Describe the various processes responsible for fluctuations in population density.

(N/A) The size of a population for any species is not a static parameter. It keeps changing over time, depending on various factors including food availability, predation pressure, and adverse weather.
In fact, these changes in population density give us an idea of what is happening to the population—whether it is increasing or decreasing. Whatever the ultimate reason, the density of a population in a given habitat during a given period fluctuates due to changes in four basic processes. Out of these four, two (natality and immigration) contribute to an increase in population density, and two (mortality and emigration) contribute to a decrease.
$(i)$ Natality: It refers to the number of births during a given period in the population that are added to the initial density.
$(ii)$ Mortality: It is the number of deaths in the population during a given period.
$(iii)$ Immigration: It is the number of individuals of the same species that have come into the habitat from elsewhere during the time period under consideration.
$(iv)$ Emigration: It is the number of individuals of the population who left the habitat and went elsewhere during the time period under consideration.