Ecology review questions to study ecosystem, biomes, food chain, biogeochemical cycles, biodiversity, ecological interactions, environmental issues, ecological succession and population ecology. Answer Key: Study guide Ecology 2 1. Explain the water cycle using a picture and/or words 2. Explain the carbon cycle using a picture and/or words 3. Explain the nitrogen cycle using a picture and/or words The water cycle describes how water evaporates from the surface of the earth, rises into the atmosphere, cools and Why are polar bears found only in the Arctic? Why does mildew grow in your shower and not (hopefully) in your sock drawer? Learn how ecologists study the interactions between organisms and their environment, and how these interactions affect where, and in what numbers, different types of organisms are found.