U4 T12: Ecosystem Energetics PDF

Legend: Titles Examples Keywords Key Info U4 T12: Ecosystem Energetics ➔ Ecosystems: Communities of organism interacting w/ their physical environment under the influence of environmental factors ➔ Ecosystem Energetics:...

Legend: Titles Examples Keywords Key Info U4 T12: Ecosystem Energetics ➔ Ecosystems: Communities of organism interacting w/ their physical environment under the influence of environmental factors ➔ Ecosystem Energetics: Study of how energy is fixed by autotrophs & made available to heterotrophs ➔ Energy is measured as biomass ◆ Biomass: Dry weight of organic matter in an organism or ecosystem -2 (tonnes C km ) First Trophic Level ➔ First Trophic Level: Primary Producers ◆ Autotrophic organisms that fix inorganic nutrient (C, N, P, O, etc) into organic molecules ◆ Carries out primary production (PP) ➔ Primary Productivity: The rate at which energy is fixed ◆ The amount of C fixed per unit area per time ➔ Gross Primary Production: Total amount of energy fixed into organic molecules in an ecosystem ◆ Energy for everything ➔ Net Primary Production: What the producer makes minus what the producer uses for itself (ERMR, Eactivity) ◆ Amount of energy for growth, measured as biomass ◆ What turns into biomass ◆ Tells how much energy is available to other trophic levels ➔ Factors affecting primary productivity: ◆ Light; More = more enzyme activity, Too much = damage ◆ Temperature; Too much = denaturation ◆ Precipitation; Affects photosynthesis ◆ Nitrogen; Soluble & washes away w/ rainfall, more limiting on land ◆ Phosphorus; DNA synthesis, insoluble in water, more limiting in water Second Trophic Level ➔ Second Trophic Level: Primary Consumers (Herbivores) ◆ Organisms that consume biomass of primary producers ◆ Use Ein to support its energy budget ◆ Excess Ein used for Egrowth ◆ Carries out secondary production to make biomass Third/Fourth Trophic Level ➔ Third/Fourth Trophic Level: Secondary/Tertiary Consumers (Carnivores/Omnivores) ◆ Organisms that consume biomass of lower trophic levels ◆ Use Ein to support its energy budget ◆ Excess Ein used for Egrowth ◆ Carries out secondary production to make biomass Decomposers/Detritivores ➔ Organisms that consume dead organic matter of all trophic levels ◆ Carries out secondary production to make biomass ◆ Important for nutrient cycling Food Webs ➔ Matter cycles in ecosystems ➔ Ultimately, energy lost as heat ➔ Energy flows thru & out of ecosystems ◆ White boxes show biomass; orange = biomass being transported to next trophic level, green = biomass to decomposers ◆ Biomass at each level shows efficiency ◆ Tends to be ~10%; NPPupper/NPPlow EE1 TO 2 = 4611/31822 = 14.5% ➔ Trophic levels can be organized as a pyramid ➔ Bottom-Up Control: Amount of resources regulates trophic structure ◆ Energy in each level determined by energy in lower levels ◆ Ex. Adding phosphorus = more algae = more energy for 2nd level ➔ Top-Down Control: Amount of predation regulates trophic structure ◆ Organisms in each level are limited by predators in the next level ◆ Ex. 1st level; phytoplankton, 2nd level; zooplankton (eats phytoplankton), 3rd level; small fish (eats zooplankton), 4th level; big fish (eats small fish) ➔ Trophic Cascade: Adding/removing the top predator (highest level) from an ecosystem, results in cascading effect down the food web ◆ Ex. Removing 4th level: Increased 3rd level organisms, decreased 2nd level organisms, increased 1st level organisms ➔ Keystone Species: Organisms that have a large impact on its ecosystem relative to its abundance  ◆ Removing the keystone species leads to destabilization of ecosystem Nutrient Cycling ➔ Nutrients: Elements required by organisms ➔ Earth is a closed system ➔ Biogeochemical Cycles: Pathways that describe how