(2) high birth and low death rates Explanation: Population growth is the change in a population over time, and can be quantified as the change in the number of individuals of any species in a population using "per unit time" for measurement. Population growth is determined by four factors, births (B), deaths (D), immigrants (I), and emigrants (E). High birth and low death rates add to the population base considerably as while the base remains intact, the erosion due to deaths is hampered.