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Deck 27: Maintaining the Internal Environment
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Question
How Do Sleeping Birds Stay Warm?
Mammals and birds are endothermic: They maintain relatively constant body temperatures regardless of the temperature of their surroundings. This lets them reliably run their metabolism even when external temperatures fall-the rates of most enzyme-catalyzed reactions slow two- to threefold for every 10°C temperature drop. Your body keeps its temperature within narrow bounds at 37°C (98.6°F), and birds maintain even higher temperatures. To stay warm like this, mammals and birds continuously carry out oxidative metabolism, which generates heat. This requires a several-fold increase in metabolic rate, which is expensive, particularly when the animal is not active. The logical solution is to give up the struggle to keep warm and let the body temperature drop during sleep, a condition known as torpor. Humans don't adopt this approach, but many other mammals and birds do. This raises an interesting question: What prevents a sleeping bird in torpor from freezing? Does its body simply adopt the temperature of its surroundings, or is there a body temperature below which metabolic heating kicks in to avoid freezing?
The graph to the right displays an experiment examining this issue in the tropical hummingbird Eulampis. The study examines the effect on metabolic rate (measured as oxygen consumption) of decreasing air temperature. Oxygen consumption was assessed over a range of air temperatures from 3° to 37°C for two contrasting physiological states: The blue data were collected from birds that were awake, the red data from sleeping torpid birds. The blue and red lines, called regression lines, were plotted using curve-fitting statistics that provide the best fit to the data.
Interpreting Data
a. How does the oxygen consumption of awake hummingbirds change as air temperature falls? Why do you think this is so? Is the change consistent over the entire range of air temperatures examined?
b. How does the oxygen consumption of sleeping torpid birds change as air temperature falls? Is this change consistent over the entire range of air temperatures examined? Explain any difference you detect.
c. Are there any significant differences in the slope of the two regression lines below 15°C? What does this suggest to you?
Mammals and birds are endothermic: They maintain relatively constant body temperatures regardless of the temperature of their surroundings. This lets them reliably run their metabolism even when external temperatures fall-the rates of most enzyme-catalyzed reactions slow two- to threefold for every 10°C temperature drop. Your body keeps its temperature within narrow bounds at 37°C (98.6°F), and birds maintain even higher temperatures. To stay warm like this, mammals and birds continuously carry out oxidative metabolism, which generates heat. This requires a several-fold increase in metabolic rate, which is expensive, particularly when the animal is not active. The logical solution is to give up the struggle to keep warm and let the body temperature drop during sleep, a condition known as torpor. Humans don't adopt this approach, but many other mammals and birds do. This raises an interesting question: What prevents a sleeping bird in torpor from freezing? Does its body simply adopt the temperature of its surroundings, or is there a body temperature below which metabolic heating kicks in to avoid freezing?
The graph to the right displays an experiment examining this issue in the tropical hummingbird Eulampis. The study examines the effect on metabolic rate (measured as oxygen consumption) of decreasing air temperature. Oxygen consumption was assessed over a range of air temperatures from 3° to 37°C for two contrasting physiological states: The blue data were collected from birds that were awake, the red data from sleeping torpid birds. The blue and red lines, called regression lines, were plotted using curve-fitting statistics that provide the best fit to the data.
Interpreting Data
a. How does the oxygen consumption of awake hummingbirds change as air temperature falls? Why do you think this is so? Is the change consistent over the entire range of air temperatures examined?
b. How does the oxygen consumption of sleeping torpid birds change as air temperature falls? Is this change consistent over the entire range of air temperatures examined? Explain any difference you detect.
c. Are there any significant differences in the slope of the two regression lines below 15°C? What does this suggest to you?
Question
How Do Sleeping Birds Stay Warm?
Mammals and birds are endothermic: They maintain relatively constant body temperatures regardless of the temperature of their surroundings. This lets them reliably run their metabolism even when external temperatures fall-the rates of most enzyme-catalyzed reactions slow two- to threefold for every 10°C temperature drop. Your body keeps its temperature within narrow bounds at 37°C (98.6°F), and birds maintain even higher temperatures. To stay warm like this, mammals and birds continuously carry out oxidative metabolism, which generates heat. This requires a several-fold increase in metabolic rate, which is expensive, particularly when the animal is not active. The logical solution is to give up the struggle to keep warm and let the body temperature drop during sleep, a condition known as torpor. Humans don't adopt this approach, but many other mammals and birds do. This raises an interesting question: What prevents a sleeping bird in torpor from freezing? Does its body simply adopt the temperature of its surroundings, or is there a body temperature below which metabolic heating kicks in to avoid freezing?
