Final answer:
Changes in population size are governed by birth rate, death rate, immigration, and emigration. Population growth rate can be predicted by the simple equation which considers births and deaths. Additionally, demographic characteristics along with density-dependent and density-independent factors also influence population size.
Step-by-step explanation:
The four factors that govern changes in population size are birth rate, death rate, immigration, and emigration. When the birth rate is larger than the death rate, the population tends to grow. Conversely, if the death rate exceeds the birth rate, the population size will decrease. If both rates are equal, the population size remains stable. Additionally, populations gain individuals through immigration and lose individuals through emigration.
The growth rate of a population can be predicted using the equation: growth rate = birth rate - death rate. Moreover, the demographic characteristics such as life expectancy and the age structure of a population can also significantly affect its growth or decline.
Nature also regulates population growth through two main types of factors: density-dependent factors, which are influenced by the population density, and density-independent factors, which affect mortality in a population regardless of its density. These factors are crucial for conservation biologists to manage populations effectively.