Why are some animals called mammals?

Animals are called mammals because they have mammary glands, which produce milk to nourish their young. This is the defining characteristic of mammals.

Here's a breakdown of why:

* Mammary Glands: These glands are present in both male and female mammals, but only become functional in females for the purpose of lactation.

* Milk Production: Milk is a nutrient-rich substance specifically designed to provide the young with the essential nourishment they need for growth and development.

* Other Defining Features: In addition to mammary glands, mammals share other characteristics, such as:

* Hair or fur: Most mammals have some form of hair or fur, even if it's only present during their early life.

* Warm-bloodedness: Mammals regulate their own body temperature, maintaining a relatively constant internal temperature.

* Live birth: Most mammals give birth to live young, with a few exceptions like the platypus and echidna.

The term "mammal" comes from the Latin word "mamma," meaning "breast," which is a direct reference to the mammary glands that are so important for this group of animals.