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Biology 12
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Metabolism and temperature
Metabolism refers to all reactions occurring in the body Metabolic rate refers to the amount or speed of reactions in the body. It can be measured by measuring temperature, rate of oxygen consumption or rate of carbon dioxide production Reactions produce waste heat. The more reactions that occur, the greater the temperature Reactions rely on enzymes
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Enzyme activity and temperature
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Metabolic rate and temperature
As temperature increases, metabolic rate increases As metabolic rate increases, temperature increases
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Size and metabolic rate
Smaller animals have a larger surface area to volume ratio than larger animals Animals lose heat from body surfaces, so smaller animals will lose more heat than larger ones Metabolic rate is usually higher in smaller animals
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Body temperature Body temperature Poikilotherms have changing body temperatures - the same as their environment eg fish, amphibians, reptiles Homeotherms have constant body temperatures regardless of the environment eg birds, mammals Ectotherms control body temperature by behaviour Endotherms control body temperature by internal mechanisms Homeotherms Poikilotherms Environmental temperature Metabolic rate Endotherms Ectotherms Environmental temperature
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Endothermy vs Ectothermy
Advantages Can survive in a wide range of conditions and habitats eg Antarctica, winter Don’t need a constant food supply to drive metabolism Have simple control mechanisms Disadvantages Must have a constant food supply to drive metabolism Have complex control mechanisms Can not survive in as wide a range of conditions and habitats eg Antarctica, winter
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Heat production Heat can be produced by: Metabolism eg respiration
Movement Voluntary eg exercise Involuntary eg shivering
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Heat loss or gain Occurs from body surfaces Uses the processes of:
Radiation Conduction Convection Evaporation
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Radiation Loss without contact
Most important in terrestrial organisms. Can be increased by Increasing surface area exposure eg basking, big ears, vasodilation, bare skin/reduced fur Can be decreased by Decreasing surface area exposure eg huddling, small ears, vasoconstriction, fur or feathers
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Conduction Loss by contact Most important in aquatic organisms
Can be increased by Increasing surface area exposure eg larger extremities, reduced fur, reducing insulation Can be decreased by Decreasing surface area exposure eg smaller extremities, increased fur, increased insulation (eg blubber)
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Convection Loss by air movements Most important in land animals
Can be increased by Increasing surface area exposure to wind eg sprawling, decreased fur Can be decreased by Decreasing surface area exposure to wind eg huddling, fluffing feathers, increased fur
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Evaporation Loss of heat due to liquid turning to gas
Most important in terrestrial organisms Can be increased by sweating, panting or wetting skin or fur Can be decreased by reducing sweating or panting, keeping surface dry or covered with thick fur or feathers
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Control of body temperature
Control of heat production Increasing or decreasing metabolic activity or movement (shivering or exercise) Control of heat loss Increasing or decreasing loss of heat from external or respiratory surfaces
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An example of negative feedback
Stimulus Negative feedback Receptor Response Modulator Effector Heat Cool down Thermoreceptors Increased sweating Hypothalamus in brain Sweat glands
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An example of negative feedback
Stimulus Negative feedback Receptor Response Modulator Effector Cold Warm up Thermoreceptors Shivering Hypothalamus in brain Muscles
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Structural adaptations
Large ears/extremities Small ears/extremities Large body size Bare skin or reduced fur Counter current exchange Small body size Dark extremities blubber Fur or feathers
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Physiological adaptations
Fluffing feather or fur Sweating Aestivation Vasodilation Vasoconstriction Hibernation Panting
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Behavioural adaptations
Basking Licking fur Clothes Migration Seeking shade Resting during heat Dipping feet in water Huddling Burrowing Nocturnal
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