APES Extinction - Shope

• Endangered Species Act
o one of the most powerful pieces of legislation ever enacted (in US)
o controversial
o designed to protect habitats (and, therefore, species)

• we do not know all species, nor do we know how many there are (we can’t even accurately guess)

• 99.99% of all species to ever exist are currently extinct

• about 10 major mass extinctions in Earth’s history (60 % - 70% of species died)

• about 5 super (mass) extinctions

• eras (geological time scale… mya = million years old)
o Pre-cambrian (600 mya)
o Paleozoic (225 mya)
o Mesozoic (65 mya)
o Cenozoic (0.1 mya)

• Cambrian Explosion
o 500 mya
o invertebrate life (multi-cellular) started from bacteria & single-celled eukaryotes in ocean
o first fish

• biggest extinction in history
o about 250 mya
o wiped out about 96% of all life on earth
o just before time of dinosaurs

• KT Extinction
o end of the dinosaurs
o no one knows exactly what happened… asteroid? volcanoes? mammals feeding on dinosaur eggs?

• most extinctions (causes)
o change climate (getting hotter or colder)
o lots of dust in the air
o we don’t exactly know

• we may be starting the 6th massive extinction