Keystone Species Overview
Without the keystone species, the ecosystem would collapse. Basically, keystone species are the species that would cause the maximum impact if it is numbers were to dwindle.
Usually trees or top carnivores are the keystone species in a habitat.Keystone species help maintain diversity as well.
Food chains with keystone species:
Plankton→Fish→Gar→Crocodile
The Crocodile was hunted into extinction sc the gar numbers exploded so the fish.
Sharks as Keystone Species:
Ocean ecosystems are very complicated, and sharks are at the top. In the ocean ecosystem, sharks prey on the sick members of the prey sometimes they scavenger the seabeds.
Intimidation
Sharks intimidate most species of fish and thus prevent over grazing.
So, if sharks are removed, the entire ecosystem will cease to exist.
NOTE: There can be more than one keystone species in an ecosystem. So save these species make sure that they cannot come under endangered keystone species. Read essay about Polar bear comes under endangered species list.