Ch 12 Instructor Guide

12: The Eukaryotes: Fungi, Algae, Protozoa, and Helminths

LEARNING OBJECTIVE CHECK YOUR UNDERSTANDING

12-1 List the defining characteristics of fungi.

Assume you isolated a single-celled organism that has a cell wall. How would you determine that it is a fungus and not a bacterium?

12-2 Differentiate asexual from sexual reproduction, and describe each of these processes in fungi.

Contrast the mechanism of conidiospore and ascospore formation.

12-3 List the defining characteristics of the three phyla of fungi described in this chapter.

List the asexual and sexual spores made by Zygomycetes, Ascomycetes, and Basidiomycetes.

12-4 Identify two beneficial and two harmful effects of fungi.

Are yeasts beneficial or harmful?

12-5 List the distinguishing characteristics of lichens, and describe their nutritional needs.

What is the role of the lichens in nature?

12-6 Describe the roles of the fungus and the alga in a lichen.

What is the role of the fungus in a lichen?

12-7 List the defining characteristics of algae.

How do algae differ from bacteria? From fungi?

12-8 List the outstanding characteristics of the five phyla of algae discussed in this chapter.

List the cell wall composition and diseases caused by the following algae: diatoms, dinoflagellates, oomycotes.

12-9 Identify two beneficial and two harmful effects of algae.

List the cell wall composition and diseases caused by the following algae: diatoms, dinoflagellates, oomycotes.

12-10 List the defining characteristics of protozoa.

Identify three differences between protozoa and animals.

12-11 Describe the outstanding characteristics of the seven phyla of protozoa discussed in this chapter, and give an example of each.

Do protozoa have mitochondria?

12-12 Differentiate an intermediate host Where does Plasmodium undergo sexual

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from a definitive host. reproduction?

12-13 Compare and contrast cellular slime molds and plasmodial slime molds.

Why are slime molds classified with amoeba and not fungi?

12-14 List the distinguishing characteristics of parasitic helminths.

Why are the drugs used to treat parasitic helminths often toxic to the host?

12-15 Provide a rationale for the elaborate life cycle of parasitic worms.

Of what value is the complicated life cycle of parasitic helminths?

12-16 List the characteristics of the two classes of parasitic platyhelminths, and give an example of each.

Differentiate Paragonimus and Taenia.

12-17 Describe a parasitic infection in which humans serve as a definitive host, as an intermediate host, and as both.

What is the definitive host for Enterobius?

12-18 List the characteristics of parasitic nematodes, and give an example of infective eggs and infective larvae.

What stage of Dirofilaria immitis is infectious for dogs and cats?

12-19 Compare and contrast platyhelminths and nematodes.

You find a parasitic worm in a baby’s diapers. How would you know whether it’s a Taenia or a Necator?

12-20 Define arthropod vector. Vectors can be divided into three major types, according to the roles they play for the parasite. List the three types of vectors and a disease transmitted by each.

12-21Differentiate a tick from a mosquito, and name a disease transmitted by each.

Assume you see an arthropod on your arm. How will you determine whether it is a tick or a flea?

NEW IN THIS EDITION

• Discussion of new uses of fungi as pesticides

• Expanded discussion of the oomycotes, including the introduction of Phytophthora into the United States; a new figure illustrating Phytophthora’s life cycle

• Discussion of heartworm

• A new Clinical Focus (MMWR) box highlighting cryptosporidial diarrhea, the most common pathogen associated with swimming

CHAPTER SUMMARY

Fungi (pp. 330–339)


1. Mycology is the study of fungi.

2. The number of serious fungal infections is increasing.

3. Fungi are aerobic or facultatively anaerobic chemoheterotrophs.

4. Most fungi are decomposers, and a few are parasites of plants and animals.

Characteristics of Fungi (pp. 331–333)

5. A fungal thallus consists of filaments of cells called hyphae; a mass of hyphae is called a mycelium.

6. Yeasts are unicellular fungi. To reproduce, fission yeasts divide symmetrically, whereas budding yeasts divide asymmetrically.

