Chapter 7, Problem 13PS

Tropical rain forests cover only about 3% of Earth’s surface, but they are estimated to be responsible for more than 20% of global photosynthesis. For this reason, rain forests are often referred to as the “lungs” of the planet, providing O₂ for life all over Earth. However, most experts believe that rain forests make little or no net contribution to global O₂ production. From your knowledge of photosynthesis and cellular respiration, can you explain why they might think this? (Hint: What happens to the energy stored as sugars in the body of a plant when that plant dies or parts of it are eaten by animals?)