Difference Between Zygotic, Gametic And Sporic Meiosis

Zygotic Meiosis

Zygotic meiosis is meiosis of a zygote immediately after karyogamy which is the fusion of two cell nuclei. This way, the organism ends its diploid phase and produces several haploid cells. These cells divide mitotically to form either larger, multicellular individuals or more haploid cells.

Zygotic meiosis takes place in some lower plants and animals. They don’t form haploid gametes, in them the male and the female sex cells are diploid and they fuse to form tetraploid zygote on fertilization. This zygote in turn undergoes meiosis to get normal diploid set of chromosomes.

What You Need To Know About Zygotic Meiosis

Zygote is the only diploid structure in the life cycle.
The dominant individual in the life cycle is haploid hence the life cycle is haplontic.
Meiosis takes place at the time of zygote germination
This life cycle appears in all fungi, many protozoa and some algae.

Gametic Meiosis

In gametic meiosis, instead of immediately dividing meiotically to produce haploid cells, the zygote divides mitotically to produce a multicellular diploid individual or a group of more unicellular diploid cells. Cells from the diploid individuals then undergo meiosis to produce haploid cells or gametes.

Haploid cells may divide to form more haploid cells, as in many yeasts but the haploid phase is not the predominant life cycle phase. In most diplonts, mitosis occurs only in the diploid phase i.e gametes usually form quickly and fuse to produce diploid zygotes.

The diploid multicellular individual is a diplont hence a gametic meiosis is also referred to as diplontic life cycle. Diplonts are:

Animals
Some brown algae
Some fungi e.g brewer’s yeast.

What You Need To Know About Gametic Meiosis

All structures except gametes are diploid.
The dominant individual in the life cycle is diploid.
Meiosis occurs only at the time of gamete formation.
Some brown and green algae, animals and many other organisms maintain this type of life cycle.

Sporic Meiosis

In sporic meiosis, the zygote divides mitotically to produce a multicellular diploid ‘’sporophyte’’. The sporophyte creates spores via meiosis which also then divides mitotically producing haploid individuals referred to as ‘’gametophytes’’. Gametophytes now produce gametes via mitosis. In many plants, the gametophyte is not only small-sized but also short-lived.

In the whole cycle, gametes are usually the only haploid cells and mitosis usually occurs only in the diploid phase. Haplodiplonts include:

Most plants
Some fungi

What You Need To Know About Sporic Meiosis

In sporic meiosis (also commonly referred to as intermediary meiosis), the zygote divides mitotically to produce a multicellular diploid sporophyte.
Meiotic division occurs during sporogenesis
Results in formation of haploid spores.
Spore divides to form gametophytes which will form gametes. Gametes fusion results in diploid sporophyte i.e having Diplohaplontic life cycle.
This life cycle is common in angiosperms.

Also Read: Difference Between Continuous And Discontinuous Variations