* Vertebral column (backbone): This is the defining feature of vertebrates, providing support and structure for the body.
* Internal skeleton: They have an internal skeleton made of bone (or cartilage in some cases), providing support and protection for organs.
* Bilateral symmetry: Their bodies are symmetrical, meaning they can be divided into two mirror images.
* Closed circulatory system: They have a heart that pumps blood through a closed system of blood vessels.
* Well-developed brain: All vertebrates have a complex brain that controls their nervous system and allows for complex behaviors.
However, they also have some important differences:
* Amphibians: They have smooth, moist skin and live both in water and on land, undergoing metamorphosis. They are cold-blooded.
* Reptiles: They have dry, scaly skin and are primarily land-dwelling. They lay eggs with leathery shells and are cold-blooded.
* Mammals: They have hair or fur and produce milk to nourish their young. They are warm-blooded.
While they share these fundamental characteristics, they have evolved over millions of years to adapt to different environments and develop unique traits.