Answer:KEYSTONE SPECIES
Explanation:
the ecosystem would be extremely different without the key stone specie or cease to exist complete .
Basically a keystone specie is a specie that helps define an ecosystem and if the specie was to die or cease to exist no other specie can take its place and the ecosystem will have to change radically and it'll be forced to introduce a whole a new habitat because the keystone specie has a huge influence on the food web
EXAMPLE :
A keystone specie could be any specie ranging from plants to fungi