Angiosperms and gymnosperms are the two major groups of vascular seed plants. Angiosperms, which are flowering plants, are the largest and most diverse group within the kingdom Plantae. With around 300,000 species, they represent approximately 80 percent of all the known green plants now living. Gymnosperms are a smaller, more ancient group, and it consists of plants that produce “naked seeds” (seeds that are not protected by a fruit). There are more than 1,000 species of gymnosperms still found on Earth.
The key difference between angiosperms and gymnosperms is how their seeds are developed. The seeds of angiosperms develop in the ovaries of flowers and are surrounded by a protective fruit. Flowers can be unisexual (e.g., male flowers and female flowers) or bisexual (the flower has both male and female parts). Gymnosperm seeds are usually formed in unisexual cones, known as strobili, and the plants lack fruits and flowers. Both groups use pollen to facilitate fertilization, though angiosperms have an incredible diversity of pollination strategies that are not found among the gymnosperms.
While angiosperms have an enormous variety of body types and forms, ranging from annual herbs to climbing vines to massive trees, gymnosperms are largely woody trees and shrubs. Gnetum is the only gymnosperm genus with climbing vines. As vascular plants, both groups contain xylem and phloem. All but the most ancient angiosperms contain conducting tissues known as vessels, while gymnosperms (with the exception of Gnetum) do not.
Many ecological niches are filled only by angiosperms. For example, carnivorous plants, submerged aquatic plants, and parasitic plants (with one possible exception) are all flowering plants. Additionally, the vast majority of plants consumed by humans for food are angiosperms, though the seeds of some gymnosperms, such as ginkgo and pine nuts, are of local importance in some places.