We know that the north pole and south pole is completely frozen, and it is the survival of the last Glacier period on earth where the much of earth that was covered with ice started to recede and we entered the Holocene which is the current Epoch we are geologically. Instead of us having glaciers in a large part of earth, we only saw it in the north pole and South pole but the temperature of this place can go low as -40oC or even more.
Asides from the horrifying temperature that can give a person Hypothermia, it can also be dark for months in a role which means it isn't exposed to sunlight and so the cold can be very terrible and it can turn the internal organs of living things into ice. We all know that live should normally not survive in this type of temperature, so how do some animals find a way to survive?
Over years, evolution and natural selection have been able to make animals live in this environment and not die even when the temperature is a straigt ticket to death, so how did this animals do it. Although there is something common about the animals living in this area and that is having heat generating tissues, and for animals like the polar bear, they remain invisible with infrared vision.
Temperatures like this isn't good for living things being especially big animals because we are made up of majorly water which can expand and become frozen when we stay in this environment and become sharp as in what we know as frostbite which leads to the death of the cells in the body. For majority of animals and humans included, our organs have a particular temperature that it can function properly such as the heart and the nervous system and this can lead to death as a result of organ failure so what do this animals that live in this areas do seperately. They are able to do two things, one is to prevent heat from leaving their body, the other is to generate heat in the body.
Wait, you must have heard of cold-blooded animals and warm-blooded animals, and this are the two types of blooded creatures that animals are created into and you might have heard in elementary school that cold blooded animals do not create their own heat like we warm blooded animals and you begin to wonder why these animals cannot create heat but actually they do create heat they do not just know how to regulate and retain the heat like warm blooded animals.
Warm blooded animals or endotherms which is made up of birds and mammals are able to maintain stable internal temperature because of the use of metabolic heat which is usually warmer than their environment. Endotherms are able to use thermogenesis to increase their body temperature in the case of a change in temperature to being more cold.
When your room is old and you are shivering, it is your body trying to increase your body heat temperature by contracting and relaxing your skeletal muscles so as to produce extra heat so as to keep the body warm but the ability to generate more energy is even found in animals that hibernate in colder regions and this is thanks to brown adipose tissues and with this tissue, the animals can produce heat without moving tissues (non-shiverring thermogenesis). While white fat stores energy that is excess, brown fat breaks down sugar and can also break down white fat to create heat generating over 300 time the heat any other tissue will produce in the body.
What hibernating animals do is that before they go into hibernation, they eat a lot so they can be able to go through and get out of hibernation and part of this process is for them to eat a lot so there can be calories to burn for energy when they have decreased physiological activities. Because they are inactive, they will have reduced temperature and their metabolic rat will also reduce (Hypothermic torpor) allowing the animals to the period of reduced or no food. One third of the total amount of energy consumed before hibernation is used to reawaken.
https://pmc.ncbi.nlm.nih.gov/articles/PMC6801758/
https://sci-hub.se/10.1152/ajpregu.1989.256.1.R42
https://www.une.edu.au/__data/assets/pdf_file/0015/32505
https://beyondpenguins.ehe.osu.edu/issue/arctic-and-anarctic-birds
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