Cycads - General Characteristics, Life Cycle, Evolution
seeds called palms plants
The cycads are a relatively small phylum (Cycadophyta) in the plant kingdom Plantae. The cycads are considered to be gymnosperms, because they bear their seeds naked on modified leaves called sporophylls. In contrast, the evolutionarily more recent angiosperms (flowering plants) bear their seeds inside of ovaries. Cycads grow in tropical and subtropical regions of the world. Cycads are sometimes referred to as "living fossils" because they are very similar to extinct species that were much more abundant several hundreds of million years ago. The foliage of many species of cycads resembles that of palm trees, and plants in the genus Cycas are commonly called "Sago palms." However, cycads are only distantly related to the palms, and their similarity is superficial.
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There are about 200 species of cycads in the world. They are endemic to tropical and subtropical regions, and are found in Central America, South America, Africa, Asia, and Australia. The greatest richness of cycad species is in Mexico and Central America. Zamia integrifolia is the only species of cycad native to the United States and is found in Florida and Georgia. Several foreign cycad species …
Cycads, like all seed-producing plants, have a dominant diploid sporophyte phase in their life cycle—this is the large, familiar, green plant seen in nature. Cycads and other gymnosperms do not have true flowers and their seeds are borne naked. In the more evolutionarily recent angiosperms (flowering plants), the seed is enveloped by a coat or fruit which originates from the ovary. All spec…
The earliest cycad fossils are from the Permian period (about 300 million years ago). Paleobotanists believe that cycads evolved from the seed ferns, a large group of primitive, seed-bearing plants with fern-like leaves. The seed ferns originated at least 350 million years ago, and became extinct more than 200 million years ago. Although cycads are considered to be gymnosperms, because they bear n…
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User Comments
about 1 year ago
actualy i want detailed information of why cycas is called as living fossils