poikilotherm

Thermophilic animals

This data is reviewed by the project of data compilation and application of Science Encyclopedia of science popularization in China.

Thermophilic animals (commonly known as cold-blooded animals) are animals except mammals and birds. Most of the animals on the earth are thermophilic animals. Variable temperature animals have no mechanism of self regulating body temperature, they can only regulate body heat emission by their own behavior or absorb heat from the external environment to improve their body temperature.

When the temperature of the external environment increases, the metabolic rate of animals increases, and the body temperature also gradually increases, so they passively leave the unfavorable environment; when the temperature of the external environment decreases, the metabolic rate of animals decreases, and the body temperature also gradually decreases. So they either move to the sun to get warm to raise their body temperature, or they go underground or in caves to hibernate, or they swim to warm waters, or they hibernate.

brief introduction

Also known as "cold-blooded animals.". It refers to animals whose body temperature changes with the change of environmental temperature. Such as reptiles, amphibians and fish.

distribution

Except for the Antarctic and Arctic, thermolabile animals are distributed in all continents.

Physiological characteristics

Animals whose body temperature changes with the change of external temperature are called thermophilic animals. In addition to birds and mammals, other animals are thermophilic animals. Their body temperature changes with the environment. This does not mean that they can never control their body temperature, they can change their body temperature by looking for a cool or warm environment, but can not directly control their body temperature, that is, they lack the physiological function to maintain a certain body temperature.

Because variable temperature animals do not need to use their own energy to warm or cool, compared with constant temperature animals, variable temperature animals with the same weight only need 1 / 10-1 / 3 of the energy to live, so they only need relatively less food. Because they are easier to store enough energy, and the breeding period of the animals is shorter.

Advantages of variable temperature

It can survive under the condition of great changes in the external environment or food supply. Because they only need less energy to maintain their body temperature and physiological functions. Energy from food can be used more for growth. Therefore, the efficiency of transforming food into body growth is higher in variable temperature animals than in constant temperature animals.

Although the number of variable temperature animals in the same environment can be tens of times that of constant temperature animals, the adaptability of variable temperature animals to the environment is weaker than that of constant temperature animals. For example, thermostatic animals can overcome the adverse factors of the environment and have longer time and wide space to obtain food.

Life habit

Life characteristics

Variable temperature animals have no internal temperature regulation system. They can't keep their body temperature constant. They need to keep their body temperature by irradiating the sun, or regulate their body temperature by action. Therefore, thermolabile animals generally do not move at night. Large cold-blooded animals, such as snakes and crocodiles, need to bask in the sun in the morning to raise their body temperature so that they can move. Therefore, they almost all move in the daytime and rest at night.

Because of the less internal heat produced by the body, the body temperature of variable temperature animals changes with the temperature of nature. For example, when snakes bask in the sun by the river, their body temperature is much higher than when they swim in the water.

Generally speaking, thermostatic animals can control the internal heat produced by the body, so as to control and adjust their body temperature. When the environment changes, thermostatic animals can always keep the body temperature unchanged. Human beings are also a kind of thermostatic animals. The constant temperature of human beings is 37 ℃. In order to keep the temperature constant, many kinds of functional tissues, such as feathers, fur and sweat glands, have evolved from natural selection and natural selection. Hair and feathers can keep warm in the cold winter; in addition, in the hot summer, the sweat glands of animals can secrete sweat, which can make the heat in the body of animals dissipate in time, so as to maintain the normal body temperature of animals. Because thermostatic animals can keep their body temperature constant all the time, they have a wider range of activities. They will not be affected by the conventional environment and climate change of nature, and can live more freely in different environments.

Biologists have long been studying why we mammals are thermostatic. The standard explanation is that thermostats need to evolve into a certain degree of predator in order to adapt to an active, predatory lifestyle. But in 2008, some experts put forward a new view: thermostatic animals not only include carnivores, but also some herbivores. Thermostability is a way to balance nutritional needs. It's too early to say, but it's a good explanation for the wasteful way of life of our animals.

