on to their progeny. Evolution of organisms occurs as a result
of this natural selection.
However, there can be some other variations, which do not offer any survival advantage
and arise only accidentally. Such variations in small populations can change the frequency
of some genes even if they are not important for survival.
This accidental change in the frequency of genes in small populations is referred to as
genetic drift.
Thus, genetic drift provides diversity (variations) without any survival advantage.
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We agree with the statement that Only variations that confer an advantage to an individual organism will survive in a population. All the variations do not have an equal chance of surviving in the environment in which they find themselves. The chances of surviving depend on the nature of variations. Different individual would have different kind of advantages. A bacteria that can withstand heat will survive better in a heat wave. Selection of variants by environmental factors forms the basis for revolutionary process.
This statement is true to some extent. There are many apparent variations which help an individual in survival. But there are certain variations which may not be beneficial, yet they are inherited through subsequent generations. The colourful plumage of peacock is a good example. The colourful plumage of a peacock helps it in finding a suitable mate but it also makes it conspicuous for its predators.
Variations are a continuous process and may not show an immediate advantage. However, under drastically changed environment, only those organisms may survive, where the variation gives them that advantage. Hence, i do not agree with this statement.