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

Mortality and emigration.

The correct answer is Option (1 ) - Mortality and emigration.

Population density in a given habitat is affected by four primary factors: natality (birth rate), mortality (death rate), immigration (individuals moving into the population), and emigration (individuals moving out of the population).

Mortality refers to the number of deaths in a population. An increase in mortality directly reduces the number of individuals in the population, thus decreasing population density.

Emigration is the movement of individuals out of a population to other areas. When individuals leave, the population density in the original habitat decreases.

Therefore, both mortality and emigration work to decrease the population density because they reduce the number of individuals in the population.

On the other hand:

Natality refers to the birth rate. An increase in natality increases the number of individuals in a population, thereby increasing population density.

Immigration is the movement of individuals into a population from other areas. When individuals enter a population, the population density in the habitat increases.

Thus, natality and immigration would increase the population density, not decrease it. Hence, the correct answer is:

1) Mortality and emigration.