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 thermodynamics states 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 thermodynamics states 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 Microorganisms and other detritivores Tertiary consumers Secondary consumers Primary consumers Primary producers Detritus Heat Sun Chemical cycling Key Energy flow Decomposition connects all trophic levels

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… NPP = GPP - R Only NPP is available to consumers

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/m 2 yr) or as biomass added per unit area per unit time (g/m 2 yr) added in that unit of time.

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

22. Our Lab We are calculating the NPP for our Fast Plants by measuring their biomass accumulated. Remember some energy is lost as heat and used in respiration.

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

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

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

26. Experiment we used to do:

27. 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.

28. 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

29. 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

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

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

32. 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

33. Fig. 55-7 Atlantic Ocean Moriches Bay Shinnecock Bay Long Island Great South Bay A B C D E F G EXPERIMENT Ammonium enriched Phosphate enriched Unenriched control RESULTS A B C D E F G 30 24 18 12 6 0 Collection site Phytoplankton density (millions of cells per mL) Nutrient enrichment experiments confirmed that nitrogen was limiting phytoplankton growth off the shore of Long Island, New York Ammonium NH 3

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

35. 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

36. Why do the fish die?

37. 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

38. Net primary production (g/m 2 ·yr) Fig. 55-8 Tropical forest Actual evapotranspiration (mm H 2 O/yr) Temperate forest Mountain coniferous forest Temperate grassland Arctic tundra Desert shrubland 1,500 1,000 5000 0 1,000 2,000 3,000 ·

39. 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?

40. 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

41. 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.

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

43. 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

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

45. 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

46. Fig. 55-11 (a) Most ecosystems (data from a Florida bog) Primary producers (phytoplankton) (b) Some aquatic ecosystems (data from the English Channel) Trophic level Tertiary consumers Secondary consumers Primary consumers Primary producers Trophic level Primary consumers (zooplankton) Dry mass (g/m 2 ) Dry mass (g/m 2 ) 1.5 11 37 809 21 4

47. 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

48. 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

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

50. 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

51. The Water Cycle Water is essential to all organisms 97% of the biosphere’s water is contained in the oceans, 2% is in glaciers and polar ice caps, and 1% is in lakes, rivers, and groundwater Water moves by the processes of evaporation, transpiration, condensation, precipitation, and movement through surface and groundwater

52. Fig. 55-14a Precipitation over land Transport over land Solar energy Net movement of water vapor by wind Evaporation from ocean Percolation through soil Evapotranspiration from land Runoff and groundwater Precipitation over ocean

53. The Carbon Cycle Carbon-based organic molecules are essential to all organisms Carbon reservoirs include fossil fuels, soils and sediments, solutes in oceans, plant and animal biomass, and the atmosphere CO 2 is taken up and released through photosynthesis and respiration; additionally, volcanoes and the combustion of fossil fuels contribute CO 2 to the atmosphere

54. Fig. 55-14b Higher-level consumers Primary consumers Detritus Burning of fossil fuels and wood Phyto- plankton Cellular respiration Photo- synthesis Photosynthesis Carbon compounds in water Decomposition CO 2 in atmosphere

55. The Terrestrial Nitrogen Cycle Nitrogen is a component of amino acids, proteins, and nucleic acids The main reservoir of nitrogen is the atmosphere (N 2 ), though this nitrogen must be converted to ammonia or nitrate for uptake by plants, via nitrogen fixation by bacteria Organic nitrogen is decomposed to ammonia by ammonification, and ammonia is decomposed to nitrate in soil by nitrification Denitrification converts nitrates back to N 2 in the atmosphere.

56. BACTERIA NITROGEN Nitrogen Fixation ammonia, nitrates

57. Organic nitrogen from metabolism ammonification ammonia nitrification nitrates denitrification N 2 BACTERIA DECOMPOSITION

58. Fig. 55-14c Decomposers N 2 in atmosphere Nitrification Nitrifying bacteria Nitrifying bacteria Denitrifying bacteria Assimilation NH 3 NH 4 NO 2 NO 3 + – – Ammonification Nitrogen-fixing soil bacteria Nitrogen-fixing bacteria BACTERIA are super important here!