7. Buds that do not separate from the mother cell form pseudohyphae.

8. Pathogenic dimorphic fungi are yeastlike at 37°C and moldlike at 25°C.

9. Fungi are classified according to rRNA.

10. Sporangiospores and conidiospores are produced asexually.

11. Sexual spores are usually produced in response to special circumstances, often changes in the environment.

12. Fungi can grow in acidic, low-moisture, aerobic environments.

13. They are able to metabolize complex carbohydrates.

Medically Important Phyla of Fungi (pp. 333–335)

14. The Zygomycota have coenocytic hyphae and produce sporangiospores and zygospores.

15. The Ascomycota have septate hyphae and produce ascospores and frequently conidiospores.

16. Basidiomycota have septate hyphae and produce basidiospores; some produce conidiospores.

17. Teleomorphic fungi produce sexual and asexual spores; anamorphic fungi produce asexual spores only.

Fungal Diseases (pp. 335–339)

18. Systemic mycoses are fungal infections deep within the body that affect many tissues and organs.

19. Subcutaneous mycoses are fungal infections beneath the skin.

20. Cutaneous mycoses affect keratin-containing tissues such as hair, nails, and skin.

21. Superficial mycoses are localized on hair shafts and superficial skin cells.

22. Opportunistic mycoses are caused by fungi that are not usually pathogenic.

23. Opportunistic mycoses can infect any tissues. However, they are usually systemic.

Economic Effects of Fungi (p. 339)


24. Saccharomyces and Trichoderma are used in the production of foods.

25. Fungi are used for the biological control of pests.

26. Mold spoilage of fruits, grains, and vegetables is more common than bacterial spoilage of these products.

27. Many fungi cause diseases in plants.

Lichens (pp. 339–340)

1. A lichen is a mutualistic combination of an alga (or a cyanobacterium) and a fungus.

2. The alga photosynthesizes, providing carbohydrates for the lichen; the fungus provides a holdfast.

3. Lichens colonize habitats that are unsuitable for either the alga or the fungus alone.

4. Lichens may be classified on the basis of morphology as crustose, foliose, or fruticose.

Algae (pp. 340–345)

1. Algae are unicellular, filamentous, or multicellular (thallic).

2. Most algae live in aquatic environments.

Characteristics of Algae (pp. 341–342)

3. Algae are eukaryotic; most are photoautotrophs.

4. The thallus of multicellular algae usually consists of a stipe, a holdfast, and blades.

5. Algae reproduce asexually by cell division and fragmentation.

6. Many algae reproduce sexually.

7. Photoautotrophic algae produce oxygen.

8. Algae are classified according to their structures and pigments.

Selected Phyla of Algae (pp. 342–344)

9. Brown algae (kelp) may be harvested for algin.

10. Red algae grow deeper in the ocean than other algae.

11. Green algae have cellulose and chlorophyll a and b and store starch.

12. Diatoms are unicellular and have pectin and silica cell walls; some produce a neurotoxin.

13. Dinoflagellates produce neurotoxins that cause paralytic shellfish poisoning and ciguatera.

14. The oomycotes are heterotrophic; they include decomposers and pathogens.

Roles of Algae in Nature (p. 344–345)

15. Algae are the primary producers in aquatic food chains.


16. Planktonic algae produce most of the molecular oxygen in the Earth’s atmosphere.

17. Petroleum is the fossil remains of planktonic algae.

18. Unicellular algae are symbionts in such animals as Tridacna.

Protozoa (pp. 345–351)

1. Protozoa are unicellular, eukaryotic chemoheterotrophs.

2. Protozoa are found in soil and water and as normal microbiota in animals.

Characteristics of Protozoa (p. 346)

3. The vegetative form is called a trophozoite.

4. Asexual reproduction is by fission, budding, or schizogony.

5. Sexual reproduction is by conjugation.

6. During ciliate conjugation, two haploid nuclei fuse to produce a zygote.

7. Some protozoa can produce a cyst that provides protection during adverse environmental conditions.

8. Protozoa have complex cells with a pellicle, a cytostome, and an anal pore.

Medically Important Phyla of Protozoa (pp. 346–351)

