REN R360 Lecture Notes - Cambrian Explosion, Paleozoic, Evolutionary Radiation
4 Mar 2013
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Life was confined to oceans and all organisms were small. Over the precambrian the shallow seas slowly began to teem with life. For most of the precambrian, life consisted of microscopic prokaryotes (eukaryotes evolved 2/3 of the way through the era). Unicellular eukaryotes and small multicellular animals fed on floating photosynthetic microorganisms. Small floating organisms, plankton, were eaten by slightly large animals. Other animals ingested sediments on the seafloor and digested the remains of organisms within them. By late precambrian, many kinds of multicellular soft-bodied animals had evolved. Cambrian period (452-488 mya) marks the beginning of the palaeozoic era. The o2 concentration was approaching its current level; the continents had come together to form several large land masses. A rapid diversification of life took place cambrian explosion. Most of the major groups of animals that have species living today appeared during this period.
