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KWL---FOOD CHAINS

Global warming presents risks such as algal blooms, fish kills, intense heat waves, and reduced drinking water. Understanding energy flows and nutrients is crucial to addressing global warming.

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KWL---FOOD CHAINS

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  1. KWL---FOOD CHAINS

  2. Chapter 47ECOSYSTEMS

  3. Impacts, Issues: Bye-Bye, Blue Bayou • Global warming presents many risks: • algal blooms and huge fish kills • intense heat waves and wildfires • less fresh drinking water • Knowledge of global energy flows and nutrients is required to address global warming

  4. Fig. 47-1, p.842

  5. p.843

  6. Ecosystem An association of organisms and their physical environment, interconnected by ongoing flow of energy and a cycling of materials

  7. Modes of Nutrition • Autotrophs • Capture sunlight or chemical energy • Producers • Heterotrophs • Extract energy from other organisms or organic wastes • Consumers, decomposers, detritivores

  8. Simple Ecosystem Model energy input from sun PHOTOAUTOTROPHS (plants, other producers) nutrient cycling HETEROTROPHS (consumers, decomposers) energy output (mainly heat)

  9. SPRING Consumers • Herbivores • Carnivores • Parasites • Omnivores • Decomposers • Detritivores fruits insects rodents, rabbits birds SUMMER fruits rodents, rabbits insects birds Seasonal variation in the diet of an omnivore (red fox)

  10. Trophic Levels • All the organisms at a trophic level are the same number of steps away from the energy input into the system • Producers are closest to the energy input and are the first trophic level

  11. Trophic Levels in Prairie Fourth-level consumers (heterotrophs): 5th Top carnivores, parasites, detritivores, decomposers Third-level consumers (heterotrophs): 4th Carnivores, parasites, detritivores, decomposers Second-level consumers (heterotrophs): 3rd Carnivores, parasites, detritivores, decomposers First-level consumers (heterotrophs): 2nd Herbivores, parasites, detritivores, decomposers Primary producers (autotrophs): 1st Photoautotrophs, chemoautotrophs

  12. Food Chain marsh hawk • A straight-line sequence of who eats whom • Simple food chains are rare in nature upland sandpiper garter snake cutworm plants

  13. marsh hawk crow garter snake cutworm flowering plants Fig. 47-4, p.845

  14. Tall-Grass Prairie Food Web marsh hawk sandpiper crow snake frog coyote weasel badger spider sparrow pocket gopher ground squirrel vole earthworms, insects grasses, composites

  15. marsh hawk Sampling of connections in a tallgrass prairie food web Higher Trophic Levels crow upland sandpiper garter snake frog weasel badger coyote spider Second Trophic Level sparrow prairie vole pocket gopher ground squirrel earthworms, insects First Trophic Level grasses, composites Fig. 47-5, p.846

  16. Energy Losses • Energy transfers are never 100 percent efficient • Some energy is lost at each step • Limits the number of trophic levels in an ecosystem

  17. Grazing Food Web Detrital Food Web Two Types of Food Webs Energy Input: Energy Input: Transfers: Transfers: Producers (photosynthesizers) Producers (photosynthesizers) energy losses as metabolic heat & as net export from ecosystem energy in organic wastes, remains energy in organic wastes, remains energy losses as metabolic heat & as net export from ecosystem herbivores decomposers decomposers carnivores detritivores detritivores decomposers Energy Output Energy Output Figure 47.6 Page 847

  18. Biological Magnification A nondegradable or slowly degradable substance becomes more and more concentrated in the tissues of organisms at higher trophic levels of a food web

  19. DDT in Food Webs • Synthetic pesticide banned in United States since the 1970s • Birds that are carnivores accumulate DDT in their tissues, produce brittle egg shells

  20. Pesticides Fig. 47-7, p.848

  21. Primary Productivity • Gross primary productivity is ecosystem’s total rate of photosynthesis • Net primary productivity is rate at which producers store energy in tissues in excess of their aerobic respiration

  22. Primary Productivity Varies • Seasonal variation • Variation by habitat • The harsher the environment, the slower plant growth, the lower the primary productivity

  23. Fig. 47-10, p.850

  24. Silver Springs Study • Aquatic ecosystem in Florida • Site of a long-term study of a grazing food web third-level carnivores (gar, large-mouth bass) 1.5 second-level consumers (fishes, invertebrates) 1.1 decomposers, detritivores (bacteria, crayfish) first-level consumers (herbivorous fishes, turtles, invertebrates) 37 primary producers (algae, eelgrass, rooted plants) 809 5

