Question

Fern prothallus is developed from?
A. Elaters
B. Spore mother cells
C. Spore
D. Zygote

Answer 1

Hint: To derive at the correct answer, you must first know that in fern, alternation of generation occurs. They have two distinct generations namely the sporophytic and the gametophytic generations. The sporophyte releases spores and the gametophyte releases gametes. The gametes fuse to give the sporophyte and the spores fuse to give the gametophyte.This cycle goes on. Now the prothallus represents the gametophyte stage in the lifecycle of a fern. If it is a gametophyte, can you guess from which it is developing?

Complete answer:
As clearly mentioned above, the life cycle of a fern is divided into two distinct phases that is the gametophytic phase and the sporophytic phase and they both alternate with each other. The plants of the gametophytic generation are all haploid and the plants of the sporophytic generation are all diploid. The prothallus represents the gametophyte. It is a small, green and heart shaped structure found in ferns. It represents the gametophyte of the fern that produces both the male and the female gametes. These gametes when fuse, lead to the formation of the sporophytic generation. As alternation of generation occurs in ferns, and as the prothallus represents the gametophyte, then it may have obviously developed from the sporophyte which had produced spores. Thus, the prothallus develops from the spore.

Thus, the correct option is C Spore.

Note:
Ferns are a group of vascular plants that fall under a separate plant kingdom Pteridophytes. They reproduce with the help of spores and they do not produce any seeds or flowers. They are different from mosses having a vascular system and have the sporophyte as the dominant phase in their life cycle.