Ecology copy.pdf

Ecosystem processes Two important processes occur in ecosystems: 1. Energy flows through ecosystems 2. Nutrients cycle through ecosystems 3  Ecological energetics Ecological energetics: the study of fixation, transfer, and...

Ecosystem processes Two important processes occur in ecosystems: 1. Energy flows through ecosystems 2. Nutrients cycle through ecosystems 3  Ecological energetics Ecological energetics: the study of fixation, transfer, and storage of energy by ecosystem components Today we study how energy flows through ecosystems… Tuesday we study how nutrients cycle through ecosystems 4  Ecological energetics In terms of energy, ecosystems are open systems that require constant input of energy Solar radiation is the * # most important source of energy in most ecosystems Biosphere is an open system ↳ can't sustain itself in terms of energentic requirements 5  Solar energy The electromagnetic spectrum is a continuum of energy Photosynthesis uses visible light as it has energy levels suitable for capture by organic molecules Physics described on pages 46-50, for interested readers FIGURE 3.2 6  Solar energy and autotrophs Green plants, algae, and cyanobacteria absorb solar energy to convert carbon dioxide and water and turn it into sugar, with oxygen produced as a by- product * Sunlight + 6CO2 + 6H2O → C6H12O6 + 6O2 * d d SUGAR was te ↓ product Stay Alive 7  Release of solar energy Solar energy, fixed by autotrophs self in their biomass, can be used by beat sun other organisms for energy-requiring processes, or released as heat (e.g. fire) Most ecosystems run using this energy (solar energy fixed by autotrophs) 8  Delayed release of solar energy Some absorbed and biologically fixed energy can be stored for long periods as peat or fossil fuels & short periods - eat lettuce from garden - transfer solar energy to you ↳ convertintohydrocarbonas 9  Photosynthesis is heart of all energy absorbed on earth Other functions of solar energy The sun also heats Earth’s surface Provides energy for other ecologically important processes: – Evaporation of water – Circulation of atmosphere – Circulation of oceans 10  Seasons In temperate zone, seasonal variation in available energy by solar radiation causes major fluctuations in biological activity I 11  First law of thermodynamics Energy can be transformed but not created or destroyed F In any system, input of energy has to equal the amount of energy stored and the output of energy Earth receives an input of solar energy Solar input equals the amount reflected, transformed in chemical form, stored as heat, and dissipated energy 12  Second law of thermodynamics Energy transformations can occur spontaneously only under conditions in which entropy of the Universe is increased energy to is needed create order Energy is needed to create order and combat entropy Energy transformations can never be totally efficient; they require energy Life requires incessant input of energy, mostly from the sun 13  Solar energy Sunlight is reflected or absorbed The absorbed energy is dissipated by re- radiation of longer-wave infrared energy (heat) Absorbed sunlight and dissipated energy are almost in perfect balance FIGURE 3.6 14  70 % radiation incoming solar Y absorbed as heat in energy the upper atmosphere the more molecules that we have in the upper atmosphere CO2 + greenhouse higgaseso go solar of up sig portion energy driving nice greenhouse sitting around earth heat 15  far less We get solar radiation Solar energy even Ojibway = in the summer vs Rainforest Amount of solar radiation varies with latitude Canadas longitude - Spread out over greater a area way earth curves relative to the Sun 900 equator narrow Grech Sun is so far away from earth by the time radiation reaches earth it is parallel 16  Solar energy Solar transmission through the atmosphere also varies with latitude 17  Greenhouse gasses Natural greenhouse gasses (carbon dioxide, water, methane) absorb some of the dissipated infrared radiation and re-radiate it in allfordirections liquid Organisms is right temperature 3 Creates the environment water to be This provides Earth with a thermal blanket , use incomingsolarradiationsynthesis As a result, Earth’s average temperature is +15°C - instead of -18°C - 18  Increases in greenhouse gasses Combustion of fossil fuels, deforestation, and agriculture have increased the atmospheric concentrations of several greenhouse gasses taking captured in the sunlight form of carbon Molecules and then produceone ejecting them back out into atmosphere at increasing levels FIGURE 3.8 19  Increases in greenhouse gasses Combustion of fossil fuels, deforestation, and agriculture have increased the atmospheric concentrations of several greenhouse gasses - 2 absorb sunlight greenhouse gas global warning 24  Global warming Anthropogenic increases in greenhouse gasses cause warming of the global climate Warmer climate may increase productivity and decomposition, but also cause more drought Major changes in biotic and abiotic environmental features are occurring 25  Global warming ↳ all species shifted northward ranges deep ocean animals ↳ ClimateChanga A Cod organisms can live on earth B Anglerfish Photo: Bill Freedman C Snake blenny From: Perry et al. (2005) Science 308: 1912-1915 27  Energy fixation in ecosystems turn solar energy into molecules Autotrophs are primary producers, providing energy stored biological foundation of ecological productivity as two carbons Photoautotrophs: tog Stuck light feeders self useSunlit to the – Plants energy transfer of into biomolecules – Algae – Cyanobacteria Chemoautotrophs: – Specialized bacteria ↳ live in deep oceanic vents ↳ pitch black ; no sunlight fom Earth's liquid in oras use heatenergy core biomolecules 35  ↳ Photoautotrophs creating energy bound up in Sugars through photosynthesis Photoautotrophs are responsible for almost all productivity in the biosphere up energy Sugars create in bound (photosynthesis) Chlorophyll and other sensitive to solar radiation pigments capture photons sugar solar radiation > - Sunlight - , CO2 HaO , Most sensitive to blue and red wavelengths of light, which is why leafs appear that green don't need light & energy they is reflected and that is reflected not used light 36 - grab red and blue parts of electromagnetic spectrum and use photosyn.  