Which of the following would necessarily decrease the density of a population in a given habitat?

Mortality and emigration

Population density in a given habitat is influenced by four processes:

(i) Natality refers to the number of births during a given period in the population that are added to the initial density.

(ii) Mortality is the number of deaths in the population during a given period.

(iii) Immigration 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 is the number of individuals of the population who left the habitat and gone elsewhere during the time period under consideration.