Scientists estimate that on Halloween 2011 the global population reached 7 billion. But how long did it take humanity to grow to this level, and how large should we expect our population to become?

In this lesson, students will explore how many people the Earth is adding and losing each minute, and use this to build an exponential model for human population growth. They’ll also predict what the world population will be in the future, and what life will be like with more and more people.

### Students will

• Given number of births and deaths that occur each minute, calculate how global population changes each year
• Given the current population, determine current growth rate as a percent of total population
• Construct an exponential equation to model human population growth over time
• Estimate future human population at various times, and discuss the potential implications for life on Earth

### Before you begin

Students should be familiar with calculating percent change, as percent growth will be the basis for the entire lesson. Because they will need to model growth in order to make predictions about future population numbers, students should also be able to write an exponential function given a starting value and growth rate.