Question

what pattern of evolution is illustrated by each of these examples: as the dinosaurs became extinct, there was an explosion of new mammal species in a relatively short period of time

Answer 1

The pattern of evolution illustrated by the scenario you described, where the extinction of dinosaurs is followed by an explosion of new mammal species in a relatively short period of time, is known as adaptive radiation.

Adaptive radiation occurs when a single ancestor species rapidly diversifies into a variety of forms to exploit different ecological niches. In this case, the extinction of the dominant dinosaurs created opportunities for mammals to diversify and occupy various ecological roles, leading to the emergence of a wide range of mammalian species.