Most coastal areas have high tides and low tides each day.
A. four; four
B. two; four
C. four; two
D. two; two

Most coastal area have two high tides and two low tides each day.

the reason the two sea urchins don't compete with each other for food, resources, etc. is because the urchins have adapted to the environment but they have also adapted to each other. this is most likely because the genes of the sea urchins.

not sure if this is what you'r looking for eubacteria and archaebacteria