Chapter 19, Problem 12A

Summary Introduction

To write:

About contractile vacuole.

Introduction:

Structures in a living organism are either an extension of a cell, some kind of formation of different macromolecules (like proteins) or can be an arrangement of different cells that are aligned to perform a particular function. Different organisms are adapted to form different structures that help them to perform their life functions. Some structures may seem similar in different organisms but have different internal structures.

Explanation of Solution

The contractile vacuole is a structure generally seen in 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.

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. An example of an organism that possesses contractile vacuole is paramecium. Paramecium has two contractile vacuoles.

Conclusion

A contractile vacuole is a water level regulating structure present in aquatic organisms. Paramecium is an example of an organism possessing a contractile vacuole.