Chapter 51 <ul><li>Ecosystems </li></ul>
Chapter 51
Ecosystems <ul><li>Many global environmental problems have emerged recently. </li></ul><ul><li>Ecosystems consist of all t...
Energy Flow and Trophic Structure <ul><li>All ecosystems consist of four components that are linked by the flow of energy:...
External energy source PRIMARY PRODUCERS CONSUMERS DECOMPOSERS ABIOTIC ENVIRONMENT Figure 51.1
External energy source PRIMARY PRODUCERS ABIOTIC ENVIRONMENT Figure 51.1 CONSUMERS DECOMPOSERS
Energy Flow and Trophic Structure <ul><li>Key points about energy flow through ecosystems. </li></ul><ul><ul><li>Energy en...
Energy Flow and Trophic Structure <ul><li>Key points about energy flow through ecosystems. </li></ul><ul><ul><li>Most net ...
Energy source: 1,254,000 kcal/m 2 /year 0.8% energy captured by photosynthesis. Of this... … 45% supports growth (Net prim...
Energy source: 1,254,000 kcal/m 2 /year Figure 51.2 … 11% enters  grazing food web … 34% enters decomposer food web as dea...
0–100 100–200 200–400 400–600 600–800 >800 Productivity ranges  (g/m 2 /yr) Figure 51.3a Terrestrial productivity
<35 35–55 55–90 >90 Productivity ranges  (g/m 2 /yr) Figure 51.3b Marine productivity
80.7% respiration 17.7% excretion 1.6% growth and reproduction Energy derived from plants Figure 51.4
Predators of decomposers: Spider Centipede Mushroom Earthworm Primary decomposers: Bacteria and archaea Millipede Nematode...
Energy Flow and Trophic Structure <ul><li>Trophic structure </li></ul><ul><ul><li>Organisms that obtain their energy from ...
Energy Flow and Trophic Structure <ul><li>Trophic structure </li></ul><ul><ul><li>Organisms at the top trophic level are n...
Trophic level 4 3 2 1 Feeding strategy Secondary carnivore Carnivore Herbivore Autotroph Grazing food chain Decomposer foo...
4 Secondary carnivore 3 Carnivore 2 Herbivore 1 Autotroph Productivity Figure 51.6b Pyramid of productivity
Energy Flow and Trophic Structure <ul><li>Food chains and food webs </li></ul><ul><ul><li>Food chains are typically embedd...
Pisaster (a sea star) Thais (a snail) Bivalves (clams, mussels) Figure 51.7a Food chain
Pisaster Thais Chitons Limpets Bivalves Acorn barnacles Gooseneck barnacles Figure 51.7b Food web
Energy Flow and Trophic Structure <ul><li>Food chains and food webs </li></ul><ul><ul><li>The maximum number of links in a...
Number of observations Number of links in food chain 10 8 6 4 2 0 Streams Lakes Terrestrial Figure 51.7c Food chains tend ...
Biogeochemical Cycles <ul><li>The path an element takes as it moves from abiotic systems through living organisms and back...
Assimilation Loss to erosion or leaching into groundwater Soil nutrient pool Decomposer food web Detritus Death Herbivore ...
Boreal forest Figure 51.9 upper
Tropical rain forest Figure 51.9 lower
Biogeochemical Cycles <ul><li>A key feature in all cycles is that nutrients are recycled and reused. </li></ul><ul><li>The...
Devegetation experiment Choose two similar watersheds. Document nutrient levels in soil organic matter, plants, and stream...
Figure 51.10a lower Clearcut Control Devegetate one watershed and leave the other intact. Monitor the amount of dissolved ...
Devegetated Net dissolved substance (kg/ha) Control 1000 800 600 400 200 0 Year Figure 51.10b Nutrient runoff results 1965...
Biogeochemical Cycles <ul><li>Nutrient flow among ecosystems links local cycles into one massive global biogeochemical cyc...
THE GLOBAL CARBON CYCLE All values in gigatons of carbon per year Physical and chemical processes: 92 2 Ocean: 40,000 Rive...
THE GLOBAL NITROGEN CYCLE Nitrogen fixing cyanobacteria Mud Decomposition of detritus into ammonia Nitrogen-fixing bacteri...
Land use Fossil fuel use Year Annual flux of carbon (10 15 g) 6 5 4 3 2 1 0 Figure 51.12a Human-induced increases in CO 2 ...
Year CO 2  concentration (ppm) 360 350 340 330 320 310 1960 1970 1980 1990 Figure 51.12b Atmospheric CO 2
Natural sources Human sources Amount of nitrogen (gigatons/year) 160 140 120 100 80 60 40 20 0 Sources of nitrogen fixatio...
