Interest Grabber

1. Interest Grabber Section 27-1 • Tapeworm Tales • Have you ever heard someone say, “That person eats so much and stays so thin, you’d think he has a tapeworm!” • 1. In the United States, the chance of having a tapeworm in your body is very rare. From clues in the above statement, how might a tapeworm affect an individual? Where would you most likely find a tapeworm in the body? • 2. On what do you think these tapeworms feed?

2. Section Outline Section 27-1 • 27–1 Flatworms A. What Is a Flatworm? B. Form and Function in Flatworms 1. Feeding 2. Respiration, Circulation, and Excretion 3. Response 4. Movement 5. Reproduction C. Groups of Flatworms 1. Turbellarians 2. Flukes 3. Tapeworms

3. Schistosome Life Cycle Primary host (human) Intermediate host(snail) Section 27-1 Flukes mature and reproduce sexually in the blood vessels of human intestines. Embryos are released and passed out with feces. Adult fluke Human intestine Embryo Ciliated larva Tailed larva After asexualreproduction, newlarvae are releasedfrom the snail into the water. They then infect humans, the primary host, by boring through their skin. Once in the water, embryos develop into swimming larvae that infect an intermediate host (snail).

4. Figure 27–3 The Anatomy of a Flatworm Section 27-1 Eyespot Freshwater flatworms have simple ganglia and nerve cords that run the length of the body. The excretory system consists of a network of tubules connected to flame cells that remove excess water and cell wastes. Ganglia Head Nervecords Gastrovascularcavity Flatworms use a pharynx to suck food into the gastrovascular cavity. Digested food diffuses from the cavity into other cells of the body. Eyespots in somespecies detect light. Excretorysystem Ovary Testes Mouth Pharynx Most flatworms are hermaphrodites, having male reproductive organs (testes) and female reproductive organs (ovaries) in the same organism. Flame cell Excretorytubule

5. Interest Grabber Section 27-2 • Too Small to Measure Up? • When digging in the soil, you can see many animals, such as insects, earthworms, and spiders. But there are many animals that you cannot see. Roundworms, for example, are so small that a shovelful of fertile soil may contain millions of these free-living worms. • 1. To see how long roundworms are, draw a line on a sheet of paper. The width of the line that you drew is the length of the shortest roundworms. Measure and record the width of the line. • 2. The width of the tip of your pinky finger is the length of the longest roundworms. Measure and record the width of your pinky. • 3. Based on this information, what is the range of length in roundworms?

6. Section Outline Section 27-2 • 27–2 Roundworms A. What Is a Roundworm? B. Form and Function in Roundworms 1. Feeding 2. Respiration, Circulation, and Excretion 3. Response 4. Movement 5. Reproduction C. Roundworms and Human Disease 1. Trichinosis-Causing Worms 2. Filarial Worms 3. Ascarid Worms 4. Hookworms D. Research on C. elegans

7. Diseases Caused by Roundworms Section 27-2 ORGANISM Trichinella Filiarial worms Ascaris Hookworms DISEASE Trichinosis Elephantiasis Ascaris infection/infestation Hookworm infection/infestation ROUTE OF INFECTION Eating undercooked meat containing larval cysts Bite of insect carrying filarial worms Eating unwashedfood contaminatedwith Ascaris Bare skin in contact with contaminated soil DESCRIPTION Larvae burrow into tissues of host, causing pain Worms block passage of fluids within lymph vessels, causing tissues to swell Worms in intestine block normal passage of food and absorption of nutrients Worms attach to intestinal wall and suck blood, causing weakness and poor growth

8. Interest Grabber Section 27-3 • Just Slinking or Wriggling in the Rain • Have you ever noticed that after a spring rain, earthworms come out of the soil and appear on driveways, in puddles, and on sidewalks? Why does this happen? • 1. An earthworm breathes through its skin. If its skin dries out, it cannot breathe. Why would an earthworm be more likely to “surface” during the rain than at other times? • 2. What types of weather conditions might be fatal for an earthworm?

