Question

based on the population graph and food web, which is the keystone species in this ecosystem and why?
a sharks since they are the top predators
b mussels since they are the most abundant species
c sea stars since they are the only predator of mussels
d seaweed since it is a food source for the limpets and turtles

Explanation:

A keystone species is one that has a disproportionately large impact on its ecosystem relative to its population size, controlling the population of other species to maintain balance. Sea stars are the sole predator of mussels in this food web; without sea stars, mussel populations would overgrow, outcompeting other species like barnacles and altering the entire ecosystem structure. Top predators (sharks), abundant species (mussels), and primary food sources (seaweed) do not fit the keystone species definition here as their removal would not cause the same drastic, disproportionate disruption.

Answer:

C. sea stars since they are the only predator of mussels