1. Dissolved oxygen or turbidity

2. Oligotrophic or eutrophic

3. Natural gas or oil fracking

4. Coal or oil

5. hydroelectric or toxic waste Love Canal

6. Stratosphere or mesosphere ozone

7. Teratogen or carcinogen Birth defects

8. Oil field or aquifer ogallala

9. Rainforest or grassland Most fertile soils

10. Nuclear or natural gas Virtually no CO 2 emissions

11. Clumped or uniform

12. A or B

13. Sedimentary or igneous limestone

14. Vitamin A or Iron anemia

15. Anthracite or bituminous Best coal

16. Nitrification or denitrificaiton Nitrites and nitrates

17. Real or not real

18. Point or nonpoint

19. Canada or Brazil Tar sands

20. CO 2 or SO 2 Criteria pollutant

21. BLM or NPS rangelands

22. Sand or Clay Smallest particle

23. Oil or coal 900 year supply left

24. Gas mileage or CFC emissions CAFE standards

25. Increasing or decreasing

26. Ticks or mosquitos malaria

27. Atlantic or pacific El Nino

28. Overhunting or habitat loss Biggest factor contributing to loss of biodiversity

29. Pesticides or climate change Rachel carson

30. Ocean sediments or atmosphere Largest carbon reservoir

31. Kyoto or Montreal Reduce greenhouse gas emissions

32. Atmosphere or Hydrosphere Impurities removed through natural processes

33. Nitrogen Fixation or Denitrification Converts nitrogen in the air into a usable form

34. Primary or Secondary Succession

35. Density Dependent or Density Independent

36. Mutualism or Commensalism

37. Logistic or exponential

38. r selected or K selected

39. Photochemical smog or industrial O 3

40. Photosynthesis or Respiration 6O 2 + C 6 H 12 O 6  6CO 2 + 6H 2 0

41. Phosphorous or sulfur Has no gaseous form