Chapter 19, Problem 18A

Summary Introduction

To describe:

Process of conjugation in paramecia.

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.

Paramecium possesses cilia all over its body. Cilia are tiny hair structure present on the body of a paramecium. It is generally present in many numbers and help in locomotion and in capturing and internalizing the prey.

Explanation of Solution

Conjugation is a process of exchange genetic material among the paramecium of two different species. It is quite different from reproduction as no offspring are produced during this process.

During conjugation, a cytoplasmic bridge is formed between the two interacting paramecia and meiosis occurs in the diploid micronuclei. Three out of the four formed micronuclei get dissolved and the fourth one undergoes mitosis. One micronucleus is exchanged between the two conjugating paramecia followed by their separation. Now, in each paramecium, the macronucleus disintegrates and the two micronuclei fuse to form new macronuclei.

A schematic representation of the conjugation process is shown below

Conclusion

Conjugation is the process of exchange of genetic material between two paramecia in which both the interacting partners exchange one haploid micronucleus. After the process of micronuclei exchange, the older macronucleus is disintegrated and a new macronucleus is formed.