GGR227H5 Lecture Notes - Lecture 2: California Condor, Ecological Extinction, Extinction Event
Document Summary
Levels of species extinction, local extinction (extirpation, ecological extinction, biological extinction (complete) Canadian grizzlies prairie population:once found as fast east as the red river in manitoba, Human settlement and land changes forced the grizzlies north and west. Extinction is natural : background extinction: typical low rate of extinction, mass extinction, 5+ events over 500 million years, 50-95% of species became extinct. 1. ordovician-silurian mass extinction (~445-440 mya: most life was in the sea, extinctions of trilobites brachiopods etc. 2. late devonian mass extinction (~375-360 mya: 3/4 of life on earth died, again mostly shallow seas and coral (took 100 million years for new corals to evolve) 3. permian-triassic mass extinction (252 mya: the great dying 96% of all species extinct, all life on earth descended from the remaining ~4, millions of years to return to previous levels of biodiversity. 4. triassic-jurassic mass extinction (~200 mya: several causes over 18 million years (climate, volcanic eruptions etc. )
