BMEN 515 Lecture Notes - Cenozoic, Pleistocene, Herbaceous Plant
26 Feb 2013
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Document Summary
The modern biota evolved during the cenozoic era. By early cenozoic ear (65 mya), the positions of the continents resembled those of today. Cenozoic was characterized by extensive radiation of mammals. Flowering plants diversified extensively and came to dominate world forests, except in cool regions. Mutations of two genes in one group of plants allowed them to use atmospheric nitrogen directly by forming symbioses w/ a few species of nitrogen-fixing bacteria; dramatically increased the amount of nitrogen available for terrestrial plant growth. Three major faunas have dominated life on earth. Species whose morphology has changed little over millions of years are known as living fossils. (e. g. horseshoe crabs). Evolutionary changes have been gradual in most groups. The most striking feature of life"s evolution is that rates of change are, on average, very slow. A likely reason is that climates have usually changed slowly. If the physical or biological environment changes rapidly, some lineages may also change rapidly.
