chapter 20: fungi - coconinohighschool · decomposer: organism that breaks ... types of fungi, all...

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What You’ll Learn■ You will identify the charac-

teristics of the fungi kingdom.■ You will differentiate among

the phyla of fungi.

Why It’s ImportantFungi decompose organic mat-ter, cleaning the environmentand recycling nutrients. Theycreate food products and medi-cines. However, fungi can alsocause significant diseases inhumans and plants.

FungiFungi

Taylor F. Lockwood

Visit to• study the entire chapter

online• access Web Links for more

information and activities onfungi

• review content with theInteractive Tutor and self-check quizzes

This white ogre mushroom(Amanita virgineoides) is nativeto Japan. It grows on forestfloors, where it feeds on decomposing leaves.

Understandingthe Photo

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20.1SECTION PREVIEWObjectivesIdentify the basic charac-teristics of the fungi kingdom.Explain the role of fungias decomposers and howthis role affects the flowof both energy and nutri-ents through food chains.

Review Vocabularydecomposer: organism

that breaks down andabsorbs nutrients fromdead organisms (p. 47)

New Vocabularyhyphamyceliumchitinhaustoriabuddingsporangium

20.1 WHAT IS A FUNGUS? 529

The Characteristics of FungiFungi are everywhere—in the air and water, on damp basement walls,

in gardens, on foods, and sometimes even between people’s toes. Somefungi are large, bright, and colorful, whereas others are easily overlooked,as shown in Figure 20.1. Many have descriptive names such as stinkhorn,

Mysterious Rings ofMushroomsUsing Prior KnowledgeHave you ever seen mush-rooms that grow in a ringlike the one shown here?The visible mushrooms areonly one part of the fungus.Beneath the soil’s surface arethreadlike filaments that maygrow a long distance away from theabove-ground ring of mushrooms.These filaments can grow for a longtime before they produce the surface mushrooms.Mushrooms that grow in rings are only one of manytypes of fungi, all of which share certain characteristics.Infer Why does a mushroom fairy ring, such as the oneshown in the photo, take on a ring shape?

What is a fungus?

(t)Roger Wilmshurst/Photo Researchers, (bl)Mark Steinmetz, (bc)Joe McDonald/Visuals Unlimited, (br)Gary Retherford/Photo Researchers

Figure 20.1Fungi vary in form, size,and color.

Bird’s nest fungi look like nests,complete with eggs.

A Brightly colored coral fungiresemble ocean corals.

B A fungus killed this insect byfeeding on its tissues.

C

A ring of mushrooms

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530 FUNGIAaron Haupt

Food source

Spore Germinatingspore

MyceliumFigure 20.2A germinating fungalspore produces hyphaethat branch to form amycelium. DescribeWhat other tasks dohyphae carry out?

puffball, rust, or ringworm. Manyspecies grow best in moist environ-ments at warm temperatures between20°C and 30°C. You are, however,probably familiar with molds thatgrow at much lower temperatures onleft-over foods in your refrigerator.

Fungi used to be classified in theplant kingdom because, like plants,many fungi grow anchored in soil andhave cell walls. However, as biologistslearned more about fungi, they real-ized that fungi belong in their ownkingdom.

The structure of fungiAlthough there are a few unicellular

types of fungi, such as yeasts, mostfungi are multicellular. The basicstructural units of multicellular fungiare their threadlike filaments calledhyphae (HI fee) (singular, hypha),which develop from fungal spores, asshown in Figure 20.2. Hyphae elon-gate at their tips and branch exten-sively to form a network of filamentscalled a mycelium (mi SEE lee um).There are different types of hyphae ina mycelium. Some anchor the fungus,some invade the food source, and oth-ers form fungal reproductive struc-tures. Use the MiniLab on this page toobserve the hyphae of some breadmold you grow.

Observe and InferGrowing Mold Spores Any mold spore that arrives in a favorable place can germinate and produce hyphae. Can you identify a condi-tion necessary for the growth of bread mold spores?

Procedure! Place two slices of freshly baked bakery bread on a plate.

Sprinkle some water on one slice to moisten its surface.Leave both slices uncovered for several hours.

@ Sprinkle a little more water on the moistened slice, andplace both slices in their own plastic, self-seal bags. Trapair in each bag so that the plastic does not touch thebread’s surface. Then seal the bags and place them in adarkened area at room temperature.

# After five days, remove the bags and look for mold.$ Remove a small piece of mold with a forceps, place it on a

slide in a drop of water, and add a coverslip. Observe themold under a microscope’s low power and high power.CAUTION: Use caution when working with a microscope,glass slides, and coverslips. Wash your hands with soapand water after working with mold. Dispose of the moldas your teacher directs.

Analysis1. Observe and Infer Did you observe mold growth on the

moistened bread? On the dry bread? How does this experi-ment demonstrate that there are mold spores in yourclassroom?

2. Draw Conclusions What conclusions can you draw aboutthe conditions necessary for the growth of a bread mold?

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You can use a magnifying glass tosee individual hyphae in molds thatgrow on bread. However, the hyphaeof mushrooms are much more diffi-cult to see because they are tightlypacked, forming a dense mass.

Unlike plants, which have cell wallsmade of cellulose, the cell walls ofmost fungi contain a complex carbo-hydrate called chitin (KI tun). Chitingives the fungal cell walls bothstrength and flexibility.

Inside hyphaeIn many types of fungi, cross walls

called septa (singular, septum) dividehyphae into individual cells that con-tain one or more nuclei, Figure 20.3.Septa are usually porous, allowingcytoplasm and organelles to flowfreely and nutrients to move rapidlyfrom one part of a fungus to another.

Some fungi consist of hyphae withno septa. Under a microscope, yousee hundreds of nuclei streamingalong in a continuous flow of cyto-plasm. As in hyphae with septa, theflow of cytoplasm quickly and effi-ciently disperses nutrients and othermaterials throughout the fungus.

Adaptations in FungiFungi can be harmful. Some cause

food to spoil. Some cause diseases, andsome are poisonous. However, theyplay an important and beneficial role.In a world without fungi, hugeamounts of wastes, dead organisms,and debris, which consist of complexorganic substances, would litter Earth.Many fungi, along with some bacteriaand protists, are decomposers. Theybreak down complex organic sub-stances into raw materials that otherliving organisms need. Thanks to theseorganic decomposers, fallen leaves,animal carcasses, and other wastes areeliminated.

