The document summarizes the subphylum Urochordata (also known as Tunicata). It discusses the key characteristics and systems of urochordata, including: - They have a tail-like structure and notochord, with a simple adult body structure of a sack with two siphons for water filtration. - Their nervous system has a single ganglia nerve plexus throughout the body. - Their digestive system involves ciliated mouth absorption and digestion primarily in the mouth and intestine. - Respiration occurs via water circulation through the pharynx. Their circulatory system involves one or two blood vessels carrying blood throughout the body.