First, we must understand the differences between ectothermic or endothermic animals.
Animals have different thermoregulation abilities. Sometimes we use the terms “cold blooded” and “warm blooded”. Most reptiles feel cold, while mammals or birds feel warmer.
You can use the terms homoeothermic and poikilothermic to give more specific descriptions. Poikllotherms’ body temperature is variable while homeotherms’ is stable. Endothermic or Ectothermic are terms that describe two types of thermoregulation. Ectotherms are able to get heat from the outside. Their body temperature is affected by the external temperature.
Endothermic species, on the contrary, have relatively consistent body temperatures. Their body temperature does not depend on the external environment. Monkeys are 38aC and walruses 38aC respectively, even though they live in very different environments.
The enzyme rate will drop sharply if the body’s temperature rises beyond its optimum level (usually 40aC for mammals). This happens because enzymes (proteins) can become damaged. The brain is the most affected organ. Because the brain controls breathing, circulation, and temperature, it is important to disrupt their normal function.
Hypothermia, a dramatic drop in body temperature, can cause brain damage and slow down metabolism.
Here’s a graph showing the relationship between the body temperature (endotherm) versus the environmental temperature (ectotherm).
We need to understand what extreme climate actually means. I will be investigating two different climates.
Endotherms can lose heat energy when they are exposed to extreme cold. However, this can be reversed in many ways.
It can lift the hairs up by contracting the muscles of the erector pili. The air between the hairs can become trapped and acts as an insulation layer. This is an uninvoluntary response of the nervous systems.
Vasoconstriction refers to the constriction of blood vessels leading to the superficial veins. This is caused in part by the sympathetic nerve system. It’s useful in exposed regions like the ears that have a large surface-volume ratio, and are therefore more vulnerable to cold.
A higher metabolic rate can increase the body’s ability to heat. Thyroxine and adrenaline, which are both produced in high amounts in cold conditions, cause an increase in the metabolic rates. This causes a general increase to muscle tone. Then, spasmodic contraction (shivering), follows.
High temperature can cause the opposite reaction to the processes described above.
The body is flattened by hairs
Vasodialation (the dialation of blood) occurs when blood returns to the surface to permit heat loss through diffusion.
Sweating can be a normal part of life.
Panting occurs. There may not be any sweat glands at all in animals except the pads of the feet. The animals pant to increase evaporation, which in turn speeds up the cooling of their blood.
The body produces less energy when the metabolic rate drops.
Arctic Polar Bears (Thalarctos maritimus)
The world’s harshest climate has been adapted well to the life of polar bears. They are active all year round. They can be seen in the Arctic Sea Ice throughout the North Polar basin.
The creamy white fur of polar bears is extremely dense. Each individual hair has hollows and contains insulation air spaces. The animal’s body heat is retained by the thick fur and large fat layer, even when it is in cold arctic temperatures. The fur doesn’t absorb water so the animal can just shake off the excess water. It has plantigrade foot (sole and heel touching ground), and five sharp claws to grip ice. The bear’s feet are protected by the cold by long hair between its pads.
Another adaptation is in how thick the sub-cutaneous oil is. For animals that live in cold climates such as seals and polar bears, the sub-cutaneous fat is thicker. The fat in seals and marine mammals like whales is known as blubber.
The tuber cinereum in the hypothalamus controls the thermoregulation of all Endotherms.
If this tiny downward projection at the base would be removed, animals would lose their ability to regulate their temperature.
The tuber cinereum can be stimulated by either nerve impulses from cold receptors on the skin or direct cooling. It is very sensitive and can react to temperature changes as small as tenths. The thermoregulator will stimulate thyroid secretion if the body temperature falls below freezing. This increases metabolism. If the body temperature is dropping, organs such the liver might be pushed to the forefront. In this case, muscle activity (shivering) may start.
Camels (Camelus). Camels can be described as large native animals living in the desert regions between Asia and Africa. There are two types. The Dromedary comes with one hump while the Bacterian comesl has two. The humps contain fat and flesh that are used to provide nutrition in times of scarcity.
The desert environment is where the camel thrives. It can survive for days without water. However, it is not clear that camels retain water in their stomachs. A camel can be provided with water by desert vegetation for many months. To replenish its water reserves, a thirsty one can consume up to 30 gallons at a given time. Salt water can also be ingested by camels due to their metabolism.
To help conserve water, a camel’s body temperature may rise as high as 6aC-8aC. The camel can withstand heat from the desert sand because of its thick, wide sole pads, and thick callosities around the ankles and chest. You can also protect your nostrils from flying dust by closing them. Your eyes are protected by long eyelashes, as well as a third one.
The Horned Toad (Phrynosoma Cornutum) is a short-tailed and short-legged member of the iguana family. It is found in Mexico and the west United States. They can adjust their body’s metabolism and heart beat to regulate their temperature.
Creatures that are cold-blooded and have scaly skin.
Reptiles can be considered ectotherm even though they regulate their body temperature to an amazing extent. However, thermoregulation is behavioral and not metabolic like endotherm.
Most reptiles are assumed to have a body temperature approximately equal to the surrounding air. But, reptiles are more comfortable than their surrounding air. In fact, lizards’ bodies can reach 40aC and 50aC higher temperatures than the surrounding air. A lizard sitting on a rock of black on a sunny, cool day will feel the difference between the rock and the air.
If its body temperature drops below freezing, the lizard might flatten against the rock to absorb the heat. It may either leave the rock if it becomes too hot or rise slightly to allow air to flow underneath. Different proportions of the body can be used to regulate temperature in snakes. There are many variations but one thing is constant: reptiles have some temperature regulation.
The animals that live in extreme environments around the globe have evolved to adapt to these conditions and will likely continue to live in them for many years to come.
