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Phylum Annelida. The polychaetes , worms, and leeches. Annelids are all segmented Series of repeated ring-like units (segments) All have a head with a well-developed cerebral ganglion (primitive brain) Many have eyes with lens and retinas
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Phylum Annelida The polychaetes, worms, and leeches
Annelids are all segmented • Series of repeated ring-like units (segments) • All have a head with a well-developed cerebral ganglion (primitive brain) • Many have eyes with lens and retinas • If an Annelid is cut in pieces, usually only the parts containing the head or tail can regenerate • Segments are divided by partitions called Septa NOAA
Each segment has a pair of excretory organs (nephridia), a ganglion, structures for locomotion, and many also have a set reproductive structures • Annelids also have a closed-circulatory system (blood vessels) • More advanced digestive system with a: • Crop: stores food prior to: • Gizzard: grinds food particles • Intestine: absorb nutrients
Nephridia are cilliated tubes open to the outside for removing wastes • Setae are bristles made of chitin on each segment that gives the worm a grip in the dirt PiotrRotkiewickz
Phylum Annelida • Class Polychaeta: the Polychaetes • Can swim or crawl and some species even build tubes or burrows of mud, sand, or calcium carbonate Karen Osborn of Scripps Oceanography
Phylum Annelida • Class Polychaeta Nick Hobgood
Phylum Annelida • Class Clitellata: Earthworms and Leeches • Only half of known leeches suck blood, the other half eat detritus and small animals www.pbs.org
Gas exchange: diffusion through skin • Circulation: closed circulatory system with many having multiple hearts • Excretion: nephridia • Digestion: Complete digestive system, mouth to pharynx to esophagus to crop to gizzard to intestines to anus • Reproduction: sexual, some hermaphrodites (earthworms) • Response to environment: light and touch sensitive organs plus they have a brain! • Movement: Setae provide traction, they can swim, crawl or burrow