nutrients move between biotic & abiotic components of an ecosystem ➔ Reservoirs: A large natural or artificial source of water where nutrients accumulate ◆ Can be short term, 200 years ◆ Can be biotic or abiotic ◆ Can be terrestrial, aquatic, or atmospheric ➔ Nutrients exist in three stages; gases (H2O, CO2), soluble (C, N, O), insoluble (P, K, Fe, Ca) ➔ Generalized Compartment Model: A model used to describe nutrient cycling, comprised of organic vs inorganic and available vs unavailable nutrients ◆ Top Left: Biotic & short term ◆ Top Right: Biotic & long term ◆ Bottom Left: Abiotic & short term ◆ Bottom Right: Abiotic & long term Carbon Cycle ➔ Carbon is the most abundant element in organisms; 50% of dry mass ➔ Used as unit of energy currency in organism & ecosystems; molecules containing carbon used for energy transfer ➔ Cycles thru all four nutrient compartments; organic, inorganic, short-term, long-term ➔ Short-Term Cycle: Rapid exchange of CO2  ◆ Atmospheric CO2 decreases in summer due to increased photosynthesis, then increases in the winter ➔ Long-Term Cycle: Exchange of carbon over millions of years through weathering, sedimentation, volcanic activity, & plate tectonics ◆ Past CO2 levels indicate increase is recent & due to human activity ◆ Concerns: CO2 levels not going back down & rising much faster than previous ➔ Most CO2 is from fossil fuels 12 ◆ Fossil Fuels: Remains of living organisms, contains C 12 12 ◆ Carbon isotopes in the atmosphere: C; 99%, C; 1% 12 ◆ Photosynthesis & enzyme functions prefer C 12 ◆ Organisms are almost 100% C 12 12 13 ◆ When fossil fuels burned, C released, dilutes atmospheric C: C ratio; extra CO2 comes from fossil fuels ➔ Greenhouse Effect: The Earth radiates the energy absorbed from the sun back into space ◆ W/o greenhouse gases, earth’s temp = ~ -20℃ ◆ W/ greenhouse gases, earth’s temp = +15℃ ➔ Generally, increased temps = more CO2 released ➔ Anthropogenic CO2: CO2 from human activity ◆ Half stays in the atmosphere ◆ The rest is absorbed by oceans Ocean Acidification: CO2 absorbed reacts with water in ocean to form carbonic acid, which dissociates into bicarbonate and protons, and the protons react with natural carbonate, forming more bicarbonate, lowering the ocean’s pH + - CO2 + H2O → H2CO3 (carbonic acid) → H + HCO3 (bicarbonate) ← + 2- 2H + CO3 (carbonate) Leads to coral bleaching & inability of shell-forming organisms to form calcium shells because they need carbonate & can’t use bicarbonate; slows rate of shell-forming & leaves them vulnerable to predation & infection Legend: Titles Examples Keywords Key Info U4 T11: Population Growth ➔ Population Growth: All of the individuals of a given species that live and reproduce in a particular place ◆ ∆𝑁/∆𝑡 ≈ 𝐵 − 𝐷, B= # of births, D = # of deaths, N = # of individuals, t = time ➔ Population Size (N): The number of individuals alive at a particular time in a particular place ◆ Influenced by births and death ➔ Per capita birth rate (b) and per capita death rate (d) ◆ b = B/N d = D/N Per Capita Growth Rate ➔ Predicts population size changes ➔ r>0; population growing, r 1; Allometry ➔ Due to need for structural support and how it is scaled across organisms with increasing mass ➔ Log transformations used to create linear graphs from allometry; create line of best line to estimate slope = scaling factor ◆ Log both sides; log Y = b log X + log a Hyperallometry: One dimension increases as the other increases faster Hypoallometry: One dimension increases as the other increase slower Daily Energy Budgets ➔ EnergyIN = EnergyOUT ◆ EnergyOUT = EnergyASSIMILATION + EnergyEXCRETION ◆ EnergyASSIMILATION = EnergyRMR + EnergyACTIVITY + EnergyPROUCTION ◆ Therefore; EnergyASSIMILATION = Energy IN - EnergyEXCRETION ➔ Assimilation: Energy used ➔ RMR: Energy for resting metabolic rate ➔ Production: Energy stored ➔ Activity: Energy for behaviour, reproduction, thermoregulation ➔ Excretion: Energy lost to environment EnergyIN ➔ Body size affects amount of energyIN  ◆ Larger organisms have larger energyIN per unit time, eat less relative to body size, slower breathing and heart rate ◆ Small organisms have higher metabolic rate A cat with a mass of 20 kg eats 20% of its body mass. Its food provides 200 J/g, what is the energyIN? 