The graph to the right displays an experiment examining this issue in the tropical hummingbird Eulampis. The study examines the effect on metabolic rate (measured as oxygen consumption) of decreasing air temperature. Oxygen consumption was assessed over a range of air temperatures from 3° to 37°C for two contrasting physiological states: The blue data were collected from birds that were awake, the red data from sleeping torpid birds. The blue and red lines, called regression lines, were plotted using curve-fitting statistics that provide the best fit to the data.
Making Inferences
a. For each five-degree air temperature interval, estimate the average oxygen consumption for awake and for sleeping birds, and plot the difference as a function of air temperature.
b. Based on this curve, what would you expect to happen to a sleeping bird's body temperature as air temperatures fall from 30° to 20°C? From 15° to 5°C?
Mammals and birds are endothermic: They maintain relatively constant body temperatures regardless of the temperature of their surroundings. This lets them reliably run their metabolism even when external temperatures fall-the rates of most enzyme-catalyzed reactions slow two- to threefold for every 10°C temperature drop. Your body keeps its temperature within narrow bounds at 37°C (98.6°F), and birds maintain even higher temperatures. To stay warm like this, mammals and birds continuously carry out oxidative metabolism, which generates heat. This requires a several-fold increase in metabolic rate, which is expensive, particularly when the animal is not active. The logical solution is to give up the struggle to keep warm and let the body temperature drop during sleep, a condition known as torpor. Humans don't adopt this approach, but many other mammals and birds do. This raises an interesting question: What prevents a sleeping bird in torpor from freezing? Does its body simply adopt the temperature of its surroundings, or is there a body temperature below which metabolic heating kicks in to avoid freezing?
The graph to the right displays an experiment examining this issue in the tropical hummingbird Eulampis. The study examines the effect on metabolic rate (measured as oxygen consumption) of decreasing air temperature. Oxygen consumption was assessed over a range of air temperatures from 3° to 37°C for two contrasting physiological states: The blue data were collected from birds that were awake, the red data from sleeping torpid birds. The blue and red lines, called regression lines, were plotted using curve-fitting statistics that provide the best fit to the data.
Making Inferences
a. For each five-degree air temperature interval, estimate the average oxygen consumption for awake and for sleeping birds, and plot the difference as a function of air temperature.
b. Based on this curve, what would you expect to happen to a sleeping bird's body temperature as air temperatures fall from 30° to 20°C? From 15° to 5°C?
Question
How Do Sleeping Birds Stay Warm?
Mammals and birds are endothermic: They maintain relatively constant body temperatures regardless of the temperature of their surroundings. This lets them reliably run their metabolism even when external temperatures fall-the rates of most enzyme-catalyzed reactions slow two- to threefold for every 10°C temperature drop. Your body keeps its temperature within narrow bounds at 37°C (98.6°F), and birds maintain even higher temperatures. To stay warm like this, mammals and birds continuously carry out oxidative metabolism, which generates heat. This requires a several-fold increase in metabolic rate, which is expensive, particularly when the animal is not active. The logical solution is to give up the struggle to keep warm and let the body temperature drop during sleep, a condition known as torpor. Humans don't adopt this approach, but many other mammals and birds do. This raises an interesting question: What prevents a sleeping bird in torpor from freezing? Does its body simply adopt the temperature of its surroundings, or is there a body temperature below which metabolic heating kicks in to avoid freezing?
The graph to the right displays an experiment examining this issue in the tropical hummingbird Eulampis. The study examines the effect on metabolic rate (measured as oxygen consumption) of decreasing air temperature. Oxygen consumption was assessed over a range of air temperatures from 3° to 37°C for two contrasting physiological states: The blue data were collected from birds that were awake, the red data from sleeping torpid birds. The blue and red lines, called regression lines, were plotted using curve-fitting statistics that provide the best fit to the data.
Drawing Conclusions How do Eulampis hummingbirds avoid becoming chilled while sleeping on cold nights?
