What happens to organisms in a closed population when mortality rates increase?

In a closed population, which is one that does not experience immigration or emigration, an increase in mortality rates leads directly to a decrease in the population size. This is because more individuals are dying than being replaced by new births. When mortality rates are high, fewer individuals survive to reproduce, which disrupts the balance necessary for population growth or stabilization.

As more individuals die, the population experiences a decline due to the decrease in the number of reproductive adults and the overall decrease in individual numbers. Thus, the correct understanding of population dynamics in this context is that heightened mortality directly correlates with a reduction in population size. This relationship underscores the importance of birth and death rates in determining the overall health and sustainability of a closed population.