Chapter 33, Problem 1STP

Summary Introduction

Introduction:

Mammals are animals with hair and mammary glands. Young mammals are fed milk from their mother's special mammary glands. In addition to these characteristic milk glands, mammals are characterized by a number of other distinctive features. Although it has disappeared in many whales, hair is a typical mammalian trait. The lower mammalian jaw is clamped directly to the skull instead of through a separate bone (quadrate) as in all other vertebrates.

Answer to Problem 1STP

Correct answer :

The correct answer is option (B) endothermy.

Explanation of Solution

Explanation/justification for the correct answer :

Option (B) endothermy. Mammals are endothermic, which means they generate internal body heat. The body heat source is internal- the result of heat generated by a high metabolic rate. So, the correct answer is option (B).

Explanation for incorrect answer :

Option (A) hair. The hair of mammals acts as insulation, sensory devices, camouflage, and waterproofing. So, this is an incorrect answer.

Option (C) four-chambered heart. Birds and mammals possess a four-chambered heart. So, this is an incorrect answer.

Option (D) internal fertilization. The internal fertilization takes place in all organisms except in fish. So, this is an incorrect answer.