All environments on earth are crowded with?

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

Where is the nictitating membrane found? a. between the eyelid and the eyeball b. between the retina and the optic nerve c. between the outer and middle ear d. in the organ of corti in the middle ear

How many pounds does the earth weigh?