plantsgymnosperms

Gymnosperms are a group of seed-producing land plants characterized by seeds that are not enclosed in an ovary or fruit. They comprise four living lineages: Coniferophyta (conifers), Cycadophyta (cycads), Ginkgophyta (Ginkgo), and Gnetophyta (gnetophytes). Fossil evidence indicates that gymnosperms first became common in the late Paleozoic era, and they once dominated many forests before angiosperms became widespread. Today, gymnosperms occupy a range of habitats, from boreal forests to desert margins, but they are generally less diverse than flowering plants.

Most gymnosperms are woody plants, often evergreen, with needle-like or scale-like leaves. Reproduction occurs in cones or strobili: male cones produce pollen, which is typically wind-dispersed, and female cones receive the pollen to fertilize ovules. Fertilization results in seeds that develop on the surface of cone scales rather than inside a fruit, which is why they are described as having naked seeds.

In their life cycle, the sporophyte generation is dominant. The gametophytes are reduced and develop within the pollen grain and the ovule. After fertilization, the seed develops on the parent plant. Some gymnosperms produce winged seeds or rely on other structures to aid dispersal, and many accumulate resin as a defense or protective mechanism.

Ecology and evolution: Gymnosperms are generally well adapted to dry or nutrient-poor soils and can form long-lived forests. They provide timber, resins, and various ornamental plants. Ginkgo biloba is the sole surviving member of its division, and several cycad groups are threatened by habitat loss and collection. Molecular and fossil evidence continue to refine the relationships among gymnosperm lineages and their place in seed-plant evolution.