Section 1

objectives

• Describe the life cycle of a moss.

• Describe the life cycle of a fern.

• Describe the life cycle of a gymnosperm.

• Compare homospory and heterospory.

vocabulary antheridium archegonium homospory sorus microspore megaspore heterospory integument micropyle ovule pollen grain pollination pollen tube figure 30-1

The life cycle of mosses alternates between clumps of gametophytes (the dominant generation) and a sporophyte that consists of a spore capsule on a bare stalk.

Capsule gametophyte

The life cycle of mosses alternates between clumps of gametophytes (the dominant generation) and a sporophyte that consists of a spore capsule on a bare stalk.

Capsule

gametophyte

Antheridium

Antheridium

A moss sporophyte begins as a thin stalk that grows from the tip of a gametophyte. The sporophyte remains attached to the game-tophyte and depends on it for nourishment. Soon, cells at the tip of a stalk form a sporangium, called the capsule. Cells in the capsule undergo meiosis to form haploid spores, which are all the same. The production of one type of spore is called homospory (hoh-MAHS-puh-ree). Therefore, the life cycle of mosses is called homosporous (hoh-MAHS-puh-ruhs) alternation of generations. When the spores are mature, the capsule splits open, and the spores are carried away by the wind. Spores that land in favorable environments may germinate and grow into new gametophytes.

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