This is the structural and functional unit of all living organisms

it is a cell.

Explanation:

the cell is the structural and functional unit of all living organisms

above statement is not a true statement about the open ocean because the open ocean has low levels of nutrients. most of the photosynthetic activity on earth occurs in the open ocean within the photic zone. organisms in the deep ocean are exposed to frigid temperatures and total darkness but it does not begin at the low-tide mark.