AP BIOLOGY

Detailed explanation-1: -In pteridophytes, the spores are produced by the sporophytic plant body by meiosis. The spores germinate to form an inconspicuous, small, multicellular, free-living, mostly photosynthetic thalloid gametophyte called as prothallus.

Detailed explanation-2: -A prothallus, or prothallium, (from Latin pro = forwards and Greek (thallos) = twig) is usually the gametophyte stage in the life of a fern or other pteridophyte. Occasionally the term is also used to describe the young gametophyte of a liverwort or peat moss as well.

Detailed explanation-3: -Prothallus refers to gametophytes of bog moss or liverwort. It is a fungus that develops from germinated spores.

Detailed explanation-4: -The key difference between thallus and prothallus is that thallus is an undifferentiated filamentous gametophyte of algae, fungi, lichens, and some liverworts while prothallus is the heart-shaped gametophyte of pteridophytes such as club mosses, horsetails, and ferns.

Detailed explanation-5: -The spore germinates and gives rise to small but multicellular free-living, inconspicuous, mostly photosynthetic thalloid gametophytes called prothallus.