What causes extinctions? • Competition from other organisms • Everything needs some space to live. • If there isn’t enough habitat/food/etc, one species must adapt, move, or die out. • Changes in the physical environment • Climate change • Animals must adapt or die out. • Chance events • Meteorite impacts, forest fires, tsunamis, etc.
Terrestrial life in the Permian • More continental area than any previous time in Earth’s history. • Wide variety of terrestrial animals: • insects, amphibians, reptiles, and therapsids (mammal-like reptiles), etc. • Wide variety of land plants: • gymnosperms (seed plants), and conifers (pine trees), etc.
Marine life in the Permian • Marine life was extremely abundant: • Common groups included the brachiopods, ammonids (squid-like animals), gastropods (sanils), bony fish, and sharks, etc. • Coral and trilobites were also present, but were less common than in earlier times.
BUT…life was in for some trouble • Approximately 246 million years ago, the largest mass extinction in the history of the Earth began. • 90 - 95 % of all marine species went extinct. • Many land species went extinct as well.
What species were affected? • Marine animals that went extinct: • all trilobites, rugose (horn) and tabulate coral, and many others. • Marine animals that were dramatically affected but did not go extinct: • bryozoans, brachiopods, ammonids (squid), sharks, fish, echinoderms (star-fish, etc), and many more. • Why?
Glaciation Extinction Theory #1 • Temperature cools across whole planet • Ice accumulates on continents • Lowers sea level continental shelf is exposed • Makes living environment difficult and creates competition for living space.
Glaciation Extinction Theory #2 • Ice accumulates on continents. • During cool climate periods, the interior of continents are often dryer. • This causes drastic climate fluctuations. • Makes survival difficult for many animals as a result of a change in the environment .
Super-Continent Formation Extinction Theory • Before the end of the Permian, there were numerous continents and large areas of continental shelf.
...Super-continent theory, continued • As the continents come together, the total shelf area decreases. • This creates competition for living space, especially in the coastal marine environment.
Volcanic Eruption Extinction Theory • Large volcanic eruptions in “Siberia” • Large volumes of sulfate gases were released • Silica-rich lava = explosive eruptions = lots of dust • Gas and dust would lower atmospheric temperature • Environmental change
Which theory is correct? • Maybe all of them. • Maybe none of them. • They all deal with climate changes and changes in the total area that animals could live. • Most likely...a combination of all of them.