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Biology 213 Chapter 55 Ecosystems and the Biosphere.

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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 & H 2 O 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 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 Generally amount of biomass decreases at successively higher trophic levels. Why? Usually amount of fixed energy in an ecosystem is measured in quantity of living material = biomass

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

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 Ecosystem Avg NPP (g dry matter/m 2 /yr) Algal beds & reefs2,500 Tropical rain forest2,200 Swamp & marsh2,000 Estuaries1,500 Temperate evergreen forest1,300 Temperate deciduous forest1,200 Savanna 900 Boreal (northern) forest 800

15 NPP for selected ecosystems Ecosystem Avg NPP (g dry matter/m 2 /yr) Woodland & shrubland700 Agricultural land650 Temperate grassland600 Upwelling in oceans500 Lake and stream250 Arctic and alpine tundra140 Open ocean125 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? –CO 2 absorbed / O 2 released –Sugars (starch) formed –Sugar used for Energy (cellular respiration) What form is carbon used by animals? –Sugar used for Energy (cellular respiration) –CO 2 released / O 2 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 CO 2

19 Biogeochemical Cycles: The Carbon cycle –CO 2 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: 1.Nitrogen fixation 2.Nitrification 3.Assimilation 4.Ammonification 5.Denitrification

24 N 2 + 8H + + 8e ATP = 2NH 3 + H ADP + 16 P i Nitrogen fixation: 2 moles of ammonia produced by prokaryotes from 1 mole of N 2 gas

25 Lightning: N 2 + O > 2 NO (nitric oxide) Nitric oxide free radical combines with O 2 to form NO 2. 2 NO + O > 2NO 2 Nitrogen dioxide dissolves in water to produce nitric and nitrous acids; 2 NO 2 + H 2 O > HNO 3 + HNO 2 These acids readily release NO 3 & NO 2 ions - utilized by plants & micro-organisms. HNO > H+ + NO 3 - (nitrate ions) HNO > H+ + NO 2 - (nitrite ions) Combustion, volcanoes, industry, and lightning can fix N 2 as nitrates & nitrites

26 Nitrification Ammonia converted to ammonium to nitrate

27 Assimilation Roots absorb: –Ammonia (NH 3 ) –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 High concentrations of nutrients as run-off from –Sewage –Agriculture –Lawns Eutrophication: enhanced phytoplankton growth due excess supply of nutrients

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

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

50 Seasonal changes in temperature

51 Visible light & IR radiation warm surface and lower part of atmosphere Atmospheric heat produces air movement, which moderates the climate Global wind map Hadley cells

52 Coriolis effect –Tendency of moving air or water to be deflected Right in the Northern Hemisphere Left in the Southern Hemisphere Does your toilet really flush straight down on the equator?


54 Atmospheric circulation Doldrums Trade winds

55 Oceanic currents Generated by uneven heating of ocean surfaces Salinity differences Surface winds

56 Major surface ocean currents Modifies temperatures and affects precipitation patterns

57 Regional precipitation differences –Influenced by latitude, elevation, topography, vegetation, distance from large bodies of water, and location –Precipitation greatest where warm air passes over ocean & then cools

58 Small  in sea surface temp  trade winds, which  sea temp, which continues until atmospheric circulation patterns & precipitation are disrupted across Pacific & Indian Oceans, & surrounding continents

59 Look at the geography of major deserts Why are they found in these locations?

60 Rain shadow

61 Sierra Nevadas California side –Moist and lush Nevada side –Dry and desert- like plant communities

62 Much of the sun’s heat is trapped in the atmosphere by CO 2 How has man influenced global climate? Increased CO 2 from burning fossil fuels What are fossil fuels? CO 2 reservoir depleted: deforestation Surface algae polluted What will happen globally? Very complex! What are the alternatives?

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