Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Phylum Platyhelminthes General Characterisitics • Bilateral symmetry • Acoelomate • Triploblastic • Dorsoventrally Flattened • Un-segmented bodies • Cephalization (has a head) Characteristics Cont. • 20,000 species • Actual organ systems present –Nervous, Digestive, Excretory Taxonomy • 3 Classes –Class Turbellaria –Class Trematoda –Class Cestoidea Class Turbellaria Planarians Free-living bottom-dwellers in aquatic environments few terrestrial species in the tropics 3,000+ species Vary widely in color, size, and shape Terrestrial ones can be up to 60cm Body Description 3 Layers Ectoderm Mesoderm Endoderm Acoelomate- have a solid mass of mesoderm cells between the ectoand endo- derms Acoelomate Design Locomotion As bottom dwellers the flat worms glide over the substrate (ground) Use cilia and muscular contractions Lay down a sheet of mucous as they travel (like slugs) Body Systems Digestive- can be simple or complex Pharynx: muscular ingestion organ Some digestion takes place outside the body Enzymes secreted on food particles; helps to break them down so the pharynx can swallow them easier. Digestive System Body System Con’t Respiratory- have none gases are exchanged over the epidermis Circulatory Protonephredia: fine networks of tubes that run the length of the body and collect waste Flame cells: bulb-like structures that force waste out of the body through openings called nephridiopores. Excretory System • Nervous: detecting and responding to environment –Simple: nerve net w/ Statocystssense gravity –Complex: nerve net and two main nerve cords with ladder like connections between • Auricles: chemoreception • Ocelli: eyespots; detect light Nervous System • Reproductive: –Most hermaphrodites –Exhibit both sexual and asexual • Asexual- transverse fission • Sexual- mutual sperm transfer Planarian Body Systems Class Trematoda • Parasitic flatworms (called flukes) • 1mm to 6cm in size • Most infect internal organs – can be blood or virtually any other organ Primary host = the host in which a parasite reproduces sexually Intermediate host = the host in which asexual reproduction occurs Fish Flukes • 30 million people infected in Asia • Caused by eating raw or improperly cooked fish • Resides in liver bile ducts • Causes fever, weight loss, joint aches, inflammation, hives, weakness, diarrhea, and an enlarged liver. Chinese Liver Fluke More Flukes • Liver Flukes –Live in the liver bile ducts of sheep and humans –Host infected by eating aquatic vegetation (watercress) • Schistosomes: blood flukes –Millions infected worldwide –Causes rash, fever, chills, inflammation, liver and spleen enlargement. Schistosoma mansoni - multiple host: Primary host = human Intermediate host = snail Causes Schistosomiasis -in humans; decays lungs liver, spleen, or intestines, occurs in tropical areas with poor sanitation/sewage. Blood Fluke Class Cestoidea • Tapeworms • 3,500 species • All are endo-parasites of vertebrates Lack a mouth and digestive tract Body consists of 3 main parts scolex: hold fast structure Strobila: the neck region Proglottids: reproductive sacs that make up 90 percent of the body Each mature proglottid is a hermaphrodite Testes produce sperm, fertilize the eggs to produce a zygote Zygotes are passed out through the feces. Sometimes, a dormant, protective cyst is formed in the intermediate host muscles ****This is why you should never eat incompletely cooked meat. Tapeworm Life cycle Tapeworm Life Cycle