Answer:
Reproduction.
Explanation:
At the cellular level indicate that the living organisms are made up of the smallest building blocks called cell. It refer to unicellular organisms i.e organism with one cell.
At the cellular level, membranes; for the whole organism, the skin is Reproduction because a single parent cell divides into two cells (offsprings), two divides into four cells and so on. It is called cell division and cell reproduction because a single cell skin divides to produce many cells.
The "set-point theory" implies that each individual is genetically programmed to carry a particular amount of body weight.
The set point is the weight range in which your specific body is programmed to work. The set point theory trusts that a man's body will battle to keep up that specific weight range.