Section 1 Platyhelminthes Chapter 34 Structure and Function of Flatworms • The phylum _____________________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 _______________with dorsoventrally flattened bodies. • They exhibit ___________________.

Section 1 Platyhelminthes Chapter 34 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. • _______________ have a spade-shaped anterior end and a tapered posterior end.

Section 1 Platyhelminthes Chapter 34 Class Turbellaria, continued Digestion and Excretion in Planarians • Planarians feed on decaying plant or animal matter and smaller organisms. • Food is ingested through the _____________. • 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.

Section 1 Platyhelminthes Chapter 34 Class Turbellaria, continued Neural Control in Planarians • The planarian nervous system is more complex than the nerve net of cnidarians. • The _______________ serve as a simple brain. • A planarian’s nervous system gives it the ability to learn. • Planarians sense light with _______________. • Other sensory cells respond to touch, water currents, and chemicals in the environment.

Section 1 Platyhelminthes Chapter 34 Class Turbellaria, continued Reproduction in Planarians • Planarians are _________________ that can reproduce sexually or asexually. • Their eggs are laid in capsules. • During asexual reproduction, their body undergoes ___________ and the two halves regenerate missing parts.

Section 1 Platyhelminthes Chapter 34 Planarian

Section 1 Platyhelminthes Chapter 34 Exploration of a Flatworm

Section 1 Platyhelminthes Chapter 34 Development of Flatworm Embryo

Section 1 Platyhelminthes Chapter 34 Classes Trematoda and Monogenea • The classes Trematoda and Monogenea consist of parasitic ______________. • 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 _________________.

Section 1 Platyhelminthes Chapter 34 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 __________ as a primary hosts and __________ as intermediate hosts. They can cause schistosomiasis.

Section 1 Platyhelminthes Chapter 34 Life Cycle of Schistosoma

Section 1 Platyhelminthes Chapter 34 Class Cestoda • About 5,000 species of ______________ 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 ___________. • The body is a series of many sections called _________________. • Tapeworms have no light-sensing organs, no mouth, no gastrovascular cavity, and no digestive organs.

Section 1 Platyhelminthes Chapter 34 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, Taeniasaginatus. Its primary host is a human and its intermediate host is a cow. Its larvae form ___________in the muscle tissue of the cow.

Section 1 Platyhelminthes Chapter 34 Life Cycle of Beef Tapeworm

Section 2 Nematoda and Rotifera Chapter 34 Objectives • Describethe body plan of a nematode. • Outlinethe relationship between humans and parasitic roundworms. • Describethe anatomy of a rotifer.

Section 2 Nematoda and Rotifera Chapter 34 Phylum Nematoda • The phylum Nematoda is made up of _________________with long, slender bodies that taper at both ends. • Roundworms are among several phyla of __________________________. • Roundworms have a digestive tract with two openings. • Most roundworms have separate sexes and are covered by a protective cuticle. • Most species are free-living; some are parasites.

Section 2 Nematoda and Rotifera Chapter 34 Phylum Nematoda, continued 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 ___________ people worldwide.

Section 2 Nematoda and Rotifera Chapter 34 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. • Infection causes the disease trichinosis. Other Parasitic Roundworms • Pinworms, genus Enterobius, are common parasites of humans. They do not cause any serious disease. • ________________infect many people in tropical countries. The most dangerous ones infect the lymphatic system and may cause ___________________.

Section 2 Nematoda and Rotifera Chapter 34 Exploration of a Roundworm

Section 2 Nematoda and Rotifera Chapter 34 Phylum Rotifera • Members of the phylum Rotifera are called rotifers. • 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 ___________. • The digestive, reproductive, and excretory systems empty into the ______________. • Some species reproduce by ____________________.

Chapter 34 Standardized Test Prep Multiple Choice 1. What does a planarian use its pharynx for? A. feeding B. movement C. reproduction D. to respond to light

Chapter 34 Standardized Test Prep Multiple Choice, continued 1. What does a planarian use its pharynx for? A. feeding B. movement C. reproduction D. to respond to light

Chapter 34 Standardized Test Prep Multiple Choice, continued 2. Where do blood flukes of the genus Schistosoma reproduce asexually? F. in water G. inside a snail H. inside a cow’s intestine J. inside a human’s blood vessels

Chapter 34 Standardized Test Prep Multiple Choice, continued 3. What does a tapeworm use its scolex for? A. to reproduce B. to attach itself to its host C. to eliminate excess water D. to force food into its mouth

Chapter 34 Standardized Test Prep Multiple Choice, continued 4. Which of the following is true of most rotifers? F. They are parasitic. G. They live in the soil. H. They feed with the help of cilia. J. They have a gastrovascular cavity.

Chapter 34 Standardized Test Prep Multiple Choice, continued The figure below shows the internal structure of a planarian of the genus Dugesia. Use the figure to answer the questions that follow.

Chapter 34 Standardized Test Prep Multiple Choice, continued 5. What type of animal is shown in the figure? A. flatworm B. tapeworm C. roundworm D. rotifer

Chapter 34 Standardized Test Prep Multiple Choice, continued 6. What is the structure labeled X? F. the brain G. the mouth H. an eyespot J. a nerve cord

Chapter 34 Standardized Test Prep Multiple Choice, continued 7. What is the structure labeled Y? A. the mouth B. a flame cell C. an eyespot D. the gastrovascular cavity

Chapter 34 Standardized Test Prep Multiple Choice, continued 8. fluke : schistosomiasis :: filarial worm : F. trichinosis G. elephantiasis H. encysted meat J. swimmer’s itch

Chapter 34 Standardized Test Prep Multiple Choice, continued The figure below shows the internal structure of a rotifer. Use the figure to answer the question that follows.

Chapter 34 Standardized Test Prep Multiple Choice, continued 9. Which structures are involved in excretion? A. K and L B. L and O C. M and N D. M and P

Chapter 34 Standardized Test Prep Short Response Planarians and rotifers eliminate water through a network of excretory structures that run the length of the body. Explain why the excretory structures in planarians and rotifers are called flame cells.

Chapter 34 Standardized Test Prep Short Response, continued Planarians and rotifers eliminate water through a network of excretory structures that run the length of the body. Explain why the excretory structures in planarians and rotifers are called flame cells. Answer: The beating of the cilia in flame cells draws water from surrounding tissue. It is the motion of the cilia that resembles the flickering of a flame.

Chapter 34 Standardized Test Prep Extended Response Base your answers to parts A & B on the information below. Parasitic flatworms have life cycles that include primary and intermediate hosts. Part A Distinguish between primary and intermediate hosts in flatworms. Part B Sequence the life cycle of a beef tapeworm. Identify the primary and intermediate hosts.

Chapter 34 Standardized Test Prep Extended Response, continued Answer: Part A Primary hosts nourish the adult parasite. Intermediate hosts nourish the larval parasite. Part B: Adult tapeworms live in the intestines of the primary host, humans. Mature proglotids are shed in the feces and release eggs. Eggs ingested by cows, the intermediate host, develop into larvae, burrow to muscle tissue, and develop into adults when a human eats infected,undercooked beef.

Table of Contents