Mammals and birds are endothermic: They maintain relatively constant body temperatures regardless of the temperature of their surroundings. This lets them reliably run their metabolism even when external temperatures fall-the rates of most enzyme-catalyzed reactions slow two- to threefold for every 10°C temperature drop. Your body keeps its temperature within narrow bounds at 37°C (98.6°F), and birds maintain even higher temperatures. To stay warm like this, mammals and birds continuously carry out oxidative metabolism, which generates heat. This requires a several-fold increase in metabolic rate, which is expensive, particularly when the animal is not active. The logical solution is to give up the struggle to keep warm and let the body temperature drop during sleep, a condition known as torpor. Humans don't adopt this approach, but many other mammals and birds do. This raises an interesting question: What prevents a sleeping bird in torpor from freezing? Does its body simply adopt the temperature of its surroundings, or is there a body temperature below which metabolic heating kicks in to avoid freezing?
The graph to the right displays an experiment examining this issue in the tropical hummingbird Eulampis. The study examines the effect on metabolic rate (measured as oxygen consumption) of decreasing air temperature. Oxygen consumption was assessed over a range of air temperatures from 3° to 37°C for two contrasting physiological states: The blue data were collected from birds that were awake, the red data from sleeping torpid birds. The blue and red lines, called regression lines, were plotted using curve-fitting statistics that provide the best fit to the data.
Drawing Conclusions How do Eulampis hummingbirds avoid becoming chilled while sleeping on cold nights?
Question
How Do Sleeping Birds Stay Warm?
Mammals and birds are endothermic: They maintain relatively constant body temperatures regardless of the temperature of their surroundings. This lets them reliably run their metabolism even when external temperatures fall-the rates of most enzyme-catalyzed reactions slow two- to threefold for every 10°C temperature drop. Your body keeps its temperature within narrow bounds at 37°C (98.6°F), and birds maintain even higher temperatures. To stay warm like this, mammals and birds continuously carry out oxidative metabolism, which generates heat. This requires a several-fold increase in metabolic rate, which is expensive, particularly when the animal is not active. The logical solution is to give up the struggle to keep warm and let the body temperature drop during sleep, a condition known as torpor. Humans don't adopt this approach, but many other mammals and birds do. This raises an interesting question: What prevents a sleeping bird in torpor from freezing? Does its body simply adopt the temperature of its surroundings, or is there a body temperature below which metabolic heating kicks in to avoid freezing?
The graph to the right displays an experiment examining this issue in the tropical hummingbird Eulampis. The study examines the effect on metabolic rate (measured as oxygen consumption) of decreasing air temperature. Oxygen consumption was assessed over a range of air temperatures from 3° to 37°C for two contrasting physiological states: The blue data were collected from birds that were awake, the red data from sleeping torpid birds. The blue and red lines, called regression lines, were plotted using curve-fitting statistics that provide the best fit to the data.
Applying Concepts
Comparing Two Data Sets Do awake hummingbirds maintain the same metabolic rate at all air temperatures? Sleeping torpid ones? At a given temperature, which has the higher metabolic rate, an awake bird or a sleeping one?
Mammals and birds are endothermic: They maintain relatively constant body temperatures regardless of the temperature of their surroundings. This lets them reliably run their metabolism even when external temperatures fall-the rates of most enzyme-catalyzed reactions slow two- to threefold for every 10°C temperature drop. Your body keeps its temperature within narrow bounds at 37°C (98.6°F), and birds maintain even higher temperatures. To stay warm like this, mammals and birds continuously carry out oxidative metabolism, which generates heat. This requires a several-fold increase in metabolic rate, which is expensive, particularly when the animal is not active. The logical solution is to give up the struggle to keep warm and let the body temperature drop during sleep, a condition known as torpor. Humans don't adopt this approach, but many other mammals and birds do. This raises an interesting question: What prevents a sleeping bird in torpor from freezing? Does its body simply adopt the temperature of its surroundings, or is there a body temperature below which metabolic heating kicks in to avoid freezing?
The graph to the right displays an experiment examining this issue in the tropical hummingbird Eulampis. The study examines the effect on metabolic rate (measured as oxygen consumption) of decreasing air temperature. Oxygen consumption was assessed over a range of air temperatures from 3° to 37°C for two contrasting physiological states: The blue data were collected from birds that were awake, the red data from sleeping torpid birds. The blue and red lines, called regression lines, were plotted using curve-fitting statistics that provide the best fit to the data.
Applying Concepts
Comparing Two Data Sets Do awake hummingbirds maintain the same metabolic rate at all air temperatures? Sleeping torpid ones? At a given temperature, which has the higher metabolic rate, an awake bird or a sleeping one?
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Deck 27: Maintaining the Internal Environment
1
How Do Sleeping Birds Stay Warm?
