22.1 What Is a Plant?

The lives of plants center on the need for sunlight, gas exchange, water, and minerals.

Over time, the demands of life on land favored the evolution of plants more resistant to the drying rays of the sun, more capable of conserving water, and more capable of reproducing without water.

The life cycle of land plants has two alternating phases, a diploid (2N) phase and a haploid (N) phase. The shift between haploid and diploid is known as the alternation of generations.

• alternation of generations (637)

• sporophyte (637)

• gametophyte (637)

22.2 Seedless Plants

Green algae are mostly aquatic. They are found in fresh and salt water, and in some moist areas on land.

Bryophytes are small because they lack vascular tissue.

Vascular tissues––xylem and phloem––make it possible for vascular plants to move fluids through their bodies against the force of gravity.

• bryophyte (641)

• vascular tissue (641)

• archegonium (642)

• antheridium (642)

• sporangium (642)

• tracheophyte (643)

• tracheid (643)

• xylem (643)

• phloem (643)

22.3 Seed Plants

Adaptations that allow seed plants to reproduce without standing water include a reproductive process that takes place in cones or flowers, the transfer of sperm by pollination, and the protection of embryos in seeds.

In gymnosperms, the direct transfer of pollen to the female cone allows fertilization to take place without the need for gametes to swim through standing water.

• seed (646)

• pollination (647)

• gymnosperm (646)

• seed coat (647)

• angiosperm (646)

• ovule (648)

• pollen grain (647)

• pollen tube (648)

22.4 Flowering Plants

Angiosperms reproduce sexually by means of flowers. After fertilization, ovaries within flowers develop into fruits that surround, protect, and help disperse the seeds.

Angiosperms are often grouped according to the number of their seed leaves, the strength and composition of their stems, and the number of growing seasons they live.

• ovary (650)

• dicot (652)

• fruit (651)

• woody plant (653)

• cotyledon (652)

• herbaceous plant (653)

• monocot (652)

Think Visually Copy and fill in the table below using information from this chapter. Fill in “yes” or “no” for each blank box.

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