AR103 Chapter Notes -Tetrapod, Continental Drift, Cenozoic
14 Mar 2014
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Chapter five: macroevolution: processes of vertebrate and mammalian. Fossils are traces or remains of organisms found in geological beds on the earth"s surface. The oldest fossils date as far back to 3 billion years ago, because they are remains of microorganisms, they are extremely small and are called mircofossils. After the organism died, these hard tissues were further impregnated with other minerals, being eventually transformed into a stone-like composition. Mineralization is the process in which parts of animals (or some plants) become transformed into stone-like structures. Mineralization usually occurs very slowly as water carrying minerals, such as silica or iron, seeps into the tiny spaces within a bone. In some cases, the original minerals within the bone or tooth can be completely replace, molecule by molecule, with other minerals. Sometimes insects were trapped in tree sap, which later became hardened and chemically altered.
