If a keystone species is removed from an ecosystem,
a. only abiotic factors can be affected.
b. only biotic factors can be affected.
c. neither abiotic nor biotic factors can be affected.
d. abiotic and biotic factors can be affected.

D. abiotic and biotic factors can be affected.

they deliver oxygen to the blood

regents of the university of california v. bakke, 438 u.s. 265 (1978), was a landmark decision by the supreme court of the united states. it upheld affirmative action, allowing race to be one of several factors in college admission policy.