Gymnosperms develop seeds on the outside of the plant. Gymnosperms have been around for millions of years. As plants evolved to dwell on land, they needed ways to conserve water and to reproduce without dispersing sperm through water. Gymnosperms responded by becoming the first plants to develop seeds for reproduction, allowing them to become the dominant type of land vegetation.
Origins of Gymnosperms
Evolving over 300 million years ago, gymnosperms were the first seed plants. A seed consists of the genetic material of the plant, food to aid in the embryo plant's early development, and a hard coating for protection of the seed. The seeds of gymnosperms -- gymno means naked and sperma means seed -- develop on the surface of the plant's reproductive structures. In contrast, angiosperms -- angio means container -- produce seeds within a specialized structure called an ovary. Angiosperms are known as flowering plants.
Types of Gymnosperms
Four primary types of gymnosperms are cycads, gingko trees, conifers and gnetophytes. The leaves of cycads look like palms, but the plant develops a central large cone for reproduction. Gingko trees are an ancient species from China and come in male and female plants. The female plants makes unpleasantly scented fruits that fall to the ground when ripe. Conifers include pines, redwoods, firs and spruce. The leaves of conifers are needle-shaped to conserve moisture, and many conifers are evergreen and keep their leaves throughout the winter. Gnetophytes have some similarities with angiosperms and include 40 species of ephedera.
A Typical Gymnosperm
The pine tree is the most studied gymnosperm. The pine produces two kinds of pine cones -- male and female. Male cones grow in clusters on the lower branches of the tree, and the female cones develop higher in the tree. Both kinds of cone take several years to develop. Pollination occurs when the pollen from the male cone is blown by the wind to the female cone, where it lodges between the cone scales. Each scale has two ovules where the seed develops. After fertilization, seeds develop on the underside of the female cone's scales. When the seed is mature, it separates from the cone and blows in the wind to a new location where it germinates and grows into a new tree.
Not all gymnosperms have seed cones. Yew trees produce seeds surrounded by a fleshy, bright red covering that attracts birds that eat the fruit and disperse the seeds. The cones of junipers look like berries and are variously colored orange, brown, purple, red or black. These cones completely surround the seed. Birds eat the berries and seeds and disperse the seeds through their droppings.