If a population has a natural increase rate of 1%, how long will it take to double in size?

The concept of how long it takes for a population to double in size based on its natural increase rate can be determined using the rule of 70. This rule states that you can estimate the doubling time of a population by dividing the constant 70 by the natural increase rate expressed as a percentage.

In this case, with a natural increase rate of 1%, you calculate the doubling time by dividing 70 by 1. This gives you 70 years. Therefore, the correct answer indicates that it will take approximately 70 years for the population to double in size.

This method provides a simplified way to assess population growth, and the result is quite useful in understanding demographic trends, particularly in ecology and environmental studies.