Mammals and birds are endothermic: They maintain relatively constant body temperatures regardless of the temperature of their surroundings. This lets them reliably run their metabolism even when external temperatures fall-the rates of most enzyme-catalyzed reactions slow two- to threefold for every 10°C temperature drop. Your body keeps its temperature within narrow bounds at 37°C (98.6°F), and birds maintain even higher temperatures. To stay warm like this, mammals and birds continuously carry out oxidative metabolism, which generates heat. This requires a several-fold increase in metabolic rate, which is expensive, particularly when the animal is not active. The logical solution is to give up the struggle to keep warm and let the body temperature drop during sleep, a condition known as torpor. Humans don't adopt this approach, but many other mammals and birds do. This raises an interesting question: What prevents a sleeping bird in torpor from freezing? Does its body simply adopt the temperature of its surroundings, or is there a body temperature below which metabolic heating kicks in to avoid freezing?
The graph to the right displays an experiment examining this issue in the tropical hummingbird Eulampis. The study examines the effect on metabolic rate (measured as oxygen consumption) of decreasing air temperature. Oxygen consumption was assessed over a range of air temperatures from 3° to 37°C for two contrasting physiological states: The blue data were collected from birds that were awake, the red data from sleeping torpid birds. The blue and red lines, called regression lines, were plotted using curve-fitting statistics that provide the best fit to the data.
Interpreting Data
a. How does the oxygen consumption of awake hummingbirds change as air temperature falls? Why do you think this is so? Is the change consistent over the entire range of air temperatures examined?
b. How does the oxygen consumption of sleeping torpid birds change as air temperature falls? Is this change consistent over the entire range of air temperatures examined? Explain any difference you detect.
c. Are there any significant differences in the slope of the two regression lines below 15°C? What does this suggest to you?
Mammals and birds are endothermic: They maintain relatively constant body temperatures regardless of the temperature of their surroundings. This lets them reliably run their metabolism even when external temperatures fall-the rates of most enzyme-catalyzed reactions slow two- to threefold for every 10°C temperature drop. Your body keeps its temperature within narrow bounds at 37°C (98.6°F), and birds maintain even higher temperatures. To stay warm like this, mammals and birds continuously carry out oxidative metabolism, which generates heat. This requires a several-fold increase in metabolic rate, which is expensive, particularly when the animal is not active. The logical solution is to give up the struggle to keep warm and let the body temperature drop during sleep, a condition known as torpor. Humans don't adopt this approach, but many other mammals and birds do. This raises an interesting question: What prevents a sleeping bird in torpor from freezing? Does its body simply adopt the temperature of its surroundings, or is there a body temperature below which metabolic heating kicks in to avoid freezing?
The graph to the right displays an experiment examining this issue in the tropical hummingbird Eulampis. The study examines the effect on metabolic rate (measured as oxygen consumption) of decreasing air temperature. Oxygen consumption was assessed over a range of air temperatures from 3° to 37°C for two contrasting physiological states: The blue data were collected from birds that were awake, the red data from sleeping torpid birds. The blue and red lines, called regression lines, were plotted using curve-fitting statistics that provide the best fit to the data.
Interpreting Data
a. How does the oxygen consumption of awake hummingbirds change as air temperature falls? Why do you think this is so? Is the change consistent over the entire range of air temperatures examined?
b. How does the oxygen consumption of sleeping torpid birds change as air temperature falls? Is this change consistent over the entire range of air temperatures examined? Explain any difference you detect.
c. Are there any significant differences in the slope of the two regression lines below 15°C? What does this suggest to you?
At lower temperatures the birds need to strive harder to keep warm. The chiller the air, the faster it flaps its wings and the faster its heart beats. The faster the wings flap the more the oxygen is consumed per unit body weight.
The more the oxygen it requires the more the circulation is enhanced and the more is the heat generated. The oxygen capacity of blood is more because the metabolic rate is more and so there is a higher cardiac output and generation of heat.
The change is seen according to the increase in temperature and it is consistent. Their oxygen requirement is lowered as the temperatures are increased. The higher the temperature increase the lesser is their metabolic rate, lesser is their oxygen requirement, and lesser the heat generated.
During a normal night when they are in torpor their muscles constantly contract and relax to maintain body warmth, if not they would freeze to death. This muscle action that keeps them from freezing must be increased and thus increasing their metabolic rates, and their oxygen requirement too.
These in turn will increase the heat generated and will ensure warmth in colder temperatures. At torpor their heart rate drops drastically to around 36 to 40 bpm at normal temperatures and so does their metabolic rate and oxygen consumption. During torpor and at lower temperatures the bpm will increase accordingly, so does their oxygen consumption, metabolic rates and heat generated.
