The Invertebrates The Worms

pork Tapeworms life cycle each proglottid can produce, fertilize and store eggs could be 1000s of eggs inside each proglottid pigs (intermediate host) eat proglottids and eggs hatch inside pig’s intestines larva burrow to the muscles of the pig larva form cysts that contain a scolex person eats improperly cooked pork, the scolex emerges and attaches to the intestine so that the proglottids can grow proglottid breaks off and released when person defecates pigs eat feces and process starts again

Pork Tapeworm Life Cycle

Other Tapeworms beef tapeworm fish tapeworm most common because man prefers rawer beef than pork fish tapeworm largest, can grow up to 18m long

Phylum Nematoda the roundworms

Phylum Nematoda tiny, cylindrical, usually less than 2.5 cm inhabit virtually every environment (hot, cold, dirt, humans, acidic) highly selective on where they live so humans do not have to fear most parasitic roundworms separate male and female roundworms round & unsegmented longitudinal muscles only

Ascaris (Read pages 357-358) an intestinal roundworm which can harm its host if the person is sensitive to the chemicals the worm produces large compared to most roundworms, up to 30cm epidermis secretes a thick cuticle for support and protections from host’s digestive enzymes 2 openings one for ingestion at the anterior end one for excretions at the posterior end inner tube is the digestive canal

Ascaris (Read pages 357-358) a human intestinal parasite “a tube within a tube” only reproduces sexually not hermaphroditic intestine cuticle mouth anus

Phylum Annelida “little rings” the segmented worms

Segmented worms segmented externally and internally each external segment is separated internally by a septum most live in salt water, but there are some freshwater and soil worms “tube within a tube” body plan outer – muscle and skin (body wall) inner – digestive tract closed circulatory system

Class Oligochaeta “the earthworm” (life process chart) the most familiar of the segmented worms segments are numbered from the anterior to the posterior end segments 32-37 have a large swelling covering them known as the clitellum

Class Oligochaeta “the earthworm” Movement externally you can see setae tiny bristles on the ventral and lateral surface of the body four pairs on each segment two muscle layers to help with movement circular layer to lengthen and thin the worm longitudinal layer to shorten and thicken the worm

Class Oligochaeta “the earthworm” Nutrition eats vegetation, refuse, and decayed organic matter order of the digestive tract: mouth – found on ventral surface of the first segment pharynx – muscular structure for drawing in food esophagus – carries food to the crop crop – stores food temporarily gizzard – grinds the food intestine – digestion of the food anus – exit point

Class Oligochaeta “the earthworm” Circulation has a closed circulatory system blood will absorb nutrients and oxygen from the digestive tract and respiratory structures and carry them to tissues all throughout the body accomplished by two vessels and one accessory vessel dorsal blood vessel – carries blood to the anterior part of the body ventral blood vessel – carries blood to the posterior part of the body aortic arches (5) – surround the esophagus and connects the dorsal and ventral blood vessels

Earthworms dorsal blood vessel aortic arches ventral blood vessel

Class Oligochaeta “the earthworm” Respiration the small vessels off of the dorsal and ventral vessels come near to the epidermis and then oxygen and carbon dioxide diffuse across the epidermis the earthworm must be kept moist to accomplish this

Class Oligochaeta “the earthworm” Excretion nephridia tubelike structures found in pairs in every segment except the first three and the last it absorbs waste from the blood and excretes it out of the pores, known as nephridiospores, in the worm’s side

Class Oligochaeta “the earthworm” Nervous system ganglia mass of nerve tissue found above and below the pharynx a ventral nerve cord extends the length of the body sensitive to light, touch, and certain chemicals Reproduction earthworms are hermaphroditic read pages 361-362

Class Hirudinea “the leeches” has anterior and posterior suckers there is no head or clitellum present many feed on blood can consume several times their own weight in blood and they need several months to digest one meal