9. Archaezoa lack mitochondria and have flagella; they include Trichomonas and Giardia.

10. Microsporidia lack mitochondria and microtubules; microsporans cause diarrhea in AIDS patients.

11. Amoebozoa are amoeba; they include Entamoeba and Acanthamoeba.

12. Apicomplexa have apical organelles for penetrating host tissue; they include Plasmodium and Cryptosporidium.

13. Ciliophora move by means of cilia; Balantidium coli is the human parasitic ciliate.

14. Euglenozoa move by means of flagella and lack sexual reproduction; they include Trypanosoma.

Slime Molds (pp. 351–352)

1. Cellular slime molds resemble amoebas and ingest bacteria by phagocytosis.

2. Plasmodial slime molds consist of a multinucleated mass of protoplasm that engulfs organic debris and bacteria as it moves.

Helminths (pp. 352–361)

1. Parasitic flatworms belong to the Phylum Platyhelminthes.

2. Parasitic roundworms belong to the Phylum Nematoda.


Characteristics of Helminths (pp. 353–355)

3. Helminths are multicellular animals; a few are parasites of humans.

4. The anatomy and life cycle of parasitic helminths are modified for parasitism.

5. The adult stage of a parasitic helminth is found in the definitive host.

6. Each larval stage of a parasitic helminth requires an intermediate host.

7. Helminths can be monoecious or dioecious.

Platyhelminths (pp. 356–358)

8. Flatworms are dorsoventrally flattened animals; parasitic flatworms may lack a digestive system.

9. Adult trematodes, or flukes, have an oral and ventral sucker with which they attach to host tissue.

10. Eggs of trematodes hatch into free-swimming miracidia that enter the first intermediate host; two generations of rediae develop; the rediae become cercariae that bore out of the first intermediate host and penetrate the second intermediate host; cercariae encyst as metacercariae; the metacercariae develop into adults in the definitive host.

11. A cestode, or tapeworm, consists of a scolex (head) and proglottids.

12. Humans serve as the definitive host for the beef tapeworm, and cattle are the intermediate host.

13. Humans serve as the definitive host and can be an intermediate host for the pork tapeworm.

14. Humans serve as the intermediate host for Echinococcus granulosus; the definitive hosts are dogs, wolves, and foxes.

Nematodes (pp. 358–361)

15. Roundworms have a complete digestive system.

16. The nematodes that infect humans with their eggs include (pinworm) Ascaris.

17. The nematodes that infect humans with their larvae include hookworm and Trichinella.

Arthropods as Vectors (pp. 361–363)

1. Jointed-legged animals, including ticks and insects, belong to the Phylum Arthropoda.

2. Arthropods that carry diseases are called vectors.

3. Vectorborne diseases are most effectively eliminated by controlling or eradicating the vectors.

THE LOOP


This chapter is divided so that you can select the units that meet the needs of your class.

Study QuestionsFungi (pp. 330–339) Review 1, 2, 4; Clinical 2Algae (pp. 340–345) Review 3Lichens (pp. 339–340) Review 3Protozoa (pp. 345–351, 355) Review 5, 6; Critical Thinking 3; Clinical 3Slime molds (pp. 351–352) Review 4; Critical Thinking 1Helminths (pp. 352–361) Review 7, 8, 9; Critical Thinking 2; Clinical 1Arthropods (pp. 361–363) Review 15

Detailed discussions of diseases caused by fungi, protozoa, and helminths appear in Part Four. If this chapter does not fit into the lecture portion of your course, you might assign it as self-study in conjunction with Part Four or laboratory exercises. Students might complete the Study Questions prior to the laboratory periods. The chapter test could be used as a posttest after students complete the laboratory exercises.

ANSWERS

Review

1. a. Systemic c. Cutaneous e. Systemic

b. Subcutaneous d. Superficial

2. a. E. coli

b. P. chrysogenum

3. As the first colonizers on newly exposed rock or soil, lichens are responsible for the chemical weathering of large inorganic particles and the consequent accumulation of soil.

