membrane bound organelles in a cell actually contain DNA of their own so they don't have to actually rely on the rest of what the cell is doing in a similar manner, just because your breathing doesn't mean that your kidneys are working at the same time each one is actually independent of its own actions
Mortality, or death rate is a measure of the number of deaths in a particular population, scaled to the size of that population, per unit of the time. In this case a factor that would result to an increased mortality rate in a population due to increased competition of water will be the density-dependent factor.
