Although metamorphic rocks typically form deep in the planet's crust, they are often exposed on the surface of the Earth. This happens due to geologic uplift and the erosion of the rock and soil above them. At the surface, metamorphic rocks will be exposed to weathering processes and may break down into sediment.
Changes in the environment may leave individuals less well adapted to compete successfully for resources such as food, water and mates. Sometimes an entire species may become unable to compete successfully and reproduce. These problems can lead to extinction.
Predatory kills their prey on the spot. Parastic keeps the host alive and feeds off of thier body over a long period of time, until they are too weak to stay alive.
