Mammals - Endothermy Study Guide

Endothermy can be defined as any heat generation mechanism without shivering that increases body temperature and resting metabolic rate.

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An endotherm is a creature that keeps its body at a metabolically favorable temperature, mostly by using heat created by internal biological operations rather than relying nearly entirely on ambient heat. The internally produced heat is mostly a byproduct of the animal's ordinary metabolism. Still, an endotherm may employ unique systems tuned to heat generation under extreme cold or low activity.

What exactly is endothermy?

Almost all animals are endothermic. Warm-bloodedness is a term used to describe this aptitude. Endothermic creatures are sometimes referred to by the word homeothermy.

Although the terms homeothermy and endothermy are sometimes used interchangeably, their meanings are not identical. Homeothermy is an organism's capacity to maintain a steady internal body temperature independent of the temperature of its surroundings.

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Generating Heat

Mammals generate heat largely by keeping their metabolic rate high. Metabolic rate is the pace at which chemical processes occur in the body's cells. More heat is produced when chemical processes in body cells occur higher.

Mammalian cells have far more mitochondria (the powerhouse of the cell) than other vertebrate cells. They produce most of the cells' ATP, their primary source of chemical energy. The presence of more of these small power plants in mammals' cells allows them to create the additional energy required to maintain a high metabolic rate.

Shivering can also temporarily increase heat production in mammals. Shivering is an involuntary muscle movement that turns part of the body's energy to heat. Shivering, like most other reactions that regulate body temperature in animals, is controlled by the hypothalamus in the brain.

The hypothalamus detects interior body temperature, and receives information from temperature sensors in the skin. When the temperature falls below a certain threshold, the hypothalamus signals the muscles contract. Heat is produced as a result of this muscle action.

Conserving Heat

Heat conservation is also crucial for most mammals to maintain a warm body temperature. In cold weather, heat loss may be a severe concern for homoeothermic animals, particularly in tiny mammals.

When the environment is cooler than the body temperature, heat is lost to the environment through the body's surface. When the body's surface area is enormous compared to the entire body size, a larger proportion of heat is lost. Because little animals have a larger surface area concerning their body size, they lose more body heat than large animals.

Mammals have several characteristics that assist them in limiting heat loss from their body surface. One method is to use hair to create an insulating layer of air near the skin.

Mammals may also save heat by limiting blood flow to the body's surface. Normally, blood transports heat from deep within the body to its surface and reduces blood flow to the surface, cooling the surface and minimizing heat loss. When the body is excessively cold, capillaries, the tiniest blood vessels, might thin or constrict. The hypothalamus regulates this process, known as vasoconstriction. It aids in the conservation of bodily heat.

Staying Cool

Most animals need to cool down to avoid overheating, whether they are very active or in a very hot environment.

Sweating is a way for many animals to expel excess heat. Sweat is a watery fluid that sweat glands in the skin generate. Sweat evaporation cools the body when it is moist on the skin. This is because the process of evaporation requires energy, which originates from the heat in the skin.

Sweat evaporation helps to reduce body temperature by using up extra heat. Sweat glands cover most of the body surface in humans and many other animal species. The hypothalamus regulates sweating by stimulating sweat glands to increase or decrease perspiration production based on body temperature.


  • Endothermy is an organism's capacity to create and preserve heat to maintain a constant, warm body temperature.

  • Endothermic animals are able to generate and conserve heat and even stay cool.


1. What is an endotherm?

Endotherms are organisms that have the ability to maintain a constant, warm body temperature.

2. Are humans endotherms?

Humans are warm-blooded creatures that maintain a consistent body temperature regardless of their surroundings, classifying them as an endotherm.

3. What animals are capable of endothermy?

Mammals, birds, and certain species of fish are capable of endothermy.

4. How do endotherms stay cool?

Sweating is a way for animals to expel heat through evaporation from the skin.

5. How do endotherms conserve heat?

Endotherms use hair to create an insulating layer of air near the skin and utilize vasoconstriction of the capillaries which limits blood flow to the surface of the body, minimizing heat loss.

6. What are the advantages of endothermy?

Endothermy has several benefits, including the capacity to inhabit thermal niches that many ectothermic species cannot, a high degree of thermal independence from external temperature, high muscular power production, and sustained activity levels, to mention a few.

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  1. Endothermy. https://www.sciencedirect.com/topics/earth-and-planetary-sciences/endothermy. Accessed on 6 Dec 2021

  2. Endothermy. https://www.britannica.com/science/endothermy. Accessed on 6 Dec 2021

  3. Endothermy in Mammals. https://www.ck12.org/book/ck-12-biology-advanced-concepts/section/16.39/. Accessed on 6 Dec 2021

  4. The Evolution of Endothermy. https://www.frontiersin.org/articles/10.3389/fphys.2018.00891/full. Accessed on 6 Dec 2021

  5. Endotherm. https://en.wikipedia.org/wiki/Endotherm. Accessed on 6 Dec 2021