[originaltext] Before I tell you about the interesting discovery related to

Before I tell you about the interesting discovery related to the tyrannosaurus rex,(23)I need to review something we studied last semester: the differences between what we commonly called cold-blooded and warm-blooded animals. In warmblooded animals, birds and mammals for examples, the body temperature normally stays within a narrow range no matter what the outside temperature is. As a result, a warm-blooded animal is usually active in both cold and hot weather because the body temperature can adjust to the temperature as in the environment.(24)On the other hand, coldblooded animals, such as most reptiles, amphibians and insects, are unable to create enough heat internally to raise their temperature above the temperature of the environment. So, for example, the temperature of a cold-blooded animal falls when the environment is cool. I hope this extension is clear. Now moving on to the tyrannosaurus rex, you may know that dinosaurs being reptiles are generally believed to have been cold-blooded.(25)Well, a recent research study has found that a chemical composition of the bone of the tyrannosaurus rex was consistent with the bone of the animal that has a very narrow range of the internal temperature, indicating that it was probably warm-blooded.
23. What is the main topic of the lecture?
24. What is likely to happen to cold-blooded animals when the weather is cold?
25. Why does the speaker discuss tyrannosaurus rex?