ENERGY

1. ENERGY PATTERNS OF ENERGY FLOW IN ECOSYSTEMS

2. WHAT IS AN ECOSYSTEM? Biological community plus all abiotic factors affecting the community “Ecosystem” first proposed by Arthur Tansley Boundaries not fixed Energy flows Cycle nutrients http://eesc.columbia.edu/courses/ees/life/lectures/lect02.html

3. LAWS OF THERMODYNAMICS • 1st LAW: Energy cannot be created or destroyed but may be transformed from one form to another • 2nd LAW: When energy is converted from one form to another, energy is lost as heat

5. ENERGY SOURCES IN BIOSPHERE • Sunlight energy – driving force • Energy distribution and carbon dioxide in atmosphere shape ecosystems and biosphere • Biosphere energy and CO2 shape world climate and weather

6. ECOSYSTEM ENERGETICS: A THERMODYNAMICS VIEW Model– characterization of observations by set of equation which express observation in nature

7. CHARLES ELTON & FOOD WEBS • 1920s, Charles Elton and others proposed: • Organisms living in the same place not only have similar tolerances of physical factors, but • Feeding relationships link these organisms into a single functional entity • Food web http://www.history.vt.edu/Barrow/Hist3144/readings/ecology/index.html

8. http://www.nature.ca/ukaliq/images/a196_fwb_e.jpg

9. OLD FIELD FOOD WEB

10. Feeding relationships of the snowshoe hare-dominated food web in the boreal forest of northwestern Canada Dominant species in yellow

11. ALFRED J. LOTKA AND THE THERMODYNAMIC CONCEPT • Alfred J. Lotka • Ecosystem as an energy-transforming machine • Set of equations representing exchanges of matter and energy among components • Characterize transfer of body mass using series of equations describing how system works

13. LINDEMAN’S SYNTHESIS 1942 – Raymond Lindeman brought Lotka’s ideas of the ecosystem as an energy-transforming machine to the attention of ecologists Incorporated: Lotka’s thermodynamic concepts Elton’s food web concept Tansley’s ecosystem concept http://www.cedarcreek.umn.edu/people/photo/LindemanRaymond1942.jpg

14. LINDEMAN’S FOUNDATIONS OF ECOSYSTEM ECOLOGY • Ecosystem is fundamental unity of ecology • Within an ecosystem, energy passes through many steps or links in a food chain • Each link in the food chain is a trophic level (feeding level)

15. Cedar Bog Lake in Minnesota…site of Raymond Lindemen’s classic research paper in 1942: "The Trophic-Dynamic Concept in Ecology“. Ecology 23:399-418

17. ODUM’S ENERGY FLUX MODEL Recognized the utility of energy and masses of elements as common “currencies” in comparative analysis of ecosystem structure and function Eugene Odum http://www.researchmagazine.uga.edu/summer2002/odum.htm

18. ODUM EXTENDED HIS MODELS TO INCORPORATE NUTRIENT CYCLING • Fluxes of energy and materials are closely linked in ecosystem function • But: • Energy enters ecosystems as light and is degraded into heat • Nutrients cycle indefinitely, converted from inorganic to organic forms and back again • Studies of nutrient cycling provides index of energy fluxes

21. Single trophic level Example food chain Odum’s “universal” model of energy flow, which can be applied to any organism

22. Energy dissipated as heat SUN Producers Consumers Detritus + Decomposers Inorganic nutrients Nutrient pool Import Export Energy Flow Nutrient Cycling

23. WHAT DO WE KNOW SO FAR? • Ecosystems • Biotic and abiotic components • Energy and nutrients • Energy transformed from one form to another • When energy is transformed, energy is lost • Sunlight is ultimate source of energy • Food webs link organisms by trophic level