4. Cellular slime molds exist as individual amoeboid cells. Plasmodial slime molds are multinucleate masses of protoplasm. Both survive adverse environmental conditions by forming spores.

5. a. Flagella e. Pseudopods i. Cilia

b. Giardia f. Entamoeba j. Balantidium

c. None g. None k. Flagella

d. Nosema h. Plasmodium l. Trypanosoma

6. Trichomonas cannot survive for long outside a host because it does not form a protective cyst. Trichomonas must be transferred from host to host quickly.

7. Ingestion.

8. Phylum: Platyhelminthes

Class: Trematode


9. The male reproductive organs are in one individual, and the female reproductive organs in another. Nematodes belong to the Phylum Aschelminthes.

Critical Thinking

1. Plasmodial slime molds have an internal transport system, called protoplasmic streaming, to ensure circulation.

2. Fish (larva) < Ingestion of fish > Mammal (adult)

Ingestion of eggs

Mammals (e.g., bears) are a more likely part of the freshwater ecosystem, so parasites would evolve to use mammalian hosts.

3. Phylum: Protozoa

Class: Mastigophora

Host: Human

Vector: Tsetse fly

Clinical Applications

1. Taenia solium; ingestion of tapeworm eggs excreted by a household member. Prevention: handwashing to break the fecal–oral cycle.

2. Coccidioides immitis; inhalation of arthrospores. Prevention: avoid working in contaminated soils.

3. Malaria; transmitted by bite of Anopheles mosquito.

CASE STUDY: THE UNFORTUNATE ALASKAN FISHING TRIP

Background

The Alaska Department of Public Health was notified that foodborne illness had occurred in fishermen aboard a fishing boat off the Alaska peninsula. The fishermen had eaten baked fish, steamed clams and mussels, boiled rice, boiled potatoes, and green salad. No alcohol was consumed.

Data

Case Symptoms Onset (hr) Foods Eaten

Clams Mussels Salmon Halibut RicePotatoes

1None — 1 x x

2 Vomiting; numbness around 2.5 4–5 x xmouth; lower back pain


3None — x x

4 Numbness of tongue and 2 5 x xjaw; tingling of fingers

5 Numbness and tingling of 1.5face and hands; dizziness

6None — 1 raw x x

7None — 1 x x

8None — 1 raw x x

9 Numbness and tingling 0.5 25–30 xaround mouth, face, and fingers; cardiopulmonary arrest. Died.

10 Vomiting; numbness of lips 2 4–5 x xand fingers; lower back pain

11 Vomiting; numbness of 1 12 x xthroat, toes, and fingers; perioral numbness

12 Lower back pain 2 6–7 x x

13 Nausea 0.5 2 x x

14 Numbness of face; paralysis 1 20–25 xof legs

15 Vomiting; numbness and 1 18–24 xtingling of jaws and arms; loss of consciousness

16 None — 1 x

17 None — x x

18 Vomiting; numbness of 2 3–4 x xmouth; tingling of fingers and toes

19 Vomiting; tingling of mouth, 2 6–7 x x


face, and fingers

20 Numbness of face and 1.5 10 xhands; dizziness

21 Paralysis of right arm; lower 1.5 15–20 xback pain

Questions

1. Identify the etiologic agent of this outbreak of food poisoning.

2. Was it food infection or intoxication?

3. How did the food get contaminated, and what item was contaminated?

4. Briefly explain how you arrived at your conclusion.

Hints

1. Make a summary table of the persons not ill.

2. Make a table of the onset of symptoms following eating.

The Solution

1. Paralytic shellfish poisoning (PSP) caused by Alexandrium toxin.

2. Intoxication.

3. Mollusks can become toxic when toxin-producing dinoflagellates create massive algal blooms known as “red tides.”

4. The diagnosis of PSP is based on patient exposure history and clinical manifestations.


Ch 12 Instructor Guide

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