Option C. Organisms were probably more complex during past eras.
A keystone species is #1 “A species that is very important to the health of a specific ecosystem”
"<span>Appearance of a trait in a population does not solely depend on its dominant or recessive nature" is the correct choice among the choices that are given in the question. The correct option among all the options that are given in the question is the second option or option "B". I hope that the answer has helped you.</span>