Introduction to Seed Plants

Seed plants are the most diverse and ecologically dominant group of plants on Earth, with nearly 400,000 species. Scientists divide them into two major groups: gymnosperms and angiosperms.

Gymnosperms are nonflowering plants and include conifers, cycads, and ginkgoes. Angiosperms are flowering plants and make up more than 90 percent of all plant species, including flowering trees, grasses, and fruit-bearing plants.

Both gymnosperms and angiosperms share key features. Their life cycles are dominated by the sporophyte stage, which is the large, visible plant. They also produce highly reduced gametophytes.

The female gametophyte develops within an ovule, which protects and feeds it. The male gametophyte is the pollen grain, which is specialized for transport.

Plants produce pollen grains in specific structures—cones in gymnosperms and anthers in angiosperms.

Wind or animals carry the pollen to the female reproductive structure in a process called pollination. Fertilization can then take place.

After fertilization, the plant forms a seed. Each seed contains a diploid embryo, stored food, and a protective outer coat. These features help the embryo survive until conditions are right for growth