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Fig. 55-1

Fig. 55-1. ECOSYSTEMS AP CHAP 55. An ecosystem consists of all the organisms living in a community, as well as the abiotic factors with which they interact. Fig. 55-2. Regardless of an ecosystem’s size, its dynamics involve two main processes: energy flow and chemical cycling

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Fig. 55-1

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  1. Fig. 55-1 ECOSYSTEMS AP CHAP 55 An ecosystem consists of all the organisms living in a community, as well as the abiotic factors with which they interact

  2. Fig. 55-2 Regardless of an ecosystem’s size, its dynamics involve two main processes: energy flow and chemical cycling Energy flows through (one way) ecosystems while matter cycles within them

  3. Physical laws govern energy flow and chemical cycling in ecosystems • The first law of thermodynamicsstates that energy cannot be created or destroyed, only transformed • Energy enters an ecosystem as solar radiation, is conserved, and is lost from organisms as HEAT! • The second law of thermodynamicsstates that every exchange of energy increases the entropy of the universe • In an ecosystem, energy conversions are not completely efficient, and some energy is always lost as HEAT!

  4. Conservation of Mass • The law of conservation of mass states that matter cannot be created or destroyed • Chemical elements are continually recycled within ecosystems • Ecosystems are open systems, absorbing energy and mass and releasing heat and waste products.

  5. Energy, Mass, and Trophic Levels • Autotrophs build molecules themselves using photosynthesis or chemosynthesis as an energy source; heterotrophs depend on the biosynthetic output of other organisms • Energy and nutrients pass from primary producers (autotrophs) to primary consumers (herbivores) to secondary consumers (carnivores) to tertiary consumers (carnivores that feed on other carnivores)

  6. Detritivores,or decomposers, are consumers that derive their energy from detritus, nonliving organic matter • Prokaryotes and fungi are important detritivores • Decomposition connects all trophic levels

  7. Fig. 55-3

  8. Fig. 55-4 Tertiary consumers Microorganisms and other detritivores Secondary consumers Primary consumers Detritus Decomposition connects all trophic levels Primary producers Heat Key Chemical cycling Sun Energy flow

  9. Energy and other limiting factors control primary production in ecosystems • Primary production in an ecosystem is the amount of light energy converted to chemical energy by autotrophs during a given time period….ie….amount of PHOTOSYNTHESIS

  10. In primary producers the main energy input is from the solar energy. In a plant, not all of the solar energy available actually makes it into the leaf. Only about 1% of visible light that strikes photosynthetic organisms is converted to chemical energy in photosynthesis.

  11. It is the energy that is incorporated into the biomass that is available for the next trophic level.

  12. In the consumer a further series of energy losses occur. The consumer will take in a certain amount of energy from the trophic level beneath it.

  13. It is generally accepted that only around 10% of the energy gained from the previous trophic level is passed on to the next level. All other energy is lost as described above. This limits the number of trophic levels in any food chain.

  14. Gross and Net Primary Production Total primary production is known as the ecosystem’s gross primary production (GPP) Since autotrophs also have to respire to obtain energy, their GPP is reduced by the amount of energy used for fuel in cell respiration.

  15. Net primary production (NPP) is GPP minus energy used by primary producers for cell respiration • Only NPP is available to consumers

  16. SO… Only NPP is available to consumers NPP = GPP - R

  17. It’s like Gross Pay – what you make Net Pay – what you bring home NPP = GPP from photosynthesis – R from cellular respiration Or GPP = NPP + R

  18. In many ecosystems, NPP is about ½ of GPP. NPP represents the storage of chemical energy that will be available to consumers. NPP can be expressed as energy per unit area per unit time (J/m2 yr) or as biomass added per unit area per unit time (g/m2 yr) added in that unit of time.

  19. Energy lost Reflected Tree Layer Shrub layer Solar Radiation Absorbed Energy accumulated as biomass Herb Layer Transmitted Energy cannot be created or destroyed so all of this has to add up.

  20. Our LabWe are calculating the NPP for our Fast Plants by measuring their biomassaccumulated. Remember some energy is lost as heat and used in respiration.

  21. Then we are measuring the transfer of energy from plants to butterfly larvae in “Secondary Production”.

  22. Primary productivity can also be determined by measuring oxygen being produced Or the amount of carbon compounds being produced Think photosynthesis.

  23. This can be done by measuring the amount of oxygen in samples of water in bottles in light and dark.

  24. Experiment we used to do:

  25. Remember…the difference between gross and net primary productivity. Gross productivity is the total amount of productivity in the environment. Net productivity is the average productivity produced at a certain period of time. Gross primary productivity is the total amount of something made in an area. Net primary productivity is the amount of that energy that can actually be used. Gross primary production is the overall total of production.

