Chapter 29, Problem 8STP

Summary Introduction

Introduction:

Amphibians include toads, frogs, salamanders, newts, and legless caecilians. Most amphibians are distinguished by moist skin without scales, four legs, exchange of gases through skin, a circulatory system with double loop, lungs, and aquatic larvae.

Answer to Problem 8STP

Correct answer:

The correct answer is option (C) lungs and a closed circulatory system.

Explanation of Solution

Explanation/justification for the correct answer:

Option (C) lungs and a closed circulatory system. Most adult amphibians breathe through their lungs. The amphibian circulatory system is closed. It consists of a double loop. The first loop takes oxygen-less blood from the heart to pick up oxygen from the lungs and skin, and then transfers the oxygen-filled blood back to the heart. During circulation in the second loop, the oxygen-filled blood travels from the heart to the body through the vessels, where oxygen spreads to the cells. So, the correct answer is option (C).

Explanation for incorrect answer:

Option (A) gills and a closed circulatory system. As larvae, most amphibians exchange gases through their skin and gills. As adults, most breathe through lungs. So, this is an incorrect option.

Option (B) gills and an open circulatory system. As larvae, most amphibians transfer gases through their skin and gills. As adults, most of them breathe through the lungs. The amphibian circulatory system is closed. It consists of a double loop. So, this is an incorrect option.

Option (D) lungs and an open circulatory system. The circulatory system of amphibians is closed. It is consists of a double loop. So, this is not the correct option.