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One of the ways life is classified is through the presence or absence of the vertebrates. Vertebrates and invertebrates evolved from a common ancestor that was speculated to have lived around 600 million years ago.
Evidence of true vertebrates began to appear 525 million years ago and ever since then, vertebrates have branches off into a long lineage that includes armoured fish and giant sauropods to wolly mammoths and modern man.
1. Mammals
Mammals are warm-blooded animals with hair or fur. Most give birth to live babies and feed them milk. They breathe with lungs and can live on land or in water. Examples are humans, dogs, and whales. They usually take good care of their babies.
2. Birds
Birds are warm-blooded and have feathers and wings. Most can fly, and all lay eggs. They have beaks and breathe with lungs. Examples include eagles, penguins, and parrots. Birds often build nests to keep their eggs safe.
3. Reptiles
Reptiles are cold-blooded with dry, scaly skin. They usually lay eggs and breathe with lungs. Many live in hot places. Snakes, lizards, and turtles are reptiles. Some reptiles can go a long time without eating.
4. Amphibians
Amphibians are cold-blooded and live in water when young and on land when older. They have smooth, wet skin and lay eggs in water. Frogs and salamanders are amphibians. They need water to keep their skin moist.
5. Fish
Fish are cold-blooded animals that live in water. They have gills to breathe and fins to swim. Most have scales and lay eggs. Examples are goldfish, salmon, and tuna. They come in many colors, shapes, and sizes.
6. Cartilaginous Fish
These fish have skeletons made of cartilage, not bone. They live in water and have fins and gills. Sharks and rays are examples of cartilaginous fish. They are often fast swimmers and great hunters.
7. Jawless Fish
Jawless fish have no jaws or bones. They have soft bodies and suck their food. Lampreys and hagfish are jawless fish and are very old types of animals. They have a slimy body to protect themselves.