Download Zoology Chapter 27 Worms and Mollusks Study Guide

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.