| A | B |
|---|
| invertebrate | an animal that has no backbone |
| vertebrate | an animal with a backbone |
| mammal | an animal that has hair or fur and feeds its young with milk produced by the mother |
| segmented worms | burrow into the soil and digest decaying matter found in it |
| sponges | they look more like plants than animals; they have a hollow body that is made of two layers of cells with a thick, jellylike layer between them |
| arthropods | has a stiff outer covering to protect and support its body, joints allow them to move |
| hydras | they have snakelike tentacles around their mouths; they have waving tentacles covered with stinging cells to help capture its prey |
| sea stars | has tough skin and spines to help protect itself from enemies; has powerful suction cups on its underside to help open the shells of the clams it eats |
| mollusks | human beings eat them; they are animals with soft bodies,some are supported and protected by one or two shells |
| fish | they lay their eggs in the water and spend their whole lives in the water |
| amphibians | they begin their lives breathing through gills, but most of them develop lungs and live on land |
| mammals | they can be found on land, in the water, and in the air |
| reptiles | they have tough scales that protect their bodies |
| birds and reptiles | both breathe air all their lives |
| birds and reptiles | both lay their eggs on land |
