Answer:
An organism whose decline or removal from a habitat causes many other species numbers to change dramatically is called keystone species.
Step-by-step explanation:
A keystone species is a species that has a dispropotionately large effect on its environment relative to its abundance.
OR
An organism whose decline or removal from a habitat causes many other species numbers to change dramatically is called keystone species.
It plays a critical role in maintaining the structure of an ecological community, affecting many other organisms in an ecosystem and helping to determine the types and numbers of various other species in the community.