Chapter 19, Problem 15A

Summary Introduction

Introduction :

Paramecium is a type of protozoa. Protozoa are animal-like protists that follow a heterotrophic mode of nutrition and are thus characterized as heterotrophs. Protozoans generally ingest other protozoans, algae, and bacteria to obtain energy and nutrition.

Answer to Problem 15A

Correct answer :

The correct answer is option (B) amount of water.

Explanation of Solution

Explanation/justification for the correct answer :

Option (B) amount of water. The contractile vacuole is specifically helpful for aquatic organisms in maintaining homeostasis or water balance in their body. The vacuole collects the excess water present in the body of the organism (generally unicellular) or the cytoplasm and then expels it outside the body or cell. The vacuole may also contain some waste products that also get expelled out along with water. Paramecium has two contractile vacuoles. So, the correct answer is option (B).

Explanation for incorrect answer :

Option (A) amount of food. The contractile vacuole is primarily responsible for regulating the amount of water inside the body of paramecium. The vacuole that regulates or stores the food is known as food vacuole. So, this is an incorrect option.

Option (C) movement. Movement or mobility is the process of how an organism moves from one to another location. Organisms follow different mode movement while others remain sessile and do not move at all. Structures that help in movement or locomotion include cilia, flagella, or pseudopodia. So, this is an incorrect answer.

Option (D) reproduction. Reproduction is the process of the formation of new organisms from the existing ones. Majorly reproduction is of two types, sexual and asexual. The contractile vacuole is not involved in reproduction. So, this is an incorrect answer.