Reproduction in Protists

Protists have an immense reproductive potential. During favourable environment condition, they may reproduce several times a day, leading to population explosion.
They have no special organelles for reproduction but reproduce both by asexual and sexual means.

1. Asexual reproduction

Asexual reproduction usually takes place by the process of fission. In fission, the body of the organism after attaining a certain size simply divided into two or more parts, each having a part of the nucleus. There are two types of fission in protists.

a) Binary fission

In binary fission, two individuals are formed from a single parent. The fission may be :-
I) Irregular - Amoeba
ii) Transverse - Paramecium
iii) Longitudinal - Euglena

b) Multiple fission

In multiple fission, the parent body divided into many daughter organisms as in Amoeba, plasmodium vivax, etc.
In multiple fission, Amoeba  secret a 3- layered, protective chitinous cyst around it and becomes inactive. Then, the nucleus divides repeatedly to form several daughter nuclei, which arrange themselves near the periphery.
Each daughter nucleus is enveloped by a small amount of cytoplasm thus forming amoebulae or pseduopodiospores.
On return of fevourable condition, the cyst breaks off liberating the young amoebulae, which grow into new amoebae.

2. Sexual reproduction

Sexual reproduction involves the formation and fusion of sex cells.
Sexual reproduction is of the following three types:-

a) Syngamy

Syngamy is the fusion of two sex cells to form zygote.
Syngamy may be of isogamous or anisogamous type.

b) Conjugation

Conjugation is a characteristic of protists ciliates. In Conjugation, two individuals of the same specie temporarly unite by the oral surface and a protoplasmic bridge is formed between them, through which exchange of nuclear material take place.

c) Autogamy

In Autogamy, the male and female gametes produced by the same unicell fuse to form a diploid zygote.

No comments

Powered by Blogger.