The permian-triassic extinction 250 million years ago wiped out about ninety percent of earth's animal species. some scientists are predicting a sixth mass extinction in the future, due to a) acid rain. b) air pollution. c) global warming. d) earthquake activity.

What do all of the above organisms have in common

How did the work of farmers and breeders in england influence the work of charles darwin

On a spring day, a middle-latitude city (about 40? north latitude) has a surface (sea-level) temperature of 10 ? c. if vertical soundings reveal a nearly constant environmental lapse rate of 6.5 ? c per kilometer and a temperature at the tropopause of –55 ? c, what is the height of the tropopause?