Living gymnosperms are divided into 4 categories.
1. Ginkgophyta: Ginkgo biloba is the only living species of Ginkgophyta. It is the world’s oldest seed plant that has survived on Earth with little change. Their leaves are large and fan-like. Their sperm are flagellated and motile. These plants greatly pollute the environment. They are disease and insect resistant.
2. Cycadophyta: Plants of Cycadophyta division are called cycads. This 200 million year old division survives today with 100 species. They are woody plants like palm trees. Their leaves resemble leathery feathers. Their sperm have flagella. They are widespread in the equatorial region. They grow in dry arid and wet wetlands. The division Cycadophyta consists of three classes. Cycadofilicales, Bennettitales and Cycadales. Zamia pygmaea cycad is the smallest gymnosperm plant in the world. Dr. Siddique Publications
3. Coniferophyta: Coniferophyta contains 550 species in 6 families. The temperate Northern Hemisphere has conifer forests. Russia has conifer forests. The world’s largest conifer forest is located in Siberia and is the world’s largest biome. Bristlecone pine is the oldest tree in the world. Its age is 5000 years. It is found in Navana and California. The tallest trees in the world are Hyperion (Sequoia sempervirens) at ± 400 feet and Coast Redwood (Sequoia gigantea) at 324 feet.
4. Gnetophyta: There are about 70 species in the Gnetophyta division. They have most similarities with herbaceous plants. Their leaves are similar to herbaceous plants. They have vessels in their xylem and spermatozoa are without flagella. The Welwitschia plant has two leaves and flower-like pods (Welwitschia is found in the Namibian desert). Double fertilization occurs in Ephedra plants of this category. The respiratory medicine ephedrine is obtained from the Ephedra plant.