How fungi obtain foodUnlike plants and some protists,

fungi cannot produce their own food.Fungi are heterotrophs, and they usea process called extracellular diges-tion to obtain nutrients. In thisprocess, food is digested outside afungus’s cells, and the digested prod-ucts are then absorbed. For example,as some hyphae grow into the cells ofan orange, they release digestiveenzymes that break down the largeorganic molecules of the orange intosmaller molecules. These small mole-cules diffuse into the fungal hyphaeand move in the free-flowing cyto-plasm to where they are needed forgrowth, repair, and reproduction.The more a mycelium grows, themore surface area becomes availablefor nutrient absorption.

Summarize the roleof fungi in maintaining equilibrium,including decay in an ecosystem.


Figure 20.3Hyphae differ in structure.

Hyphae withoutsepta look likebranching,multinucleatecells.

B

Septa divide thehyphae of manytypes of fungiinto cells.

A

NucleiCytoplasm

Cytoplasm

Septum

Cell wall

Cell wall

Nuclei

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Different feeding relationshipsFungi have different types of food

sources. A fungus may be a sapro-phyte, a mutualist, or a parasitedepending on its food source.

Saprophytes are decomposers andfeed on waste or dead organic mate-rial. Mutualists live in a symbioticrelationship with another organism,such as an alga. Parasites absorbnutrients from the living cells of theirhosts. Parasitic fungi may producespecialized hyphae called haustoria,(huh STOR ee uh), which penetrateand grow into host cells where theydirectly absorb the host cells’ nutri-ents. You can see a diagram of hausto-ria invading host cells in Figure 20.4.

Reproduction in FungiDepending on the species and on

environmental conditions, a fungusmay reproduce asexually or sexually.Fungi reproduce asexually by fragmen-tation, budding, or producing spores.

Fragmentation and buddingIn fragmentation, pieces of hyphae

that are broken off a mycelium growinto new mycelia. For example, whenyou prepare your garden for planting,you help fungi in the soil reproduceby fragmentation. This is because,every time you dig into the soil, yourshovel slices through mycelia, frag-menting them. Most of the fragmentswill grow into new mycelia.

532 FUNGI

haustoria from theLatin word haurire,meaning “to drink”;The hyphae thatinvade the cells of a host to absorbnutrients are calledhaustoria.

(l)Mark Steinmetz, (r)Sherman Thompson/Visuals Unlimited

Fungalhypha

Haustorium Host cell

Fungi can produce haustoria that growinto host cells and absorb their nutrients.

B

Figure 20.4Fungi may be parasites, mutu-alists, or saprophytes.

A parasiticfungus is killingthis Americanelm tree.

A

The saprophyticturkey-tail fungus(Trametes versicolor)decomposes thetissues in this deadtree branch.

C

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The unicellular fungi called yeastsoften reproduce by a process called budding—a form of asexual repro-duction in which mitosis occurs and anew individual pinches off from theparent, matures, and eventually sepa-rates from the parent. You can see ayeast cell and its bud in Figure 20.5.

Reproducing by sporesRecall that a spore is a reproductive

cell that can develop into a new organ-ism. Most fungi produce spores. Whena fungal spore is transported to a placewith favorable growing conditions, athreadlike hypha emerges and beginsto grow, eventually forming a newmycelium. The mycelium becomesestablished in the food source.

In some fungi, after a while, spe-cialized hyphae grow away from therest of a mycelium and produce aspore-containing structure called a sporangium (spuh RAN jee uhm)(plural, sporangia)—a sac or case inwhich spores are produced. The tinyblack spots you see in a bread mold’smycelium are a type of sporangium.

In fact, for most fungi, the specializedreproductive hyphal structures wherethe fungal spores are produced areusually the only part of a fungus youcan see, and the sporangia often makeup only a very small fraction of thetotal organism.

Many fungi can produce two typesof spores—one type by mitosis andthe other by meiosis—at differenttimes during their life cycles. Oneimportant criterion for classifyingfungi into divisions is their patterns ofreproduction, especially sexual repro-duction, during the life cycle.

The adaptive advantages of spores

Many adaptive advantages of fungiinvolve spores and their production.First, the sporangia protect sporesand, in some cases, prevent them from drying out until they are ready tobe released. Second, most fungi pro-duce a large number of spores at onetime. For example, a puffball thatmeasures only 25 cm in circumferencecan produce about 1 trillion spores.


sporangium fromthe Greek wordssporos, meaning“seed,” andangeion, meaning“vessel”; Spores are produced in a sporangium.

(l)Ralph C. Eagle/Photo Researchers, (r)Simko/Visuals Unlimited

Most yeastsreproduceasexually bybudding.

A

Many fungi, suchas this bread mold,can produce sporesasexually.

B

Color-enhanced SEM Magnification: 2 250�

Figure 20.5Fungi reproduce asexuallyby budding, fragmentation,or spore production.

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Understanding Main Ideas1. Identify the characteristics of the fungi kingdom.2. Describe how a fungus obtains nutrients.3. What role do fungi play in food chains?4. How are the terms hypha and mycelium related?

Thinking Critically5. Imagine you are a mycologist (scientist who stud-

ies fungi) who finds an inhabited bird’s nest.

Explain why you would expect to find several dif-ferent types of fungi growing in the nest.

6. Measure in SI Outline the steps you would taketo calculate the approximate number of spores ina puffball fungus with a circumference of 10 cm.For more help, refer to Measure in SI in the SkillHandbook.

SKILL REVIEWSKILL REVIEW

534 FUNGI(l)William J. Weber/Visuals Unlimited, (r)Michael Fodgen/Earth Scenes

Producing so many spores increasesthe germination rate and improves thespecies survival chances.

Finally, fungal spores are small andlightweight and can be dispersed bywind, water, and animals such as birdsand insects. The wind will dispersethe spores that the puffballs you see inFigure 20.6 are releasing. Spores dis-persed by wind can travel hundreds ofkilometers. In the Problem-Solving Labon this page, you can learn about thedispersal methods of a plant fungusthat causes the disease called chestnutblight in chestnut trees.

