To explain why gymnosperms are different than angiosperms, we need to describe each group first.
Angiosperms are the largest group of plants in the plant kingdom. They are known as the flowering plants and consist of 250,000 species. The name angiosperm is Greek in origin. Angeion means vessel; sperma means seed. This name refers to the fact that the seeds from these plants are formed inside containers called fruits.
Gymnosperms are plants that produce seeds in the open spaces of cones. One good example of this is pine cones with their flap like parts. The Greek word gymno means naked, and again sperma means seed. In evolution, gymnosperms are more primitive than angiosperms.
Angiosperms are the most sophisticated of the plant forms and have adapted to survive in a wide range of climates and places. This group consists of flowering ornamentals and all vegetables and edible fruits. They are also the source of the world's hardwoods.
Gymnosperms include all of the conifers: cedar, redwood, juniper, cypress, fir, pine, and the giant sequoias. Softwoods such as pine and fir are used to make paper, lumber, and plywood. They are a source of turpentine, rosin, and pitch. Also included with gymnosperms are many ornamental shrubs, such as varieties of Chamaecyparis (false cypress), American arborvitae, the maidenhair tree, Ginkgo biloba, and the least typical of the gymnosperms, the cycads.
Gymnosperms do not produce flowers, barring a few exceptions. They do not bear fruit. Gymnosperms were the first seed plants and they bear their ovules and seeds exposed. The ovules are on scales, which are arranged in the cone-like structures. They lack the folded, marginally-sealed carpels that characterize flowering plants.
Angiosperms have ovules that are enclosed in a carpel. A carpel consists of a stigma, a style, and an ovary. The seeds of angiosperms contain either one or two cotyledons-a seed leaf; a food-storage structure. Because of this characteristic, angiosperms are subdivided into two major groups-the dicots (di-, "two"), and the monocots (mono-, "one").
Gymnosperms rely on the airborne transport of their pollen, and most produce huge amounts of pollen. The pollen-receptive structures are the ovules, rather than the stigma portion of the carpels, as in angiosperms.
Most gymnosperms lack vessels in the xylem (wood). They have a different structure, tracheids, which perform the same function as xylem. Angiosperms have both vessels and tracheids.
One fascinating fact about gymnosperms is that this group includes the oldest and largest trees known. The Bristle Cone Pine, some of which are over 4,000 years old, are the oldest living plants. The Giant Redwood, which can reach over 300 feet tall, are the tallest plants known. Both these plants are native to California.