The decision whether it needs to be divided or not depends on the size. The bigger a cell is, the more food it needs. Since the food is taken in through the membrane, if a cell is too big, the membrane cannot let enough food in to keep the cell healthy. It has to divide and become two smaller cells. Both cells then preform daily functions.
Genes are responsible for all the functions mentioned above in the cells.
These cells are in contact with the environment continually. Activity of interest - Research the life span of the above 6 types of cells. Make a report using the scientific method and include a graph. Red Blood Cells have an average life span of 120 days. Genes regulate all of the functions a cell needs in order to survive.