The change is seen according to the increase in temperature but, it is not consistent. Their oxygen requirement is lowered as the temperatures are increased. The higher the temperature increase the lesser is their metabolic rate, lesser is their oxygen requirement, and lesser the heat generated. But, they have a need for more oxygen till around 15degree C and constancy in their oxygen requirement is seen from then onwards. Meaning there is no need for extra oxygen.
This is because they generally are in such temperatures when in torpor and so from this temperature onwards maintenance of their heat and oxygen consumption is pretty normal.
The changes seen in the oxygen consumption of birds that are awake according to the increase in temperature is consistent. Their oxygen requirement is lowered as the temperatures are increased. The higher the temperature increase the lesser is their metabolic rate, lesser is their oxygen requirement, and lesser the heat generated.
The changes seen in the oxygen consumption of birds in torpor according to the increase in temperature it is not consistent. Their oxygen requirement is lowered as the temperatures are increased. The higher the temperature increase the lesser is their metabolic rate, lesser is their oxygen requirement, and lesser the heat generated. But, they have a need for more oxygen only till around 15degree C and not after that. Constancy in their oxygen requirement is seen from then onwards.
Constancy in their oxygen requirement is seen from then onwards. This is because they generally are in such temperatures when in torpor. These temperatures are not new to these birds, so from this temperature onwards maintenance of their heat and oxygen consumption is pretty normal.
The more the oxygen it requires the more the circulation is enhanced and the more is the heat generated. The oxygen capacity of blood is more because the metabolic rate is more and so there is a higher cardiac output and generation of heat.
The change is seen according to the increase in temperature and it is consistent. Their oxygen requirement is lowered as the temperatures are increased. The higher the temperature increase the lesser is their metabolic rate, lesser is their oxygen requirement, and lesser the heat generated.
During a normal night when they are in torpor their muscles constantly contract and relax to maintain body warmth, if not they would freeze to death. This muscle action that keeps them from freezing must be increased and thus increasing their metabolic rates, and their oxygen requirement too.
These in turn will increase the heat generated and will ensure warmth in colder temperatures. At torpor their heart rate drops drastically to around 36 to 40 bpm at normal temperatures and so does their metabolic rate and oxygen consumption. During torpor and at lower temperatures the bpm will increase accordingly, so does their oxygen consumption, metabolic rates and heat generated.
The change is seen according to the increase in temperature but, it is not consistent. Their oxygen requirement is lowered as the temperatures are increased. The higher the temperature increase the lesser is their metabolic rate, lesser is their oxygen requirement, and lesser the heat generated. But, they have a need for more oxygen till around 15degree C and constancy in their oxygen requirement is seen from then onwards. Meaning there is no need for extra oxygen.
This is because they generally are in such temperatures when in torpor and so from this temperature onwards maintenance of their heat and oxygen consumption is pretty normal.
The changes seen in the oxygen consumption of birds that are awake according to the increase in temperature is consistent. Their oxygen requirement is lowered as the temperatures are increased. The higher the temperature increase the lesser is their metabolic rate, lesser is their oxygen requirement, and lesser the heat generated.
The changes seen in the oxygen consumption of birds in torpor according to the increase in temperature it is not consistent. Their oxygen requirement is lowered as the temperatures are increased. The higher the temperature increase the lesser is their metabolic rate, lesser is their oxygen requirement, and lesser the heat generated. But, they have a need for more oxygen only till around 15degree C and not after that. Constancy in their oxygen requirement is seen from then onwards.
Constancy in their oxygen requirement is seen from then onwards. This is because they generally are in such temperatures when in torpor. These temperatures are not new to these birds, so from this temperature onwards maintenance of their heat and oxygen consumption is pretty normal.
2
How Do Sleeping Birds Stay Warm?
Mammals and birds are endothermic: They maintain relatively constant body temperatures regardless of the temperature of their surroundings. This lets them reliably run their metabolism even when external temperatures fall-the rates of most enzyme-catalyzed reactions slow two- to threefold for every 10°C temperature drop. Your body keeps its temperature within narrow bounds at 37°C (98.6°F), and birds maintain even higher temperatures. To stay warm like this, mammals and birds continuously carry out oxidative metabolism, which generates heat. This requires a several-fold increase in metabolic rate, which is expensive, particularly when the animal is not active. The logical solution is to give up the struggle to keep warm and let the body temperature drop during sleep, a condition known as torpor. Humans don't adopt this approach, but many other mammals and birds do. This raises an interesting question: What prevents a sleeping bird in torpor from freezing? Does its body simply adopt the temperature of its surroundings, or is there a body temperature below which metabolic heating kicks in to avoid freezing?
