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| heat transfer by means of physical contact between two surfaces of different temperature |
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| movement of heat by the movement of a fluid (liquid or gas) across a surface |
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| emission of heat as electromagnetic radiation |
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| a cooling mechanism by which the animal loses water molecules to the vapour state that are more energetic than the mean energy of the remaining molecules |
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| an animal whose body temperature is determined mainly by heat exchange with the environment; little internal heat generation by the animal; some may thermoregulate by behaviour |
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| an animal that maintains a favourable body temperature mainly by the internal generation of heat, which endotherms produce at much higher levels than do ectotherms (but behaviour is important too) |
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| an animal that maintains a favourable body temperature by a mixture of behavioural methods and by the internal generation of heat |
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increased heat generation in a certain region of the animal
"Patchy endotherm" |
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| increased heat generation at a certain time |
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| Where does metabolic heat come from? |
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Energy transformation in cells
exergonic reactions produce ATP
endergonic reactions produce ADP + P |
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| Endotherm body temperature response as function of environmental temperature |
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Definition
| body temperature is constant while environment temperature varies |
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| Ectotherm body temperature response as function of environmental |
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Definition
| Body temperature = environment temperature (will equilibriate with surroundings) |
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| How would a bass's activity level compare at lower and higher temperatures? What about a river otter's activity level? |
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Bass: metabolic rate increases linearly with increase in temperature; does not vary much with change in temperature.
Otter: Metabolic rate increases to cool or heat up the body |
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| why does an ectotherm's metabolic rate increase with increasing temperature? |
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Definition
Biochemical reations go faster at higher temperatures
Q10 = (reaction rate @ T) / (reaction rate @ T-10)
Answer is usually 2-3 |
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| Why does an endotherm metabolic rate increase with decreasing temperature? |
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| Endotherms give themselves extra metabolic work to do, in order to maintain constant body temperature. |
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| The idea that spinning the ATP cycle faster will generate more heat. (Endotherms increase metabolic rate to warm up) |
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| How do ectotherms thermoregulate? |
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| Mainly by behaviour, not by altering the metabolic rate |
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| Which have smaller body size, ectotherms or endotherms? |
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| Ectotherms. Because of the volume to surface area ratio, ectotherms would gain or lose too much heat |
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| In dinosaurs, high volume to surface area ratio, so body heat can be retained without having high metabolic rate |
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| an increase in the diameter of blood vessels under the skin to absorb heat from the surroundings more quickly. Warmed blood then moves by convection to the interior of the body |
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can thermoregulate by moving to warmer or colder areas, or by orienting the body with respect to the sun to either increase or reduce warming.
Panting can result in cooling down because of heat loss by evaporation |
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| How do ectotherms withstand the cold? |
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Definition
| Ectotherms are able to withstand low body temperatures because of increased membrane fluidity. |
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| Heterotherm thermoregulation |
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Definition
Shivering-like muscle movements (honeybees, female Burmese python, Flying insects)
Huddling together (bee swarm) |
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| Endotherm thermoregulation |
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Definition
high basal metabolic rate
leaky plasma membranes use ATP to pump out excess ions, increasing metabolic rate |
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| Ecdotherm circulation: vasoconstriction |
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Definition
keeps heat in the body core when the animal needs to conserve heat
Preserves vital organs at the expense of the extremities (frostbite) |
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| Endotherm circulation: Vasodilation |
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Definition
| dumps heat to the outside when the animal needs to cool down |
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| Endotherm circulation: countercurrent heat exchangers |
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Definition
retain body heat inside the core by collecting heat from the blood before it passes into the extremities
Preserves heat by giving heat from artery to vein instead of losing to the environment |
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Definition
seek warmer, cooler areas
bathe
huddle
physical activity |
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| muscle contraction that expends energy but does not do any work outside the body (requires ATP) |
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| Nonshivering thermogenesis |
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Definition
| uses uncouplers to allow electron transport to take place in the inner mitochondrial membrane without ATP synthesis |
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| A protein called thermogenin. Works by forming an alternative channel through the membrane, apart from the ATP synthase complex, by which H+ ions can diffuse into the mitochondrial matrix. This channel lacks the machinery to make ATP using the energy of flowing H+ ions |
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Located in the hypothalamus, has an adjustable setpoint, above which cooling measures are taken and below which heating measures are taken.
