February 15, 2012
Chapter 34 Notes: Flatworms, Roundworms and Rotifers
Section 1 Platyhelminthes Section 2 Nematoda and Rotifera
34-1 Objectives
Summarize the distinguishing characteristics of flatworms.
Describe the anatomy of a planarian.
Compare free-living and parasitic flatworms.
Diagram the life cycle of a fluke.
Describe the life cycle of a tapeworm.
Structure and Function of Flatworms
· The phylum Platyhelminthes includes organisms called flatworms. · They are more complex than sponges but are the simplest animals with bilateral symmetry. · Their bodies develop from three germ layers: · ectoderm · mesoderm · endoderm · They are acoelomates with dorsoventrally flattened bodies. · They exhibit cephalization. · The classification of Platyhelminthes has undergone many recent changes.
Characteristics of Flatworms February 15, 2012
Class Turbellaria · The majority of species in the class Turbellaria live in the ocean. · The most familiar turbellarians are the freshwater planarians of the genus Dugesia. · Planarians have a spade-shaped anterior end and a tapered posterior end.
Class Turbellaria Continued
Digestion and Excretion in Planarians
· Planarians feed on decaying plant or animal matter and smaller organisms. · Food is ingested through the pharynx. · Planarians eliminate excess water through a network of excretory tubules. · Each tubule is connected to several flame cells. · The water is transported through the tubules and excreted from pores on the body surface.
Class Turbellaria Continued
Neural Control in Planarians
· The planarian nervous system is more complex than the nerve net of cnidarians. · The cerebral ganglia serve as a simple brain. · A planarian’s nervous system gives it the ability to learn. · Planarians sense light with eyespots. · Other sensory cells respond to touch, water currents, and chemicals in the environment.
Eyespots February 15, 2012
Class Turbellaria Continued
Reproduction in Planarians
· Planarians are hermaphrodites that can reproduce sexually or asexually. · Their eggs are laid in capsules. · During asexual reproduction, their body undergoes fission and the two halves regenerate missing parts.
Class: turbeIlaria
Classes Trematoda and Monogenea The classes Trematoda and Monogenea consist of parasitic flukes. · Some are endoparasites; others are ectoparasites.
Structure of Flukes · A fluke clings to the tissues of its host by an anterior sucker and a ventral sucker. · A fluke’s nervous system is similar to a planarian’s, but simpler. · The external surface of a fluke is covered by a protective layer called the tegument. February 15, 2012
Classes Trematoda and Monogenea Continued Reproduction and Life Cycle of Flukes · Most flukes have highly developed reproductive systems and are hermaphroditic. · Fertilized eggs are stored in a fluke’s uterus until they are ready to be released. · Flukes have complicated life cycles that involve more than one host species. · For example, the trematode blood flukes of the genus Schistosoma use humans as a primary hosts and snails as intermediate hosts. They can cause schistosomiasis.
Life Cycle of Flukes
Class Cestoda · About 5,000 species of tapeworms make up the class Cestoda. · Tapeworms can live in the intestines of almost all vertebrates.
Structure of Tapeworms · Tapeworms are surrounded by a tegument. · They attach to the host with a scolex. · The body is a series of many sections called proglottids. · Tapeworms have no light-sensing organs, no mouth, no gastrovascular cavity, and no digestive organs. February 15, 2012
Class Cestoda Continued Reproduction and Life Cycle of Tapeworms
· Nearly all tapeworms are hermaphrodites. Each proglottid contains male and female reproductive organs and little else. · New proglottids are added to the front of the tapeworm. Older proglottids grow, mature, and begin producing eggs. · Eggs in one proglottid are usually fertilized by sperm from a different proglottid, possibly a different individual. · An example is the beef tapeworm, Taenia saginatus. Its primary host is a human and its intermediate host is a cow. Its larvae form cysts in the muscle tissue of the cow.
