2. Briefly describe the carbon cycle. How does human activity impact the carbon cycle and why? (20pts) 3. List three factors that determine population size. (15 pts) 4. What is one method an ecologist may use to estimate size of a population? Briefly describe how the method is employed in a field experiment. (10pts) 5. Draw a curve for logistic growth and a curve for exponential growth. Be sure to label the axis. (20 pts) 6. What characteristics are typical of a K-selected species? What characteristics are typical of an r-selected species? Give examples of animals that fit each description. (20 pts)