The graph to the right displays an experiment examining this issue in the tropical hummingbird Eulampis. The study examines the effect on metabolic rate (measured as oxygen consumption) of decreasing air temperature. Oxygen consumption was assessed over a range of air temperatures from 3° to 37°C for two contrasting physiological states: The blue data were collected from birds that were awake, the red data from sleeping torpid birds. The blue and red lines, called regression lines, were plotted using curve-fitting statistics that provide the best fit to the data.
Making Inferences
a. For each five-degree air temperature interval, estimate the average oxygen consumption for awake and for sleeping birds, and plot the difference as a function of air temperature.
b. Based on this curve, what would you expect to happen to a sleeping bird's body temperature as air temperatures fall from 30° to 20°C? From 15° to 5°C?
Mammals and birds are endothermic: They maintain relatively constant body temperatures regardless of the temperature of their surroundings. This lets them reliably run their metabolism even when external temperatures fall-the rates of most enzyme-catalyzed reactions slow two- to threefold for every 10°C temperature drop. Your body keeps its temperature within narrow bounds at 37°C (98.6°F), and birds maintain even higher temperatures. To stay warm like this, mammals and birds continuously carry out oxidative metabolism, which generates heat. This requires a several-fold increase in metabolic rate, which is expensive, particularly when the animal is not active. The logical solution is to give up the struggle to keep warm and let the body temperature drop during sleep, a condition known as torpor. Humans don't adopt this approach, but many other mammals and birds do. This raises an interesting question: What prevents a sleeping bird in torpor from freezing? Does its body simply adopt the temperature of its surroundings, or is there a body temperature below which metabolic heating kicks in to avoid freezing?
The graph to the right displays an experiment examining this issue in the tropical hummingbird Eulampis. The study examines the effect on metabolic rate (measured as oxygen consumption) of decreasing air temperature. Oxygen consumption was assessed over a range of air temperatures from 3° to 37°C for two contrasting physiological states: The blue data were collected from birds that were awake, the red data from sleeping torpid birds. The blue and red lines, called regression lines, were plotted using curve-fitting statistics that provide the best fit to the data.
Making Inferences
a. For each five-degree air temperature interval, estimate the average oxygen consumption for awake and for sleeping birds, and plot the difference as a function of air temperature.
b. Based on this curve, what would you expect to happen to a sleeping bird's body temperature as air temperatures fall from 30° to 20°C? From 15° to 5°C?
For every five-degree air temperature interval, the average oxygen consumption for birds that are awake is around liters 5 to 6 kg/h. but, this change is seen according to the increase in temperature and it is consistent. Their oxygen requirement is lowered as the temperatures are increased. The higher the temperature increase the lesser is their metabolic rate, lesser is their oxygen requirement, and lesser the heat generated. And so after an increase to 30 degree C it drops.
For a bird in torpor is the requirement is liters 3 to 4 kg/h. The change is seen according to the increase in temperature but, it is not consistent. Their oxygen requirement is lowered as the temperatures are increased.
The higher the temperature increase the lesser is their metabolic rate, lesser is their oxygen requirement, and lesser the heat generated. But, they have a need for more oxygen till around 15degree C and constancy in their oxygen requirement is seen from then onwards. Meaning there is no need for extra oxygen and so there is a drop in consumption too.
The higher the temperature increase the lesser is their metabolic rate, lesser is their oxygen requirement, and lesser the heat generated. But, in a drop in temperature from 30 degree C the body's heat gradually increases. The lower the temperature drops the higher the body temperature increases because, at lower temperatures the birds need to strive harder to keep warm. The chiller the air, the faster it flaps its wings and the faster its heart beats.
At lower temperatures below 15 degree C to 5 degree C. The faster the wings flap the more the oxygen is consumed per unit body weight; this increase in metabolic rate increases body heat.
The higher the temperature increase the lesser is their metabolic rate, lesser is their oxygen requirement, and lesser the heat generated. But, they have a need for more oxygen only till around 15degree C and constancy in their oxygen requirement is seen from then onwards.
Meaning there is no need for extra oxygen and so there is a drop in consumption too. This ensures that their body temperatures too will change according to their metabolic rates. But, below 15 degree C to 5 degree C muscle activity is increased. The more the oxygen is consumed per unit body weight, the more is the increase in metabolic rate, which in turn increases body heat.
