Animation 20.1 Life Cycle of a Moss

INTRODUCTION

A moss is a member of the plant phylum Bryophyta. These plants, along with the liverworts (Hepatophyta) and hornworts (Anthocerophyta), lack well-developed vascular systems. They lack a distinctive kind of fluid-conducting cell—the tracheid—and are referred to collectively as nonvascular land plants.

The life cycle of a moss, like all plants, is characterized by an alternation of generations. A diploid generation, called the sporophyte, follows a haploid generation, called the gametophyte, which is in turn followed by the next sporophyte generation.

Video titled: Animation 20.1 Life Cycle of a Moss

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Textbook Reference: Key Concept 21.3 Sex in Fungi Involves Multiple Mating Types, p.508

CONCLUSION

Alternation of generations is a feature of all plants. The nonvascular plants are unique, however, in that the gametophyte generation, rather than the sporophyte generation, is the most conspicuous.

The green, "leafy" mosses on the banks of streams are all haploid gametophytes. The diploid generation of the plant arises after a haploid gametes from gametophyte plants fuse during fertilization. The resulting diploid zygote grows into the sporophyte—the long stalked structure bearing a sporangium. This sporophyte is a new generation in the life cycle, yet the new organism can never leave the gametophyte, because it depends on the gametophyte for its nutrients.

When the sporangium breaks open and releases its haploid spores, a new generation of gametophytes can germinate.

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