Why elephants do not explode: how nature copes with large size
N-yes, there’s obviously something wrong with this animal:
The weather is obviously cold, and yet this tiny little lump of fur rushes over the ice, searches for something, sniffs out, rushes to and fro, without interruption, without rest — it constantly hunts, hunts, hunts. Shrews usually behave this way. In the video - a short-tailed shrew. Shrews are very strange animals. They do not slow down, they rarely sleep. They behave like tightly compressed springs, constantly spend a lot of energy, and then, if necessary, spend more. They can weigh less than a coin, and must constantly eat, move, hunt. No other animal behaves that way.
')
This small fry is the easiest mammal known to science. This shrew lives in the Mediterranean and in some places in Asia. She is known as the Etruscan shrew, or dwarf polydent , and, like our friend from the video, she constantly moves - making an average of 13 movements per second. Imagine that you are trying to do something (at least blink) 13 times per second. Madness.
To maintain this pace, her heart beats faster than hummingbirds (a record 1500 beats per minute). Therefore, shrews need to burn a lot of fuel. Therefore, they constantly have to breathe air and eagerly eat. Each gram of her body uses 67 times more oxygen than people, and every day she eats almost twice her own weight - it's just to stay alive. Two times its own weight!
A shrew can die of hunger without eating just 4-5 hours.
Proceeding from this need, shrews spend their lives in fierce hunting, grabbing and biting. If you go to YouTube and search for " Shrew vs ", you can see how they are fighting against an insane amount of scary animals (including scorpions and snakes). And we would not bet against shrews.
But something in connection with these shrews causes a certain concern (except for the alarming ease with which they are able to destroy the garter snake . This is an extreme form of life.
Just for you to appreciate their appetite (and not only in shrews, but in general in all small mammals), we will conduct the following exercise. Below you see two mammals, one large and one small. Above is a vole (a small fluffy rodent the size of a mouse), and an African elephant, the largest land mammal in the world, below. Both voles and elephants love to eat grass. Before each of them a bunch of fresh grass is drawn.
Your task is to adjust the size of the portion of grass that the animal should eat daily. Trust the intuition and move the slider so that the portion is the right size [ you cannot drag interactive JavaScript to GeekTimes, so those who are interested can refer to the original article - approx. trans. ].
Not exactly what you expected, right? We thought that the vole would need less food, since it is so small. But no - the daily ration of the vole reaches 80% of its weight, while for an elephant it is only 5%. That is, judging by the size, the vole's appetite greatly exceeds the elephant's appetite. Each gram of vole needs 16 times more feed than gram of elephant.
Why? There is something wrong here. What if large and small animals are arranged differently? Literally, right from the very basics.
If you hold a small animal in your hand, for example, a mouse (do not try to hold the shrew, it will bite you), you will feel how the energy in it is buzzing and downright pours over the edge. Many small animals (mice, chipmunks, squirrels) behave the same way. On the other hand, the largest animals (elephants, whales, rhinos) live more slowly and more easily. Obviously a superficial difference between large and small animals, but how deeply do these differences take root?
At first glance, the elephant and vole are not very different.
Both are mammals. Consist of cells. They live on the surface, eat, defecate, breathe oxygen, move. An elephant can be imagined as a very, very large vole, having a different shape and enlarged bones to support a huge weight, but at the same time working on the same principles.
But the mystery of dinner remains. If a piece of an elephant can survive on 1/16 of the feed required by a vole of the same size, then they must somehow differ internally. But how?
Here's another hint on the chart.
[ in the original of the article given an interactive version of the schedule - approx. trans. ]
Each point on the graph indicates a separate animal. From left to right, the size of animals increases. The leftmost point is a dwarf polydent, weighing less than a coin. To the right of her mouse, squirrel, rabbit, fox, lion, tiger, and so on. From the right side is an elephant.
The graph shows the appetite of animals, not to grass, but to oxygen. The graph is looking for the answer to the question: which animals move so much that they consume more oxygen per unit of weight? That is, if you take a small piece of the same size from a shrew, a fox, a lion and an elephant, which one would consume more oxygen?
There is the same trend as with food. The smallest animals (shrew, vole) consume oxygen much faster (therefore they are higher on the graph). With the transition to larger animals their oxygen demand is reduced. When moving to the right, the points are lower and lower.
As with food, which, per unit weight, voles need 16 times more than an elephant, and with the oxygen they breathe. The vole consumes 11 times more oxygen per unit of weight than the elephant.
Therefore, an elephant can not be called a giant vole. A large animal's metabolism is slower - it consumes less air, burns less fuel and emits less heat than a shallow creature. And it must be this way. To find out why, it is necessary to conduct a mental experiment. It is good that the experiment is not real, because it includes a self-igniting elephant.
