Which process increases or decreases a population's size by moving individuals into or out of the population?

Which process increases or decreases a population's size by moving individuals into or out of the population?

• A. Immigration
• B. Reproduction
• C. Mutation
• D. Disease

Answer: (A)

Population size changes when individuals move into or out of a population, a process called migration. When individuals come from outside, the population grows; when they leave, it shrinks. Immigration is the entry of individuals into the population, making it larger. Reproduction adds new individuals within the population but doesn’t involve moving existing members between populations. Mutation changes genetic makeup, not the number of individuals. Disease can reduce numbers, but that happens through illness and mortality rather than movement between populations.

Population size changes when individuals move into or out of a population, a process called migration. When individuals come from outside, the population grows; when they leave, it shrinks. Immigration is the entry of individuals into the population, making it larger. Reproduction adds new individuals within the population but doesn’t involve moving existing members between populations. Mutation changes genetic makeup, not the number of individuals. Disease can reduce numbers, but that happens through illness and mortality rather than movement between populations.