AP BIOLOGY

Detailed explanation-1: -The life cycle of nonvascular seedless plants can be described as follows: The male gametophyte produces flagellated sperm that must swim to the egg formed by the female gametophyte. For this reason, sexual reproduction must happen in the presence of water.

Detailed explanation-2: -Seedless vascular plants still depend on water during fertilization, as the flagellated sperm must swim on a layer of moisture to reach the egg. This step in reproduction explains why ferns and their relatives are more abundant in damp environments.

Detailed explanation-3: -Nonvascular plants are low-growing, reproduce with spores, and need a moist habitat.

Detailed explanation-4: -Nonvascular plants (often referred to collectively as the bryophytes) include three groups: the mosses (Bryophyta), approximately 15, 000 species; liverworts (Hepaticophyta), approximately 7500 species; and hornworts (Anthocerophyta), approximately 250 species (Table 1).