  26. Primary productivity is the amount of light energy converted to chemical energy during a period of time. It is the photosynthetic output of an ecosystem’s autotrophs. The NPP is an ecosystem’s GPP minus the energy used by producers in their own cellular respiration (R). So NPP = GPP – R GPP = NPP + R

  27. Tropical rain forests, estuaries, and coral reefs are among the most productive ecosystems per unit area • Marine ecosystems are relatively unproductive per unit area, but contribute much to global net primary production because of their volume

  28. Fig. 55-6 · Net primary production (kg carbon/m2·yr) 0 1 3 2

  29. Primary Production in Aquatic Ecosystems In marine and freshwater ecosystems, both light and nutrients control primary production

  30. Nutrient Limitation • More than light, nutrients limit primary production in the ocean and in lakes • A limiting nutrient is the element that must be added for production to increase in an area • Nitrogen and phosphorous are typically the nutrients that most often limit marine production

  31. Fig. 55-7 EXPERIMENT Long Island Shinnecock Bay G F E C D Moriches Bay B Nutrient enrichment experiments confirmed that nitrogen was limiting phytoplankton growth off the shore of Long Island, New York Great South Bay Atlantic Ocean A Ammonium NH3 RESULTS 30 Ammonium enriched Phosphate enriched 24 Unenriched control 18 Phytoplankton density (millions of cells per mL) 12 6 0 C B D A E G F Collection site

  32. Table 55-1 What is the limiting factor in this area? IRON

  33. Upwelling of nutrient-rich waters in parts of the oceans contributes to regions of high primary production • The addition of large amounts of nutrients to lakes has a wide range of ecological impacts • In some areas, sewage runoff has caused eutrophication of lakes, which can lead to loss of most fish species

  34. Why do the fish die?

  35. Primary Production in Terrestrial Ecosystems • In terrestrial ecosystems, temperature and moisture affect primary production on a large scale • Evapotranspiration is related to net primary production

  36. Fig. 55-8 3,000 Tropical forest · 2,000 Net primary production (g/m2·yr) Temperate forest 1,000 Mountain coniferous forest Desert shrubland Temperate grassland Arctic tundra 0 0 500 1,500 1,000 Actual evapotranspiration (mm H2O/yr)

  37. On a more local scale, a soil nutrient is often the limiting factor in primary production What is the limiting factor in this soil example?

  38. Energy transfer between trophic levels is typically only 10% efficient • Secondary production of an ecosystem is the amount of chemical energy in food converted to new biomass during a given period of time

  39. Production Efficiency • When a caterpillar feeds on a leaf, only about one-sixth of the leaf’s energy is used for secondary production • An organism’s production efficiency is the fraction of energy stored in food that is not used for respiration or other processes that do not lead to biomass in the organism.

  40. Fig. 55-9 When a caterpillar feeds on a leaf, only about one-sixth of the leaf’s energy is used for secondary production 200 6 Plant material eaten by caterpillar 200 J 67 J Cellular respiration 100 J Feces 33 J Growth (new biomass)

  41. Trophic Efficiency and Ecological Pyramids • Trophic efficiency is the percentage of production transferred from one trophic level to the next • It usually ranges from 5% to 20% • Trophic efficiency is multiplied over the length of a food chain • Approximately 0.1% of chemical energy fixed by photosynthesis reaches a tertiary consumer • A pyramid of net production represents the loss of energy with each transfer in a food chain

  42. Fig. 55-10 Energy transfer between trophic levels is typically only 10% efficient Tertiary consumers 10 J Secondary consumers 100 J Primary consumers 1,000 J Primary producers 10,000 J 1,000,000 J of sunlight

  43. In a biomass pyramid, each tier represents the dry weight of all organisms in one trophic level • Most biomass pyramids show a sharp decrease at successively higher trophic levels • Certain aquatic ecosystems have inverted biomass pyramids: producers (phytoplankton) are consumed so quickly that they are outweighed by primary consumers

  44. Fig. 55-11 Trophic level Dry mass (g/m2) Tertiary consumers 1.5 Secondary consumers 11 Primary consumers 37 Primary producers 809 (a) Most ecosystems (data from a Florida bog) Trophic level Dry mass (g/m2) Primary consumers (zooplankton) 21 Primary producers (phytoplankton) 4 (b) Some aquatic ecosystems (data from the English Channel)

  45. Biological and geochemical processes cycle nutrients between organic and inorganic parts of an ecosystem • Life depends on recycling chemical elements • Nutrient circuits in ecosystems involve biotic and abiotic components and are often called biogeochemical cycles

  46. Biogeochemical Cycles • Gaseous carbon, oxygen, sulfur, and nitrogen occur in the atmosphere and cycle globally • Less mobile elements such as phosphorus, potassium, and calcium cycle on a more local level

  47. Fig. 55-13 Reservoir B Reservoir A All elements cycle between organic and inorganic reservoirs Organic materials available as nutrients Organic materials unavailable as nutrients Fossilization Living organisms, detritus Coal, oil, peat Respiration, decomposition, excretion Assimilation, photosynthesis Burning of fossil fuels Reservoir C Reservoir D Inorganic materials available as nutrients Inorganic materials unavailable as nutrients Weathering, erosion Minerals in rocks Atmosphere,soil, water Formation of sedimentary rock

  48. In studying cycling of water, carbon, nitrogen, and phosphorus, ecologists focus on four factors: • Each chemical’s biological importance • Forms in which each chemical is available or used by organisms • Major reservoirs for each chemical • Key processes driving movement of each chemical through its cycle

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