  25. Pyramid of Energy Flow • Primary producers trapped about 1.2 percent of the solar energy that entered the ecosystem • 6-16% passed on to next level decomposers + detritivores = 5,080 21 top carnivores carnivores 383 herbivores 3,368 producers 20,810 kilocalories/square meter/year Figure 47.13 Page 851

  26. All Heat in the End • At each trophic level, the bulk of the energy received from the previous level is used in metabolism • This energy is released as heat energy and lost to the ecosystem • Eventually all energy is released as heat

  27. Biogeochemical Cycle • The flow of a nutrient from the environment to living organisms and back to the environment • Main reservoir for the nutrient is in the environment

  28. Three Categories • Hydrologic cycle • Water • Atmospheric cycles • Nitrogen and carbon and oxygen • Sedimentary cycles • Phosphorus and sulfur

  29. Hydrologic Cycle Atmosphere precipitation onto land 111,000 wind-driven water vapor 40,000 evaporation from land plants (evapotranspiration) 71,000 evaporation from ocean 425,000 precipitation into ocean 385,000 surface and groundwater flow 40,000 Land Ocean Figure 47-15 Page 853

  30. Hubbard Brook Experiment • A watershed was experimentally stripped of vegetation • All surface water draining from watershed was measured • Removal of vegetation caused a six-fold increase in the calcium content of the runoff water

  31. Hubbard Brook Experiment losses from disturbed watershed time of deforestation losses from undisturbed watershed Figure 47-17 Page 854

  32. Water Use and Scarcity • Most of Earth’s water is too salty for human consumption • Desalinization is expensive and requires large energy inputs • Irrigation of crops is the main use of freshwater

  33. Negative Effects of Irrigation • Salinization, mineral buildup in soil • Elevation of the water table and waterlogging • Depletion of aquifers

  34. Carbon Cycle • Carbon moves through the atmosphere and food webs on its way to and from the ocean, sediments, and rocks • Sediments and rocks are the main reservoir

  35. Carbon in the Oceans • Most carbon in the ocean is dissolved carbonate and bicarbonate • Ocean currents carry dissolved carbon

  36. Carbon in Atmosphere • Atmospheric carbon is mainly carbon dioxide • Carbon dioxide is added to atmosphere • Aerobic respiration, volcanic action, burning fossil fuels • Removed by photosynthesis

  37. Greenhouse Effect • Greenhouse gases impede the escape of heat from Earth’s surface Figure 47-22, Page 858

  38. Global Warming Long-term increase in the temperature of Earth’s lower atmosphere

  39. Carbon Dioxide Increase • Carbon dioxide levels fluctuate seasonally • The average level is steadily increasing • Burning of fossil fuels and deforestation are contributing to the increase

  40. Other Greenhouse Gases • CFCs - synthetic gases used in plastics and in refrigeration • Methane - produced by termites and bacteria • Nitrous oxide - released by bacteria, fertilizers, and animal wastes

  41. Nitrogen Cycle • Nitrogen is used in amino acids and nucleic acids • Main reservoir is nitrogen gas in the atmosphere

  42. Nitrogen Cycle gaseous nitrogen (N2) in atmosphere nitrogen fixation by industry food webs on land uptake by autotrophs excretion, death, decomposition uptake by autotrophs fertilizers nitrogenous wastes, remains NO3- in soil nitrogen fixation dentrification ammonification 2. Nitrification NH3-,NH4+ in soil NO2- in soil 1. Nitrification leaching leaching Figure 47-25 Page 860

  43. Nitrogen Fixation • Plants cannot use nitrogen gas • Nitrogen-fixing bacteria convert nitrogen gas into ammonia (NH3) • Ammonia and ammonium can be taken up by plants

  44. Ammonification & Nitrification • Bacteria and fungi carry out ammonification • conversion of nitrogenous wastes to ammonia • Nitrifying bacteria convert ammonium to nitrites and nitrates

  45. Nitrogen Loss • Nitrogen is often a limiting factor in ecosystems • Nitrogen is lost from soils via leaching and runoff • Denitrifying bacteria convert nitrates and nitrites to nitrogen gas

  46. Human Effects • Humans increase rate of nitrogen loss by clearing forests and grasslands • Humans increase nitrogen in water and air by using fertilizers and by burning fossil fuels • Too much or too little nitrogen can compromise plant health

  47. Phosphorus Cycle • Phosphorus is part of phospholipids and all nucleotides • It is the most prevalent limiting factor in ecosystems • Main reservoir is Earth’s crust; no gaseous phase

  48. Human Effects • In tropical countries, clearing lands for agriculture may deplete phosphorus-poor soils • In developed countries, phosphorus runoff is causing eutrophication of waterways

  49. Eutrophication Experiments Fig. 47-28, p.863

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