Alteration of Generations
Alternation of Generations is also known as metagenesis. In Plants, there are 2 phases of the life-cycle:
- Gametophyte/sexual phase.
- Sporophyte/asexual phase
- The zygote(2n) divides to form the sporophyte(2n) and spores(n) divide to form the gametophyte(n).
- The sporophyte plant is diploid(2n), it produces spores(n) after meiosis.
- The gametophyte plant is haploid(n), it produces gametes(n) that undergo fertilization to form the zygote(2n).
- These 2 phases alternate each other in the life-cycle.
There are 3 types of life-cycles, depending upon the duration of gametophyte & sporophyte generations.
- The plant body is gametophyte.
- The main part of life-cycle is gametophyte.
- Sporophyte generation is very reduced & is represented by a single cell i.e., the zygote that immediately undergoes meiosis.
- Zygotic meiosis occurs.
- Seen in most Algae.