What are the factors affecting population growth?

(N/A) The size of a population is not static. It keeps changing with time,depending on factors such as food availability,predation pressure,and weather conditions. The four main factors that determine population growth are:
$1$. Natality $(B)$: The number of births during a given period in the population.
$2$. Mortality $(D)$: The number of deaths during a given period in the population.
$3$. Immigration $(I)$: The number of individuals of the same species that have come into the habitat from elsewhere during a given period.
$4$. Emigration $(E)$: The number of individuals of the population who left the habitat and gone elsewhere during a given period.
If $N$ is the population density at time $t$,then its density at time $t+1$ is given by the equation:
$N_{t+1} = N_t + [(B + I) - (D + E)]$
Population density will increase if the number of births plus the number of immigrants $(B + I)$ is more than the number of deaths plus the number of emigrants $(D + E)$; otherwise,it will decrease.