Why do waves that travel through basalt have a higher velocity than a wave traveling through sand?

What type of specimens where you able to see under each of the microscopes in the microscope activity

The image shows the evolution of a species of fish. a few fish from a population developed different social behaviors and evolved into different species. two fish according to the image, the fish underwent . the new species of fish had mating seasons that were different from that of the original fish. because of the differences in mating seasons, the fish underwent reproductive isolation. this mode of isolation would be .

Coral have a symbiotic relationship with what in order to eat?