Answer to Question #223225 in Zoology for Debbie

Question

Distinguish between binary fission and conjugation in paramecium and ensure that you can explain other protozoans reproduce.

Answer 1

Paramecia display a form of sexual reproduction. Two paramecia come along side one another, make contact, and form a cytoplasmic bridge (conjugation). The micronucleus of each organism duplicates twice to form four micronuclei. Three of the micronuclei fragment and disappear, leaving one micronucleus per organism. That micronucleus divides, forming a pair of micronuclei. The conjugated paramecia exchange one of their micronuclei. Each new pair of micronuclei unites to form a single micronucleus. The macronucleus in each paramecium, having dissolved and disappeared, reforms in each organism. The paramecium will then reproduce by simple mitosis (binary fission, a form of asexual reproduction). In this process, genetic material duplicates, followed by organ duplication. The cell divides, forming two individuals.

Protozoans reproduce asexually by binary fission or multiple fission. Many protozoan species also exchange genetic material by sexual means (typically, through conjugation), but this is generally decoupled from the process of reproduction, and does not immediately result in increased population.