All annelids and arthropods have a body plan. Unlike annelids, arthropods also have a coelom, and a segmented body. The circulatory system of annelids is closed, while the circulatory system of arthropods is opened.
Arthropods are invertebrate organism that possess a stiff exoskeleton, a segmented body, and paired jointed appendages. Arthropods include insects, crustaceans, myriapods, and arachnids. Arthropods possess an open circulatory system; a system without blood vessels. The circulatory system of arthropods is made up of a tube (the heart), and an open hemocoel (in which the blood moves).
Annelids are invertebrate animals that have a body cavity, movable bristles, and a segmented body. Annelids include earthworms, and leeches. The circulatory system of annelids is closed; blood circulates through a closed system of blood vessels.
