Biology 213 Chapter 55

1. Biology 213 Chapter 55 Ecosystems and the Biosphere

2. You will be able to… • Compare & contrast food chains, webs, and pyramids • Explain Bioaccumulation & magnification • Describe C cycle, N cycle, P cycle & H2O cycle in the biotic and abiotic environment. • Examine human influence on natural cycles • Describe role of the sun in • Creating seasons • Weather systems • Developing ocean currents • Creating a climate and weather

3. Energy flow through an ecosystem • Linear • Sun to producer to consumer to decomposer Is the sun the only source of energy for food webs?

4. Energy flow through an ecosystem A food chain

5. Food chains, webs, & trophic levels.

6. Food chains, webs, & trophic levels. Trophic relationships important in endangered wildlife management: e.g. DDT  Bald Eagle & Condors

7. Ecological pyramids Express progressive reduction in #’s of: • Organisms • Biomass • energy found in successive trophic levels

8. Food chains, webs, & trophic levels. Not all animals or plants are eaten. Portions (beaks, shells, bones, etc.) not digested. Matter & energy transfer not efficient.

9. Pyramids of biomass Usually amount of fixed energy in an ecosystem is measured in quantity of living material = biomass Generally amount of biomass decreases at successively higher trophic levels. Why?

10. Pyramid of biomass: If you want to support a lot of humans, what should you feed them?

11. Pyramids of energy • What happens to the energy? • Undigested parts • Entropy • Energy • expended in • “hunting” & • processing food

12. Bioaccumulation: build up of toxins in an organism Biological magnification: increasing concentration in successive trophic levels

13. Gross primary productivity (GPP) • Rate at which photosynthesis captures energy • Net primary productivity (NPP) • Energy remaining after plants and other producers carry out cellular respiration What do you think are the most productive ecosystems?

14. NPP for selected ecosystems EcosystemAvg NPP (g dry matter/m2/yr) Algal beds & reefs 2,500 Tropical rain forest 2,200 Swamp & marsh 2,000 Estuaries 1,500 Temperate evergreen forest 1,300 Temperate deciduous forest 1,200 Savanna 900 Boreal (northern) forest 800

15. NPP for selected ecosystems EcosystemAvg NPP (g dry matter/m2/yr) Woodland & shrubland 700 Agricultural land 650 Temperate grassland 600 Upwelling in oceans 500 Lake and stream 250 Arctic and alpine tundra 140 Open ocean 125 Desert and semi-desert scrubland 90 Extreme desert (rock, sand, ice) 3

16. Why is Carbon important in the ecosystem? • What form is carbon used by plants? • CO2 absorbed / O2 released • Sugars (starch) formed • Sugar used for Energy (cellular respiration) • What form is carbon used by animals? • Sugar used for Energy (cellular respiration) • CO2 released / O2 absorbed (see Joseph Priestly’s experiments) Remember: • C forms the “skeleton” for every biomolecule

17. How does Carbon cycle in the environment? • Biotic factors: • plants and animals: gaseous form • Trees store carbon • Seashells: solid form calcium carbonate • Abiotic factors: • Atmospheric gas: circulates globally • Mineral compounds: limestone • Fossil fuels – remnants of ancient plants • and marine critters

18. Biogeochemical Cycles: The Carbon cycle • Carbon dioxide is the most important gas (0.038% of air) • gas phase allows for global circulation • Carbon enters plants as CO2

19. Biogeochemical Cycles: The Carbon cycle • CO2 returned to the environment: • Cellular respiration • Combustion & volcanoes • Erosion of limestone • Decomposition

20. Carbon cycle Carbon Reservoirs: in billions of metric tons: Atmosphere: 720 Fossil fuels: 4,000 Ocean: 39,000 Soils: 1500 Carbonates: 100,000,000 Land plants: 560 • most C is in rocks (carbonates & sediments) • most C not in rocks is dissolved in ocean • ~ 3 x more C in soils than in land plants • Methane hydrates under sea floor

21. Carbon Cycle

22. Nitrogen cycle Why is nitrogen important to living things? How is it used? Proteins, DNA, Chlorophyll formation.

23. Nitrogen cycle • Five steps: • Nitrogen fixation • Nitrification • Assimilation • Ammonification • Denitrification

24. Nitrogen fixation:2 moles of ammonia produced by prokaryotes from 1 mole of N2 gas N2 + 8H+ + 8e- + 16 ATP = 2NH3 + H2 + 16ADP + 16 Pi

