* Warm-blooded: They maintain a constant internal body temperature, unlike reptiles or amphibians.
* Hair/Fur: They have hair or fur covering their bodies, which helps with insulation and communication.
* Give birth to live young: Dogs do not lay eggs; they give birth to live puppies.
* Mammary glands: Female dogs possess mammary glands that produce milk to nourish their offspring.
* Three middle ear bones: This unique feature enhances their hearing abilities.
* Diaphragm: Dogs, like other mammals, use a diaphragm muscle for breathing.
* Four-chambered heart: A highly efficient heart that separates oxygenated and deoxygenated blood.
These shared characteristics, along with their genetic similarities, firmly place dogs within the class Mammalia.