IB Environmental Systems and Societies (ESS) Practice Exam

The correct term for the number of years it would take a population to double its size at its current growth rate is known as "doubling time." This concept is fundamental in demography and population studies, as it quantitatively expresses how quickly a population is expanding based on its rate of growth. Doubling time can be calculated using the rule of 70, which divides 70 by the annual percentage growth rate to estimate the time it takes for the population to double.

Life expectancy refers to the average number of years that an individual is expected to live, which is distinct from the concept of population doubling. The fertility rate measures the average number of children a woman will have during her lifetime, impacting population growth but not directly describing how long it would take a population to double. Population growth itself describes the increase in the number of individuals in a population over time but does not specify the time required for doubling. Additionally, understanding doubling time is critical in assessing the sustainability of resources and planning for future societal needs.