GEF

Unit 3  |  Primary Sustainability Issues 83 CHECK YOUR UNDERSTANDING 1. Where do the majority of our global energy resources come from? Why should we be concerned about the reliance on nonrenewable sources? 2. What alternative energy sources are available? What are the benefits and limitations of different renewable sources? 3. What is the Green Revolution in agriculture? What are some benefits and drawbacks of GMOs? 4. What are some of the chemicals raising concern among scientists and environmental organizations? What are the adverse effects of exposure to these chemicals on humans and wildlife? 5. How much freshwater is available for direct human use? Is there equal distribution of access to safe drinking water across the world? Why is water scarcity a major sustainability challenge? ASSESS YOUR UNDERSTANDING Select the best answer from the choices provided. 1. Approximately what percentage of global energy use is derived from fossil fuels? a. 25 percent b. 10 percent c. 80 percent d. 100 percent 2. Polychlorinated biphenyls (PCBs) are an example of environmental toxins that can          in the fatty tissues of living organisms. a. Fossilize b. Biodegrade c. Bioaccumulate d. Reproduce