Why are fish not afraid of cold and heat all year round?

Why are fish not afraid of cold, while people are afraid of cold and heat?

If someone asks me this question on a hot day of thirty or forty degrees Celsius, I may ask him why he doesn't buy more waterproof air conditioners for fish. After all, the weather is so hot! It's only 1 1 month now, but many people in Chengdu have put on down jackets. Undeniably, everyone's physique is different, so the degree of fear of cold is different, but this is mainly related to years of living habits, not where the body is weak.

However, the fundamental reason why people are afraid of cold is that our body temperature is relatively constant, so human beings are not only afraid of cold, but also afraid of heat. But among all the creatures on the earth, except birds and mammals, other animals are essentially warm-blooded animals. Although the body temperature cannot be directly changed and controlled by body functions, the growth efficiency of these cold-blooded animals is higher, and even the breeding period is much shorter. For example:

If a warm-blooded animal is compared with a warm-blooded animal with the same weight, warm-blooded animals only need one-tenth to one-third of the energy of the former to live normally, so they need less food, but they can accumulate the energy they need. Of course, although there are a large number of warm-blooded animals, they can overcome environmental changes to a certain extent, but their adaptability to nature as a whole is not as strong as that of warm-blooded animals, because warm-blooded animals often have a longer life cycle, and they can also find the food they need within a wide enough boundary.

There are obvious differences in the temperature of living environment between fish and animals:

Fish was born hundreds of millions of years before humans. At present, there are more than 30,000 species of fish whose names we know on the earth, and this number is increasing at the rate of 100 per year. Someone should have heard the saying that "human beings first evolved from fish", because fish is the lowest creature among vertebrates and the earliest known vertebrate on earth. At present, the oldest fish fossil discovered by scientists is about 500 million years ago, when it was still in the late CAMBRIAN.

Usually, we mainly divide fish animals into saltwater fish and freshwater fish. As the name implies, saltwater fish refers to fish animals that live in an environment similar to the sea, while freshwater fish mainly live in rivers and lakes. But we can see from another classification of fish that the water temperature in the living environment of different fish animals is also very different, because fish are also divided into tropical fish, temperate fish and cold water fish.

Obviously, the temperature difference between tropical zone, temperate zone and cold zone is very large. If we put tropical fish in cold areas, they will die, just as those fish and animals who know how to live in the sea can't survive once they are put in fresh water. In any limited ecosystem, there is an obvious interdependence between animals and plants and the natural environment. Even highly intelligent human beings, if we lose the technology we have at present, the living territory we can choose will become more cramped.

The special functions of fish and animals are not afraid of cold!

Fish and animals do have many special functions, but the one who is not afraid of cold is not counted! Some people may find it ridiculous. Fish that eat and sleep in water may even drown, but this phenomenon does exist in nature. In water, the range of activities of different fish and animals may be different, that is to say, some deep areas under water are not suitable for them to swim. We call this depth limit the critical depth.

You know, the fundamental reason why fish and animals can swim in the water is that they have swollen swim bladders, which is equivalent to the lifebuoy of our human society. However, if the fish sinks to a critical depth, its swim bladder will be unable to complete the volume adjustment because of excessive external pressure. At this time, the fish will continue to sink uncontrollably to the bottom of the water, gradually have difficulty breathing, and then slowly drown in the place they are most familiar with.

I believe many people know that different fish and animals have different special functions, such as flying fish-ray (usually only 20 to 30 cm long, just like the wings of dragonflies when their ventral fins are unfolded), walking fish-turtle shell climbing perch (like to live in muddy and slow-flowing waters, even if they leave water, they will not die in a short time), and vocal fish-Ji Kang eel.