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What is the critical factor for physical performance in animals?
What is the critical factor for physical performance in animals?
Animals in humid environments lose water more rapidly than those in dry environments.
Animals in humid environments lose water more rapidly than those in dry environments.
False
What is the primary function of evaporative cooling mechanisms in animals?
What is the primary function of evaporative cooling mechanisms in animals?
Preventing animals from falling off the thermal cliff into a critical state
The amount of water vapour in air can be expressed in terms of ______________________.
The amount of water vapour in air can be expressed in terms of ______________________.
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What is the term for the point at which an animal can no longer maintain its body temperature and dies?
What is the term for the point at which an animal can no longer maintain its body temperature and dies?
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As air temperature increases, the relative humidity decreases.
As air temperature increases, the relative humidity decreases.
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Match the following terms with their definitions:
Match the following terms with their definitions:
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What is the term for the rise in body temperature above the optimal range that becomes fatal?
What is the term for the rise in body temperature above the optimal range that becomes fatal?
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Which of the following birds exhibits a binomial pattern of night and day temperatures?
Which of the following birds exhibits a binomial pattern of night and day temperatures?
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A hibernating animal's body temperature can drop by up to 40°C due to antifreeze proteins in their blood.
A hibernating animal's body temperature can drop by up to 40°C due to antifreeze proteins in their blood.
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What is the characteristic of body temperature variation in normothermic mammals?
What is the characteristic of body temperature variation in normothermic mammals?
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What is the main assumption of the Scholander-Irving Model?
What is the main assumption of the Scholander-Irving Model?
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The amplitude of the circadian cycle (RT) scales negatively with body mass (Mb) according to the formula: RT = _______________________ * Mb-0.37.
The amplitude of the circadian cycle (RT) scales negatively with body mass (Mb) according to the formula: RT = _______________________ * Mb-0.37.
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Endotherms are thermoconformers and exhibit poikilothermy.
Endotherms are thermoconformers and exhibit poikilothermy.
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Endothermy is an energetically costly process that results in high, normothermic body temperature.
Endothermy is an energetically costly process that results in high, normothermic body temperature.
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What is the thermoneutral zone (TZ) in the Scholander-Irving Model?
What is the thermoneutral zone (TZ) in the Scholander-Irving Model?
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Match the following terms with their corresponding descriptions:
Match the following terms with their corresponding descriptions:
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The Scholander-Irving Model depicts the relationship between resting metabolic rate (RMR) and ______________ temperature in endothermic animals.
The Scholander-Irving Model depicts the relationship between resting metabolic rate (RMR) and ______________ temperature in endothermic animals.
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What is the purpose of allowing body temperatures to increase during the day in arid environments?
What is the purpose of allowing body temperatures to increase during the day in arid environments?
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Match the following terms with their definitions:
Match the following terms with their definitions:
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In response to food limitation, some animals exhibit a _______________________________________ response, which increases the amplitude of their body temperature variation.
In response to food limitation, some animals exhibit a _______________________________________ response, which increases the amplitude of their body temperature variation.
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Birds, on average, have lower body temperatures than mammals.
Birds, on average, have lower body temperatures than mammals.
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What happens to an animal's body temperature when it reaches the extreme points of the Scholander-Irving Model?
What happens to an animal's body temperature when it reaches the extreme points of the Scholander-Irving Model?
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Study Notes
Thermoregulation in Endotherms
- Endotherms produce their own body heat from metabolism and maintain a constant body temperature, unlike ectotherms that conform to their environment.
- Endothermic homeothermy involves maintaining a constant body temperature, whereas ectotherms exhibit poikilothermy, or a variable body temperature.
Body Temperature Variation
- Body temperatures vary among different groups of mammals, with a range of over 10°C within each group.
- Birds have higher body temperatures on average, with a high range between passerines and non-passerines.
The Scholander-Irving Model
- The model depicts the relationship between resting metabolic rate (RMR) and ambient temperature in endothermic animals.
- The assumption is that animals maintain a constant body temperature, with a thermoneutral zone (TZ) where energy expenditure is minimal.
- The model is based on measurements from animals in metabolic chambers, with air temperatures identical to operative temperatures.
Thermoregulation in Natural Environments
- Body temperatures remain constant until extreme temperatures are reached, at which point animals' physiological systems become overwhelmed.
- Animals in dry environments lose water more rapidly than those in humid environments due to the "steepness" of the [H₂O vapour] gradient.
Humidity
- Humidity refers to the amount of water vapour in the air, which depends on the temperature.
- Absolute humidity is the vapour density (mg H2O L-1), partial pressure (kPa), or the amount of water vapour in the air.
- Relative humidity is the percentage of water vapour when the air is saturated.
- Saturation deficit is the difference between the capacity and the actual amount of water vapour in the air.
Physical Performance and the "Thermal Cliff"
- CTmin refers to the critical minimum temperature, below which an animal can no longer maintain its body temperature and dies.
- The critical factor for physical performance is the optimal temperature, and even small increases above the optimal range can be dangerous.
- Lethal hyperthermia occurs when body temperature rises above the optimal range, and evaporative cooling mechanisms are crucial for preventing this.
Body Temperature Variation
- There is a circadian cycle in normothermic body temperature, with typically lower temperatures at rest.
- The amplitude of the circadian cycle (RT) scales negatively with body mass (Mb), with RT = 11.066 * Mb-0.37.
- Body temperature variation is seen in species like the crested barbet, with a 4°C decrease at night and rewarming during the day.
- Starving responses can slightly increase the amplitude and decrease body temperatures in response to food limitation.
Heterothermy
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Heterothermy refers to the ability of some endotherms to exhibit facultative hypothermic responses, or reversible, controlled reductions in body temperature.
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This allows for energy conservation, as metabolic rates are lowered.
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Categories of heterothermic responses include hibernation, daily torpor, and shallow rest-phase.
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Hibernation involves a reduction in body temperature for days/weeks, with a pronounced drop in temperature (up to 40°C).
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Daily torpor involves a reduction in body temperature for hours/days, with a pronounced drop in temperature.
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Shallow rest-phase involves a reduction in body temperature for hours/single rest phase, with a shallow drop in temperature.
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Description
Learn about thermoregulation in endotherms, including homeothermy, Scholander-Irving model, variation in body temperature, and thermoregulation in natural environments.