Figure 20.6A passing animal or the pressure of raindropsmay have caused these puffballs to dischargethe cloud of spores that will be dispersed bythe wind.

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Analyze InformationWhy are chestnut trees sorare? The American chestnuttree (Castanea dentata) hasalmost disappeared from theUnited States, Italy, and Francebecause of a disease known aschestnut blight, which is causedby the fungus Cryphonectriaparasitica. Since 1900, three tofour billion trees have been lostto chestnut blight.

Solve the ProblemFact: Spores of C. parasitica land on the bark of Americanchestnut trees and germinate. Hyphae grow below the barkand form a canker (diseased tissue) that spreads, producinglarge areas of dead tissue. Eventually, the nutrient and watersupplies of the tree are cut off, and the tree dies.Fact: C. parasitica reproduces by forming spores that are car-ried by wind, insects, birds, and rain to other trees that thenbecome infected.Fact: The Japanese chestnut tree Castanea crenata is resistantto the C. parasitica fungus. This resistance is partially due tothe existence of weak fungal strains that cannot kill their host.

Thinking Critically1. Predict Why would it be difficult to control the disease by

preventing spores from landing on healthy trees?2. Interpret Data Based on how this fungus grows, why

can’t fungicides applied to the bark of an infected tree killthe fungus?

3. Describe Suggest a solution to the problem in the UnitedStates knowing about the resistance of the Japanese chest-nut species and the existence of weak disease-causing fungal strains. (Hint: Think about DNA technology.)

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The Diversity of Fungi20.2

ZygomycotesHave you ever taken a slice of bread from a bag and seen some black spots

and a bit of fuzz on the bread’s surface? If so, then you have probably seenRhizopus stolonifer, a common bread mold. Rhizopus is probably the mostfamiliar member of the phylum Zygomycota (zy goh mi KOH tuh). Manyother members of about 1000 species of zygomycotes are also decomposers.Zygomycotes reproduce asexually by producing spores. They produce adifferent type of spore when they reproduce sexually. The hyphae ofzygomycotes do not have septa that divide them into individual cells.

Growth and asexual reproductionWhen a Rhizopus spore settles on a moist piece of bread, it germinates

and hyphae begin to grow. Some hyphae called stolons (STOH lunz) growhorizontally along the surface of the bread, rapidly producing amycelium. Some other hyphae form rhizoids (RI zoydz) that penetratethe food and anchor the mycelium in the bread. Rhizoids secrete enzymesneeded for extracellular digestion and absorb the digested nutrients.

Asexual reproduction begins when some hyphae grow upward anddevelop sporangia at their tips. Asexual spores develop in the sporangia.When a sporangium splits open, hundreds of spores are released.

SECTION PREVIEWObjectivesIdentify the four majorphyla of fungi.Distinguish among theways spores are producedin zygomycotes, ascomy-cotes, and basidiomycotes.Summarize the ecologicalroles of lichens and mycorrhizae.

Review Vocabularyspore: type of haploid (n)

reproductive cell thatforms a new organismwithout the fusion ofgametes (p. 508)

New Vocabularystolonrhizoidzygosporegametangiumascusascosporeconidiophoreconidiumbasidiumbasidiosporemycorrhizalichen

Zygomycotes Ascomycotes

Basidiomycotes Deuteromycotes

Classify As you read Section 20.2, list the characteristics of the four major phyla of fungi under the appropriate tab.

Label each tab as shown.

Draw a mark at the midpoint of a sheet of paper along the side edge. Then fold the top and bottom edges in to touch the midpoint.

Fold in half from side to side.

Open and cut along the inside fold lines to form four tabs.

STEP 1

STEP 3

STEP 2

STEP 4

Fungi Make the following Foldable to help you organizethe main characteristics of the four major phyla of fungi.

20.2 THE DIVERSITY OF FUNGI 535

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Those that land on a moist food sup-ply germinate, form new hyphae, andreproduce asexually again.

Producing zygosporesSuppose that the bread on which

Rhizopus was growing began to dryout. This unfavorable environmentalcondition could trigger the fungus toreproduce sexually. When zygomy-cotes reproduce sexually, they pro-duce zygospores (ZI guh sporz),which are thick-walled spores that canwithstand unfavorable conditions.

Sexual reproduction in Rhizopusoccurs when haploid hyphae from twocompatible mycelia, called plus andminus mating strains, grow togetherand fuse. Where the haploid hyphae

fuse, they each form a gametangium(ga muh TAN ghee uhm), a structurecontaining a haploid nucleus. Whenthe haploid nuclei of the two gametan-gia fuse, a diploid zygote forms. Thezygote develops a thick wall, becominga dormant zygospore.

A zygospore may remain dormantfor many months, surviving periods ofdrought, cold, and heat. When envi-ronmental conditions are favorable,the zygospore absorbs water, under-goes meiosis, and germinates to pro-duce a hypha with a sporangium.Each haploid spore formed in thesporangium can grow into a newmycelium. Look at Figure 20.7 to seehow Rhizopus reproduces both sexu-ally and asexually.

536 FUNGI(l)James Richardson/Visuals Unlimited, (r)John D. Cunningham/Visuals Unlimited

Asexual Reproduction Sexual Reproduction

Meiosis

Germination

Zygospore

Sporangium

Hypha

Spores (n)

Sporangia

Rhizoids

Stolon

+ Matingstrain (n)

– Matingstrain (n)

Gametangia

Spores (n)

Figure 20.7During its life cycle, the black bread mold,Rhizopus stolonifera,reproduces both asexu-ally and sexually.

LM Magnification: 100� LM Magnification: 27�

These Rhizopussporangia arefilled withthousands ofhaploid spores.

BZygospores formwhere gametangiahave fused.

A

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AscomycotesThe Ascomycota is the largest phy-

lum of fungi, containing about 30 000species. The ascomycotes are alsocalled sac fungi. Both names refer totiny saclike structures, each called anascus, in which the sexual spores ofthe fungi develop. Because they areproduced inside an ascus, the sexualspores are called ascospores.

