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Lecture 2

Lecture 2 - Temperature I - Principles of Thermal Biology

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Biology 2601A/B
Graeme Taylor

LECTURE 2: TEMPERATURE I – PRINCIPLES OF THERMAL BIOLOGY Temperature  A measure of the speed or intensity of the incessant random motions that all the atoms and molecules of any substance undergo on an atomic-molecular scale. More exactly, the temperature of a substance is proportional to the product of the mean square speed of the random molecular motions and the molecular mass (HWA, p. 227) Temperature and Heat  Temperature – intensity of motion by the atoms in the object  Heat – amount of energy in the object  Temperature determines the direction of heat transfer (WARM  COOL)  Energy can be gained through radiation o Direct radiation from the sun (short-wave) o Indirect radiation from the sky that is reflected from the sun o Long-wave radiation (infrared) emitted from all the molecules in the sky, plants in the surrounding environment, the ground – in return, the organism is emitting radiation back out based off its body temperature o Metabolic heat production – however, not all organisms produce metabolic heat o Conduction – transfer of energy from a solid to a solid o Convection – transfer of energy from a solid to a fluid o Evaporation – water loss (transpiration in plants, respiration in mammals) Definitions: (Animal) Thermal Biology  Endotherms – generate internal heat (metabolic heat)  Ectotherms – rely on external temperatures to determine T bbody temperature)  Homeotherms – defend a constant body temperature  Poikilotherms – allow body temperature to vary  Heterotherms – have more than one temperature set point, or switch between homeo- and poikilothermy  Regional endothermy/heterothermy – different Tbin different parts of the body Relationship between Temperature and Metabolism in an Ectotherm  Metabolic rate increases exponentially (approximately) as temperature increases  M = a10 nTb o M = metabolic rate o a and n are constants o Tb= body temperature  logM = log(a) + nTb o logM is a linear function  Intercept = log(a)  Slope = n o Can be used to compare different organisms Q10 The Temperature Coeffi
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