Final answer:
The major factors that determine a population's growth rate include birth rate, death rate, immigration, and emigration. A population grows when the birth rate plus immigration exceeds the death rate plus emigration. Mutation and gene flow can introduce new genetic variation, which is different from factors affecting growth rate.
Step-by-step explanation:
The major factors that determine a population’s growth rate are birth rate and death rate, as well as immigration and emigration. The growth rate of a population can be calculated using the formula: growth rate = (birth rate + immigration rate) – (death rate + emigration rate). This calculation allows ecologists to determine if a population is increasing, decreasing, or remaining stable in size.
When the birth rate is higher than the death rate, a population is likely to grow. Conversely, if the death rate exceeds the birth rate, the population size will tend to decrease. Immigration contributes to population growth by increasing the number of individuals who are moving into the population, while emigration decreases it by representing individuals who leave. To maintain a stable population size, the combined rate of births and immigration must be equal to the combined rate of deaths and emigration.
In terms of evolutionary forces that can introduce new genetic variation into a population, these are mutation and gene flow, rather than the demographic factors that affect growth rate.