AIIMS 2005 Zoology Theories of Evolution Assertion Reason Question

To understand the question fully, we need to evaluate both the Assertion and the Reason provided, as well as their interrelation.

Assertion:

"Human ancestors never used their tails and so the tail expressing gene has disappeared in them."

Analysis of Assertion: This statement is misleading. While it is true that modern humans do not have functional tails, this is not primarily due to their "lack of use" as suggested. Instead, the absence of tails in humans is a result of evolutionary changes over millions of years. The gene for tail formation may still exist in a dormant state, or it might have been lost through genetic drift or natural selection. The idea that the tail expressing gene has "disappeared" is an oversimplification and does not accurately represent the complexities of genetic inheritance and evolution.

Reason:

"Lamarck's theory of evolution is popularly called theory of continuity of germ plasm."

Analysis of Reason: This statement is incorrect. Lamarck's theory is actually known for proposing the inheritance of acquired characteristics, where traits developed during an organism's lifetime can be passed on to offspring. The term "continuity of germ plasm" is associated with August Weismann, who argued that only the germ cells (sperms and eggs) can pass traits to the next generation, thereby separating somatic (body) changes from hereditary changes. Thus, the Reason is factually incorrect.

Conclusion:

Since both the Assertion and the Reason are false, the correct answer to the question is:

D) If both Assertion and Reason are false statements.

Clarification of Incorrect Options:

• Option A: This option states both the Assertion and Reason are true, with the Reason explaining the Assertion. This is incorrect because both statements are false.

• Option B: Similar to Option A, this indicates both are true but the Reason does not explain the Assertion. Again, this is incorrect as both are false.

• Option C: This suggests the Assertion is true while the Reason is false. This is also incorrect since both the Assertion and the Reason are false.

Summary:

In summary, the Assertion misrepresents evolutionary processes regarding the tail gene in humans, while the Reason incorrectly attributes a concept to Lamarck that belongs to Weismann. Therefore, both statements fail to hold true, leading us to select option D as the correct response.

This analysis emphasizes the importance of understanding the nuances of evolutionary biology and the historical context of various theories, ensuring clarity in interpreting assertions and reasoning in exam questions.