The sequence of events between any given phase in one generation and that similar phase in the next succeeding generation constitute a life cycle. Two types of life cycle are zygotic meiosis and gametic meiosis.
Zygotic Meiosis : The organism spends most of its life cycle in haploid (1n) condition. The zygote is the only diploid (2n) stage that divides by meiosis (that is why called zygotic meiosis) and again produces vegetative cells with 1n chromosome number.
Gametic Meiosis :The organism spends most of its life cycle in the 2n condition. The gametes are only 1n that are produced by meiosis that is why called gametic meiosis. The gametes fuse to form zygote that grows to form the diploid individual.
Zygotic Meiosis vs Gametic Meiosis
Zygotic Meiosis1. Zygote is the only diploid structure in the life cycle.
2. The dominant individual in the life cycle is haploid hence the life cycle is haplontic.
3. Meiosis takes place at the time of Zygote germination.
4.This life cycle appears in all fungi and some algae.
Gametic Meiosis
1. All structures except gametes are diploid.
2. The dominant individual in the life cycle is diploid hence the life cycle is diplontic.
3. Meiosis occurs only at the time of gamete formation.
4. Some brown and green algae, animals and many other organisms maintain this type of life cycle.
