Eukaryotes Notes

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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 four 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.	Why are microsporidia classified as fungi? Are yeasts beneficial or harmful?
12-5    List the distinguishing characteristics of lichens, and describe their nutritional needs.	What is the role of 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, and oomycotes.
12-9    Identify two beneficial and two harmful effects of algae.
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 from a definitive host.	Where does Plasmodium undergo sexual reproduction?
12-13  Compare and contrast cellular slime molds and plasmodial slime molds.	Why are slime molds classified with amebae 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.
12-21  Differentiate 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?

 

Fungi (pp. 320–331)

ASM 6.2: Microorganisms provide essential models that give us fundamental knowledge about life processes.

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. 321–325)

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 parent cell form pseudohyphae.
8. Pathogenic dimorphic fungi are yeast-like at 37°C and mold-like 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 Fungi (pp. 326–328)

14. The Zygomycota have coenocytic hyphae and produce sporangiospores and zygospores.
15. Microsporidia lack mitochondria and microtubules; they cause diarrhea in AIDS patients.
16. The Ascomycota have septate hyphae and produce ascospores and frequently conidiospores.
17. Basidiomycota have septate hyphae and produce basidiospores; some produce conidiospores.
18. Teleomorphic fungi produce sexual and asexual spores; anamorphic fungi produce asexual spores only.

Fungal Diseases (pp. 328–330)

19. Systemic mycoses are fungal infections deep within the body that affect many tissues and organs.
20. Subcutaneous mycoses are fungal infections beneath the skin.
21. Cutaneous mycoses affect keratin-containing tissues such as hair, nails, and skin.
22. Superficial mycoses are localized on hair shafts and superficial skin cells.
23. Opportunistic mycoses are caused by fungi that are not usually pathogenic.
24. Opportunistic mycoses can infect any tissues. However, they are usually systemic.

Economic Effects of Fungi (pp. 330–331)

25. Saccharomyces and Trichoderma are used in the production of foods.
26. Fungi are used for the biological control of pests.
27. Mold spoilage of fruits, grains, and vegetables is more common than bacterial spoilage of these products.
28. Many fungi cause diseases in plants.

Lichens (pp. 331–332)

ASM 5.4: Microorganisms, cellular and viral, can interact with both human and non-human hosts in beneficial, neutral, or detrimental ways.

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. 332–337)

ASM 6.1: Microbes are essential for life as we know it and the processes that support life (e.g., in biogeochemical cycles and plant and/or animal microflora).

1. Algae are unicellular, filamentous, or multicellular (thallic).
2. Most algae live in aquatic environments.

Characteristics of Algae (pp. 332–337)

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. 334–336)

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. 337)

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. 337–342)

ASM 5.4: Microorganisms, cellular and viral, can interact with both human and non-human hosts in beneficial, neutral, or detrimental ways.

1. Protozoa are unicellular, eukaryotic chemoheterotrophs.
2. Protozoa are found in soil and water and as normal microbiota in animals.

Characteristics of Protozoa (pp. 337–338)

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 Protozoa (pp. 338–342)

9. Trichomonas and Giardia lack mitochondria and have flagella.
10. Euglenozoa move by means of flagella and lack sexual reproduction; they include Trypanosoma.
11. Amebae include Entamoeba and Acanthamoeba.
12. Apicomplexa have apical organelles for penetrating host tissue; they include Plasmodium and Cryptosporidium.
13. Ciliates move by means of cilia; Balantidium coli is the human parasitic ciliate.

Slime Molds (pp. 342–343)

1. Cellular slime molds resemble amebae 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. 343–351)

ASM 5.4: Microorganisms, cellular and viral, can interact with both human and non-human hosts in beneficial, neutral, or detrimental ways.

1. Parasitic flatworms belong to the phylum Platyhelminthes.
2. Parasitic roundworms belong to the phylum Nematoda.

Characteristics of Helminths (pp. 343–351)

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. 344–349)

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. 349–351)

15. Roundworms have a complete digestive system.
16. The nematodes that infect humans with their eggs include Ascaris, Trichuris, and Enterobius.
17. The nematodes that infect humans with their larvae include hookworms and Trichinella.

Arthropods as Vectors (pp. 351–353)

1. Jointed-legged animals, including ticks and insects, belong to the phylum Arthropoda.
2. Arthropods that carry diseases are called vectors.
3. Vector-borne diseases are most effectively eliminated by controlling or eradicating the vectors.