Alternation of Generation: Metagenesis.

Alternation of generation...Metagenesis.

METAGENESIS:
DEFINITION:
"The alternation of generation that reproduces asexually (by budding or fission) with a generation that reproduces sexually (by eggs and sperms) is called alternation of generation"
FOR EXAMPLE:
Coelentrates like Obelia.
EXPLANATION:

1. Obelia colony does not bear gonads and is therefore sexless representing asexual reproduction.
2. It develops by budding and is diploid.
3. It contains three types of zooids: polyps and medusae.
4. Polyps reproduce asexually by budding to give medusae.
5. The medusae are set free by the parent colony and swim in water. It is free living.
6. The medusae give rise to egg and sperms - acting as reproductive organs.
7. On fertilization the oosperms again develop into an asexual obelia colony.

CONCLUSION:

Free type swimming medusoid sexual alternate with sessile polypoid asexual.