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KEY - Zoology Chapter 27 Worms and Mollusks Study Guide / Mr. Lemmons Section 27-1 / Flatworms Vocabulary Terms: acoelomate, coelom, pharynx, flame cell, ganglion, eyespot, hermaphrodite, fission, scolex, proglottid, testis 1. To what Kingdom do flatworms belong? Kingdom Animalia 2. To what Phylum do flatworms belong? Phylum Platyhelminthes 3. What are the key characteristics of flatworms? (bold in textbook) Flatworms are soft, flattened worms that have tissues and internal organ systems. They are the simplest animals to have three embryonic germ layers, bilateral symmetry, and cephalization. 4. Flatworms have bilateral symmetry. What does this mean? (p. 662) Only a single imaginary plane can divide the body into two equal halves; they have a left and right side. 5. Most flatworms exhibit cephalization and have a distinct head. What does cephalization mean? The concentration of sense organs and nerve cells at the front end of the body. 6. What are the three embryonic tissue layers? Ectoderm; Endoderm; Mesoderm 7. Diffusion helps flatworms perform what essential bodily functions? Respiration, excretion, and circulation. 8. Most parasitic flatworms do not have a complex digestive system or lack one completely. Why? They obtain nutrients from foods already digested by their host. 9. Some free-living flatworms reproduce asexually by fission. Describe this process. The organism splits into and each half grows new parts to become a complete organism. 10. Free-living marine or freshwater flatworms; turbellarians. Class Turbellaria 11. Internal or external flatworms that usually infect the internal organs of their host; flukes. Class Trematoda 12. As adults these parasitic flatworms are long and adapted to live inside the intestines of their hosts; tapeworms. Class Cestoda 13. Explain how walking barefoot affects a person’s chance of becoming infected with the blood fluke Schistosoma. If people go barefoot, the skin on the lower parts of their feet is exposed. Therefore, it is more likely that Schistosoma larvae will be able to penetrate the skin. 14. How can humans become infected with a tapeworm by eating meat from a cow? By eating undercooked or raw meat that contains the cyst form of the tapeworm. The cysts then mature into adult tapeworms in the human’s intestine. 27-2 Roundworms Vocabulary Terms: pseudocoelom, anus 15. To what Kingdom do roundworms belong? Kingdom Animalia 16. To what Phylum do roundworms belong? Phylum Nematoda 17. A single rotting apple can contain how many roundworms? 90,000 roundworms 18. What are the key characteristics of roundworms? (bold in textbook) Roundworms are unsegmented worms that have pseudocoeloms and digestive systems with two openings – a mouth and an anus. 19. Group of parasitic roundworms that are transmitted from host to host through biting insects, especially mosquitoes: Filarial Worms 20. Group of parasitic roundworms that cause malnutrition and are spread by eating food that are not washed properly: Ascarid Worms 21. Group of parasitic roundworms that us sharp teethlike structures to enter unprotected feet of a host: Hookworms 22. How is trichinosis transmitted and how could its transmission to humans be most easily interrupted? Eating raw or incompletely cooked pork. Avoid eating meat contaminated with Trichinella cysts and cook all meat thoroughly. 23. Draw a person with one leg affected by elephantiasis. (Figure 27-9) Figure 27-9 on page 691 24. Ascaris lumbricoides, a parasitic roundworm, can block the host's intestine absorbing the host's digested food. This can cause severe malnutrition. Blockage of the intestine can be severe enough that it causes death. List the 5 steps in the sequence of an Ascaris infection of a human being. (Figure 27-10) 1) A human ingests food or water containing Ascaris eggs; 2) The eggs travel to the small intestine and develop into larvae; 3) Larvae enter blood vessels and are carried to the lungs; 4) Larvae are coughed up and swallowed. They then travel to the small intestine where they develop maturity; 5) Eggs are released and leave the host in feces. 27-3 Annelids Vocabulary Terms: septum, setae, crop, gizzard, closed circulatory system, gills, nephridium, clitellum 25. To what Kingdom do annelids belong? Kingdom Animalia 26. To what Phylum do annelids belong? Phylum Annelida 27. What are the key characteristics of an annelid? (bold in textbook) Annelids are worms with segmented bodies. They have a true coelom that is lined with tissue derived from mesoderm. 28. Draw & label the three germ layers of an annelid showing its true coelom. (Figure 27-12) 29. Earthworm food digestion begins with food entering the mouth and waste exiting at the anus. In between the mouth and anus, list the digestive system organs and their functions. Mouth (food and soil enters) > pharynx (pumps food into esophagus) > esophagus (carries food to crop) > crop (food storage) > gizzard (grinds food) > intestine (nutrients are absorbed) > anus (exit for food waste) 30. Annelids have a ____________________ circulatory system. Closed circulatory system 31. How does an earthworm breath (respire)? Through their moist skin. 32. Two earthworms can fertilize each other’s eggs. True or False 33. Live in soil or freshwater; has only a few setae; includes earthworms. Class Oligochaeta 34. External parasites that feed on the blood and body fluids of their host; leeches. Class Hirudinea 35. Marine annelids with pairs of paddle like appendages, each of which carry setae; includes sandworms and bloodworms. Class Polychaeta 36. Earthworms grow up to 4 meters in the tropics; What length of castings (= feces) have been found? 18 centimeters in length 37. Describe the medicinal use of leeches. They suck in blood and reduce swelling after surgery; they also have an anti-clotting agent which helps relieve pressure and congestion in healing tissue 38. Describe how earthworms contribute to the health of plants. They aerate soil and create tunnels through which plant roots can grow and water can arrive. They also bring minerals from deeper soil to the surface, fertilize soil with their feces, and decompose soil. 27-4 Mollusks Vocabulary Terms: trochophore, foot, mantle, shell, visceral mass, radula, siphon, open circulatory system 39. To what Kingdom do mollusks belong? Kingdom Animalia 40. To what Phylum do mollusks belong? Phylum Mollusca 41. What are the key characteristics of a mollusk? (bold in textbook) Mollusks are soft-bodied animals that usually have an internal or external shell. 42. The mollusk phylum is diverse. But many mollusks share similar developmental stages. Many aquatic mollusks have a free-swimming larval stage called a trochophore (TRAHK-oh-fawr). Draw and label this stage. (Figure 27-20) 43. The body plan of most mollusks include a: foot, mantle, shell, and a visceral mass 44. Mollusks that are shell-less or single-shelled; move by using a muscular foot located on the ventral side; snails, slugs, sea hares, limpets, nudibranchs. Class Gastropoda 45. How can a shell-less gastropod protect itself? Land slugs hide under a rock or log; Sea hares squirt ink; Some nudibranchs have foul-tasting or poisonous chemicals; Some nudibranchs recycle the nematocysts from cnidarians, moving the stinging cells to their own surface. 46. Mollusks that have two shells held together by one or two powerful muscles; clams, oysters, mussels, and scallops. Class Bivalvia 47. How can a scallop move? Flapping their shells 48. Soft-bodied mollusks in which the head is attached to a single foot. The foot is divided into tentacles with sucking disks or arms; octopi, squid, cuttlefishes, and nautiluses. Class Cephalopoda 49. Concerning shells, how does an octopus compare with a squid? Octopi have no shell while squid have only a thin rod-like shell known as a pen. 50. How can mollusks be used to monitor environmental conditions? Some mollusks concentrate pollutants and microorganisms in their tissues. Scientists can check the levels of pollutants in mollusk tissue to monitor the level of pollutants in the environment in which the mollusks are found.