Q. Life cycle in ferns is ____
NTA AbhyasNTA Abhyas 2022
Solution:
Based on the predominant stage found, the life cycles of the lower plants can be divided into three types:
1. In the Haplontic life cycle, the major phase is gametophytic and haploid. The gametes fuse to form a diploid zygote, which undergoes meiosis to revert the haploid phase. The meiosis is called zygotic meiosis or terminal meiosis. This is common in most algae.
2. In the Diplontic life cycle, the major phase is sporophytic and diploid. The gametes are formed by meiotic division and represent the gametophytic generation. Gametes fuse to revert the sporophytic condition. The meiosis is called gametic meiosis or initial meiosis. This is seen in Gymnosperms and Angiosperms.
3. Haplo-diplontic life cycle is seen in Bryophyta, where the gametophyte is predominant, and gametic fusion results in the formation of the sporophyte. Spores of the sporophyte are formed by meiosis. The meiosis is called sporic meiosis or intermediate meiosis.
In Pteridophyta, sporophyte phase is predominant and the spores are formed by meiotic division which forms the gametophyte. The haploid phase is for a lesser tenure and gametic fusion restores sporophytic generation. This is called diplo-haplontic life cycle.
1. In the Haplontic life cycle, the major phase is gametophytic and haploid. The gametes fuse to form a diploid zygote, which undergoes meiosis to revert the haploid phase. The meiosis is called zygotic meiosis or terminal meiosis. This is common in most algae.
2. In the Diplontic life cycle, the major phase is sporophytic and diploid. The gametes are formed by meiotic division and represent the gametophytic generation. Gametes fuse to revert the sporophytic condition. The meiosis is called gametic meiosis or initial meiosis. This is seen in Gymnosperms and Angiosperms.
3. Haplo-diplontic life cycle is seen in Bryophyta, where the gametophyte is predominant, and gametic fusion results in the formation of the sporophyte. Spores of the sporophyte are formed by meiosis. The meiosis is called sporic meiosis or intermediate meiosis.
In Pteridophyta, sporophyte phase is predominant and the spores are formed by meiotic division which forms the gametophyte. The haploid phase is for a lesser tenure and gametic fusion restores sporophytic generation. This is called diplo-haplontic life cycle.