Describe the changes that a country undergoes as it passes through the three stages of the demographic transition. Use the United States as an example.

In stage 1, both birthrate and death rate are high, and the population grows slowly. Stage 1 describes the US for the early years of history. Then during Stage 2, improvements in health care, sanitation, and nutrition all people to live longer and reduce the death rate. The birthrate however, remains high during this stage so the population increases rapidly. This occurred in the US in the 1800s. Eventually, birthrate decreases to match the low death rate and the population growth slows and eventually stops. This is the US today.

The troposphere gets warmer as altitude increases.