Crabs and prawns, woodlice and centipedes, all have many more jointed legs than insects – millipedes even have two pairs on each segment. In contrast an earthworm, although composed of many segments, has no legs at all, and the body does not have a distinct head. Slugs, snails and starfish have a very different structure that is not based on segments.
Vertebrates
A monkey is a vertebrate, meaning it has a backbone. Birds, fish, lizards (reptiles), frogs (amphibians) and mammals, such as dogs and people are all vertebrates. They breathe with lungs or gills, and have a central heart. None of them has six legs, and their bodies are not divided into segments.
Beach fleas
These strange creatures are similar to insects in appearance, but they have ten legs, rather…
