Cycling of Matter in Ecosystems Chapter 4.7

1. Cycling of Matter in EcosystemsChapter 4.7

2. IMPORTANT!!! Energy FLOWS through ecosystems and must be continually supplied by the sun. Matter is CYCLED through ecosystems and is used over and over again.

3. Energy FLOWS through ecosystems Pyramid of energy flow – review from section 4.4: Where does the energy go?

4. Energy FLOWS through ecosystems • Where does the energy go? • solar energy  chemical energy stored in chemical bonds of glucose • chemical energy  mechanical energy and heat (glucose broken down and energy is used by organisms for growth, movement, cellular processes, reproduction – much heat is given off)

5. Matter is CYCLED in ecosystems

6. The “players” in the cycling of matter: atmosphere water – freshwater and saltwater the earth organisms

7. The processes involved: • photosynthesis and respiration - passing matter through foodwebs • decomposition - returns matter to earth • dissolution - dissolving matter into water • degassification, denitrification, evaporation, transpiration - matter goes into atmosphere • precipitation, nitrogen fixation – matter goes from atmosphere • lithification, erosion, sedimentation, uplifting, volcanism - geologic processes that move matter between earth/atmosphere • combustion - human activities put matter into the atmosphere (burning fossil fuels, trees, etc.)

8. Biogeochemical cycles: 1. water cycle 2. carbon cycle 3. nitrogen cycle 4. phosphorus cycle 5. sulfur cycle

9. Earth’s Atmosphere Composition of earth’s atmosphere: 78% nitrogen 21% oxygen 1% other gases (water, carbon dioxide, nitrous oxide and others)

10. Layers of the atmosphere • Troposphere – where weather occurs, where life is found • Stratosphere – contains ozone layer, absorbs UV light from sun • Mesosphere – very cold • Thermosphere – farthest from earth

11. The Water Cycle

12. The water cycle is altered by man’s activities: 1. We withdraw large quantities of freshwater. 2. We clear vegetation and increase runoff, reduce filtering, and increase flooding. 3. We add nutrients like fertilizers and modify the quality of the water. 4. The earth’s water cycle may be speeding up due to a warmer climate. This could change global precipitation patterns and may intensify global warming (water vapor increases in the troposphere).

13. The Carbon Cycle Why do living things need the element carbon for survival?Carbon is a component of all organic molecules: * proteins * carbohydrates * lipids * nucleic acids

14. The Carbon Cycle http://earthobservatory.nasa.gov/Library/CarbonCycle/carbon_cycle4.html

15. Movement of carbon into plants for photosynthesis • Stomata – openings on the underside of leaves, guard cells control opening • What comes in through stomata that the plant needs? • What goes out through the stomata that the plant needs?

16. Where carbon exists in the environment • In organisms’ bodies in carbohydrates (including glucose), fats, oils • In the atmosphere as carbon dioxide • Dissolved in the ocean • In carbon sinks (carbon reservoirs, where the element sits for a long time without cycling in the environment): examples are fossil fuels underground, large forests, limestone, deep ocean sediments, soil

17. The Carbon Cycle (Terrestrial) Fig. 4-29, p. 79

18. The Carbon Cycle (Marine) Fig. 4-29, p. 78

19. Four main types of processes that move carbon through the carbon cycle: 1. biological processes – PS, CR, decomposition 2. geochemical processes – erosion, volcanic activity 3. mixed biogeochemical processes – burial and decomposition of dead organisms fossil fuels 4. human activities – burning fossil fuels, cutting/burning forests

20. Human impact on carbon cycle: Excess carbon dioxide being added to the atmosphere through our use of fossil fuels and our destruction of the world’s photosynthesizing vegetation has contributed to global warming. The natural greenhouse effect is being strengthened by increasing temperatures.

21. The Nitrogen Cycle Living organisms use nitrogen to make DNA, RNA, proteins – nitrogen is critical for life! Even though the atmosphere is 78% nitrogen, only certain bacteria can get it directly from the air in a process called nitrogen fixation: N2 (nitrogen gas)    NO3 (nitrate)

22. The Nitrogen Cycle Some plants called legumes have nitrogen-fixing bacteria in their root nodules Examples: peas, beans, clover Other bacteria fix nitrogen in the soil into nitrates that plants can take up from the soil

23. The Nitrogen Cycle Animals, including humans, must get nitrogen from food

24. The Nitrogen Cycle Fig. 4-31 p. 80

25. The Nitrogen Cycle What are two ways that nitrogen can be fixed from the atmosphere?

26. Human activities affect the nitrogen cycle 1. In burning fuel, we add nitric oxide into the atmosphere. It can be converted to NO2 gas and nitric acid, and it can return to the earth’s surface as acid rain. 2. Nitrous oxide that comes from livestock, wastes, and inorganic fertilizers we use on the soil can warm the atmosphere and deplete the ozone layer. 3. We destroy forests, grasslands, and wetlands, and, thus, release large amounts of nitrogen into the atmosphere. 4. We pollute aquatic ecosystems with agricultural runoff and human sewage. 5. We remove nitrogen from topsoil with our harvesting, irrigating, and land-clearing practices. 6. Increased input of nitrogen into air, soil, and water is affecting the biodiversity toward species that can thrive on increased supplies of nitrogen nutrients.

27. The Phosphorus Cycle • Phosphorus is used by living organisms in DNA, RNA, ATP – also critical for life! • Phosphorus is not common in the biosphere and therefore, is a limiting factor in ecosystems • Unlike CO2 and N2, phosphorus does not go into the atmosphere – it cycles between the earth, water and living things

28. The Phosphorus Cycle Fig. 4-33 p. 82

29. Man interferes with the phosphorus cycle in harmful ways. 1. We mine phosphate rock to produce fertilizers and detergents. 2. We cut down tropical forests and, thereby, reduce the phosphorus in tropical soils. 3. We compromise aquatic systems with animal waste runoff and human sewage.

30. Nitrates and Phosphates in Fertilizers Nitrates and phophates are used in fertilizers to stimulate plant growth These nutrients can wash from agricultural areas into water supplies and cause eutrophication – process in which bodies of water receive excess nutrients Aquatic plants grow faster - if algae, then it is called an algal bloom – water appears green, may have a film of algae on top, blocks sunlight Satellite image of eutrophication of the northern Caspian Sea – notice the greenish water in the northern area

31. Eutrophication When these plants die and decompose, oxygen in the water is used up, which can kill fish and other animals – called a fish kill Narragansett Bay, R.I.

32. The Sulfur Cycle Significance of sulfur: • part of two amino acids • cysteine and methionine • involved in anaerobic respiration • hydrogen sulfide is a source of energy for chemosynthesis • coal is high in sulfur – released when burned • used in many processes and products by humans (fertilizers, processing phosphates, producing cellophane, fungicide, medicine, etc) Structure of cysteine

33. The Sulfur Cycle

34. The Sulfur Cycle Fig. 4-34 p. 83

35. Humans have affected the sulfur cycle • Burning coal and oil, refining oil, and producing some metals from ores all add sulfur to the environment. • 2. Sulfur compounds in the atmosphere can be converted to sulfuric acid that falls as acid deposition.

36. Review of Biogeochemical Cycling • What are the major cycles that occur in our biosphere? • How does the atmosphere play a role in each? • What are global warming, eutrophication, and acid deposition and how have humans contributed to each? • Which of the cycles, if thrown off balance, would have the most immediate catastrophic affect to the biosphere? Can you pick ONE or all they all important and intertwined?