For a bird in torpor is the requirement is liters 3 to 4 kg/h. The change is seen according to the increase in temperature but, it is not consistent. Their oxygen requirement is lowered as the temperatures are increased.
The higher the temperature increase the lesser is their metabolic rate, lesser is their oxygen requirement, and lesser the heat generated. But, they have a need for more oxygen till around 15degree C and constancy in their oxygen requirement is seen from then onwards. Meaning there is no need for extra oxygen and so there is a drop in consumption too.
The higher the temperature increase the lesser is their metabolic rate, lesser is their oxygen requirement, and lesser the heat generated. But, in a drop in temperature from 30 degree C the body's heat gradually increases. The lower the temperature drops the higher the body temperature increases because, at lower temperatures the birds need to strive harder to keep warm. The chiller the air, the faster it flaps its wings and the faster its heart beats.
At lower temperatures below 15 degree C to 5 degree C. The faster the wings flap the more the oxygen is consumed per unit body weight; this increase in metabolic rate increases body heat.
The higher the temperature increase the lesser is their metabolic rate, lesser is their oxygen requirement, and lesser the heat generated. But, they have a need for more oxygen only till around 15degree C and constancy in their oxygen requirement is seen from then onwards.
Meaning there is no need for extra oxygen and so there is a drop in consumption too. This ensures that their body temperatures too will change according to their metabolic rates. But, below 15 degree C to 5 degree C muscle activity is increased. The more the oxygen is consumed per unit body weight, the more is the increase in metabolic rate, which in turn increases body heat.
3
How Do Sleeping Birds Stay Warm?
Mammals and birds are endothermic: They maintain relatively constant body temperatures regardless of the temperature of their surroundings. This lets them reliably run their metabolism even when external temperatures fall-the rates of most enzyme-catalyzed reactions slow two- to threefold for every 10°C temperature drop. Your body keeps its temperature within narrow bounds at 37°C (98.6°F), and birds maintain even higher temperatures. To stay warm like this, mammals and birds continuously carry out oxidative metabolism, which generates heat. This requires a several-fold increase in metabolic rate, which is expensive, particularly when the animal is not active. The logical solution is to give up the struggle to keep warm and let the body temperature drop during sleep, a condition known as torpor. Humans don't adopt this approach, but many other mammals and birds do. This raises an interesting question: What prevents a sleeping bird in torpor from freezing? Does its body simply adopt the temperature of its surroundings, or is there a body temperature below which metabolic heating kicks in to avoid freezing?
The graph to the right displays an experiment examining this issue in the tropical hummingbird Eulampis. The study examines the effect on metabolic rate (measured as oxygen consumption) of decreasing air temperature. Oxygen consumption was assessed over a range of air temperatures from 3° to 37°C for two contrasting physiological states: The blue data were collected from birds that were awake, the red data from sleeping torpid birds. The blue and red lines, called regression lines, were plotted using curve-fitting statistics that provide the best fit to the data.
Drawing Conclusions How do Eulampis hummingbirds avoid becoming chilled while sleeping on cold nights?
Mammals and birds are endothermic: They maintain relatively constant body temperatures regardless of the temperature of their surroundings. This lets them reliably run their metabolism even when external temperatures fall-the rates of most enzyme-catalyzed reactions slow two- to threefold for every 10°C temperature drop. Your body keeps its temperature within narrow bounds at 37°C (98.6°F), and birds maintain even higher temperatures. To stay warm like this, mammals and birds continuously carry out oxidative metabolism, which generates heat. This requires a several-fold increase in metabolic rate, which is expensive, particularly when the animal is not active. The logical solution is to give up the struggle to keep warm and let the body temperature drop during sleep, a condition known as torpor. Humans don't adopt this approach, but many other mammals and birds do. This raises an interesting question: What prevents a sleeping bird in torpor from freezing? Does its body simply adopt the temperature of its surroundings, or is there a body temperature below which metabolic heating kicks in to avoid freezing?
The graph to the right displays an experiment examining this issue in the tropical hummingbird Eulampis. The study examines the effect on metabolic rate (measured as oxygen consumption) of decreasing air temperature. Oxygen consumption was assessed over a range of air temperatures from 3° to 37°C for two contrasting physiological states: The blue data were collected from birds that were awake, the red data from sleeping torpid birds. The blue and red lines, called regression lines, were plotted using curve-fitting statistics that provide the best fit to the data.
