Biology · Plant Kingdom · NEET
| Ploidy | Haploid (n) | Diploid (2n) |
| What it produces | Gametes (egg, sperm) | Spores |
| Cell division used | Mitosis (already n) | Meiosis (2n to n) |
| Starts from | A spore (n) | A zygote (2n) |
| Dominant in | Algae, bryophytes (mosses) | Ferns, gymnosperms, angiosperms |
| Example (moss) | Leafy green moss plant | Small capsule on a stalk |
A gametophyte is the haploid (n) body that produces gametes (male and female sex cells). A sporophyte is the diploid (2n) body that produces spores through meiosis. So the simple test: if a plant body makes gametes it is a gametophyte, if it makes spores it is a sporophyte. They are two different phases of the same plant's life, not two different plants.
Gametophyte = haploid = n (one set of chromosomes). Sporophyte = diploid = 2n (two sets). This is fixed and NEET tests it a lot. Trick to remember: the gametophyte is 'half' (haploid, n) so it can make gametes that fuse to restore the full (2n) number in the zygote, which grows into the sporophyte.
The gametophyte makes GAMETES (egg and sperm). The sporophyte makes SPORES (by meiosis). Note the meaning inside the words: 'gameto-phyte' = gamete plant, 'sporo-phyte' = spore plant. The gametes fuse to form the zygote (2n), and spores grow into new gametophytes (n).
In plants, gametes are made by MITOSIS from the already-haploid gametophyte (the gametophyte is n, so it does not need to reduce again). Spores are made by MEIOSIS in the diploid sporophyte (2n reduces to n). This is a common NEET confusion: in plants meiosis makes spores, not gametes. In animals, meiosis directly makes gametes, so do not mix the two.
In algae (like Spirogyra) and bryophytes (mosses, liverworts) the GAMETOPHYTE (n) is dominant and free-living. In pteridophytes (ferns), gymnosperms and angiosperms the SPOROPHYTE (2n) is dominant. NEET memory line: as plants evolved higher, the sporophyte grew bigger and the gametophyte shrank. In a moss the sporophyte is small and depends on the gametophyte; in a fern it is the opposite.
Gametophyte (n) makes gametes by mitosis, two gametes fuse to form a zygote (2n), the zygote grows into the sporophyte (2n). The sporophyte makes spores by meiosis (spores are n), and each spore grows into a new gametophyte (n). This alternating pattern is called alternation of generations. So the two bodies keep giving rise to each other in a loop.
The leafy green moss plant you see is the GAMETOPHYTE (n). It starts as a protonema stage (first gametophyte stage from a spore), then becomes the leafy stage that bears sex organs. The sporophyte is the small brown stalk-and-capsule that grows on top and depends on the gametophyte for food. NEET has directly asked that protonema is the first stage of the moss gametophyte.
Match the plant with the kind of life cycle it exhibits: (a) Spirogyra (b) Fern (c) Funaria (d) Cycas — List II: (i) Dominant diploid sporophyte vascular plant with highly reduced gametophyte (ii) Dominant haploid free-living gametophyte (iii) Dominant diploid sporophyte alternating with reduced gametophyte called prothallus (iv) Dominant haploid leafy gametophyte with partially dependent sporophyte
Assertion A: The first stage of gametophyte in the life cycle of moss is the protonema stage. Reason R: Protonema develops directly from spores produced in capsule.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
The zygote (2n) is the very first cell of the sporophyte. When two gametes from the gametophyte fuse, the diploid zygote forms and then grows into the sporophyte. So the zygote belongs to the sporophyte phase, not the gametophyte.
Spores are haploid (n). They are made by meiosis from the diploid (2n) sporophyte, so the chromosome number is halved. Each haploid spore grows by mitosis into a haploid gametophyte.
As plants moved to land and evolved higher, the diploid sporophyte became larger, longer-living and independent, while the gametophyte became smaller. In bryophytes the gametophyte still leads and the sporophyte depends on it; in pteridophytes, gymnosperms and angiosperms the sporophyte is the big main plant.
It is the life cycle pattern where a haploid gametophyte and a diploid sporophyte alternate, each producing the other: gametophyte makes gametes to form the sporophyte, and the sporophyte makes spores to form the gametophyte.
