If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content
Current time:0:00Total duration:1:26

Video transcript

There are two different kinds of metabolisms we ascribe to animals today, warm-blooded like us humans are creatures that control their body temperatures, body temperatures tend to be warm, we're at ninety eight point six and our body temperature doesn't vary, unless we're sick, it doesn't vary with the outside temperature. Lizards, and a lot of other kinds of animals, of course, are what we call cold-blooded, not really cold-blooded technically, but what that means is their body temperatures, internal body temperature is much more labile, much more sensitive to the environment, when it's cold outside, their body temperature is cold, when it's hot their body temperature warms up. What were dinosaurs? Well we don't really know the answer to that question, actually based on some of the evidence of posture and locomotion we actually think that some of these more predatory dinosaurs might've been warm-blooded, whereas some of the larger vegetarian animals might have been cold-blooded, but we don't know that directly. But one thing is certain, that birds are warm-blooded animals and birds are a kind of dinosaur so somewhere in the evolution of dinosaurs warm-bloodedness eveolved. Maybe in those dinosaurs that aren't strictly classified as birds, maybe Tyrannosaurus was warm-blooded, we don't know that for sure but it's a good supposition.