BILD 3 Chapter Notes - Chapter 15: Dorsal Nerve Cord, Cambrian Explosion, Ordovician
Document Summary
Ended with permian extinction: 251 mya: biggest mass extinction in history, except for precambrian microbial mass extinction due to rising atmospheric oxygen, wiped out ~90% of all marine animal species, unsure about causes. About 300 million years long, divided into 6 periods: cambrian, ordovician, silurian, devonian, carboniferous, and permian, ordovician period, most living multicellular organisms in ocean; land mostly barren rock, fossilized spores found; looked like primitive plants. Life no longer confined to seas: trilobites appear in fossil record. Amphibians lay eggs in water, and juveniles often aquatic, so restricted to areas with suitable aquatic habitat: some animals acquired new adaptation for reproducing away from water: amniotic egg. Embryo surrounded by membranes that allow gas exchange, but prevent embryo from drying out. Life goes on: a short history of nearly everything. Most living things (99. 9%) compost to nothing. To become fossil: must die in right place.
