Annelids include earthworms, polychaete worms, and leeches. They all have segmented bodies. This means that their bodies are formed by many segments throughout their bodies. Each segment contains elements of a different bodily system such as nervous, circulatory, etc. Segmented bodies allows for very efficient movement due to the muscle contraction being " localized" from the segments. All annelids except leeches also have hair-like structures, called setae. They help attach the worms to the surface. They can be found all over the world, in both terrestrial and marine environments.