Q.Define conjugation.

Conjugation is the temporary union of two ciliates for mutual exchange of micronuclear (genetic) material, restoring genetic variability without directly increasing cell number.

Ciliates such as Paramecium have two types of nuclei — a large, polyploid macronucleus controlling metabolic/vegetative functions, and one or more small, diploid micronuclei responsible for genetic continuity. In conjugation, two compatible individuals of different mating types come together and adhere at their oral surfaces, forming a cytoplasmic bridge. Within each partner, the micronucleus undergoes meiosis to form haploid pronuclei, while the macronucleus degenerates. Each partner then exchanges one haploid, migratory pronucleus with the other through the cytoplasmic bridge; the exchanged pronucleus fuses with the stationary pronucleus retained by the partner, restoring the diploid condition — essentially mutual, internal fertilisation of nuclei rather than of whole cells. The partners then separate (now called exconjugants), and each regenerates a new …

Conjugation is the characteristic sexual reproductive process of ciliate protozoans, involving temporary fusion and mutual exchange of genetic material between two individuals rather than fusion of separate gametes.

Definition: In ciliates, conjugation is a temporary union of two individuals (conjugants) of compatible mating types. The two cells adhere at their oral (peristomal) surfaces, and a cytoplasmic bridge forms between them.

Process (brief): The diploid micronucleus of each conjugant undergoes meiosis to form haploid micronuclei; most degenerate, leaving one that divides mitotically into a 'stationary' and a 'migratory' pronucleus. The migratory pronucleus of each conjugant crosses the bridge and fuses with the stationary pronucleus of the partner, forming a synkaryon in each cell. The old macronucleus disintegrates and a new macronucleus reorganizes from the synkaryon. The two individuals then separate (exconjugants) and resume independent binary fiss …