AP BIOLOGY

Detailed explanation-1: -During their life cycles, both brown algae and land plants alternate between two multicellular forms: the gametophyte and the sporophyte. The gametophyte develops sexually active reproductive cells, which, when they merge, create the sporophyte. In turn, spores produced by the sporophyte give rise to the gametophyte.

Detailed explanation-2: -The sporophyte is typically not photosynthetic and so is parasitic (dependent) on the gametophyte for its nutrition.

Detailed explanation-3: -Ferns. In most ferns, for example, in the leptosporangiate fern Dryopteris, the gametophyte is a photosynthetic free living autotrophic organism called a prothallus that produces gametes and maintains the sporophyte during its early multicellular development.