25. Combustion, volcanoes, industry, and lightning can fix N2 as nitrates & nitrites Lightning: N2 + O2 --------------> 2 NO (nitric oxide) Nitric oxide free radical combines with O2 to form NO2. 2 NO + O2 ---------------> 2NO2 Nitrogen dioxide dissolves in water to produce nitric and nitrous acids; 2 NO2 + H2O -------> HNO3 + HNO2 These acids readily release NO3 & NO2 ions - utilized by plants & micro-organisms. HNO3 --------> H+ + NO3- (nitrate ions) HNO2 --------> H+ + NO2- (nitrite ions)

26. Nitrification Ammonia converted to ammonium to nitrate

27. Assimilation • Roots absorb: • Ammonia (NH3) • Ammonium ions • Nitrate ions • Make plant proteins, nucleic acids, & chlorophyll

28. Ammonification • Nitrogen compounds released as wastes: • Urea in urine • Uric acid in bird poop • Compounds are decomposed into ammonia by bacteria

29. Denitrification • Nitrate ions reduced to gaseous nitrogen by denitrifying bacteria • Reverse nitrogen fixing process • Anaerobic environments: deep soil, swamps, deep ocean

30. Nitrogen cycle Both Carbon & Nitrogen cycles involve gas, biological, & geochemical reservoirs

31. Phosphorus cycle • Phosphorus erodes from rock as inorganic phosphate • Animals obtain it from their diet • Plants obtain it from the soil • Does not have a gaseous phase, so cycles more locally

32. Phosphorus cycle: no gas phase N and P are the major limiting factors for plant growth

33. Guano happens! • Sea bird deposits • Bat caves • Used extensively in agriculture as a fertilizer • Used in detergents • Run-off enters streams

34. Eutrophication: enhanced phytoplankton growth due excess supply of nutrients • High concentrations of nutrients as run-off from • Sewage • Agriculture • Lawns

35. Eutrophication: enhanced phytoplankton growth due excess supply of nutrients • Phytoplankton “bloom” • Phytoplankton die and are eaten by bacteria • Oxygen levels depleted & fish die

36. Dr. David Schindler is an ecologist who worked at the Experimental Lakes Project in northern Ontario • performed several experiments on eutrophication that led to ban on phosphates in detergents

37. Phosphates are the culprit

38. Hydrologic cycle • Renews supply of water • Involves exchange of water btwn land, ocean, atmosphere, and organisms • Water enters atmosphere by evaporation and transpiration • Water leaves atmosphere as precipitation • “Distillation” purifies water

39. Water Basins: Lakes, Oceans, Ice How much fresh water is there?

41. Transpiration and Evaporation • Solar energy drives evaporation • Evaporation: ocean surface is main reservoir • Transpiration: plants release over 95% of water they absorb back into air

42. Condensation and precipitation • Solar E drives surface winds • Winds carry moist air inland and up over mountains • Cooling air loses moisture as condensation • Precipitation: rain, sleet, snow, hail, & fog

43. Storage: percolation and ground water • Aquifers may take hundreds of years to replenish • Underground aquifers supply water for • Streams • Agriculture • Wells

44. Ogallala Aquifer: ~95 % used for irrigation. High Plains = 65 % of total irrigated acreage in USA. Overuse: 175,000 wells, irrigating > 15 million acres. Depleted much faster than natural rate of recharge. Some states 40 x higher.

45. Hydrologic cycle

46. Bottom-up processes Availability of resources e.g. nutrient minerals controls # of producers, which controls # of herbivores, which controls # of predators, etc.

47. Top-down processes: • Increase in top predators cascades down food web

48. Sunlight: primary source of energy • Combo of Earth’s spherical shape • & axis tilt concentrate solar E at equator. • Inclination of Earth’s axis primarily determines • the seasons

49. Amount of solar radiation reaching Earth • 30% reflected back • 47% absorbed by atmosphere • 23% runs hydrologic cycle • 1% drives wind and ocean currents • 0.02% captured by photosynthesis • 0.0001% used by Culhane for tanning

50. Seasonal changes in temperature