What system of the human body benefits directly from the action of microorganisms? a. cardiovascular b. digestive c. respiratory d. urinary

What percentage of light hits earth's surface directly?

Rarefaction is used for which of the following? a. creating a representative sample b. studying how disease impacts populations c. rediscovering species thought to be instinct d. determining which sea creatures live in an area

Which feature would you expect to find in a population in which sexual selection depends on male competition?