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Dynamic Energy Budget Theory by I. Tânia Sousa

Explore the basics of energy flows vs. mass flows, state variables, and metabolic processes in organisms using the Dynamic Energy Budget Theory. Delve into assimilation, dissipation, growth, maintenance, and metabolic heat production.

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Dynamic Energy Budget Theory by I. Tânia Sousa

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  1. DynamicEnergy Budget Theory - I Tânia Sousa withcontributionsfrom : Bas Kooijman

  2. Energyflows vs. Massflows • Fluxes • Parameters = • StateVariables

  3. Exercises • What wouldbetheexpression for a parameterthatistheequivalentof for thesomaticmaintenanceassociatedwith volume? • Suggestions: • Write as a functionof - energyspent in themaintenanceofstructurebuiltwith 1 unitof reserve energy per unit time - energyspent in themaintenanceofmaturitybuiltwith 1 unitof reserve energy per unit time

  4. A DEB organismAssimilation, dissipationandgrowth • Metabolism in a DEB individual. • Rectangles are state variables • Arrows are flows of foodJXA, reserveJEA, JEC, JEM, JET, JEG, JER, JEJor structureJVG. • Circles are processes • The full square is a fixed allocation rule (the kappa rule) • The full circles are the priority maintenance rule. Feeding ME- Reserve Mobilisation Assimilation Offspring MER MaturityMaintenance Reproduction Growth SomaticMaintenance Maturation MH - Maturity MV - Structure

  5. 3 types of aggregated chemical transformations • Assimilation: X(substrate)+M  E(reserve) + M • linked to surface area • Dissipation: E(reserve) +M  M • somatic maintenance: linked to surface area & structural volume • maturity maintenance: linked to maturity • maturation or reproduction overheads • Growth: E(reserve)+M  V(structure) + M • Compounds: • Organic compounds: V, E, X and P • Mineral compounds: CO2, H2O, O2 and Nwaste

  6. Exercises • Obtain theaggregatedchemicalreactions for assimilation, dissipationandgrowthconsideringthatthechemicalcompositions are: food CH1.8O0.5N0.2, reserve CH2O0.5N0.15, faeces CH1.8O0.5N0.15,structure CH1.8O0.5N0.15and NH3. • Identify in theseequationsyXE, yPEandyEV. • Constraintsonthe yield coeficients • Degreesoffreedom

  7. Exercises • What istherelationshipbetweentheseequationsand, ,,, , and . • Compute the total consumptionof O2. • Writeit as a functionof, and . • Compute theaggregatechemicaltransformation • Thestoichiometryoftheaggregatechemicaltransformationthatdescribestheorganismhas 3 degreesoffreedom: anyflowproducedorconsumed in theorganismis a weightedaverageofanythreeotherflows

  8. Exercises • Write theenergy balance for eachchemical reactor (assimilation, dissipationandgrowth) • Compute the total metabolicheatproductionas a function of , and . • Iftheorganismtemperatureisconstantthenthemetabolicheat must beequal to theheatreleased • Indirectcalorimetry (estimatingheatproductionwithoutmesuringit) : Dissipatingheatisweighted sum ofthreemassflows: CO2, O2andnitrogeneouswaste (Lavoisier in the XVIII century).

  9. Dissipating heat Steam from a heap of moist Prunus serotina litter illustrates metabolic heat production by fungi

  10. Heat increment of feeding • Definition: • O2consumption that is associated with assimilation per unit of ingested food • Strange name relates to common practice to take pT+ JOwhich generally does not hold true • Exercise: What is the relationship between O2 consumption and heat production

  11. Metabolic rates: the effect of temperature • Allmetabolic rates dependontemperatureandalldependonthesameway (evolutionaryprinciple) Daphnia magna reproduction young/d ln rate ingestion 106 cells/h growth, d-1 • TheArrheniusrelationshiphasgoodempiricalsupport • TheArrheniustemperatureisgivenbyminustheslope: thehighertheArrheniustemperaturethe more sensitiveorganisms are to changes in temperature aging, d-1 104 T-1, K-1

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