60. Nitrogen accumulation in a pond

61. The Phosphorus Cycle Phosphorus is a major constituent of nucleic acids, phospholipids, and ATP Phosphate (PO 4 3– ) is the most important inorganic form of phosphorus The largest reservoirs are sedimentary rocks of marine origin, the oceans, and organisms Phosphate binds with soil particles, and movement is often localized DOES NOT CYCLE IN THE ATMOSPHERE

62. Fig. 55-14d Leaching Consumption Precipitation Plant uptake of PO 4 3– Soil Sedimentation Uptake Plankton Decomposition Dissolved PO 4 3– Runoff Geologic uplift Weathering of rocks

63. Decomposition and Nutrient Cycling Rates Decomposers (detritivores) play a key role in the general pattern of chemical cycling Rates at which nutrients cycle in different ecosystems vary greatly, mostly as a result of differing rates of decomposition The rate of decomposition is controlled by temperature, moisture, and nutrient availability Rapid decomposition results in relatively low levels of nutrients in the soil

64. Human activities now dominate most chemical cycles on Earth As the human population has grown, our activities have disrupted the trophic structure, energy flow, and chemical cycling of many ecosystems

65. How have humans impacted our ecosystems? 1) Agriculture and N cycling In agriculture, we have depleted our N resources and added back with fertilizers which have harmed our ecosystems.

66. 2) Contamination of Aquatic Ecosystems When excess nutrients are added to an ecosystem, the critical load (minimal amt plants can absorb) is exceeded Remaining nutrients can contaminate groundwater as well as freshwater and marine ecosystems and cause eutrophication

67. 3) Acid Precipitation Combustion of fossil fuels is the main cause of acid precipitation North American and European ecosystems downwind from industrial regions have been damaged by rain and snow containing nitric and sulfuric acid Acid precipitation changes soil pH and causes leaching of calcium and other nutrients

68. Fig. 55-19 Year 20001995 1990 19851980 19751970 19651960 4.0 4.1 4.2 4.3 4.4 4.5 pH

69. 4) Toxins in the Environment Humans release many toxic chemicals, including synthetics previously unknown to nature One reason toxins are harmful is that they become more concentrated in successive trophic levels Biological magnification concentrates toxins at higher trophic levels, where biomass is lower

70. Fig. 55-20 Lake trout 4.83 ppm Concentration of PCBs Herring gull eggs 124 ppm Smelt 1.04 ppm Phytoplankton 0.025 ppm Zooplankton 0.123 ppm

71. Brier Creek fish kill report looks at material used in mining, wastewater treatment In a status report on the incident, Savannah River­keeper said the characteristics of the fish kill are indicative of poisoning by aluminum sulfate – used as a coagulant in kaolin mining and sewage treatment.

72. 5) Greenhouse Gases and Global Warming One pressing problem caused by human activities is the rising level of atmospheric carbon dioxide Due to the burning of fossil fuels and other human activities, the concentration of atmospheric CO 2 has been steadily increasing

73. Fig. 55-21 CO 2 CO 2 concentration (ppm) Temperature 1960 300 Average global temperature (ºC) 1965197019751980 Year 19851990199520002005 13.6 13.7 13.8 13.9 14.0 14.1 14.2 14.3 14.4 14.5 14.6 14.7 14.8 14.9 310 320 330 340 350 360 370 380 390 What we know for sure: The concentration of atmospheric CO2 has been steadily increasing.

74. The Greenhouse Effect and Climate CO 2, water vapor, and other greenhouse gases reflect infrared radiation back toward Earth; this is the greenhouse effect could cause global warming and climatic change Northern coniferous forests and tundra show the strongest effects of global warming

75. Depletion of Atmospheric Ozone Life on Earth is protected from damaging effects of UV radiation by a protective layer of ozone molecules Destruction of atmospheric ozone probably results from chlorine-releasing pollutants such as CFCs produced by human activity Ozone depletion causes DNA damage in plants and poorer phytoplankton growth

76. Ozone layer thickness (Dobsons) Fig. 55-23 Year ’05 2000 ’95’90’85 ’80 ’75’70 ’65 ’60 1955 0 100 250 200 300 350 Satellite studies suggest that the ozone layer has been gradually thinning since 1975

78. Fig. 55-24 O2O2 Sunlight Cl 2 O 2 Chlorine Chlorine atom O3O3 O2O2 ClO How free chlorine in the atmosphere destroys ozone. ozone

79. Ozone depletion causes DNA damage in plants and poorer phytoplankton growth

80. Fig. 55-25 (a) September 1979(b) September 2006 Scientists first described an “ozone hole” over Antarctica in 1985; it has increased in size as ozone depletion has increased An international agreement signed in 1987 has resulted in a decrease in ozone depletion

81. DO YOUR PART!