BIOL488 Lecture Notes - Cambrian Explosion, Evolutionary Radiation, Lycopodiopsida
Document Summary
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. In seas, crinoids reached their greatest diversity, forming meadows on the sea floor. The permian (297-251 mya: continents coalesced into the supercontinent pangaea, near the end, reptiles greatly outnumbered the amphibians, late in the period, the lineage leading to mammals diverged from one reptilian group. In fresh waters, the permian period was a time of extensive diversification of ray-finned fishes: massive volcanic eruptions resulted in outpourings of lava that covered large areas of. Few organisms that survived found themselves in a relatively empty world at the start of the.