Life Cycle of a Tapeworm
Canine Tapeworm February 15, 2012
The Pork Tapeworm
Monsters Inside Me - The Pork Tapeworm
34-2 Nematoda and Rotifera
Objectives:
· Describe the body plan of a nematode.
· Outline the relationship between humans and parasitic roundworms.
· Describe the anatomy of a rotifer.
Phylum Nematoda ·· The phylum Nematoda isis mademade upup ofof roundwormsroundworms withwith long, long,slender slender bodies bodies that that taper taper at both at both ends. ends. ·· Roundworms are amongamong severalseveral phylaphyla ofof pseudocoelomates. ·pseudocoelomatesRoundworms have. a digestive tract with two openings. ·· MostRoundworms roundworms have have a digestive separate tract sexes with and two are openings. covered by a · Mostprotective roundworms cuticle have. separate sexes and are covered by ·aMost protective species cuticle are free-living;. some are parasites. · Most species are free-living; some are parasites. February 15, 2012
Phylum Nematoda Continued Ascarids Ascaris · The genus Ascaris infects pigs, horses, and humans. · The eggs enter hosts through contaminated food or water, develop into larvae in the intestines, and can infect the lungs. · The eggs are spread in the hosts’ feces.
Hookworms · Hookworms are intestinal parasites that feed on blood. · The eggs produce larvae in soil, and the larvae enter hosts through the feet. · Hookworms infect about one billion people worldwide.
Phylum Nematoda Continued Trichinella · The genus Trichinella infects humans and other mammals. · Adults live in intestines and larvae form cysts in muscles. · People usually become infected from undercooked pork. Bear meat too. · Infection causes the disease trichinosis.
Other Parasitic Roundworms · Pinworms, genus Enterobius, are common parasites of humans. They do not cause any serious disease. · Filarial worms infect many people in tropical countries. The most dangerous ones infect the lymphatic system and may cause elephantiasis. · Heartworm in dogs is a filarial worm
Monsters inside me - Filarial Worms, the 40 year parasite · (2:04 + :30 advertisement)
Baylisascaris sp. Also known as the raccoon roundworm, Baylisascaris is a parasite that can be deadly if ingested. If it makes its way to your brain it can cause blindness, paralysis and even death.
Monsters inside me - Baylisascaris February 15, 2012
Phylum Rotifera
· Members of the phylum Rotifera are called rotifers. 1750 species · Most rotifers are tiny, transparent, free-living animals that live in fresh water. · Some can survive without water for long periods. · Although tiny, they are truly multicellular and have specialized organ systems. · They use the crown of cilia around their mouth to sweep food into the mastax. · The digestive, reproductive, and excretory systems empty into the cloaca. · Some species reproduce by parthenogenesis.
34 Review -Flatworms Roundworms & Rotifers
1. Describe asexual reproduction in Planarians.
2. Describe physical characteristics of flatworms.
3. Explain the lack of circulatory and respiratory systems in flatworms.
4. Describe the cause of Schistosomiasis
5. Describe the relationship between the word “Turbellarians” and the phrase “free-living”
6. Discuss the anatomy of tapeworms and their relationship with humans.
7. To which phylum do roundworms belong?
8. Roundworms have a fluid-filled cavity called what?
9. How many openings does the Roundworm digestive tract have?
10. List the invertebrates that are other than coelomates. February 15, 2012
11. Explain why a roundworm’s digestive tract can be considered an advancement over a gastrovascular cavity.
12. Describe the nematode Ascaris lumbricoides how infects humans.
13. List the genus names of roundworms that live a parasitic life.
14. Describe what a rotifer uses to collect excess water in order to remove the water from the body.
15. Describe hermaphroditic of tapeworms. Discuss the reproductive nature of Planarians. Define and provide an example of parthenogenesis.
16. Describe the structure through which Tapeworms absorb food from the host.
17. Explain the steps by which humans can avoid trichinosis.
18. Describe a cloaca. List organisms you are studying that have this structure.
19. Describe the evolutionary history hypothesis of parasitic flatworms
20. Describe the nervous system of a planarian.