Density is defined as the number of individuals in a population in a given unit of space. To illustrate, in the United States, we often talk about the number of people per square mile. In New York City there are many more people per square mile than there are in Samburg, Tennessee. Now you give some examples of population density. A third characteristic of population dynamics is called natality .
Natality adds to the number in a population by reproduction.
Another way to speak of natality is in terms of birthrate - the rate at which new individuals are added to a given population through birth. The fourth example of population dynamics is mortality. Mortality is the number of deaths in a given time or place, in other words the death rate of the population. For example, if there is a population of 900 oak trees in a forest and after 10 years 140 have died, the mortality is 140 per 10 years, or 14 oaks per year. The final characteristic of population change for this lesson is age distribution .