Today, in the world there are more than 400,000 species of flora. All of them took place only a few ancient plants.
Some species have disappeared from the face of the earth, because they were unable to adapt to changing conditions or did not survive the competition from other newly emerged plants.
The oldest known plants aresimple blue-green algae. They were single-celled organisms to function with one devoid of the cell nucleus. Among the blue-green algae found both single-celled and multicellular organisms capable of photosynthesis. The process of photosynthesis contributed to the atmosphere of the Earth oxygen.
About 2.6 billion years ago, in the Proterozoicera, the earth filled red and green algae. In the Late Paleozoic (Silurian) having the oldest higher plants called Rhyniophyta or psilophytes. They were shoots but no roots and leaves. Rhyniophyta reproduce by spores. They grew partly on land or in water.
The emergence of higher spore plants
About 400-360 million years ago appearfirst spread Moss ferns and plants belonging to the higher spore plants. On land the process of separation begins at the plant root, stem and leaf, having supporting tissue and vascular conduction system.
The first land plants were small in size. Gradually appeared larger forms of plants - ferns, having roots with root hairs. In the Paleozoic era ferns were huge plants have filled the land. But due to the fact that their propagation water was needed, they grew only in areas having high humidity.
Gymnosperms and angiosperms
360-280 million years ago (Carboniferousperiod) appeared seed ferns, have become the ancestors of all gymnosperms. Dominated while huge tree ferns gradually die off and form deposits of coal.
In the Permian period of the Paleozoic appear ancient gymnosperms. In place of an endangered tree-ferns and seed come herbaceous ferns.
Around 240 million years ago occurredMesozoic era. Its Triassic any modern gymnosperms, and in the Jurassic - early angiosperms. They have a flower inside which there is pollination, fertilization and fruit formation. It should include angiosperms herbaceous plants, trees and shrubs.
About 70 million years ago Cenozoic era begins, the planet is filled with existing to this day angiosperms and gymnosperms.
The evolution of plants - a very complex and lengthythe process by which the world appeared all the modern variety of plants, including algae, ferns, bryophytes and flowering plants.