During asexual reproduction, asco-mycotes produce a different kind ofspore. Fungal hyphae grow up fromthe mycelium and elongate to form conidiophores (kuh NIH dee uh forz).Chains or clusters of asexual sporescalled conidia develop from the tipsof conidiophores. Wind, water, andanimals disperse these haploid spores.Some conidia and conidiophores areshown in Figure 20.8.

Important ascomycotesYou’ve probably encountered a few

types of sac fungi in your refrigeratorin the form of blue-green, red, andbrown molds on decaying foods.Other sac fungi are familiar to farmersand gardeners because they causeplant diseases such as apple scab andergot of rye. Learn more about thedangers of fungi in the Connection toSocial Studies at the end of this chapter.

Not all sac fungi have a bad reputa-tion. Ascomycotes can have many different forms, as you can see inFigure 20.9. Morels and truffles aretwo edible members of this phylum.Perhaps the most economicallyimportant ascomycotes are the yeasts.

Yeasts are unicellular sac fungi thatrarely produce hyphae and usuallyreproduce asexually by budding.Yeasts are anaerobes and ferment sug-ars to produce carbon dioxide andethyl alcohol. Because yeasts producealcohol, they are used to make wineand beer. Other yeasts are used in

baking because they produce carbondioxide, the gas that causes breaddough to rise and take on a light, airytexture. Use the BioLab at the end ofthis chapter to experimentally deter-mine the temperature at which yeastsfunction most efficiently.

Yeasts are also important tools forresearch in genetics because they havelarge chromosomes. A vaccine for thedisease hepatitis B is produced bysplicing human genes with those ofyeast cells. Because yeasts multiplyrapidly, they are an important sourceof the vaccine.

537(t)Dr. Dennis Kunkel/Phototake, NYC, (bl)Matt Meadows, (br)David Dennis/Tom Stack & Associates

Figure 20.9Many ascomycotes are cupshaped or have cup-shapedindentations that are linedwith asci.

The orangecuplikestructures ofthis ascomycoteare visible onthe dead bark.

B

Morels are prized fortheir flavor.

A

Color-enhanced SEM Magnification: 305�

Figure 20.8Most ascomycotesreproduce asexually by producing conidia in structures calledconidiophores.

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Figure 20.10Basidiomycotes have many differ-ent forms, and what you see aretheir reproductive structures.

A typical mushroom, suchas this Mycena, has a capthat sits on top of a stalk.

C

BasidiomycotesOf all the diverse kinds of fungi, you

are probably most familiar with someof the about 25 000 species in thephylum Basidiomycota. Mushrooms,puffballs, stinkhorns, bird’s nest fungi,and bracket fungi are all basidiomy-cotes. So are the rust and smut fungi.Use the MiniLab to distinguish somemushroom species.

Basidia and basidiosporesBasidiomycotes have club-shaped

hyphae called basidia (buh SIHD ee uh)that produce spores and give themtheir common name—club fungi.Basidia usually develop on short-lived,visible reproductive structures thathave varied shapes and sizes, as youcan see in Figure 20.10. Spores calledbasidiospores are produced in basidiaduring reproduction.

A basidiomycote, such as a mush-room, has a complex reproductivecycle. How does a mushroom repro-duce? Study Figure 20.11 to find out.

538

ClassifyExamining Mushroom GillsSpore prints can often help in mush-room identification by revealing thepattern of a mushroom’s gills and thecolor of its spores. Use this techniqueto see how a mushroom’s gills arearranged.

Procedure! Break off the stalks from some grocery

store mushrooms. Place the caps in apaper bag for a few days.

@ When the undersides of the caps are very dark brown, setthe caps, gill side down, on a white sheet of paper. Be surethat the gills are touching the surface of the paper.

# After leaving the caps undisturbed overnight, carefully liftthe caps from the paper and observe the results.

$ Wash your hands with soap and water. Dispose of fungi asyour teacher directs.

Analysis1. Observe What color are the spores on the paper?2. Compare How does the pattern of spores on the paper

compare with the arrangement of gills on the undersideof the mushroom cap that produced it?

Shelf fungi, such as this sulfur shelf, oftengrow on tree branches and fallen logs.

B

Smuts are parasites thatattack plants such as corn.

A

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20.2 THE DIVERSITY OF FUNGI 539Mark Steinmetz

Meiosis

+ Mating typeBasidiospore

Stipe

Gills

Cap

Button

Newmycelium

– Mating type

+ –

Basidiospores

Basidium

Haploid nuclei fu

seBasidia

Stalk and cap Above ground,a mushroom consists of a stalkthat supports a cap.

AA

Spore germinationWhen a basidiospore germinates, it produceshyphae of either matingstrain � or �.

CC

Hyphae fusionWhen differenthyphae meet, theyfuse and form anew myceliumcontaining cellswith two haploidnuclei.

DD

Button formation Themycelium forms a compactmass, a button, just belowthe soil’s surface. A buttondevelops into a stalk and cap.

EE

Spore productionIn the basidia, haploidnuclei fuse. Meiosisoccurs, producing fourhaploid nuclei thatdevelop intobasidiospores.

FF

Gills The undersides of mostcaps have thin sheets of tissue,called gills, which contain basidiathat produce basidiospores. Winddisperses mature spores.

BB

Mycena pura

The Life of a MushroomFigure 20.11What you call a mushroom is a reproductive structure of the fun-gus. Most of the fungus is underground and not visible. A singlemushroom can produce hundreds of thousands of spores as aresult of sexual reproduction. Most types of mushrooms have noasexual reproductive stages in their life cycle. Critical ThinkingWhy are spores of mushrooms produced above ground?

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DeuteromycotesThere are about 25 000 species of

fungi classified as deuteromycotes,which have no known sexual stage intheir life cycle, unlike the zygomy-cotes, ascomycotes, and basidiomy-cotes. Although the deuteromycotesmay only be able to reproduce asexu-ally, another possibility is that theirsexual phase has not yet beenobserved by mycologists, biologistswho study fungi.

Diverse deuteromycotesIf you’ve ever had strep throat,

pneumonia, or other kinds of bacter-ial infection, your doctor may haveprescribed penicillin—an antibioticproduced from a deuteromycote thatis commonly seen growing on fruit, as shown in Figure 20.12. Otherdeuteromycotes are used in the mak-ing of foods, such as soy sauce andsome kinds of blue-veined cheese.Still other deuteromycotes are usedcommercially to produce substancessuch as citric acid, which gives jams,jellies, soft drinks, and fruit-flavoredcandies a tart taste.

