Which processes increase a population's size?

• A. Death and emigration
• B. Birth and immigration
• C. Death and immigration
• D. Birth and emigration

Answer: (B)

Population size changes based on additions and losses of individuals. Additions come from births within the population and from immigration from outside. Losses come from deaths and from emigration, where individuals leave the population. So the processes that increase a population’s size are birth and immigration, because they add new individuals. If births plus immigration exceed deaths plus emigration, the population grows.