Hermit crabs have a soft belly and live in the ocean. to protect themselves, they crawl into discarded snail shells and use them for homes. which symbiotic relationship describes the association of hermit crabs and snails?

a. commensalism

b. mutualism

c. parasitism

d. competition

The gene that causes sickle-cell disease is present in a higher percentage of residents of sub-saharan africa than among those of african descent living in the united states. even though this gene causes sickle-cell disease, it also provides some protection from malaria, a serious disease that is widespread in sub-saharan africa but absent in the united states. discuss an evolutionary process that could account for the different percentages of the sickle-cell gene among residents of the two regions.

Growth of chest hair, deepening of the voice, and muscle growth are secondary sex characteristics. which most likely affects the development of these traits? testes ovaries prostate gland vulva

Match the types of competition to their descriptions