Angiosperm

Angiosperms are the flowering plants, by far the largest and most varied group of land plants, with roughly 300,000 to 370,000 known species. They range from duckweeds a few millimeters across to oaks and eucalyptus trees, and include grasses, cereals, fruit trees, vegetables and most garden flowers. Almost all the plant food people eat comes from them.

Two innovations define the group. The flower is a short shoot of modified leaves: sepals, petals, pollen-producing stamens and carpels, in which ovules are sealed inside an ovary. After pollination, by insects, birds, bats, wind or water, a pollen tube carries two sperm to an ovule. One fertilizes the egg to form the embryo, and the other fuses with two nuclei to form endosperm, the seed's food store; this endosperm-forming double fertilization is found only in angiosperms. The ovary then ripens into a fruit that helps disperse the seeds. Most angiosperms are either monocots, with one seed leaf, or eudicots, with two, plus a few early-branching lineages such as water lilies.

The oldest undisputed fossils of flowering plants are about 130 million years old, from the Early Cretaceous, and the group then rose quickly to dominate most land habitats, helped by coevolution with animal pollinators.