In Vertebrate Groups the table had a column for body temperature. Here is what it means.
Key idea
Birds and mammals are endotherms: they make heat inside their bodies and keep a fairly steady temperature. Fish, amphibians and reptiles (and most invertebrates) are ectotherms: their temperature follows their surroundings.
Why it works
Making heat costs energy, and energy comes from food. So a mouse needs much more food for its size than a lizard does. In return, the mouse stays active on a cold night. A lizard warms itself by basking in the sun and cools off in the shade or a burrow, and it slows down when it is cold.
Worked examples
Worked example: Read the chart
At an air temperature of 10 °C, about how warm is each animal?
- The mouse line stays at about 37 °C.
- The lizard line is at about 12 °C, near the air temperature.
Answer: Mouse about 37 °C; lizard about 12 °C.
Worked example: Which is which?
A frog's body temperature rises from 10 °C to 25 °C as a pond warms. Endotherm or ectotherm?
- Its temperature follows its surroundings.
Answer: An ectotherm.
Common mistake
Thinking "cold-blooded" animals have cold blood. A lizard basking in the sun can be as warm as a person, or warmer; its temperature simply depends on its surroundings. Scientists prefer the word "ectotherm."