Integrates information about air temperature and internal body temperature |
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| why would the mammalian thermostat turn up its setpoint? |
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To fight infection (fever)
speeds phagocytosis of the invader
speeds repair of damaged tissues
interferes with iron metabolism of bacteria |
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a lowering of body temperature below its normal range. It can be a natural response to stress
Protective when environment too cold or food is not available
slow heart beat
slower metabolism
less nerve conduction
unconsciousness |
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Definition
regulated hypothermia - a brief inactive state resulting from a lowering of the thermostat's setpoint to save energy
Short term - daily
only in small active endotherms such as hummingbirds |
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a form of regulated hypothermia - a prolonged inactive state resulting from a lowering of the thermostat's setpoint to save energy
setpoint lowered 20 degrees to escape unfavorable living conditions |
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| the term that has been applied to a possible future state when parts of the earth that are currently inhabited become too hot for human life |
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heat stress; if our body temperature goes above 42 degrees C, we die
nasea, convulsions, organ failure, bacterial toxins |
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a way of expressing temperature that takes into account our ability to cool by the evaporation of sweat. Temperatuer is measured by a wet cloth around the bulb of a thermometer.
Depends on air temperature and relative humidity
If temperature reaches above 35, humans cannot survive for more than a few hours |
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| Decribe three forms of thermogenesis (heat production) in endotherms. Assume that the animal is not engaged in any other useful activity - it's just trying to keep warm. |
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Definition
First, endotherms maintain a high basal metabolic rate, largely owing to the energy (and the associated heat production) that must be expended pumping ions across leaky membranes.
Second, shivering. This is muscle activity for its own sake – or rather, for the sake of oxidizing glucose or fat and making ATP, with the associated heat production. The muscle activity has the function of hydrolyzing ATP to ADP + Pi, which can then cycle back to the mitochondrion and keep electron transport (and heat production) going.
Third, nonshivering thermogenesis, which oxidizes brown fat. In this case, thermogenin makes the inner mitochondrial membrane permeable to H+; the proton gradient built up by electron transport is dissipated when the protons diffuse back into the mitochondrial matrix, and no ATP is made; consequently, no muscle activity or other cellular work need be undertaken to keep electron transport going. |
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| where is the body's thermostat? What happens to it when we suffer an infection, and why? Under what circumstances would it be turned down? |
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| The body’s thermostat is in the hypothalamus. When we have an infection the thermostat’s set point is moved up, giving us a fever. It is thought that fever discourages many pathogens and speeds our defenses to the infection site. The thermostat would be turned down in periods of regulated hypothermia; the lower set point would result in less energy being expended and less oxygen being consumed at the times when one or both of these are in short supply. |
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| How might a reptile thermoregulate in a natural setting such as a desert? |
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Definition
| By behaviour (for example, moving between warmer and cooler microclimates); by accelerating heart rate and dilating blood vessels near the skin to absorb heat from the environment, or slowing heart rate and constricting vessels to conserve heat in the body core; by panting to lose heat by evaporation. |
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| If a biochemical reaction produces a product molecule at the rate of 17.8 micromole/min at 15degrees C, and at the rate of 37.4 micromole/min at 25degrees C, what is the Q10? |
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Definition
Q10 = Rate(T) / Rate (T-10)
= 37.4 micromole/min / 17.8 micromole/min
= 2.10 |
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| How does a countercurrent heat exchanger act to lessen the loss of heat from a goose's leg? |
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| Cold venous blood passing into the body core from the flipper picks up heat from warm arterial blood passing out of the body core into the flipper. The heat in the arterial blood, instead of being lost to the surrounding water, is taken back to the body core. |
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