Answer:Multicellular organisms are composed of more than one cell, with groups of cells differentiating to take on specialized functions. In humans, cells differentiate early in development to become nerve cells, skin cells, muscle cells, blood cells, and other types of cells
Explanation:
4. Gene Pool is not a mechanism, thus your answer!
If you are implying one these choices not needed for survival it would be parents only when you can survive on your own (I'm not that sure but I hope this helped the slightest but)
It is called hydrosphere
It is the total water in Earth.
Fairly sure that would be secondary succession.
