Kingdom Protista - Reproduction

Description:

Reproduction in protists can occur both by sexual and asexual modes.

Asexual Reproduction

Involves only one parent. All young ones produced have the same genetic constitution hence called clones.

Asexual reproduction can occur in the following ways −

• Binary fission − Division of parent cell into two equal daughter cells.

• Multiple fission − Division of parent cell into several daughter cells.

• Plasmotomy − Division of multinucleate protist into two or more multinucleate offspring by the division of cytoplasm without the division of nucleus.

• Spore formation − Spores are structures which are produced during unfavourable conditions.

• Budding − Small outgrowth develops from the parent body which separates and develops into a new individual.

Sexual Reproduction

Sexual reproduction involves two processes −

• Meiosis − Reduces the number of chromosomes from 2n to n.

• Fertilization − Fusion of two n gametes to form 2n zygotes (fertilized).

There are two methods of sexual reproduction −

Syngamy

• Complete fusion of two gametes to produce a diploid zygote.

• It can by isogamy (fusion of two similar gametes), anisogamy (fusion of two dissimilar gametes) and oogamy (large non-motile gametes are fertilized by smaller motile gametes).

Conjugation

• Temporary union of two individuals to exchange their haploid pronuclei to form a zygote nucleus.

• Each individual with zygote nucleus produces daughter individuals by binary fission.