Question

Describe what happens when a keystone species is removed from a population.

Answer 1

If a keystone species is removed from an ecosystem, that said ecosystem would dramatically change or cease to exist entirely. If the keystone species is a herbivorous prey, the vegetation in the ecosystem would overgrow; and the main predators of the prey item would decrease dramatically until the adapt to a different prey item. If the keystone species is a carnivorous predator, the prey of the predator would overpopulate and devour lots of the vegetation; lowering the food supply for other prey, causing a dramatic decrease in the predators of the other prey. This situation would cause the complete downfall of the ecosystem while the prior situation would most likely only cause a dramatic change.

Answer 2

A keystone species is a vital element for the entire ecosystem (not for its abundance but for its influence). As such, if it were to be extinct, it would cause a domino effect among dependent species: lowering the presence of a keystone species will lead to a decline of its dependent species, then the overpopulation of the latter's usual prey, and then the lowering of the latter's preys and so on: a trophic cascade.