Some of the more commonly found examples of gymnosperms are pines, spruces, cedars and sequoias. The less abundant varieties include the cycads, such as the sago palm, and the maidenhair tree or Ginkgo biloba. Overall, there are more than 1,000 species of gymnosperms encompassing 14 plant families.
Gymnosperms are seed-bearing plants that do not produce fruits or flowers. They are heterosporous and produce gametophytes and spores that are embedded within their parental diploid tissues. The seeds of gymnosperms either develop on the scales or leaves of the plant, often in a protected manner such as the pine cone, or at the tips of short stalks, such as in the case of the Ginkgo biloba.
Together with the angiosperms, which produce fruits or flowers, gymnosperms represent the spermatophytes, or seed-producing plants. The conifers, most of which are evergreens, represent the widest variety of gymnosperms, with more than 600 species. Conifers are a source of a significant economic commodity in the form of lumber.
Gymnosperms are commonly accepted as the group from which the angiosperms evolved, but which particular group they came from remains, in the words of Charles Darwin, "an abominable mystery." A wide variety of gymnosperms have been suggested as possible ancestors of the fruit- and flower-producing angiosperms. It is believed that the gymnosperms themselves originated about 319 million years ago during the late Carboniferous period.