Depending upon the stage, when meiosis occurs, the meiosis is of three types : Gametic, zygotic and sporic.
- Gametic or terminal meiosis : In most animals and some lower plants meiosis takes place during the formation of gametes (gametogenesis). Such a meiosis is described as gametic or terminal meiosis. When two gametes fuse in fertilization, the diploid zygote is formed. Gametic meiosis results in diplontic life cycle
Q. 1. How many types of meiosis are there ? Explain.
Ans. Depending upon the stage, when meiosis occurs, the meiosis is of three types : Gametic, zygotic and sporic.
-
Gametic or terminal meiosis : In most animals and some lower plants meiosis takes place during the formation of gametes (gametogenesis). Such a meiosis is described as gametic or terminal meiosis. When two gametes fuse in fertilization, the diploid zygote is formed. Gametic meiosis results in diplontic life cycle.
-
Zygotic or initial meiosis : In some lower plants meiosis takes place in the zygote and the resulting organisms are haploid. It is called zygotic or initial meiosis. Organisms having zygote meiosis have haplontic life cycle.
-
Sporic or intermediate meiosis : In most of the
plants, meiosis occurs at the time of sporogenesis. It is called sporic or intermediate meiosis. Spore gives rise to a new gametophytic phase in the life cycle. The gametophyte produces gametes. The life of plant is said to be diplo-haplontic because of the presence of diploid and haploid multicellular phases.