Mutualism:Mycorrhizae and Lichens

Certain fungi live in a mutualisticassociation with other organisms.Two of these mutualistic associationsthat are also symbiotic are called myc-orrhizae and lichens.

MycorrhizaeA mycorrhiza (my kuh RHY zuh) is

a mutualistic relationship in which afungus lives symbiotically with aplant. Most of the fungi that formmycorrhizae are basidiomycotes, butsome zygomycotes also form theseimportant relationships.

How does a plant benefit from amycorrhizal relationship? Fine, thread-like hyphae grow harmlessly around orinto the plant’s roots, as shown inFigure 20.13. The hyphae increasethe absorptive surface of the plant’sroots, resulting in more nutrientsentering the plant. Phosphorus, cop-per, and other minerals in the soil areabsorbed by the hyphae and thenreleased into the roots. In addition, the

540 FUNGI

mycorrhiza fromthe Greek wordsmykes, meaning“fungus,” andrhiza, meaning“root”; Mycorrhizaeare mutualistic rela-tionships betweenfungi and plants.

(bl)Envision/Agence Top, (br)Barry L. Runk /Grant Heilman Photography

The antibiotic penicillin is derivedfrom Penicillium mold, shownhere growing on an orange.

B

Bleu cheese has a dis-tinctive flavor. The bluesplotches are patches offungal spores.

AFigure 20.12Many deuteromy-cotes are useful.

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fungus also may help to maintain waterin the soil around the plant. In turn,the mycorrhizal fungus benefits byreceiving organic nutrients, such assugars and amino acids, from the plant.

About 80 to 90 percent of all plantspecies have mycorrhizae associatedwith their roots. Plants of a species thathave mycorrhizae grow larger and aremore productive than those that don’t.In fact, some species cannot survivewithout mycorrhizae. Some orchid

seeds, for example, usually do not ger-minate without a symbiotic fungus toprovide water and nutrients.

LichensIt’s sometimes hard to believe that

the orange, green, and black blotchesthat you see on rocks, trees, andstone walls are alive. The blotchesmay look like flakes of old paint or pieces of dried moss, but they areforms of lichens. See Figure 20.14.


Figure 20.13The fungal part of amycorrhiza surroundsplant roots (A). The redfilaments in the plantcells are fungal hyphae(B). Infer How doesmycorrhiza benefit ahost plant?

Figure 20.14Lichens have a varietyof forms.

Some lichens form crust-like growths on barerocks and stone walls.

A

Each stalk ofthese Britishsoldier lichens isabout 3 cm tall.

B

Some lichens resembleleaves, like these lichensgrowing on a dead twig.

C

Stained LM Magnification: 100�

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542 FUNGI

Figure 20.15Cladina stellaris isa common lichenon the tundraand a favoritefood of caribouand reindeer.

A lichen (LI kun) is a symbiotic asso-ciation between a fungus, usually anascomycote, and a photosyntheticgreen alga or a cyanobacterium, whichis an autotroph.

The fungus portion of the lichenforms a dense web of hyphae in whichthe algae or cyanobacteria grow.Together, the fungus and its photo-synthetic partner form a structure thatlooks like a single organism. Use theProblem-Solving Lab to find out moreabout a lichen’s structure.

Lichens need only light, air, andminerals to grow. The photosyntheticpartner provides the food for bothorganisms. The fungus, in turn, pro-vides its partner with water and min-erals that it absorbs from rain and theair, and protects it from changes inenvironmental conditions.

There are about 20 000 species oflichens. They range in size from lessthan 1 mm to several meters in diame-ter. Most lichens grow slowly, increas-ing in diameter only 0.1 to 10 mm peryear. Some lichens may be thousands ofyears old.

Found worldwide, lichens are pio-neers, being among the first to colonizea barren area. Lichens live in ariddeserts, on bare rocks exposed to bitter-cold winds, and just below the timber-line on mountain peaks. On the arctictundra, lichens, such as the one shownin Figure 20.15, are the dominant formof vegetation. Both caribou and muskoxen graze on lichens there, much likecattle graze on grass elsewhere.

Not only are lichens pioneers, butthey are also indicators of pollutionlevels in the air. The fungus readilyabsorbs materials from the air. If pollu-tants are present, they kill the fungus.Without the fungal part of a lichen, thephotosynthetic partner also dies.

Describe the compo-nents that make up a lichen andwhat each contributes.

Think CriticallyWhat’s inside a lichen?A lichen consists of a fungusand an alga or cyanobac-terium that live symbioti-cally. The prefix sym means“together,” and biotic means“life.” The word symbiosisdescribes the fact that thereare two different life formsliving together.

Solve the ProblemYou find a lichen and make a thin slice through it. You mag-nify the slice under the microscope and draw what youobserve—the diagram above.

Thinking Critically1. Outline Using color as a clue, list the letters that identify

the algal and fungal parts of the lichen.2. Explain Structure C is a reproductive part. After examin-

ing it, you conclude that this is a reproductive structure ofan ascomycote. Explain how you knew this.

3. Experiment Scientists have wondered if the parts of alichen can survive by themselves. Describe an experimentthat might answer this question.

AA CC

BB

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Origins of FungiMycologists hypothesize that the

ascomycotes and the basidiomycotesevolved from a common ancestor andthat the zygomycotes evolved earlier,as you can see in Figure 20.16.

Although fossils can provide cluesas to how organisms evolved, fossilsof fungi are rare because fungi arecomposed of soft materials. The old-est fossils that have been identified asfungi are over 400 million years old.

Understanding Main Ideas1. What occurs underground between the time a

basidiospore germinates and a mushroom buttonforms?

2. Explain how the deuteromycotes differ frommembers of the other divisions of fungi. Explainhow they are all similar.

3. Who are the partners in a mycorrhizae? Describehow each partner benefits in a mycorrhizal relationship.

4. How does a hyphae called a stolon differ from a rhizoid?

Thinking Critically5. You are working with a team of environmental

engineers to monitor air pollution levels. Howmight you use lichens to collect data and deter-mine the air quality?

