Biology · Plant Kingdom · NEET
Zygotic meiosis means the zygote is the very first cell to divide by meiosis. The male and female gametes fuse to make a diploid (2n) zygote, and instead of growing into a body, this zygote at once divides by meiosis to make haploid (n) cells. So the zygote is the ONLY diploid cell in the whole life cycle. The main plant body stays haploid. This gives the haplontic life cycle. Example: Chlamydomonas, Spirogyra, Volvox (green algae). It is also called 'initial meiosis' because meiosis happens at the start, right after fertilisation.
In gametic meiosis, meiosis directly produces the gametes. The plant body is diploid (2n) and dominant, and the only haploid (n) cells are the gametes themselves. There is no haploid body and no spore stage. When two gametes fuse, the zygote grows straight into a new diploid body. This gives the diplontic life cycle. Fucus (a brown alga) is the NCERT example. Note: this is the SAME pattern as in animals and humans, which is why gametic meiosis feels familiar.
In sporic meiosis, meiosis produces spores (not gametes). Because meiosis makes spores, the plant has BOTH a diploid spore-making body (sporophyte, 2n) and a haploid gamete-making body (gametophyte, n). The two bodies alternate — this is the haplo-diplontic life cycle with true alternation of generations. It is seen in bryophytes (mosses, liverworts), pteridophytes (ferns), gymnosperms and angiosperms. Remember: 'sporic = spores come out of meiosis'.
The answer is Chlamydomonas. NEET 2017 gave the options Marchantia, Fucus, Funaria and Chlamydomonas. Chlamydomonas is a green alga and is haplontic, so its zygote does meiosis at once (zygotic meiosis). Marchantia and Funaria are haplo-diplontic (sporic meiosis) and Fucus is diplontic (gametic meiosis). So only Chlamydomonas fits zygotic meiosis.
Match them one-to-one: Zygotic meiosis → Haplontic (dominant haploid body, only zygote is 2n). Gametic meiosis → Diplontic (dominant diploid body, only gametes are n). Sporic meiosis → Haplo-diplontic (both 2n sporophyte and n gametophyte, alternation of generations). NEET often asks the life cycle name and the meiosis type in the same question, so learn them as a pair.
Meiosis is the step that halves the chromosome number, so wherever meiosis happens, that is where the switch from 2n to n takes place. If it happens in the zygote, everything after (the body) is haploid. If it happens to make gametes, everything before (the body) is diploid. If it happens to make spores, the body before meiosis is 2n (sporophyte) and the body grown from spores is n (gametophyte). This is why NEET ploidy questions always start from 'where is meiosis?'.
Zygotic meiosis is characteristic of
Life cycle of Ectocarpus and Fucus respectively are
Try the real previous-year questions from this chapter — each with the answer and a full solution.
They describe the same thing from two angles. 'Zygotic meiosis' names WHERE meiosis happens (in the zygote), and 'haplontic' names the life cycle you get (a dominant haploid body with only the zygote diploid). If a plant shows zygotic meiosis, it is haplontic. Example: Chlamydomonas, Spirogyra, Volvox.
Both show gametic meiosis. In humans and in Fucus the body is diploid and meiosis directly makes the haploid gametes, with no haploid body and no spore stage. This is the diplontic life cycle. NEET uses Fucus as the plant example of this pattern.
Yes. Bryophytes (mosses, liverworts), pteridophytes (ferns), gymnosperms and angiosperms all show sporic meiosis, so they all have a haplo-diplontic life cycle with alternation of generations (a 2n sporophyte and an n gametophyte). What changes between groups is only WHICH body is dominant.
In both, meiosis is sporic — it happens in the sporophyte (2n) to make haploid spores. In a moss it occurs inside the capsule; in a fern it occurs in the sporangia (in the spore mother cells) on the sporophyte. The spores then grow into the gametophyte (protonema/leafy body in moss, prothallus in fern).
Because NEET repeatedly asks it directly (e.g. 'Zygotic meiosis is characteristic of…', 2017) and also uses it to solve ploidy and life-cycle matching questions. Once you know where meiosis sits, you can instantly tell which cells are n or 2n and name the life cycle, saving time in the exam.
