angiosperms

Angiosperms, or flowering plants, are the largest and most diverse group of land plants, with about 300,000 species. They are defined by producing flowers and fruits, and by seeds enclosed within a fruit rather than exposed on a cone or naked on a seed coat.

Key features include flowers bearing stamens and carpels; the ovary develops into a fruit. A distinctive process is double fertilization: one sperm fertilizes the egg to form a zygote, while a second sperm fuses with two polar nuclei to form the triploid endosperm that nourishes the developing embryo.

Life cycle and reproduction: The sporophyte is dominant. Pollen and ovules give rise to male and female gametophytes within the flower. Pollination is often aided by animals, but many species are wind-pollinated. After fertilization, fruits disperse seeds by animals, gravity, wind, or water.

Taxonomy and evolution: Angiosperms are divided into basal angiosperms and several major lineages, including magnoliids, and the two largest clades, Monocotyledons (monocots) and Eudicotyledons (eudicots). The group underwent rapid diversification beginning in the Cretaceous and now inhabits nearly all terrestrial environments.

Ecology and human use: Angiosperms dominate most ecosystems and are a principal source of food, fiber, and medicines. They include staple crops such as rice, wheat, and maize, as well as fruits, vegetables, legumes, oils, timber, and garden and ornamental plants.