6. Compare and Contrast What are the similaritiesand differences between the fungal reproductivestructures, ascospores and conidiophores? Formore help, refer to Compare and Contrast in theSkill Handbook.

SKILL REVIEWSKILL REVIEW


PRESENT CENOZOIC PALEOZOIC PRECAMBRIANMESOZOICSpecies numbers are approximate and subject to change pending discoveries or extinctions.

Zygomycotes1000 species

Basidiomycotes25 000 species

Protists

Archaebacteria

Eubacteria

Deuteromycotes25 000 species

Ascomycotes30 000 species

Lichens20 000 species

Figure 20.16This diagram shows therelationships of fungi.

FUNGI

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544 FUNGI

Before YouBegin

Does temperature affectthe rate of carbon dioxideproduction by yeast? Lookat the experimental setuppictured at the right. Asyeast metabolizes in thestoppered container, thecarbon dioxide that is produced is forced outthrough the bent tubeinto the open tube, whichcontains a solution of bro-mothymol blue (BTB).Carbon dioxide causeschemical reactions thatresult in a color change inthe BTB. Differences in thetime required for thiscolor change to occur indi-cate the relative rates ofcarbon dioxide productionby yeasts.


Yeast cells

Does temperature affectyeast metabolism?

ProblemHow can you determine the affect of temperature on themetabolism of yeast? Brainstorm ideas among the membersof your group.

HypothesesDecide on one hypothesis that you will test. Your hypothesismight be that low temperature slows down the metabolicactivity of yeast, or that a high temperature speeds up themetabolic activity of yeast.

ObjectivesIn this BioLab, you will:■ Measure the rate of yeast metabolism using a BTB color

change as a rate indicator.■ Compare the rates of yeast metabolism at several

temperatures.■ Use the Internet to collect and compare data from other

students.

Possible Materialsbromothymol blue solution water/yeast mixture

(BTB) test-tube rackstraw 250-mL beakers (3)small test tubes (4) ice cubeslarge test tubes (3) Celsius thermometer orone-hole stoppers with glass temperature probe

tube inserts for large test hot platetubes (3) graduated cylinder

yeast/white corn syrup mixture glass-marking pencilwater/white corn syrup 10 cm of rubber tubing (3)

mixture aluminum foil

Safety PrecautionsCAUTION: Always wear goggles in the lab. Be careful inattaching rubber tubing to the glass tube inserts in the stoppers. Avoid touching the top of the hot plate. Wash your hands thoroughly at the end of your experiments.

Skill HandbookIf you need help with this lab, refer to the Skill Handbook.

PREPARATIONPREPARATION

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ANALYZE AND CONCLUDEANALYZE AND CONCLUDE

1. Check Your Hypothesis Explain whether your data support yourhypothesis. Use your experimental data to support or reject your hypothe-sis concerning temperature effects on the rate of yeast metabolism.

2. Use the Internet How did the data you collected compare with that ofother students? Compare experimental designs. Did differences in experi-mental design account for any differences in data collected?

3. Make Inferences What must be the role ofwhite corn syrup in this experiment?

4. Identify Variables Describe some variablesthat your group had to control in this experi-ment. Explain how you controlled each variable.

5. Draw Conclusions Did your experiment clearlyshow that differences in rates of yeast metabolismwere due to temperature differences?

6. What errors did your groupmake? How could you improve the experiment?ERROR ANALYSIS

1. Decide on ways to test your group’s hypothesis.2. Record your procedure, and list the materials and amounts of solutions that

you will use. Design a data table for recording your observations.3. Pour 5 mL of BTB solution into a test tube. Use a straw to

blow gently into the tube until you observe a series ofcolor changes. Cover this tube with aluminum foil, and setit aside in a test-tube rack. Record your observations of the color changes caused by carbon dioxide in your breath.

Check the PlanDiscuss the following to decide on your procedure.1. What data on color change and time will you collect?

How will you record your data?2. What variables will you control?3. What control will you use?4. Assign tasks for each member of your group.5. Make sure your teacher has approved your

experimental plan before you proceed further.6. Carry out your experiment. Visit

to post your data.7. Check with your teacher for

instructions on disposal of yeast and BTB. CLEANUP AND DISPOSAL

PLAN THE EXPERIMENTPLAN THE EXPERIMENT

30 mL yeast/corn syrup solution

5 mLbromothymolblue solution

Find this BioLab using the link below, and postyour data in the data table provided for thisactivity. Using the additional data from otherstudents on the Internet, analyze the com-bined data and briefly describe your experi-mental design.

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546 FUNGICourtesy Department of Plant Pathology, The Ohio State University

The Dangers of Fungi

Fungi are both friend and foe. Some, such asmushrooms, provide food. Other fungi pro-

duce antibiotics such as penicillin. Many othersbreak down dead tissue and recycle organic mol-ecules, thereby keeping Earth from being buriedunder tons of unusable organic debris. Yet, fungialso damage crops, buildings, and animals.

Fungi cause many plant diseases that can killplants and cause sickness and death in animalsthat feed on infected plants. Fungi also directlycause some human diseases.

Plant pathogens Fungi that cause the plantdiseases called rusts are difficult to control. Rustsare successful because they are pleomorphic—each species produces many kinds of spores thatcan infect different hosts. The wind can spreadtheir spores over hundreds of miles. For exam-ple, Puccinia graminis is a fungus that causesblack stem rust in cereal grains, such as rice andwheat. P. graminis produces five kinds of spores,some of which also infect barberry plants.

Rye, another cereal plant, can host the fungusClaviceps purpurea, which causes a disease calledergot. Animals contract ergot after eating infectedrye. Human epidemics of ergot poisoning haveoccurred throughout history after people ate foodmade from grain infected by C. purpurea.

Fungi can also cause major losses of timber.For example, near the end of the nineteenthcentury, chestnut seedings infected with the fungus Endothia parasitica were brought into the United States. By 1950, E. parasitica haddestroyed most of the country’s chestnut trees.Other fungi have devastated the North Ameri-can populations of elm trees and eastern andwestern white pines.

In addition to infecting live trees, fungi damage structures built of wood. When ships

were primarily wooden, dry rot always threat-ened their loss. Fungi cause dry rot when theygrow in moist wooden structures.

