The Life Cycle in Ferns

Ferns are a group of plants that belong to the division Pteridophyta. They have a unique life cycle known as the diplohaplontic life cycle, which is characterized by the alternation of generations between a haploid gametophyte and a diploid sporophyte. The correct answer to the given question is option B, diplohaplontic.

Diplohaplontic Life Cycle
The diplohaplontic life cycle in ferns involves two distinct stages: the gametophyte stage and the sporophyte stage. Let's take a closer look at each of these stages:

Gametophyte Stage (Haploid)
The gametophyte stage is the haploid stage in the fern life cycle. It begins with the germination of a haploid spore. The spores are produced by meiosis in the sporangia, which are located on the underside of the fern fronds. The spore germinates and grows into a small, heart-shaped structure called a prothallus. The prothallus is the gametophyte and is the independent, free-living stage of the fern.

The prothallus produces both male and female gametes. The male gametes, called sperm, are produced in structures called antheridia, while the female gametes, called eggs, are produced in structures called archegonia. The sperm are released and swim through a film of water to reach the archegonia, where fertilization takes place. This results in the formation of a zygote, which marks the beginning of the sporophyte stage.

Sporophyte Stage (Diploid)
The sporophyte stage is the diploid stage in the fern life cycle. The zygote develops into a mature sporophyte, which is the familiar fern plant that we typically see. The sporophyte consists of roots, stems, and leaves. It is attached to the gametophyte by a structure called the foot.

The mature sporophyte produces sporangia on the underside of its fronds. The sporangia contain diploid cells called spore mother cells, which undergo meiosis to produce haploid spores. These spores are released into the environment and can germinate to begin the gametophyte stage once again, completing the life cycle of the fern.

Conclusion
In conclusion, the life cycle in ferns is diplohaplontic, which means it alternates between a haploid gametophyte stage and a diploid sporophyte stage. The gametophyte is the haploid stage that produces gametes, while the sporophyte is the diploid stage that produces spores. This life cycle allows ferns to reproduce and propagate successfully in their environment.

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.