Chapter 33, Problem 1TY

Choanocytes are

1. a. a group of protists that are believed to have given rise to animals.
2. b. specialized cells of sponges that function to trap and eat small particles.
3. c. cells that make up the gelatinous layer in sponges.
4. d. cells of sponges that function to transfer nutrients to other cells.
5. e. cells that form spicules in sponges.

Summary Introduction

Introduction: Sponges belong to the group Porifera of invertebrate animals. These organisms are characterized by the presence of pores on their body surface. They are the simplest type of invertebrates of animal kingdom.

Answer to Problem 1TY

Correct answer: The specialized cells that function to trap and eat small particles are choanocytes. Hence, the correct answer is option b.

Explanation of Solution

Reason for correct answer:

Choanocytes are the specialized cells that are present in various different types of sponges. These cells are also called collar cells and possess a central flagellum. The central flagellum is surrounded by a collar of thin microvilli. These cells are very important as they form choanoderm, a type of layer found in sponges. These cells play a vital role in trapping and eating tiny particles.

Option b. is given as “specialized cells of sponges that function to trap and eat small particles”.

Choanocytes or collar cells are specialized cells of sponges that are very important for eating or trapping smaller particles present in the aquatic environment. Hence, the correct answer is option b.

Reasons for incorrect answer:

Option a. is given as, “a group of protists that are believed to have given rise to animals”.

Choanocytes are not the group of protists that have given rise to animals. They are specialized cells of sponges. Hence, option a. is incorrect.

Option c. is given as, “cells that make up the gelatinous layer in sponges”.

A gelatinous layer of sponges are called mesohyl. These layers are formed due to the cell to cell connections in sponges, and not because of choanocytes. Hence, option c. is incorrect.

Option d. is given as, “cells of sponges that function to transfer nutrients to other cells”.

Choanocytes perform the function of trapping and killing of small particles. These cells are not involved in the transfer of nutrients to other cells. Hence, option d. is incorrect.

Option e. is given as, “cells that form spicules in sponges”.

Spicules are the structures that provide support to the body of sponges. These spicules are formed by calcium carbonate or silica, and not by choanocytes. Hence, option e. is incorrect.

Hence, the options a., c., d., and e. are incorrect.

Conclusion

Choanocytes are specialized collar cells of sponges that have evolved to eat and trap smaller particles by creating water currents.