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Across 1. The number of people the planet can support on a sustained basis. 4. ___ effect: A rise in the earth’s surface temperature caused by heat trapped by excess carbon dioxide in the atmosphere; global warming. 5. ___ Racism: The dumping of toxic wastes with disproportionate frequency at or very near areas with high concentrations of minorities. 6. The systematic increase in worldwide surface temperatures. 7. The process by which a community acquires the characteristics of city life. 8. The scientific study of the interdependencies that exist between humans and our physical environment. 9. Any system of interdependent parts that involves human beings in interaction with one another and the physical environment. 10. ” ___ Theory: the Principle that a population tends to grow faster than the subsistence (food) level needed to sustain it.

Down 2. The total number of people per unit of area, usually per square mile. 3. ___ Pollution: When industries take water from rivers and lakes and return it heated and polluted.