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3.2 Phylum Annelida Segmented Worms What are segmented worms? • Characteristics: • bilateral symmetry, metameric body plan • coelom present • paired, epidermal setae • ventral nerve cords and ganglia • metanephridia and protonephridia How do segmented worms work? • adapted to live outside of a host • if parasitic, they are ectoparasites • metamerism allows for loss of part of the body without death • coelom allows room for organs • Respiration • rely on diffusion, must remain moist • some have parapodia, which serve as gills • Circulation • blood found in a closed circulatory system • transports oxygen and nutrients • one or more “hearts” • Feeding • one way digestive system (2 openings) • proboscis brings food into mouth • can be carnivores, parasites or scavengers • Nervous Function • sense light, chemicals and touch • one or more ganglia • dorsal and ventral nerve cords • Locomotion • some move using parapodia • most have setae on ventral side for moving and borrowing • Reproduction • sexual - exchange sperm and form a cocoon of eggs • asexual - regeneration or budding Assignment • Take your own notes over the rest of the section. p. 50-53 3.3 Phylum Nematoda • What are roundworms (Nematodes)? • between 16,000 and 500,000 species • found in nearly every habitat • Characteristics: • bilateral symmetry, no segments, coelom • round, covered with tough cuticle, molt to grow • one-way digestive tract How do round worms work? • Respiration • rely on diffusion • no circulatory system • Feeding • carnivores, herbivores, omnivores, parasites or scavengers • use teeth or jaws to obtain food • Nervous Function • Simple nervous system with no brain • Reproduction • dioecious, males smaller than females • external fertilization • egg and sperm leave body through cloaca
