What is an invertebrate?
Animals can be classified as either vertebrates or invertebrates.
Invertebrates are animals that don't have a backbone. Some have soft bodies, like worms, slugs and jellyfish. Other invertebrates, like insects, spiders and crustaceans, have a hard outer casing called an exoskeleton. This protects their body a bit like a suit of armour.
Vertebrates have a backbone inside their body. They include mammals, birds, fish, amphibians and reptiles.