Take a large mammal and place it next to a small one. As you can see, the elephant is much larger than the mouse.
How much larger? The mouse weighs about 20 grams, the elephant - 5000 kg. In other words, 250,000 times larger. But there is a problem. With an increase in growth, the volume of an animal grows faster than its surface area (cubic degree versus square). If the mouse had grown 250,000 times, its body would contain trillions and trillions of warm cells, so it would be very hot. The surface area of its heat-removing skin also increased.
That is the problem. There are trillions of hot cells inside the elephant, but it lacks the surface to release this heat. Its volume is 250,000 times larger than that of a mouse, and the surface area is only 5,000 times larger — that is, a huge amount of energy has nowhere to go.
And if an elephant burned fuel at the same speed as a mouse or a shrew, its insides would have heated up terribly, and at some point it would have just exploded!
But the elephants do not explode. Our friend, an imaginary elephant, surprised by what exists, asks: “Isn’t my big ears used to remove additional heat?”
In fact, elephants use their large and thin ears to dissipate heat in the manner of a car radiator - a large surface area radiates heat well. But unlike the radiator, the elephant’s ears do not have enough space to get rid of the heat that we are discussing.
If an elephant had enough skin to release all this heat, it would have a huge amount of folds, like a giant golf ball, or, as John Bonner, a professor at Princeton University, says, like a "giant walnut."
So why are real elephants not ignited? We already know the answer - elephants do not burn fuel at the same rate as mice. That is why for their size they have a rather modest appetite.
If you dig deeper and get to a typical cage of an elephant, and then compare it with a typical mouse cage, it turns out that these two cells behave differently.
Elephant cages are not lazy. They work all the time, but compared to the mouse, the elephant's cells do the job more slowly, burn less fuel to do it, and due to the increased efficiency, they stay colder (although some certain cells of large animals do not fit into this scheme).
Therefore, elephants (and we, fortunately, too) are not prone to self-ignition. An elephant is built of colder matter than a mouse. And although the elephant has much more small heating elements in the body, each of them works with the temperature set at a small value. As John Bonner writes:
Large animals, in principle, could not exist if their cells metabolism was not slowed down. They would either die of hunger, or ignite, or it would happen at the same time.
As we now know, shrews are on the other end of the scale. They are made from more hungry and hot stuff. They look like Mexican jumping beans in a shaker [ These seeds are affected by caterpillars, and if you sharply heat such a bean, the caterpillar inside will begin to shrink, pulling at the same time for the thread and forcing the bean to move // approx. trans. ].
Without their tiny heaters tuned to maximum warm-up, shrews would freeze and die. This explains their hellish appetite. They are so hungry because their cells are hungry. If the shrew cannot find food, then, as John Bonner writes, she will experience “irreversible internal damage in a few hours.” She will die of hunger.
All the dwarf polydentus muscles belong to a rapidly contracting variety — there is not a single fiber of slowly contracting muscles among them — and because of this, it surpasses even the fastest of human sprinters. Its cells are filled with mitochondria, microscopic sources of cell nutrition. It is these superpowers that allow the multi-jaw muscles to contract faster than any other known creature. She breathes 15 times per second, performs 13 movements per second, and trembles 60 times per second. It is because of these cells that the polytunis are so hungry all the time.
Therefore, at the cellular level, the metabolic rate of each creature - the amount of oxygen consumed, the energy burned, the heat emitted - is adjusted as a result of evolution to solve problems related to its size. Large creatures are not giant versions of small ones, they are created from cooler and quieter parts. Their internal stoves are slower.
As far as we know, this rule works for most animals on the planet, not only for mammals, but also for birds, fish, crustaceans, snails, amphibians, reptiles, insects, etc. Because of this rule, our mammal ancestors were able to grow from twitching, sharp, shrew-like creatures hiding in the holes under the world of dinosaurs, into clumsy giants inhabiting our world today.
And it is good that such a difference exists. Imagine what it would be like if large animals had the same temperament, appetite, needs, like a frantically hungry shrew? It would be so terrible that it would be like a Hollywood movie!
The 1959 killer Shrews [ The Killer Shrews ] feature film tells about the handsome captain Lorna Sherman, whose food ship stuck to the shore of an isolated island where the geneticist and his beautiful daughter Anna live. Anna's father brought out a new kind of “blood-chilling and terribly poisonous” giant shrews, which should eat “every day food three times their weight”, or die of starvation. And then suddenly a hurricane cuts them off from civilization, and hungry shrews discover the warm taste of human flesh ...
True, the script does not reach this point, but we know what poor Anna and Lorn think about when shrews gnaw themselves at the clay wall of the laboratory, sniffing at human flesh: “It's very dangerous to play with large-scale cell biology settings,” or, as Lorn prefers to say “Shoot! Immediately!"
