Scientists Say: Endotherm and Ectotherm

Endotherm and ectotherm (nouns, “END-oh-therm” and “EK-toh-therm”)

Endotherms and ectotherms are two types of animals. They control their body temperatures in different ways. Endotherms can control how much heat they generate internally to maintain a certain body temperature. So they tend to stay at about the same temperature no matter the temperature of their environment changes. Ectotherms, meanwhile, depend mainly on outside heat sources to control their body temperature. As a result, they tend to warm up and cool down with their environment.

Endotherms are sometimes called “warm-blooded.” Such animals include birds and mammals. That’s why your body runs at about 37° Celsius (98.6° Fahrenheit) whether it’s summer or winter. Endotherms can ramp up their internal heat production when they’re cold. Or lower it when they’re hot. They also can shiver to warm up, or sweat or pant to cool down. This internal control helps endotherms survive a wide range of external temperatures. But it requires a lot of energy from food.

Educators and Parents, Sign Up for The Cheat Sheet

Weekly updates to help you use Science News Explores in the learning environment

Client key* E-mail Address* Go

Thank you for signing up!

There was a problem signing you up.

Ectotherms are sometimes called “cold-blooded.” These animals include fish, reptiles, amphibians and invertebrates. Ectotherms cannot dial their internal heat production up or down. They control their body temperature in other ways. For instance, a reptile might bask in the sun to warm up or seek shade to cool down. Fish can likewise move between warmer and cooler waters. Using outside sources to warm up and cool down requires less food energy.

Why do animals need to control their body temperatures at all? Well, if the water inside an animal’s body freezes, that can rupture its cells. If a creature gets too hot, the proteins inside its cells can stop working. And many life forms must maintain a narrow range of body temperatures to ensure that the chemical reactions inside their cells run properly.

In a sentence

Some ectotherms such as polar fish produce anti-freezing proteins that keep ice from forming inside their cells when it’s very cold.  

Check out the full list of Scientists Say.