1. a) Explain the possible pathways a water molecule can take as it makes its way through the water cycle. Use the following terms in your explanation: precipitation, evaporation, runoff, transpiration, condensation, percolation, and precipitation. Start with the molecule falling as precipitation. (4 points)

b) What is one way water can cycle through sheep in a pasture? (2 points)

c) Earth is heated by global warming. How is the water cycle affected by global warming? (2 points)

2. A squirrel breathes out CO2 and a green plant releases O2. How are the squirrel and the green plant connected in the oxygen cycle? (4 points)

3. a) Explain how dead plants can be formed into fossil fuels. (4 points)

b) How does fossilized carbon get back into the atmosphere? (2 point)

c) Living organisms need nitrogen to build proteins and nucleic acids, but nitrogen cannot be used by plants in its gaseous state. How does a plant get the nitrogen from the soil? Name one of the nitrogen compounds produced in the process. (2 points)

4. a) Describe one way that technology has helped the environment. (4 points)

b) Describe two ways that technology has hurt the environment. (4 points)

5. a) What is a greenhouse gas and how does it affect the temperature of Earth? (2 points)

b) How does global warming affect the spread of diseases and the habitats of the animals on Earth? (2 points)

c) How is the carbon cycle related to global warming? (2 points)

6. The graph below shows a yeast cell population growing in a container of sugar over a period of 20 hours. Yeast will consume the sugar and build up waste products. Some of these wastes are poisonous to the yeast.

a) What has happened to the yeast population after hour 10? Why? (2 points)

b) Predict what will happen as more time passes. (2 points)

c) At hour 16, how does the carrying capacity in the container compare to the yeast population? Explain. (2 points)

7. a) Some populations of the world, like Africa's, have high fertility rates of over 7.0. Explain one factor that contributes to this high fertility rate. (2 points)

b) What are two things that can be done to encourage sustainable resources for Earth's human population? (2 points)

8. A community wants to build an energy source to replace its coal power plant. People want it to be safe and renewable and have the smallest effect on the environment.
a) Choose an energy source for this community. (2 points)

b) Explain why this energy source meets its goals. (2 points)

c) Describe one possible drawback of this energy source. (2 points)