24. AUTOTROPHS - PRODUCERS Photoautotrophs - Sunlight energy, Green plants Chemoautotrophs - Chemical energy, certain bacteria Primary producers – capture energy from sunlight Transform sunlight energy to chemical energy Sugars, starch, ATP http://www.scienceclarified.com/images/uesc_01_img0028.jpg http://141.150.157.117:8080/prokPUB/figures/normal/p323-006.jpg

25. PRIMARY PRODUCTION • Producers capture energy of light • Transform sunlight energy into energy of chemical bonds in carbohydrates • 6CO2 + 6H2O → C6H12O6 + 6O2 • For each g of C assimilated, 39 kj energy stored • Gross primary production = total energy assimilated by primary producers • Net primary producion = energy accumulated (in stored form) by primary producers • GPP – NPP = Respiration • Energy consumed by producers for maintenance and biosynthesis

26. Energy lost and unavailable to consumers Partitioning gross primary productivity into respiration and net primary productivity GPP NPP

27. NUTRIENTS STIMULATE PRIMARY PRODUCTION • Terrestrial production may be nutrient limited • N most common limiting element • Aquatic systems often strongly nutrient-limited • Open ocean • Addition of nutrients may stimulate unwanted production

28. Effects of fertilization with N & P on primary production in a salt marsh dominated Carex subspathecea in southern Hudson Bay, Canada.

30. AQUATIC ECOSYSTEMSRESPONSIVE TO PHOSPHORUS 1975 1994 http://www.umanitoba.ca/institutes/fisheries/eutro.html

31. Slow-moving coastal plain stream choked with algal bloom caused by nitrogen and phosphorus from upstream farmland. http://wps.prenhall.com/wps/media/objects/57/58641/51_8089ic.gif

32. GLOBAL PRIMARY PRODUCTION • Correlates with annual precipitation (when light not limiting) • Note relationship among tundra, deserts, and tropics • Oceans – nutrient poor • CO2 Source of carbon • Follows 1st Law of Energy

34. Grams carbon/m2/yr for globe, as calculated from satellite imagery. Oceans = 46%, land = 54%

35. PRIMARY PRODUCTION VARIES AMONG ECOSYSTEMS • Maximum under favorable conditions • Intense sunlight • Warm temperatures • Abundant precipitation • Nutrients

36. NPP vs. Temperature + Precipitation

37. HETEROTROPHS - CONSUMERS • Get energy from external sources • “Animals” • Primary consumers • Secondary consumers • Tertiary consumers • Carnivores • Decomposers • Detritivores • Eat dead organic matter

38. Tertiary consumers Decomposers Secondary consumers Primary consumers Primary producers

39. Tertiary consumers Decomposers Secondary consumers Primary consumers Primary producers

40. ECOLOGICAL PYRAMIDS Trophic levels placed in order Reflects: Numbers of organisms at each level Biomass of each level Energy at each level

41. ECOLOGICAL PYRAMIDS Elton observed predators tended to be larger and less numerous than their prey - described as the ‘pyramid’ of numbers or biomass Elton hypothesized that this occurred because predators have to be larger than prey

42. PYRAMID OF NUMBERS # CONSUMERS=TOP CARNIVORES # DECOMPOSERS # CONSUMERS # HERBIVORES # PRIMARY PRODUCERS

43. PYRAMID OF BIOMASS kg CONSUMERS=TOP CARNIVORES kg CONSUMERS kG DECOMPOSERS kg HERBIVORES kg PRIMARY PRODUCERS

44. PYRAMID OF ENERGY kJ CONSUMERS=TOP CARNIVORES kJ CONSUMERS kJ DECOMPOSERS kJ HERBIVORES kJ PRIMARY PRODUCERS

45. NUMBERS PYRAMID

46. NUMBERS PYRAMID http://www.bbc.co.uk/schools/gcsebitesize/img/bi01010.gif

47. BIOMASS PYRAMID

48. BIOMASS PYRAMID

49. BIOMASS AND (NUMBERS) PYRAMID

50. ENERGY PYRAMID