What is the main idea behind the model of a molecular clock?
a. that neutral mutations accumulate at a steady rate
b. that certain traits are under the pressure of natural selection
c. that segments of DNA can be compared with segments of RNA
d. that phenotypes, not genotypes, are affected by natural selection

do yall know the answer?

stimulus is a change in the environment that causes an organism to react. the response is the reaction to the stimulus. some examples of stimuli for zebras are drought, to many predators, and bad feeding grounds such as dead grass or plants. zebras respond to stimuli just like all other living organisms