Why is the grizzly bear considered a keystone species that exists within a metapopulation?
a. Grizzly bears require many thousands of miles of preserved land, because they are large animals.
b. Grizzly bears have functions that increase biodiversity, but presently the population is subdivided into isolated subpopulations.
c. When grizzly bears are present, so are many other species within a diverse landscape.
d. Grizzly bears are a source population for many other types of organisms across several population types.
e. All of these are correct.