- 95-98% of species which have ever lived are dead.
- There have been 5 mass extinctions in the last 500 MY
- Fossils disappear from some strata representing geologic periods. i.e., most life disappeared. e.g., Permian extinction was huge - very few fossils in the Triassic period. In strata above that there are signs of life again.
- Mass extinctions precede explosions of different species because there is very little competition.
- Fossil evidence of small mammals at the time of the dinosaurs.
- Changes in skeleton show development of marsupials and eventually placentals
- 65 MYA another mass extinction (KT event) probably caused by an asteroid. The small mammals were able to survive and flourish. Eventually, the largest animals were mammals rather than reptiles.
- 35 MYA first monkeys and apes.
- Extinctions are escalating worldwide and some feel that human activity may cause the 6th mass extinction.
- Habitat destruction is the primary cause while introduced species is the secondary cause.
- There are 100,000 people over the Atlantic Ocean at any given time. Global travel has increased the destruction of habitat and the movement of introduced species.
- Humans are the worst weed species (introduced species). Most mobile, resourceful, and adaptable.
- Leafy spurge is an invasive weed species which destroys pasture land. The flea beetle eats the leafy spurge. Example of fighting one weed species with another. research must be done to identify which species to use and the possible risks.
- We must slow the rate of human-caused extinctions.