Human pathogens Although bacteria andviruses cause most human diseases, fungi causetheir share. Most fungi are dermatophytes, that is,they invade skin, nails, and hair. Among the morecommon human fungal infections are ringwormand athlete’s foot. Some fungal spores can beinhaled into the lungs where they can establish aninfection that can spread throughout the body.

Fungi can cause substantial economic loss,disease, and even death. But their critical role inrecycling organic matter and their benefit as asource of food and medicinal drugs are essentialto human survival on Earth.

Wheat attacked by the fungus Puccinia graminis

Reproduction Many fungi reproduce both asex-ually and sexually. In a short report, discuss theadvantage of having two kinds of reproduction.

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Section 20.1Vocabularybudding (p. 533)chitin (p. 531)haustoria (p. 532)hypha (p. 530)mycelium (p. 530)sporangium (p. 533)

What is afungus?

Vocabularyascospore (p. 537)ascus (p. 537)basidiospore (p. 538)basidium (p. 538)conidiophore (p. 537)conidium (p. 537)gametangium (p. 536)lichen (p. 542)mycorrhiza (p. 540)rhizoid (p. 535)stolon (p. 535)zygospore (p. 536)

The Diversityof Fungi

STUDY GUIDESTUDY GUIDE

CHAPTER 20 ASSESSMENT 547(t)Mark Steinmetz, (c)Matt Meadows, (b)John Gerlach/Visuals Unlimited

To help you review thephyla of Fungi, use the OrganizationalStudy Fold on page 535.

Section 20.2

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Key Concepts■ Zygomycotes form asexual spores in a

sporangium. They reproduce sexually byproducing zygospores.

■ Ascomycotes reproduce asexually by pro-ducing spores called conidia and sexuallyby forming ascospores.

■ In basidiomycotes, sexual spores are produced on club-shaped structures calledbasidia.

■ Deuteromycotes may reproduce only asexually.

■ Fungi play an important role in decompos-ing organic material and recycling thenutrients on Earth.

■ Certain fungi associate withplant roots to form mycor-rhizae, a symbiotic relationshipbetween a fungus and a plant.

■ A lichen, a symbiotic associa-tion of a fungus and an alga orcyanobacterium, survives inmany inhospitable habitats.

Key Concepts■ The structural units of a fungus are

hyphae, which grow and form a mycelium.■ Fungi are heterotrophs that carry out

extracellular digestion. A fungus may be a saprophyte, a parasite, or a mutualist in a symbiotic relationship with another organism.

■ Many fungi produce both asexual and sex-ual spores. One criterion for classifyingfungi is by their patterns of reproduction,especially sexual reproduction, during thelife cycle.

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Review the Chapter 20 vocabulary words listed inthe Study Guide on page 547. Determine if eachword is true or false. If false, replace the under-lined word with the correct vocabulary word.

1. Hyphae are threadlike filaments thatdevelop from fungal spores.

2. Club-shaped hyphae that produce spores arecalled basidia.

3. A mychorrhiza is a symbiotic associationbetween a fungus and a photosyntheticgreen alga or cyanobacterium.

4. The saclike structure in which sexual sporesdevelop is called a conidiophore.

5. A network of hyphae filaments make up amycelium.

6. Most fungi function as ________ in theirenvironments.A. consumers C. decomposersB. producers D. autotrophs

7. Which of the following is a type of asexualreproduction in fungi?A. sporangium C. myceliumB. budding D. haustoria

8. Mushrooms, puffballs, and bracket fungibelong to the group called ________.A. club fungi C. ZygomycotaB. sac fungi D. Deuteromycota

9. Which drawing represents a zygospore?

10. Fungi sometimes live in a mutualistic rela-tionship with a plant. They might help theirhost by ________.A. using the food supplied by the hostB. using energy made by the hostC. supplying water to the hostD. providing the host with spores

11. Soy sauce, citric acid, and penicillin all comefrom ________.A. club fungiB. sac fungiC. zygomycotesD. deuteromycotes

12. The basic structural unit of a multicellularfungus is a ________.A. sporeB. hyphaeC. stalkD. mycellium

13. The complex carbohydrate found in the cellwalls of most fungi is ________.A. chitinB. celluloseC. glycogenD. starch

14. Unlike other fungi, ________ are known toreproduce only asexually.A. zygomycotes C. basidiomycotesB. ascomycotes D. deuteromycotes

15. The photo at rightshows bread mold structures that are called ________.A. hyphaeB. rhizoidsC. zygosporesD. sporangia

16. Open Ended Your neighbor is pulling upmushrooms that are growing in his lawn. Hetells you that he heard mushrooms won’tcome back again if they are quicklyremoved. What would you tell him?

17. Infer Why is being able to produce sporesthat can be widely dispersed such an impor-tant adaptation for fungi?

18. Describe When you transplant flowers,shrubs, or trees, why is it a good idea toleave the soil intact around a plant’s roots?

548 CHAPTER 20 ASSESSMENT

A. B. C. D.

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19. Concept Map Use the following terms: spo-rangia, rhizoids, hyphae, stolons, mycellium.

20. Since theintroduction of penicillin, fungi have playeda major role in the development of antibioticmedicines. Visit tofind out more about some examples of fungithat have been used in the development ofantibiotics. Why was the development ofpenicillin so important to the United States?Write an essay that explains what you findout about the development of antibiotics.Share your information with the class.

REAL WORLD BIOCHALLENGE

Bread mold consists of

that grow horizontallyand produce a

5.

called

thatabsorbfood

calledthat grow upward

and end in

4.2. 3.

1.

CHAPTER 20 ASSESSMENT 549

ca.bdol.glencoe.com

Constructed Response/Grid InRecord your answers on your answer document.

28. Open Ended Describe the ways that fungi reproduce.29. Open Ended Summarize the role of fungi in maintaining and disrupting equilibrium, including

diseases in plants and animals.

ca.bdol.glencoe.com/standardized_test

Multiple ChoiceUse the diagram to answer questions 21 and 22.

