The extinction vortex is what happens as a population decreases and becomes more vulnerable to extinction from a variety of causes. begins when one species in an ecosystem goes extinct and other species follow. is what happens when competing species fight over a single niche, often driving both species to extinction. is a spiral of events that occur once a species has become overcrowded through excess reproduction. is a spiral of events that includes introduction of competing species, overexploitation, and disease, in that order.