What is the term used to describe the time required to clear 50% of a given quantity hormone from the blood

What did hunter gathers do to alter the environment?

The bacteria inside a tube worm would be analogous to what organism in the ocean ecosystem near the waters surface? a. photosynthetic algae b. shrimp c. clown fish d. parasitic lamprey

There are fewer than 100 naturally occurring elements in the universe, but there are millions of different unified substances. explain how this can be true.