The weather is obviously cold, and yet this tiny little lump of fur rushes over the ice, searches for something, sniffs out, rushes to and fro, without interruption, without rest — it constantly hunts, hunts, hunts. Shrews usually behave this way. In the video - a short-tailed shrew. Shrews are very strange animals. They do not slow down, they rarely sleep. They behave like tightly compressed springs, constantly spend a lot of energy, and then, if necessary, spend more. They can weigh less than a coin, and must constantly eat, move, hunt. No other animal behaves that way.
')
This small fry is the easiest mammal known to science. This shrew lives in the Mediterranean and in some places in Asia. She is known as the Etruscan shrew, or dwarf polydent , and, like our friend from the video, she constantly moves - making an average of 13 movements per second. Imagine that you are trying to do something (at least blink) 13 times per second. Madness.
To maintain this pace, her heart beats faster than hummingbirds (a record 1500 beats per minute). Therefore, shrews need to burn a lot of fuel. Therefore, they constantly have to breathe air and eagerly eat. Each gram of her body uses 67 times more oxygen than people, and every day she eats almost twice her own weight - it's just to stay alive. Two times its own weight!
A shrew can die of hunger without eating just 4-5 hours.
Proceeding from this need, shrews spend their lives in fierce hunting, grabbing and biting. If you go to YouTube and search for " Shrew vs ", you can see how they are fighting against an insane amount of scary animals (including scorpions and snakes). And we would not bet against shrews.
There is something wrong
But something in connection with these shrews causes a certain concern (except for the alarming ease with which they are able to destroy the garter snake . This is an extreme form of life.
Just for you to appreciate their appetite (and not only in shrews, but in general in all small mammals), we will conduct the following exercise. Below you see two mammals, one large and one small. Above is a vole (a small fluffy rodent the size of a mouse), and an African elephant, the largest land mammal in the world, below. Both voles and elephants love to eat grass. Before each of them a bunch of fresh grass is drawn.
Your task is to adjust the size of the portion of grass that the animal should eat daily. Trust the intuition and move the slider so that the portion is the right size [ you cannot drag interactive JavaScript to GeekTimes, so those who are interested can refer to the original article - approx. trans. ].
Not exactly what you expected, right? We thought that the vole would need less food, since it is so small. But no - the daily ration of the vole reaches 80% of its weight, while for an elephant it is only 5%. That is, judging by the size, the vole's appetite greatly exceeds the elephant's appetite. Each gram of vole needs 16 times more feed than gram of elephant.
Why? There is something wrong here. What if large and small animals are arranged differently? Literally, right from the very basics.
Big idea
If you hold a small animal in your hand, for example, a mouse (do not try to hold the shrew, it will bite you), you will feel how the energy in it is buzzing and downright pours over the edge. Many small animals (mice, chipmunks, squirrels) behave the same way. On the other hand, the largest animals (elephants, whales, rhinos) live more slowly and more easily. Obviously a superficial difference between large and small animals, but how deeply do these differences take root?
At first glance, the elephant and vole are not very different.
Both are mammals. Consist of cells. They live on the surface, eat, defecate, breathe oxygen, move. An elephant can be imagined as a very, very large vole, having a different shape and enlarged bones to support a huge weight, but at the same time working on the same principles.
But the mystery of dinner remains. If a piece of an elephant can survive on 1/16 of the feed required by a vole of the same size, then they must somehow differ internally. But how?
Big vs. Small - Deep Differences
Here's another hint on the chart.
[ in the original of the article given an interactive version of the schedule - approx. trans. ]
Each point on the graph indicates a separate animal. From left to right, the size of animals increases. The leftmost point is a dwarf polydent, weighing less than a coin. To the right of her mouse, squirrel, rabbit, fox, lion, tiger, and so on. From the right side is an elephant.
The graph shows the appetite of animals, not to grass, but to oxygen. The graph is looking for the answer to the question: which animals move so much that they consume more oxygen per unit of weight? That is, if you take a small piece of the same size from a shrew, a fox, a lion and an elephant, which one would consume more oxygen?
There is the same trend as with food. The smallest animals (shrew, vole) consume oxygen much faster (therefore they are higher on the graph). With the transition to larger animals their oxygen demand is reduced. When moving to the right, the points are lower and lower.
As with food, which, per unit weight, voles need 16 times more than an elephant, and with the oxygen they breathe. The vole consumes 11 times more oxygen per unit of weight than the elephant.
Therefore, an elephant can not be called a giant vole. A large animal's metabolism is slower - it consumes less air, burns less fuel and emits less heat than a shallow creature. And it must be this way. To find out why, it is necessary to conduct a mental experiment. It is good that the experiment is not real, because it includes a self-igniting elephant.
Mystery of exploding elephant
Take a large mammal and place it next to a small one. As you can see, the elephant is much larger than the mouse.
