Soaking Up the Sun

Think about taking a walk along a creek. You see a lizard on a rock. Is it sleeping? No! It’s warming itself in the sun.

Lizards, snakes, and other reptiles are ectotherms. Fish, insects, and frogs are, too. Ectotherms can’t make much heat inside their bodies. To warm up, they get heat from their environment.

The sun shines on the lizard. It warms the lizard’s back. The lizard soaks up the sun’s heat.

Energy from the sun helps this desert lizard dart and dash.

This desert lizard sits in the sun to warm up. 

Heat From the Inside

As you walk, you see squirrels. They are chasing each other around a tree.

Unlike the lizard, the squirrels don’t need the sun to warm them. That’s because they are endotherms. Endotherms make enough heat inside their bodies to keep warm.

Squirrels don’t have to wait for the sun. They can be active right away. So can birds. So can you. That’s right! You are an endotherm, too.

What’s In a Name?

Ectotherm comes from two Greek words. Ektos means “outside.” Thermos means “warm.” An ectotherm gets warmth from outside its body.

Endotherm comes from the Greek word endo.  That means “within.” An endotherm gets warmth from inside its body.