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3 Phyla of Worms – Notes Common A long, thin invertebrate with BILATERAL symmetry, a nervous system, and Characteristics cephalization of All Worms Simplest animal to have a true organs like a brain! Reproduction - Sexual (hermaphroditic – male and female reproductive organs) First with and Asexual – Fission (breaking into pieces) Organ Systems! Many are parasites- (good/bad relationship) live on or in a host Three Phyla Characteristics of Flatworms A. Platyhelminthes (flatworms) B. Nematoda (roundworms) C. Annelida (segmented worms) A. Soft flattened worms with true tissues and internal organs. B. Simplest animals to have bilateral symmetry and cephalization. 1. Feeding – some carnivorous, most parasitic; one opening into gut; pharynx sucks in food and releases waste 2. Respiration/ Circulation/ Excretion – No respiratory No circulatory system, system; Obtain nutrients and oxygen by diffusion directly into cells. Simple excretory system of specialized cells. 3. Response/Movement – ganglia= groups of nerves in head control nervous system (like a brain); “ladder” of nerves run over body; eyespot detects light; move by cilia and squirming using outer layer of muscle tissue Diseases caused by Flatworms A. Flukes-Usually infect internal organs of host – Example: The blood fluke Schistosoma- causes tissue damage that could result in death B. Tapeworms – Long, flat, and have adaptations for life inside intestines of host Characteristics of Roundworms A. Body plan- First animals to have a one way digestive system with mouth and anus (tube within in a tube); B. First animals to have a fluid filled body cavity called a pseudocoelom- “false body cavity” 1. Feeding- many are carnivores with grasping mouthparts, some herbivores, many are parasites 2. Respiration/Circulation/ Excretion- No Respiratory or Circulatory Systems; rely on diffusion. Simple excretory organs. 3. Response/movement -have ganglia (brain) and simple nervous system, have muscular system and move like snakes Diseases caused by Roundworms Characteristics of Segmented worms A. Trichinella causes painful cysts in the muscle tissue of humans and other animalstransmitted by eating undercooked meat containing worm eggs B. Filarial worms cause Elephantiasis- fluid buildup that causes abnormally large limbs – transmitted through the bite of insects like mosquitos C. Ascarids cause malnutrition in humans, horses, cows, etc by filling the intestinal tract of its host and absorbing all nutrients D. Hookworms attach to the lungs and intestines and suck blood – common in humans(1/4 of world population); larvae pierce the skin & burrow into the body. Can severely damage internal organs. Transmitted through humans’ and other animals’ waste. (Wear Shoes!) A. Body Plan- tube within a tube, digestive system with mouth and anus; body divided into sections called septa that are specialized for different functions. First animals to have true circulatory system and coelom – body cavity. 1. Feeding- predators to filter feeders; use pharynx to get food, stored in crop, ground up in gizzard, absorbed in intestine. 2. Circulation/ Respiration/ Excretion- closed circulatory system with vessels; breath through gills or through skin; have excretory organs called nephridia 3. Response/Movement- have ganglia in each segment of the head, nervous system; move by contracting and relaxing muscles Intestine Clitellum Gizzard Anus Dorsal blood vessel Aortic Crop arches Brain Esophagus Ventral Blood Vessel Mouth Ecology of Segmented Worms Pharynx Ventral Nerve Cord Segments A. Aerate, mix, and fertilize the soil- have created some of the most fertile soils on earth! B. Tunnels provide passage ways for plant roots and water C. Important in the diets of many other animals such as birds, toads and snakes; marine annelids important in the diets of fishes, crabs, and lobsters