paleozoic life

موضوع: paleozoic life 2007-12-17, 9:20 pm

Paleozoic Life

At the beginning of the Paleozoic, life existed only in or near the ocean. Trilobites, shellfish, corals, and sponges appeared, followed by the first fish. Land plants appeared near the end of the Ordovician and for the first time we see the green of land plants in our global view. Huge forests and swamplands formed during the warm climate of the Mississippian and Pennsylvanian periods that later fossilized into the giant coal beds of the eastern United States. Animal life also moved onto the land, first the arthropods , then the amphibians, and later the reptiles. The most abundant animals on land and sea during the Paleozoic were those like shellfish and insects that lacked backbones, so the Paleozoic is often called "The Age of Invertebrates."

The Paleozoic was also marked by several mass extinctions: geologically short periods of time during which large numbers of life forms died out. Mass extinctions occurred at the end of the Ordovician, the Devonian, and the worst one of all at the end of the Permian, when about 95% of all life on Earth died! These mass dyings were probably caused by climate changes and periods of giant volcanic eruptions.
We can follow the development of life in detail during the Paleozoic, because at the beginning of that Era, life forms developed hard parts like shells, teeth, bones, and woody parts that were easily preserved as fossils. Earlier life forms were single-celled and soft-bodied, so older rocks contain few fossils.

موضوع: يلا يا شباب 2007-12-17, 9:22 pm

يلا يا جماعة اقروا الموضوع ده وقولولى رايكوا فيهعايز ردود جميلة..... afro

موضوع: رد: paleozoic life 2007-12-18, 12:03 pm

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