Describe three major factors that have contributed to Earth's population growth.

-Fertility rate: The factor which affects the growth of the population in the biggest way is the fertility rate.

-Mortality rate: A key factor affecting the growth of the population is the death, or mortality, rate. Just as the birth of new people increases the population size, deaths decrease it.

-Immigration and Emigration: Cross-border migration is the act of people moving from one country to another. It affects the population size of both the host and destination countries. Emigration is caused by a number of factors, such as fleeing war, finding education, seeking new jobs or joining family members. When a person emigrates from a country, its population shrinks.