Eurytherm

Some living things like heat and cold.

They can live in many places. This helps them stay safe. It lets them live in many lands.

Small water bugs can live in very hot or very cold spots.

Even big whales can live in many parts of the sea.

Humans can live in many places too. We are very good at this!

Some living things can live in many temperatures. We call these living things eurytherms. This name comes from their ability to handle heat or cold.

Being a eurytherm is a big advantage. It helps animals live in new areas. It also helps them survive ice ages. Some animals are the opposite. We call them stenotherms. They can only live in a small range of temperatures. This is why many coral reefs are dying now. The ocean is getting too warm for them.

Many animals are eurytherms. The green crab lives in many waters.

It can live in water as cold as 8 °C. It can also live in water as warm as 35 °C. Killer whales are also eurytherms.

They live in many parts of the ocean. They can handle water from 0 °C to 35 °C.

Tardigrades are very extreme eurytherms.

They can enter a state called a tun. In this state, they lose most of their water. They can survive temperatures as low as –273 °C. They can also survive 150 °C. This helps them endure many harsh places.

Some living things can handle many different temperatures. We call these creatures eurytherms. This ability lets them live in very hot or very cold places. Most mammals, including humans, are eurytherms. Being a eurytherm is a big advantage for survival. It helps a species live in new areas. It also helps animals survive ice ages. This is different from stenotherms. Stenotherms can only live in a very small temperature range.

How a eurytherm works depends on its body. Some are regulators, which keep their internal temperature steady. Humans are good examples of these regulators. We use sweating to cool down. Our sweat glands make water that evaporates to cool our blood. We also use shivering to get warm. Shivering makes our muscles move to create heat. This can also help our bodies make a special fat. This fat uses a protein called thermogenin to make heat.

Other eurytherms are conformers. Their internal temperature changes with the world around them. Tardigrades are extreme examples of these creatures. They can enter a state called a tun. In this state, they lose almost all their water. This allows them to survive near absolute zero. They can even handle temperatures of 150 °C. They use special proteins to handle ice forming in their bodies.

Many famous animals show this amazing trait. The green crab lives from Iceland to Australia. It can survive water from 8 °C to 35 °C.

Killer whales are also eurytherms. They live in nearly every part of the ocean. They can handle water from 0 °C to 35 °C.

Even plants like the black spruce are eurytherms. They live from Indiana to the Arctic Circle. They can endure temperatures as cold as –85 °C.

This ability is often linked to proteins. The proteins in eurytherms can work in many temperatures. This is why they can stay healthy in different climates. Some animals, like the desert pupfish, live in very specific spots. They can function in water from 8 °C to 42 °C. In places like the Colorado River Delta, this is vital. The ability to handle heat or cold is a key to success. It is why many species thrive while others, like coral, struggle.

A eurytherm is an organism capable of functioning across a wide range of ambient temperatures. This classification includes all life stages, from larvae to adults. Most mammals, including humans, are considered eurytherms. This ability is a major evolutionary advantage. It allows species to inhabit diverse geographic areas. It also helps them survive environmental crises like ice ages. This capacity is often linked to the tolerance of the organism's proteins. In contrast, stenothermic organisms can only operate within a very narrow temperature range.

Eurythermic organisms use different thermal coping mechanisms to survive. They can be categorized as either regulators or conformers. Regulators, such as endotherms, maintain a consistent internal body temperature regardless of the environment. Conformers, like tardigrades, allow their internal physiology to vary with the external temperature. Regulators often use behavior to assist with homeostasis. For example, reptiles use basking or burrowing to manage heat. Humans also use behavior, such as wearing clothing or using air conditioning.

Humans demonstrate complex internal regulation through thermogenesis. When cold, humans use shivering to create heat through involuntary muscle contractions. This process signals the body to produce irisin, a hormone. Irisin helps convert white fat into brown fat. This brown fat contains a protein called thermogenin. Thermogenin performs non-shivering thermogenesis by uncoupling the electron transport in the mitochondrion. This process causes energy to be lost as heat instead of being stored as ATP. To cool down, humans rely on sweat evaporation. Eccrine sweat glands produce a watery fluid that evaporates to cool the blood.

Tardigrades are extreme examples of eurythermal conformers. They can enter an anhydrobiotic state known as a tun. In this state, they reduce their bodily water to just 1–3% weight. This allows them to survive temperatures from –273 °C to 150 °C. Their survival in extreme cold is a form of cryptobiosis called cryobiosis. Unlike some organisms that use antifreeze proteins, tardigrades tolerate ice formation. They use ice nucleating proteins to manage this process in their extracellular water. Scientists speculate they could theoretically survive the temperatures found on Mars.

Many animals show the success of eurythermy through their wide ranges. The green crab is a common littoral species. It lives from Iceland and Norway to South Africa and Australia. It can survive water temperatures between 8 °C and 35 °C. The desert pupfish is another example found in places like the Colorado River Delta. This fish functions in waters ranging from 8 °C to 42 °C. Killer whales are considered a cosmopolitan species. They inhabit nearly every latitude of the ocean. They can withstand water temperatures from 0 °C to 35 °C.

Plants also exhibit eurythermal traits, particularly in boreal forests. Boreal deciduous conifers, such as the black spruce, are cold-eurythermic. The black spruce grows from Indiana to the Arctic Circle. It can endure temperatures as low as –85 °C and as warm as 20 °C.

This is very different from stenothermic plants like the banyan tree. Tropical plants often have a narrow tolerable range, such as 10 °C to 25 °C. Eurythermy provides the mobility and agility necessary for survival in changing climates.

The biological cost of eurythermy is often seen in the struggle of stenotherms. Coral reefs provide a notable example of this vulnerability. Most coral species are stenothermic and sensitive to heat. Rising ocean temperatures cause corals to expel their zooxanthellae algae. This algae provides the coral with food and color. When expelled, the coral undergoes bleaching. This has caused a 50% mortality rate in corals off Cape York, Australia. Globally, there is a 12% bleaching rate in observed reefs. The ability to handle thermal shifts is a primary factor in evolutionary fitness.