Question: Why does a fish have scales on it's body?

Vera Weisbecker answered on 22 Jun 2011:

The scales are to protect it from harm, e.g. a bite or a scratch. Scales are a really ancient part of the body of vertebrates (animals with a backbone – e.g. fish, frogs, lizards, humans). They were originally like a tortoise shell, surrounding the whole body of the fish. But then throughout evolutionary time, they broke up into smaller bits which helped the fish be a bit more flexible. The scales of modern fish (like herrings) are amazing – the yare a bit like a chain mail, with lots of tiny elements that overlap like shingles. So you have the benefit of protection without having to compromise on safety!