What forms of life were present during earth's first age, the hadean era?
a. crustaceans and fish but no land animals
b. bacteria
c. the same life that is present today
d. none

How can you keep track of variables in a science experiment?

Amino acids contain the elements carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur. of the 20 amino acids found in humans, 11 are called "nonessential" because they can be manufactured by the body when needed. which elements in these 11 amino acids are commonly obtained from the metabolism of sugar molecules?

What two conditions must be present for osmosis to occur?