Chapter 28, Problem 8STP

Summary Introduction

Introduction :

Amphibians are vertebrates. The name Amphibians itself suggests that they can live on both lands as well as in water. They were the first vertebrates who can survive on the land. However, they need water bodies to fertilize their eggs. Amphibians have moist skin and they are tetrapod animals which means they have two pairs of legs viz. Forelegs and Hindlegs. Some have tails while in some tails are absent. Amphibians have three-chambered hearts and they are mostly ammoniotelic.

Answer to Problem 8STP

Correct answer :

Option D) They were the first animals to evolve lungs.

Explanation of Solution

Explanation/justification for the correct answer :

Lungs are the respiratory organs that help in respiration. They are the sac-like structure which is usually present in the pairs in the thoracic cavity. The basic unit of lungs which helps in gaseous exchange is alveoli.

Amphibians were not the first ones to evolve lungs as the lungs were already present in some fishes which are known as Lung Fishes or Dipnoi. They have both the lungs as well as the air bladder to store air and maintaining buoyancy. Three species of Lung fishes are still present on earth and are commonly known as African lungfish, Australian lungfish and American lungfish.

Explanation for incorrect answer :

Option (A) Many lack legs during part of their life cycle. The larvae of amphibians usually lack legs therefore, this statement is correct.

Option (B) Many spend part of their life cycle in water and part on land. As amphibians release their eggs in water bodies, therefore, their larvae develop in water. Hence, they spend the part of their life cycle in the water when in the larvae stage and some part on land when they are adults.

Option (C) Most depends on outside water sources to keep their bodies moist Average sized features are against in population X. Amphibians usually live in moist places such as swampy areas, near the water bodies as they need a water source to keep their body moist.