Thermostatic animals are a little bit of a waste of heat, unlike some animals that produce heat when they need it. For example, leatherback turtles store the heat they usually generate, and use the heat in their bodies to keep the body temperature at 10 ° C or higher than the temperature of the sea water when swimming. Swordfish selectively supply heat to their eyes and brain when hunting, while some sharks and tuna swim long distances to keep their body temperature above water temperature. Even some insects produce heat when they need it.

So why do most mammals and birds turn their thermostats to the maximum? Thirty years ago, zoologists Albert Bennett of the University of California and Irvine and John Ruben of the University of Oregon worked together to explain this phenomenon. They suggest that the evolution of homeostasis is related to the energy of animals. They found that mammals and birds have stronger aerobic metabolism ability than other animals, can provide more oxygen for muscles, and can maintain consumption for a long time. As a result, they have more endurance when chasing prey or competing with rivals. There is no doubt about that. But Bennett and Reuben put forward a more controversial problem: higher oxygen metabolism inevitably leads to faster metabolism. In other words, physical strength determines homeostasis.

But not many people agree with this view. The reason for the relationship is not enough: aerobic capacity depends on the development of cardiovascular system and muscle, while resting metabolic rate mainly depends on brain and internal organs. Some reptiles, such as the giant lizard, have high oxygen metabolism but low resting metabolic rate. Some mammals and birds keep their body temperature to a minimum during rest or hibernation to reduce consumption.

There are other controversies. For example, carnivorous dinosaurs have a strong ability of oxygen metabolism. Most researchers believe they are evolving into birds. But are they thermostatic? Reuben insisted that the answer was No. Even if he agrees with the idea of oxygen metabolism. He said that carnivorous dinosaurs were very powerful and consumed a lot of energy, but their metabolism was very low. His conclusion is based on the so-called respiratory turbinate bone theory. Carnivorous dinosaurs did not absorb turbinate bone. The spiral bone or cartilage in the nasal passages of birds and mammals can reduce the loss of water during breathing, especially when the metabolism of exercise is accelerated.

So there is not necessarily a connection between energy and thermostability, but why do they have such a great influence? Marcel Klaassen and Bart noLet of the Netherlands Institute of ecology try to explain by stoichiometry, studying how animals get enough nutrition. The problem with herbivores is how they get enough nitrogen to convert it into protein, DNA and RNA in their bodies. Suppose you only eat leaves, and you have too much carbon in your body instead of nitrogen. Some reptiles are herbivores, but their lifestyles are totally different. Robert Espinoza of California State University says that herbivorous lizards sometimes eat small vertebrates, which helps them overcome malnutrition.

In 2008, Marcel and Bart Nolette proposed a new idea: nitrogen can explain why birds and mammals evolved into thermostatic animals. "If a bucket of leaves provides you with a fifth of the nitrogen you need every day, then you need to eat five buckets of leaves every day. How to deal with the excess carbon and burn it as heat is constant temperature," Marcel said Opponents of this view are coming down on their own: higher metabolism leads to more protein consumption, so more nitrogen needs to be absorbed. Marcel and Bart Nolette calculated that modern birds and mammals consume four times more nitrogen than reptiles of similar size.

You might think there's an easier way to get rid of the excess carbon, but actually constant temperature is a very clean solution. The easiest way is to exhale excess carbon into gas. Constant temperature animals, because they want to keep constant temperature, must consume energy frequently and regularly; while cold-blooded animals such as crocodiles consume less energy and can consume it selectively, so not eating for a long time will not endanger their lives.

Methods of adjusting temperature

Snakes bask in the sun on rocks

Fish change to different depths in the water

Desert animals are buried in sand during the day

Insects vibrate their wings to warm their flying muscles.

enzymatic activity

effect

When the body temperature of the animals with variable temperature is at the optimum temperature, the enzyme activity is high; when the body temperature is below the optimum temperature, the enzyme activity is low. It can be explained that the survival activity of thermophilic animals is lower than that of thermostatic animals.

The body function of constant temperature animals can be maximized at any time. The body reaction ability of animals is related to the body temperature. When the body temperature is appropriate, it will reflect the agility and strength. For example, the snake of variable temperature animals, in the morning, due to the external environment

Chinese PinYin : Leng Xue Dong Wu