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    1. 1. Chapter 51 <ul><li>Ecosystems </li></ul>
    2. 2. Chapter 51
    3. 3. Ecosystems <ul><li>Many global environmental problems have emerged recently. </li></ul><ul><li>Ecosystems consist of all the organisms that live in an area along with the nonbiological components. </li></ul><ul><li>Energy and nutrient flows link the biotic and abiotic environments. </li></ul>
    4. 4. Energy Flow and Trophic Structure <ul><li>All ecosystems consist of four components that are linked by the flow of energy: </li></ul><ul><ul><li>Primary producers </li></ul></ul><ul><ul><li>Consumers </li></ul></ul><ul><ul><li>Decomposers </li></ul></ul><ul><ul><li>Abiotic environment (Fig. 51.1) </li></ul></ul>
    5. 5. External energy source PRIMARY PRODUCERS CONSUMERS DECOMPOSERS ABIOTIC ENVIRONMENT Figure 51.1
    6. 6. External energy source PRIMARY PRODUCERS ABIOTIC ENVIRONMENT Figure 51.1 CONSUMERS DECOMPOSERS
    7. 7. Energy Flow and Trophic Structure <ul><li>Key points about energy flow through ecosystems. </li></ul><ul><ul><li>Energy enters ecosystems in the form of sunlight that is used in photosynthesis by producers. </li></ul></ul><ul><ul><li>Plants use only a tiny fraction of the total radiation that is available to them. </li></ul></ul><ul><ul><li>Only a tiny fraction of fixed energy actually becomes available to consumers. </li></ul></ul>
    8. 8. Energy Flow and Trophic Structure <ul><li>Key points about energy flow through ecosystems. </li></ul><ul><ul><li>Most net primary production that is consumed enters the decomposer food web. </li></ul></ul><ul><ul><li>From there, only a small fraction is used for secondary production by herbivores and carnivores. </li></ul></ul><ul><ul><li>Most energy fixed during photosynthesis is used for respiration, not synthesis of new tissues. (Fig. 51.2) </li></ul></ul>
    9. 9. Energy source: 1,254,000 kcal/m 2 /year 0.8% energy captured by photosynthesis. Of this... … 45% supports growth (Net primary production) … 11% enters grazing food web … 34% enters decomposer food web as dead material … 55% lost to respiration Figure 51.2
    10. 10. Energy source: 1,254,000 kcal/m 2 /year Figure 51.2 … 11% enters grazing food web … 34% enters decomposer food web as dead material 0.8% energy captured by photosynthesis. Of this... … 45% supports growth (Net primary production) … 55% lost to respiration
    11. 11. 0–100 100–200 200–400 400–600 600–800 >800 Productivity ranges (g/m 2 /yr) Figure 51.3a Terrestrial productivity
    12. 12. <35 35–55 55–90 >90 Productivity ranges (g/m 2 /yr) Figure 51.3b Marine productivity
    13. 13. 80.7% respiration 17.7% excretion 1.6% growth and reproduction Energy derived from plants Figure 51.4
    14. 14. Predators of decomposers: Spider Centipede Mushroom Earthworm Primary decomposers: Bacteria and archaea Millipede Nematodes Pillbugs Salamander Figure 51.5 Puffball Puffball 305 nm 49.4 µm
    15. 15. Energy Flow and Trophic Structure <ul><li>Trophic structure </li></ul><ul><ul><li>Organisms that obtain their energy from the same type of source occupy the same trophic level. </li></ul></ul><ul><ul><li>Each feeding level within an ecosystem represents a trophic level. </li></ul></ul>
    16. 16. Energy Flow and Trophic Structure <ul><li>Trophic structure </li></ul><ul><ul><li>Organisms at the top trophic level are not eaten by any other organisms. </li></ul></ul><ul><ul><li>Productivity is highest at the lowest trophic level. (Fig. 51.6a,b) </li></ul></ul>
    17. 17. Trophic level 4 3 2 1 Feeding strategy Secondary carnivore Carnivore Herbivore Autotroph Grazing food chain Decomposer food chain Cricket Maple tree leaves Owl Shrew Earthworm Dead maple leaves Cooper’s hawk Robin Figure 51.6a Trophic levels
    18. 18. 4 Secondary carnivore 3 Carnivore 2 Herbivore 1 Autotroph Productivity Figure 51.6b Pyramid of productivity
    19. 19. Energy Flow and Trophic Structure <ul><li>Food chains and food webs </li></ul><ul><ul><li>Food chains are typically embedded in more complex food webs. (Fig. 51.7a,b) </li></ul></ul>
