what are reptiles and birds. Ectothermic or endothermic?

Answer 1

Warm-blooded creatures, like mammals and birds, try to keep the inside of their bodies at a constant temperature. They do this by generating their own heat when they are in a cooler environment, and by cooling themselves when they are in a hotter environment. To generate heat, warm-blooded animals convert the food that they eat into energy. They have to eat a lot of food, compared with cold-blooded animals, to maintain a constant body temperature. Only a small amount of the food that a warm-blooded animal eats is converted into body mass. The rest is used to fuel a constant body temperature.

Cold-blooded creatures take on the temperature of their surroundings. They are hot when their environment is hot and cold when their environment is cold. In hot environments, cold-blooded animals can have blood that is much warmer than warm-blooded animals. Cold-blooded animals are much more active in warm environments and are very sluggish in cold environments. This is because their muscle activity depends on chemical reactions which run quickly when it is hot and slowly when it is cold. A cold-blooded animal can convert much more of its food into body mass compared with a warm-blooded animal.

Answer 2

Dinosaurs were arbitrarily classified as reptiles long before we had sufficient evidence of their true nature. Clearly they are more closely related to birds. All mammals, dinosaurs and birds shared a last common ancestor that was a reptile. Perhaps birds and dinosaurs shared a later last common ancestor that was also a reptile. Birds evolved over a 150 million years ago and therefore they survived at least 90 million years with dinosaurs as dinosaurs. They weren't really transitional. Perhaps birds evolved from an early theropod but that just makes them a separate branch of dinosaur. The problem is that since they were initially classified as reptiles, it has become muddled and difficult to properly classify them IMO.

Answer 3

Reptiles are ectothermic, also called cold-blooded.
Birds (and mammals) are endothermic, also called warm-blooded.

Answer 4

Reptiles are cold blooded or ectothermic.
Birds are warm blooded or endotermic.