Drawing Conclusions How do Eulampis hummingbirds avoid becoming chilled while sleeping on cold nights?
Eulampis hummingbird when in torpor is a little different from the rest of the hummingbirds. Their muscles constantly contract and relax to maintain body warmth, if not they would freeze to death. This muscle action that keeps them from freezing must be increased and thus increasing their metabolic rates too.
The Eulampis maintains a body temperature of 18 degree C to 20 degree C during torpor. These birds are a little different in that their oxygen consumption because their oxygen consumption decreases linearly with the decrease in temperature from 30 degree C to 18 degree C. but, after this there is a reverse in their reaction.
There was an increase in oxygen consumption with decrease in temperature. The increase in the oxygen consumption was noticed till the temperature dropped to 5 degree C. this was called as the metabolic adaptations that these birds adapt according to their origins.
The Eulampis maintains a body temperature of 18 degree C to 20 degree C during torpor. These birds are a little different in that their oxygen consumption because their oxygen consumption decreases linearly with the decrease in temperature from 30 degree C to 18 degree C. but, after this there is a reverse in their reaction.
There was an increase in oxygen consumption with decrease in temperature. The increase in the oxygen consumption was noticed till the temperature dropped to 5 degree C. this was called as the metabolic adaptations that these birds adapt according to their origins.
4
How Do Sleeping Birds Stay Warm?
Mammals and birds are endothermic: They maintain relatively constant body temperatures regardless of the temperature of their surroundings. This lets them reliably run their metabolism even when external temperatures fall-the rates of most enzyme-catalyzed reactions slow two- to threefold for every 10°C temperature drop. Your body keeps its temperature within narrow bounds at 37°C (98.6°F), and birds maintain even higher temperatures. To stay warm like this, mammals and birds continuously carry out oxidative metabolism, which generates heat. This requires a several-fold increase in metabolic rate, which is expensive, particularly when the animal is not active. The logical solution is to give up the struggle to keep warm and let the body temperature drop during sleep, a condition known as torpor. Humans don't adopt this approach, but many other mammals and birds do. This raises an interesting question: What prevents a sleeping bird in torpor from freezing? Does its body simply adopt the temperature of its surroundings, or is there a body temperature below which metabolic heating kicks in to avoid freezing?
The graph to the right displays an experiment examining this issue in the tropical hummingbird Eulampis. The study examines the effect on metabolic rate (measured as oxygen consumption) of decreasing air temperature. Oxygen consumption was assessed over a range of air temperatures from 3° to 37°C for two contrasting physiological states: The blue data were collected from birds that were awake, the red data from sleeping torpid birds. The blue and red lines, called regression lines, were plotted using curve-fitting statistics that provide the best fit to the data.
Applying Concepts
Comparing Two Data Sets Do awake hummingbirds maintain the same metabolic rate at all air temperatures? Sleeping torpid ones? At a given temperature, which has the higher metabolic rate, an awake bird or a sleeping one?
Mammals and birds are endothermic: They maintain relatively constant body temperatures regardless of the temperature of their surroundings. This lets them reliably run their metabolism even when external temperatures fall-the rates of most enzyme-catalyzed reactions slow two- to threefold for every 10°C temperature drop. Your body keeps its temperature within narrow bounds at 37°C (98.6°F), and birds maintain even higher temperatures. To stay warm like this, mammals and birds continuously carry out oxidative metabolism, which generates heat. This requires a several-fold increase in metabolic rate, which is expensive, particularly when the animal is not active. The logical solution is to give up the struggle to keep warm and let the body temperature drop during sleep, a condition known as torpor. Humans don't adopt this approach, but many other mammals and birds do. This raises an interesting question: What prevents a sleeping bird in torpor from freezing? Does its body simply adopt the temperature of its surroundings, or is there a body temperature below which metabolic heating kicks in to avoid freezing?
The graph to the right displays an experiment examining this issue in the tropical hummingbird Eulampis. The study examines the effect on metabolic rate (measured as oxygen consumption) of decreasing air temperature. Oxygen consumption was assessed over a range of air temperatures from 3° to 37°C for two contrasting physiological states: The blue data were collected from birds that were awake, the red data from sleeping torpid birds. The blue and red lines, called regression lines, were plotted using curve-fitting statistics that provide the best fit to the data.
Applying Concepts
Comparing Two Data Sets Do awake hummingbirds maintain the same metabolic rate at all air temperatures? Sleeping torpid ones? At a given temperature, which has the higher metabolic rate, an awake bird or a sleeping one?
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