AIIMS 2003 Zoology Mammals Assertion Reason Question

To analyze the given question regarding the classification of bats and whales as mammals, let's break down the assertion and the reason provided:

Assertion

Bats and whales are classified as mammals.

• This statement is true. Both bats and whales belong to the class Mammalia. Mammals are characterized by their ability to produce milk (lactation), presence of hair or fur, and typically, a four-chambered heart.

Reason

Bats and whales have four-chambered hearts.

• This statement is also true. One of the defining features of mammals is their four-chambered heart, which consists of two atria and two ventricles. This structure allows for efficient separation of oxygenated and deoxygenated blood, supporting higher metabolic rates, which is essential for active animals like bats and whales.

Correct Answer

B) Both Assertion and Reason are true but Reason is not the correct explanation of Assertion.

Explanation of the Correct Answer

• While it is true that both the assertion and the reason are correct, the reason does not directly explain why bats and whales are classified as mammals. The classification of mammals is based on several characteristics, of which having a four-chambered heart is just one. Other significant features include the presence of mammary glands and hair. Thus, while the reason is true, it does not serve as the sole basis for classifying bats and whales as mammals.

Why Other Options Are Incorrect

• Option A: Both Assertion and Reason are true and Reason is the correct explanation of Assertion.

  • This is incorrect because, as explained, the reason (having a four-chambered heart) does not provide a direct explanation for why bats and whales are classified as mammals.

• Option C: Assertion is true but Reason is false.

  • This is incorrect since both the assertion and the reason are indeed true.

• Option D: Both Assertion and Reason are false.

  • This is incorrect since both statements are true.

Summary

In summary, the correct answer is option B because both the assertion and reason are true, but the reason does not sufficiently explain the classification of bats and whales as mammals. Understanding the characteristics of mammals provides a broader context for their classification beyond just the presence of a four-chambered heart.