Population Dynamics is the sequence of population changes characteristic of a particular organism, it also focuses on these changes — how, when, and why they occur. It is the branch of life sciences that studies the size and age composition of populations as dynamic systems, and the biological and environmental processes driving them. Population Dynamics changes in the number of individuals in a population or the vital rates of a population over time. It is widely regarded as the exponential law of Malthus, as modeled by the Malthusian growth model.