Chapter 4

1. Chapter 4 The Nitrogen Cycle and the Phosphorus Cycle

2. Review: What is the difference between matter and energy in an ecosystem?

3. Review: Why is the Carbon Cycle important?

5. Root Nodules with Nitrogen Fixing Bacteria

6. Effects of Human Activities on the Nitrogen Cycle • Human activities such as production of fertilizers now fix more nitrogen than all natural sources combined. Figure 3-30

7. Effects of Human Activities on the Nitrogen Cycle • We alter the nitrogen cycle by: • Adding gases that contribute to acid rain. • Adding nitrous oxide to the atmosphere through farming practices which can warm the atmosphere and deplete ozone. • Contaminating ground water from nitrate ions in inorganic fertilizers. • Releasing nitrogen into the troposphere through deforestation.

8. Phosphorus Cycle Phosphorus is use by cells and to make DNA

9. mining Fertilizer excretion Guano agriculture weathering uptake by autotrophs uptake by autotrophs leaching, runoff Dissolved in Soil Water, Lakes, Rivers Land Food Webs Marine Food Webs Dissolved in Ocean Water death, decomposition death, decomposition weathering sedimentation settling out uplifting over geologic time Rocks Marine Sediments Fig. 3-31, p. 77

10. Unlike the other biogeochemical cycles, the phosphorus cycle does not have a gaseous phase.

11. Effects of Human Activities on the Phosphorous Cycle • We remove large amounts of phosphate from the earth to make fertilizer. • We reduce phosphorous in tropical soils by clearing forests. • We add excess phosphates to aquatic systems from runoff of animal wastes and fertilizers.

12. The End

14. Gaseous nitrogen (N2) in atmosphere Food webs on land Nitrogen fixation Fertilizers Uptake by autotrophs Loss by denitrification Excretion, death, decomposition Uptake by autotrophs Nitrogen-rich wastes, remains in soil Ammonia, ammonium in soil Nitrate in soil Nitrification Ammonification Loss by leaching Loss by leaching Nitrite in soil Nitrification Fig. 3-29, p. 75

15. Review: Phosphorus Cycle Why is the Phosphorus Cycle important? How is the Phosphorus Cycle different from other biogeochemical cycles?

16. The Water Cycle Figure 3-26

17. Water’ Unique Properties • There are strong forces of attraction between molecules of water. • Water exists as a liquid over a wide temperature range. • Liquid water changes temperature slowly. • It takes a large amount of energy for water to evaporate. • Liquid water can dissolve a variety of compounds. • Water expands when it freezes.

18. High projection Low projection CO2 emissions from fossil fuels (billion metric tons of carbon equivalent) Year Fig. 3-28, p. 74

19. The Nitrogen Cycle: Bacteria in Action Figure 3-29

20. Nitrogen fixation by natural processes Global nitrogen (N) fixation (trillion grams) Nitrogen fixation by human processes Year Fig. 3-30, p. 76

21. The Phosphorous Cycle Figure 3-31

22. The Sulfur Cycle Figure 3-32

23. Water Sulfur trioxide Acidic fog and precipitation Sulfuric acid Ammonia Ammonium sulfate Oxygen Hydrogen sulfide Sulfur dioxide Plants Volcano Dimethyl sulfide Industries Animals Ocean Sulfate salts Metallic sulfide deposits Decaying matter Sulfur Hydrogen sulfide Fig. 3-32, p. 78