Final answer:
Segmented body plans are characterized by repeated segments, as seen in annelids like earthworms and leeches. These organisms have metamerism, bilateral symmetry, a coelomic cavity, and well-developed organ systems, including digestive, circulatory, and nervous systems.
Step-by-step explanation:
Animals with a segmented body plan have their bodies divided into multiple similar units known as segments. This type of organization is seen in the Phylum Annelida, which includes organisms such as earthworms and leeches. These animals exhibit metamerism, where both external and internal structures are repeated in each segment. Annelids are characterized by bilateral symmetry, and they have a well-developed coelomic cavity that acts as a hydroskeleton, aiding in movement.
Physiologically, annelids possess a complete digestive system with a mouth, pharynx, esophagus, crop, and intestines. They have a circulatory system with several pairs of hearts and blood vessels for transporting nutrients and oxygen throughout their body segments. The nerve cord and simple brain constitute their nervous system. Notably, polychaetes and oligochaetes are two main groups within the annelids, distinguished by the presence or absence of parapodia and bristles used for locomotion.