20 kg x 1000 = 20 000g EnergyIN = 20 000g x 0.20 x 200 J/g = 800 000 J / 1000 = 800 kJ EnergyEXCRETION ➔ Excretion through heat, urine, feces, sweat, etc ➔ Many ways to assimilate more energy and excrete less energy ◆ Ex. Chewing, selection palatable foods, length of gut, food retention time ➔ Energy from excretion is assimilated by other organisms such as decomposers EnergyASSIMILATION ➔ Scales with body mass ➔ Plasticity: An organism changing a biological variable during specific times ◆ Ex. Birds changing their gut sizes depending on the season A cat with energyIN = 800 kJ, excretes 50g of urea (10 J/g) and 200g of feces (250 J/g), what is the energyASSIMILATION and energyEXCRETION? energyEXCRETION = (50g x 10 J/g) + (200g x 250 J/g) = 50 500 J / 1000 = 50.5 kJ energyASSIMILATION = energyIN - energyEXCRETION = 800 kJ - 50.5 kJ = 749.5 kJ EnergyRMR ➔ Rate of energy consumption at which chemical energy is converted to heat and external work ➔ Units: calories/time or J/time ➔ Scales with body mass; hypoallometric ➔ Body mass and RMR graphs have the same slope across different organisms, Y 0.75 = aX ➔ Mass specific metabolic rate graphs always have negative b (b-1)  ➔ Mass specific metabolic rate decreases as mass increases; whole metabolic rate increases as mass increases ➔ Absolute slope to mass specific = slope - 1 ➔ Determines how much food needed, measure of total energy, and pressure on energy supplies in ecosystem ➔ Types of metabolic rate: ◆ Resting Metabolic Rate (RMR): Consumption at rest but during routine activities ◆ Basal Metabolic Rate (BMR): Consumption at complete rest ; lowest possibles metabolic rate ◆ Standard Metabolic Rate (SMR): Consumption at specified temperatures in ectotherms ◆ Field Metabolic Rate (FMR): Consumption in wild animals Measuring Metabolic Rate ➔ Direct Calorimetry: Measures rate of heat leaving the body; expensive and cumbersome, inefficient for large organisms ➔ Indirect Calorimetry: ◆ Respirometry: Measures rate of gas exchange with environment (O2 consumed or CO2 produced) ◆ Material-Balance Method: Measures chemical energy content of organic matter entering and leaving the body At 22°C during the day (8 hours) and 16°C at night (15 hours), a 20 kg cat spends 0.5 J/g·h during the day and 1 J/g·h during the night. What is energyRMR? Day: energyRMR = 0.5 J/g·h x 20 000g x 8 h = 80 000 J Night: energyRMR = 1 J/g·h x 20 000g x15 h = 300 000 J Day + Night: energyRMR = 80 000 J + 300 000 J = 380 000 J / 1000 = 380 kJ EnergyACTIVITY ➔ Increases heat generated; may offset thermoregulation costs ➔ Includes most forms of movement A 20 kg cat runs for 1 hour, which uses 10 J/g·h. What is energyACTIVITY? energyACTIVITY = 10 J/g·h x 20 000g x 1 h = 200 000 J = 200kJ EnergyPRODUCTION ➔ Organisms with balanced energy budgets have 0 energyPRODUCTION; all food consumed is used ➔ More than enough energy consumed, energyPRODUCTION positive and mass increases ➔ Not enough energy consumed, energyPRODUCTION negative and mass decreases If energyIN = 800 kJ, energyRMR = 380 kJ, energyEXCRETION = 50.5 kJ, and energyACTIVITY = 200 kJ, what is energyPRODUCTION? EnegyPRODCUTION = energyIN - energyEXCRETION - energyRMR - energyACTIVITY = 800 kJ - 50.5 kJ - 380 kJ - 200 kJ = 169.5 kJ Therefore the cat will increase in mass because energyPRODUCTION is positive