The word gymnosperm refers to a group of plants that produces their seeds uncovered; exposed to the air rather than contained in flowers or pods. The term comes from a Greek word that literally means naked seeds. There are up to 900 species of gymnosperms alive today. Plants that are classified as gymnosperms include the conifer, the ginkgo, the cycad, and the gnetophyta.
Gymnosperms are sporophytes, which means they reproduce by producing spores rather than seeds. These trees produce spores, which are released in pollen. The pollen carries sperm cells which seek out egg cells contained in macrospores. The type of cell produced is determined by the cone it is produced in. Gymnosperms produce both pollen cones and ovulate cones. Sperm cells are produced by pollen cones, and ovulate cones produce egg cells. When the sperm cells join with egg cells in the seed, an embryo can potentially grow into a new full-sized tree.
Fossil evidence shows that gymnosperms have been around for as long as 380 million years, meaning they have existed on Earth for nearly as long as there have been insects. During the Mesozoic era, scorpion flies used proboscis to feed on pollen and aid in pollination millions of years before nectar-feeding insects evolved.
Of the four types of gymnosperms, the conifer is the most prevalent. Conifers make up as many as 630 species of gymnosperms, more than two-thirds of the total number of species of the plants. Conifers are woody plants. Their lumber is the primary type of wood used for construction throughout the world. The plants are known for their long, thin leaves that are often referred to as needles. The leaves generally stay green and intact throughout the year, leading to the classification of many conifers as evergreens. Conversely, there is only one species of ginkgo alive today, which is considered to be a living fossil.