1. Warmup An ecologist is concerned that the population of an endangered species of plant continues to drop. List as many possible causes for a dropping population as you can think of.

2. JANUARY 24, 2011

3. Learning Goal You will be able to describe how the carbon and nitrogen cycles work, and how they’re currently imbalanced. You’ll understand how abiotic factors affect soil quality for growing plants.

4. Carbon Cycle

5. Nitrogen Cycle Plants with nitrogen-affixing nodules in their roots: legumes, clover, alfalfa, soybeans, peas, peanuts, and beans.

6. Soil Quality  Acidity  Salinity  Carbon  Nitrogen  Phosphorous Why use manure, guano, compost, or other materials to enrich the soil? How would you cycle farmland crops to maintain its nitrogen levels?