The problem with this syllogism is that it is an invalid form. A lizard is not a reptile because it is cold-blooded. Amphibians, insects, arachnids (such as spiders), and fish are also cold-blooded. Just insert one of those categories in place of “reptiles” and you’ll immediately see that this form of syllogism is false.
All fish are cold-blooded animals.
A lizard is a cold-blooded animal.
Therefore, a lizard is a fish.
The following is a valid form:
All reptiles are cold-blooded animals.
A lizard is a reptile.
Therefore a lizard is cold-blooded.