An intertidal species of seastar helps to maintain the diversity of the intertidal region by controlling the mussel population. Without the seastar, the mussel population would crowd out other species and take over their territory. The seastar could be called a(n)

a. indicator species
b. keystone species
c. foundation species
d. aggressive species
e. repressor species

b. keystone species

Explanation:

The keystone species is the species which exerts an effect on the communities in which they grow. Such species helps in maintaining the diversity of local animal species.

The keystone species is the dominant predator species. It controls the population of the predator species.  

According to the given situation, the seastar is the dominant predator species which is capable of controlling the population of the mussel species. Hence, the seastar could be a keystone species.

option a is correct i.e.

explanation:

in context to the membrane of nerve impulse, the outer membrane of neuron is semi permeable that is only sodium ions can pass through the membrane i.e. smaller ions can pass through the membrane while larger ions cannot pass through it.

the generally accepted parts of modern cell theory include: all known living things are made up of one or more cells. all living cells arise from pre-existing cells by division. the cell is the fundamental unit of structure and function in all living organisms.