| A | B |
|---|
| Mammal | Warm-blooded animal with fur which feeds milk to its young. |
| Fish | Cold-blooded animal with scales and gills which lives in the water. |
| Amphibian | Cold-blooded animal with gills and later lungs. |
| Bird | Warm-blooded animal with feathers which lays eggs. |
| Reptile | Cold-blooded animal with dry scaly skin and lungs. |
| Marsupial | Mammal with a pouch. |
| Monotreme | Mammal which lays eggs. |
| Placental | Mammal which bears live young. |
| Salamanders and Newts | Amphibians with tails. |
| Frogs and Toads | Amphibians without tails. |
| Turtles and Tortoises | Reptiles with shells. |
| Crocodiles and Alligators | Crocodilians |
| Fish, Amphibians, and Reptiles | The groups of cold-blooded vertebrates. |
| Birds and Mammals | The groups of warm-blooded vertebrates. |
| Reptiles and Fish. | The groups of vertebrates with scales. |
| Fish, Amphibians, Reptiles, and Birds. | Vertebrate groups which lay eggs. |
| Jawless Fish | The earliest group of fish. |
| Lobe-finned fish | Fish which may be the ancestors of amphibians. |
| Caecilians | Amphibians which look like worms. |
| Primates | Mammal group which includes human beings. |