9. Section Outline Section 27-3 • 27–3 Annelids A. What Is an Annelid? B. Form and Function in Annelids 1. Feeding and Digestion 2. Circulation 3. Respiration 4. Excretion 5. Response 6. Movement 7. Reproduction C. Groups of Annelids 1. Oligochaetes 2. Leeches 3. Polychaetes D. Ecology of Annelids

10. Compare/Contrast Table Section 27-3 Comparing Flatworms, Roundworms, and Annelids CHARACTERISTIC Shape Segmentation Body cavity Digestion and excretion Respiration FLATWORMS Flattened No Acoelomate Gastrovascular cavity with one opening only; flame cells remove metabolic wastes Through skin; no respiratory organs ROUNDWORMS Cylindrical with tapering ends No Pseudocoelomate Tube-within-a-tube digestive tract; opening at each end; metabolic wastes excreted through body wall Through skin; no respiratory organs ANNELIDS Cylindrical with tapering ends Yes Coelomate Tube-within-a-tube digestive tract; opening at each end; nephridia remove metabolic wastes Through skin; aquatic annelids breathe through gills

11. Compare/Contrast Table continued Section 27-3 Comparing Flatworms, Roundworms, and Annelids CHARACTERISTIC Circulation Response Movement Reproduction FLATWORMS No heart, blood vessels,or blood Simple brain; nerve cords run length of body; eyespot and other specialized cells that detect stimuli Gliding, twisting,and turning Sexual (hermaphrodites); asexual (fission) ROUNDWORMS No heart, blood vessels,or blood Several ganglia in head region; nerve cords run length of body; several types of sense organs Thrashing Sexual (primary males and females) ANNELIDS Blood circulated through blood vessels in closed circulatory system Well-developed nervous system with brain and several nerve cords; many sense organs Forward peristaltic movement Sexual (some are hermaphrodites; some have separate sexes)

12. Figure 27–16 The Anatomy of an Earthworm Anus Setae Body segments Dorsalblood vessel Gizzard Crop Clitellum Mouth Brain Ganglion Circular muscle Ventralblood vessel Ringvessels Reproductiveorgans Ganglia Nephridia Longitudinalmuscle Section 27-3

13. Interest Grabber Section 27-4 • The Same Yet Different • Have you ever eaten clams? Gone clamming? Seen clams in the supermarket? How about octopi? Have you ever seen an octopus in a movie or in an aquarium? • 1. Clams and octopi are members of the phylum Mollusca. Although they have similarities, they have some differences, too. What is one characteristic they share? • 2. What is one way that these animals differ from one another?

14. Section Outline Section 27-4 • 27–4 Mollusks A. What Is a Mollusk? B. Form and Function in Mollusks 1. Body Plan 2. Feeding 3. Respiration 4. Circulation 5. Excretion 6. Response 7. Movement 8. Reproduction C. Groups of Mollusks 1. Gastropods 2. Bivalves 3. Cephalopods D. Ecology of Mollusks

15. Compare/Contrast Table Section 27-4 Comparing the Three Major Groups of Mollusks MOLLUSK GROUP Gastropods Bivalves Cephalopods SHELL Shell-less orsingle-shelled Two shells held together by oneor two muscles Internal shell orno shell FOOT Muscular foot located on ventral side and used for movement Burrowing species have muscular foot. Surface-dwelling species have either no foot or a “reduced” foot. Head is attached to a single foot. The foot is divided into tentacles or arms. EXAMPLES Snail, slug, sea hare, nudibranch Clam, oyster, mussel, scallop Octopus, squid, cuttlefish, nautilus

16. Figure 27–21 The Mollusk Body Plan Section 27-4 Squid Snail Shell Mantle cavity Foot Gills Digestive tract Clam Earlymollusk

17. Figure 27–23 The Anatomy of a Clam Coelom Stomach Heart Shell Nephridium Adductor muscle Mouth Anus Excurrentsiphon Adductormuscle Incurrentsiphon Gills Mantle cavity Intestine Mantle cavity Foot Section 27-4