Chapter 24, Problem 31A

Summary Introduction

Introduction :

Cnidarians and sponges were the first animals that evaluated from a multicellular ancestor. Most sponges live in marine water. Sponges have no tissues, no organs, and most have no symmetry. Sponges belong to the phylum Porifera that contains between 5000 to 10000 members.

Answer to Problem 31A

Correct answer :

The correct answer is option (D) tissues.

Explanation of Solution

Explanation/justification for the correct answer :

Option (D) tissues. Sponges do not have any tissues or organs. Sponge embryos do not develop endoderm or mesoderm and therefore, they do not develop tissues. So, the correct answer is option (D).

Explanation for incorrect answer :

Option (A) filter feeding. Sponge gets its food by filtering small particles from water. This process of filtering is known as filter feeding. It is one of the main characteristic of sponge. So, this is an incorrect option.

Option (B) digestion inside cells. In a sponge's body nutrients and oxygen dissolved in water enter through the pores, food particles cling to the cells. The digestion of nutrients takes place inside each cell. So, this is an incorrect answer.

Option (C) asymmetry. Sponges show asymmetrical appearance of their bodies. This is one of the main characteristic of sponge. So, this is an incorrect answer.