PBS Evolution, Episode 3
Extinctions are a normal aspect of evolution. It is estimated that 9 in 10 species that have ever existed have gone extinct. There have been several huge extinction events in the Earth's history, sparked by cataclysmic events such as meteor strikes. However, there is a growing concern that we are in the midst of the next great extinction event -- caused by human activity. The exact causes vary, from hunting to the introduction of invasive species, but the result is a decrease in the biodiversity within the remaining ecosystems.
Key Concepts: Geologic strata, Permian extinction, food webs, food chains, Triassic, dinosaur extinction, invasive species, poeaching, biodiversity, interdependence.
Answer Key: Available at the biology instructor resources subscription page.