AP BIOLOGY

Detailed explanation-1: -They studied the fossil record of extinctions at the end of the Cretaceous period–when the dinosaurs and many other species disappeared–and now suggest that most died out gradually as falling sea levels and volcanic eruptions took their toll.

Detailed explanation-2: -Past mass extinctions were caused by extreme temperature changes, rising or falling sea levels and catastrophic, one-off events like a huge volcano erupting or an asteroid hitting Earth.

Detailed explanation-3: -To test this prediction, we designed a “gradual extinction” paradigm in which the aversive event (a foot-shock) was gradually eliminated (Figure 1). The idea was to change the association of the cue from shock to no shock gradually enough so as to avoid the creation of a new memory.

Detailed explanation-4: -There are two main types of extinction: Mass extinction and background extinction.