Is a chemical substance that organisms require to live.

What is the next step in muscle contraction after the actin changes shape? (apex)

What is used to keep track of the gamates and possible offsprings combination

Which best describes the nucleus of an atom a. it is where all of the particle s of the atom are located b. it is the negatively charged part of the atom c. it is where the electrons and the protons are located d. it is the part of the atom with the greatest mass