Chemoautotrophs Chemoautotrophs are specialized bacteria that get energy from inorganic chemicals (e.g. by oxidizing sulphide minerals) The energy released by these exothermic reactions drives biosynthesis of CO2 and H2O to form glucose Example: at volcanic deep sea vents, chemoautotrophic bacteria provide all the energy for these very special ecosystems 37  organisms Heterotrophs other on all that are not Earth autotrophs Other-feeders Feed on other heterotrophs Herbivores Feed on autotrophs Carnivores feed on row autotrophs , 9 themselves heterotrophs use the fixed in order to energy the through grow of process decomposition Omnivores Detritivores38  Heterotrophs Other - feeders Note: not all plants are autotrophs ↳ cyanobacteria Example: Ghost pipe (Monotropa uniflora) has no 6. chlorophyll; it derives energy from surrounding trees via a mycorrhizal fungus · not all plants can photosynthesize 39  Ecological productivity > - how quickly does the plant grow Productivity: rate at which energy is fixed (in mass is autotrophs) and rate at which biomass is org added to an anism accumulating (organisms and ecosystems) Measured on dry weight basis (due to water flux) Biomass standardized to area (tons of dry weight per unit area; t/ha) Productivity standardized per unit time (t/ha/year) ↳ amount of may go water up/down throughout day ↳ CO2 in dry mass 40  Ecological productivity Gross Primary Production: total amount of solar energy fixed by autotrophs nowdry much plot mass in that Respiration: amount of energy used by autotrophs for their metabolism (plants use ¼ to ¾ energy for respiration) Net Primary Production: gross primary production minus ↳ used respiration by autotrophs by autotrophs in of process NPP = GPP - R growing 41  Productivity of major biomes Most productive habitats with low environmental constraints: warm and humid climate, fertile soil Tropical Boreal rainforest: forest: 9.0 tC/ha/yr 3.6 tC/ha/yr ↳ net primary production Temperate Tundra: deciduous 0.65 tC/ha/yr forest: ↳ go w out sun 5.4 tC/ha/yr for periods of time ↳ solar radiation in is different coming 43  Productivity of major biomes Open oceans have low net primary productivity (0.57 tC/ha/year) because of low nutrient availability Reefs and estuaries have high productivities comparable to terrestrial ecosystems Reefs: Estuaries: 9.0 tC/ha/yr 8.1 tC/ha/yr Mangrove forest -> high level of net 44  Productivity and production Open oceans, in spite of their low productivity, account for a large amount of global production due to their vast area photosynthetic single organisms cell Global net production floating around – Total continental: 48.3 109 tC/yr – Total marine: 24.9 109 tC/yr – Total world: 73.2 109 tC/yr 45  Food chain Food chain: linear representation of feeding interactions and energy transfer Only a part of the energy of the food can be absorbed or utilized Herbivores assimilate 10% of energy in their food Carnivores assimilate 20% of energy in their food 48  Energy transfer in ecosystems At each trophic level, a large part of energy is lost as respiration mostof energnation 80 % 90 % - FIGURE 3.20 51  Ecological pyramids Due to inefficiency of energy transfers, the productivity declines with increasing trophic level FIGURE 3.21 52  Predators and ecological energetics / Number of predators that can be supported varies across ecosystems, based on ecological pyramids / 53  Humans and ecological energetics “Three hundred trout are needed to support one person for a year. The trout, in turn, must consume 90,000 frogs, that must consume 27 million grasshoppers, that live off 1,000 tons of grass.” - Tyler Miller, Jr. American Chemist (1971) 1 person 80 %-90% of at energy each level is lost 300 trout based & on caloric intake 90,000 frogs 27,000,000 grasshoppers 1 ton grass 54  Humans and ecological energetics 7.9 billion humans Z secondary consumers Y primary consumers X primary producers An open question: How many humans can the ecosystems of Earth sustain according to ecological energetics? Some ecologists argue Earth can sustain 10 billion people, but only if we eat at lower trophic levels 58  Biomagnification - accumulation of toxic materials as move up Humans produce toxic pyramid substances that do not occur naturally (e.g. > - lots of mercury organochlorides or DDT) eat) and substances in unnaturally high top animals eatove S quantities (e.g. mercury) in food chain high levels of toxins Some of them eat so much accumulate in food chains, producing unexpected effects 59 Biomagnification 60  DDE in tissues led to birds laying thin wall eggs d crush eggs and break ↓ O for offspring years ↓ BAD !! 62  Biomagnification High concentrations of DDT lead to near extinction of many hawks and eagles 63