When plants appeared on Earth?

Scientists believe that when life began on Earth, now more than two billion years, the only forms of life lived in the sea. The land was empty and lifeless.

For a long time the existence of creatures remained restricted to the liquid medium where living plants as green algae. .

Then a few tufts of green plants appeared on land. They have been developed, perhaps for some types of green algae. Estimates based on molecular analyzes suggest that the event would have occurred early, perhaps 500-600 million years ago. But we have only fossil evidence now approx. 450 million years.

The first land plants looked very much like some green muscles grow dark and damp places today.

Plants are strongly diversified and terrestrial environment, about 400 million years ago, there were already more complex forms that resembled the present ferns, having roots, stem and leaves, and a system of tubes that circulate sap (plants Vascular). These plants reproduce by spores.

In the next stage, there were plants that reproduce by seed; there were among the first cordaitalele, then cicadalele and related species with gingko tree (which is a "living fossil", a survivor of an era old).

To appear first dinosaurs, vast forests and tree ferns seed plants, such as those mentioned above, occupied vast lands.

Conifers occurred slightly later, 300 million years ago. This group includes many known species of trees such as pines, firs, spruces, cedars. All these trees have seeds not enclosed in a fruit, hence the name "gymnosperms" given plants of this group.

The first angiosperm plant (in which the seed was housed in a fruit) has been developed over 150 million years. They are often called in familiar language, "flowering plants", although their distinctive feature is rather the existence of fruit which protects the seeds. Heavily protected their seeds gave them an advantage over the plant with seeds exposed and thus have increased in number and variety. Today, the plants are angiosperms almost everywhere in the world and is the most diverse group of land plants.

Source: descopera.ro

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