How much larger? The mouse weighs about 20 grams, the elephant - 5000 kg. In other words, 250,000 times larger. But there is a problem. With an increase in growth, the volume of an animal grows faster than its surface area (cubic degree versus square). If the mouse had grown 250,000 times, its body would contain trillions and trillions of warm cells, so it would be very hot. The surface area of its heat-removing skin also increased.
That is the problem. There are trillions of hot cells inside the elephant, but it lacks the surface to release this heat. Its volume is 250,000 times larger than that of a mouse, and the surface area is only 5,000 times larger — that is, a huge amount of energy has nowhere to go.
And if an elephant burned fuel at the same speed as a mouse or a shrew, its insides would have heated up terribly, and at some point it would have just exploded!
But the elephants do not explode. Our friend, an imaginary elephant, surprised by what exists, asks: “Isn’t my big ears used to remove additional heat?”
In fact, elephants use their large and thin ears to dissipate heat in the manner of a car radiator - a large surface area radiates heat well. But unlike the radiator, the elephant’s ears do not have enough space to get rid of the heat that we are discussing.
If an elephant had enough skin to release all this heat, it would have a huge amount of folds, like a giant golf ball, or, as John Bonner, a professor at Princeton University, says, like a "giant walnut."
So why are real elephants not ignited? We already know the answer - elephants do not burn fuel at the same rate as mice. That is why for their size they have a rather modest appetite.
Look deeper
If you dig deeper and get to a typical cage of an elephant, and then compare it with a typical mouse cage, it turns out that these two cells behave differently.
Elephant cages are not lazy. They work all the time, but compared to the mouse, the elephant's cells do the job more slowly, burn less fuel to do it, and due to the increased efficiency, they stay colder (although some certain cells of large animals do not fit into this scheme).
Therefore, elephants (and we, fortunately, too) are not prone to self-ignition. An elephant is built of colder matter than a mouse. And although the elephant has much more small heating elements in the body, each of them works with the temperature set at a small value. As John Bonner writes:
Large animals, in principle, could not exist if their cells metabolism was not slowed down. They would either die of hunger, or ignite, or it would happen at the same time.
As we now know, shrews are on the other end of the scale. They are made from more hungry and hot stuff. They look like Mexican jumping beans in a shaker [ These seeds are affected by caterpillars, and if you sharply heat such a bean, the caterpillar inside will begin to shrink, pulling at the same time for the thread and forcing the bean to move // approx. trans. ].
Without their tiny heaters tuned to maximum warm-up, shrews would freeze and die. This explains their hellish appetite. They are so hungry because their cells are hungry. If the shrew cannot find food, then, as John Bonner writes, she will experience “irreversible internal damage in a few hours.” She will die of hunger.
All the dwarf polydentus muscles belong to a rapidly contracting variety — there is not a single fiber of slowly contracting muscles among them — and because of this, it surpasses even the fastest of human sprinters. Its cells are filled with mitochondria, microscopic sources of cell nutrition. It is these superpowers that allow the multi-jaw muscles to contract faster than any other known creature. She breathes 15 times per second, performs 13 movements per second, and trembles 60 times per second. It is because of these cells that the polytunis are so hungry all the time.
Small is different from big
Therefore, at the cellular level, the metabolic rate of each creature - the amount of oxygen consumed, the energy burned, the heat emitted - is adjusted as a result of evolution to solve problems related to its size. Large creatures are not giant versions of small ones, they are created from cooler and quieter parts. Their internal stoves are slower.
As far as we know, this rule works for most animals on the planet, not only for mammals, but also for birds, fish, crustaceans, snails, amphibians, reptiles, insects, etc. Because of this rule, our mammal ancestors were able to grow from twitching, sharp, shrew-like creatures hiding in the holes under the world of dinosaurs, into clumsy giants inhabiting our world today.
And it is good that such a difference exists. Imagine what it would be like if large animals had the same temperament, appetite, needs, like a frantically hungry shrew? It would be so terrible that it would be like a Hollywood movie!
The 1959 killer Shrews [ The Killer Shrews ] feature film tells about the handsome captain Lorna Sherman, whose food ship stuck to the shore of an isolated island where the geneticist and his beautiful daughter Anna live. Anna's father brought out a new kind of “blood-chilling and terribly poisonous” giant shrews, which should eat “every day food three times their weight”, or die of starvation. And then suddenly a hurricane cuts them off from civilization, and hungry shrews discover the warm taste of human flesh ...
True, the script does not reach this point, but we know what poor Anna and Lorn think about when shrews gnaw themselves at the clay wall of the laboratory, sniffing at human flesh: “It's very dangerous to play with large-scale cell biology settings,” or, as Lorn prefers to say “Shoot! Immediately!"
Source: https://habr.com/ru/post/370875/
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