    20. 20. Pisaster (a sea star) Thais (a snail) Bivalves (clams, mussels) Figure 51.7a Food chain
    21. 21. Pisaster Thais Chitons Limpets Bivalves Acorn barnacles Gooseneck barnacles Figure 51.7b Food web
    22. 22. Energy Flow and Trophic Structure <ul><li>Food chains and food webs </li></ul><ul><ul><li>The maximum number of links in any food chain or web ranges from 1 to 6. (Fig. 51.7c) </li></ul></ul><ul><ul><ul><li>Hypotheses offered to explain this: </li></ul></ul></ul><ul><ul><ul><ul><li>Energy transfer may limit food-chain length. </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Long food chains may be more fragile. </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Food-chain length may depend on environmental complexity. </li></ul></ul></ul></ul>
    23. 23. Number of observations Number of links in food chain 10 8 6 4 2 0 Streams Lakes Terrestrial Figure 51.7c Food chains tend to have few links. Average number of links = 3.5 1 2 3 4 5 6
    24. 24. Biogeochemical Cycles <ul><li>The path an element takes as it moves from abiotic systems through living organisms and back again is referred to as its biogeochemical cycle. (Fig. 51.8) </li></ul>
    25. 25. Assimilation Loss to erosion or leaching into groundwater Soil nutrient pool Decomposer food web Detritus Death Herbivore Uptake Plants Death Consumption Feces or urine Figure 51.8
    26. 26. Boreal forest Figure 51.9 upper
    27. 27. Tropical rain forest Figure 51.9 lower
    28. 28. Biogeochemical Cycles <ul><li>A key feature in all cycles is that nutrients are recycled and reused. </li></ul><ul><li>The overall rate of nutrient movement is limited most by decomposition of detritus. </li></ul><ul><li>The rate of nutrient loss is a very important characteristic in any ecosystem. (Fig. 51.10a,b) </li></ul>
    29. 29. Devegetation experiment Choose two similar watersheds. Document nutrient levels in soil organic matter, plants, and streams. Figure 51.10a upper
    30. 30. Figure 51.10a lower Clearcut Control Devegetate one watershed and leave the other intact. Monitor the amount of dissolved substances in streams.
    31. 31. Devegetated Net dissolved substance (kg/ha) Control 1000 800 600 400 200 0 Year Figure 51.10b Nutrient runoff results 1965–66 1966–67 1967–68 1968–69 1969–70
    32. 32. Biogeochemical Cycles <ul><li>Nutrient flow among ecosystems links local cycles into one massive global biogeochemical cycle. </li></ul><ul><ul><li>The carbon cycle and the nitrogen cycle are examples of major, global biogeochemical cycles. (Fig. 51.11, 51.13a) </li></ul></ul><ul><ul><li>Humans are now disrupting almost all biogeochemical cycles. This can have very harmful effects. (Fig. 51.12a,b; 51.13b) </li></ul></ul>
    33. 33. THE GLOBAL CARBON CYCLE All values in gigatons of carbon per year Physical and chemical processes: 92 2 Ocean: 40,000 Rivers: 1 Land, biota, soil, litter, peat: 2000 Decomposition: 50 Respiration: 50 Photosynthesis: 102 Physical and chemical processes: 90 Deforestation: 1.5 Fossil fuel use: 6.0 Atmosphere: 750 (in 1990) +3.5 per year Aquatic ecosystems Terrestrial ecosystems Human–induced changes Figure 51.11
    34. 34. THE GLOBAL NITROGEN CYCLE Nitrogen fixing cyanobacteria Mud Decomposition of detritus into ammonia Nitrogen-fixing bacteria in roots and soil Industrial fixation Protein and nucleic acid synthesis Atmospheric nitrogen (N 2 ) Bacteria in mud use N-containing molecules as energy sources, excrete (N 2 ) Run–off Lightning and rain Figure 51.13a
    35. 35. Land use Fossil fuel use Year Annual flux of carbon (10 15 g) 6 5 4 3 2 1 0 Figure 51.12a Human-induced increases in CO 2 flux over time 1860 1880 1900 1920 1940 1960 1980
    36. 36. Year CO 2 concentration (ppm) 360 350 340 330 320 310 1960 1970 1980 1990 Figure 51.12b Atmospheric CO 2
    37. 37. Natural sources Human sources Amount of nitrogen (gigatons/year) 160 140 120 100 80 60 40 20 0 Sources of nitrogen fixation Lightning Biological fixation Fossil fuels Nitrogen fertilizer Nitrogen- fixing crops Figure 51.13b

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