Chapter 29, Problem 4STP

Summary Introduction

Introduction:

The roundworms are on pseudocoelomates branch according to their evolutionary tree. Roundworms are also known as nematodes. They are found in both marine and freshwater habitats and on land. Some are parasites on plants and animals.

Answer to Problem 4STP

Correct answer:

The correct answer is option (C) Materials diffuse through their body walls.

Explanation of Solution

Explanation/justification for the correct answer:

Option (C) Materials diffuse through their body walls. Pseudocoelomates do not have respiratory or circulatory organs. They depend on diffusion to transfer nutrients and gases across their bodies. Most roundworms exchange gases and excrete metabolic waste through their moist outer body coverings. So, the correct answer is option (C).

Explanation for incorrect answer:

Option (A) Their digestive tract is used for gas exchange. In pseudocoelomates, the outer body covering or epidermis tissues exchange gases and excrete metabolic wastes. The digestive tract is not used for gas exchange. So, this is an incorrect option.

Option (B) Gas exchange occurs through the endoderm tissue. In pseudocoelomates, the outer body covering or epidermis tissues exchange gases and excrete metabolic wastes. So, this is an incorrect option.

Option (D) Materials exchange in the primitive respiratory system. Pseudocoelomates do not have respiratory or circulatory organs. They depend on diffusion to transfer nutrients and gases across their bodies. So, this is not the correct option.