21. Structure A and structure Brepresent a ________ and________.A. fungal capsule—myceliumB. spore—hyphaC. hypha—lichenD. lichen—mycelium

22. The process illustrated is called ________.A. photosynthesis C. germinationB. fertilization D. host invasion

23. Which group of fungi produces sexualspores on a clublike structure?A. zygomycotes C. basidiomycotesB. ascomycotes D. deuteromycotes

24. Which fungi reproduce only asexually?A. zygomycotes C. basidiomycotesB. ascomycotes D. deuteromycotes

Use the information below and your knowledgeof science to answer questions 25–27.The metabolic activity of yeasts at various tem-peratures is shown in the table below. A chemicalindicator added to the yeast solution changedcolor when yeast cells were metabolizing.

25. The yeasts were most active at ________.A. 2°C C. 37°CB. 25°C D. 22°C

26. Yeast cells were metabolizing at ________.A. 2°C and 25°C C. 2°CB. 2°C and 37°C D. 25°C and 37°C

27. The rate of a chemical reaction is notaffected by ________.A. temperature C. a catalystB. reactant concentration D. buoyancy

A

B

Metabolic Activity of Yeasts

Temperature of Yeast Solution Time Needed for Color Change

2°C No color change

25°C 44 minutes

37°C 22 minutes

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550 BIODIGEST UNIT 6 REVIEW

Viruses, Bacteria, Protists, and FungiArchaebacteria and eubacteria occupy most habitats on Earth,

and protists and fungi are almost as diverse. But, viruses enterand take over their cells and the cells of all other organisms.

VirusesThere are many kinds of viruses, nonliving parti-

cles, most of which can cause diseases in theorganisms they infect. Most viruses are muchsmaller than the smallest bacterium, and nonerespire or grow.

StructureViruses consist of a core of DNA or RNA sur-

rounded by a protein coat, called a capsid. Thecapsid may be enclosed by a layer called an enve-lope that is made of phospholipids and proteins.Depending on their nucleic acid content, virusesare classified as either DNA or RNA viruses.

ReplicationViruses replicate only inside cells. First, a virus

attaches to a specific molecule on a cell’s mem-brane. Then, it enters the cell where it beginseither a lytic or a lysogenic cycle. In the lytic cycle,the viral nucleic acid causes the host to producenew virus particles that are then released, killingthe host. In the lysogenic cycle, the viral DNAbecomes part of the host’s chromosome for awhile, and later may enter a lytic cycle.

BacteriaA bacterium is a unicellular prokaryote. Most of

its genes are contained in a circular chromosomein the cytoplasm. A cell wall surrounds its plasmamembrane. Bacteria may be heterotrophs, photo-synthetic autotrophs, or chemosynthetic auto-trophs. They reproduce asexually by binary fissionand sexually by conjugation.

AdaptationsMany bacteria are obligate aerobes, needing

oxygen to respire. Some bacteria called obligateanaerobes are killed by oxygen. Still other bacteriacan live either with or without oxygen. Some bac-teria can produce endospores to help them surviveunfavorable environmental conditions.

ImportanceSome bacteria cause diseases. Other bacteria fix

nitrogen, recycle nutrients, and help make foodproducts and medicines.

Color-enhanced SEM Magnification: 10 000�


Bacteria occur in three basicshapes: spheres,rods, and spirals.


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A rchaebacteria are unicellular prokary-otes, most of which survive in

extremely harsh environments. A group ofarchaebacteria that produce methane livein the intestinal tracts of animals and insewage treatment plants. A second groupthrives in hot, acidic environments, such asin the thermal springs of YellowstoneNational Park or around the hot vents onocean floors. A third group survive inextremely salty water such as that found inUtah’s Great Salt Lake.

Archaebacteria: The Extremists

Utah’s Great Salt Lake

551

The beating cilia of aparamecium producewater currents for collecting food.

Color-enhanced TEM Magnification: 4000�

Viruses, Bacteria, Protists, and Fungi

ProtistsDistribution: worldwide in aquatic andmoist habitatsNiches: producers, herbivores, predators,parasites, and decomposersNumber of species: more than 60 000Size range: less than 2 micrometers inlength to greater than 100 meters (328 feet)in length


ProtistsKingdom Protista is a diverse group of hetero-

trophic, autotrophic, parasitic, and saprophyticeukaryotes. Although many protists are unicellular,some are multicellular. They all live in aquatic orvery moist places.

Protozoans: Animal-like protistsAnimal-like protists known as protozoans are

unicellular, heterotrophic organisms. Many proto-zoans are classified based on their adaptations forlocomotion in the environment.

Phylum Rhizopoda is composed of the proto-zoans called amoebas that use pseudopodia,extensions of their plasma membrane, to moveand engulf prey. Phylum Mastigophora is com-posed of protozoans that use flagella to movearound. Some parasitic protozoan species thathave flagella cause disease, but other flagellatedspecies are helpful. Members of the phylum

Ciliophora move by beating hairlike projectionscalled cilia. Paramecium is a widely studied ciliate.

Sporozoans are grouped together because theyare all parasites and many produce spores. Mosthave very complex life cycles with different stages.Plasmodium, the protozoans that cause the dis-ease malaria, have a sexual stage in mosquitoesand an asexual stage in humans.

Plasmodium may infect more than one hundred millionpeople every year in African and South American countries.

(t)Meckes/Ottawa/Photo Researchers, (c)Dr. Dennis Kunkel/Phototake, NYC, (b)Leonard L.T. Rhodes/Earth Scenes


Algae: Plantlike ProtistsAutotrophic protists are called algae. They are

grouped on the basis of body structure and thepigments they contain. Photosynthetic algae pro-duce a great deal of Earth’s atmospheric oxygen.They are unicellular and multicellular.

EuglenasUnicellular algae that can be both autotrophs

and heterotrophs are classified in the phylumEuglenophyta. Most species have chlorophyll forphotosynthesis. When there is no light, someeuglenas can ingest food.

DiatomsUnicellular algae called diatoms are classified in

phylum Bacillariophyta. In addition to chlorophyll,diatoms contain carotenoids, pigments with agolden-yellow color. Diatoms live in both saltwaterand freshwater environments.

DinoflagellatesDinoflagellates, members of the phylum

Dinoflagellata, are unicellular algae surrounded byhard, armorlike plates and propelled by flagella.They may contain a variety of pigments, includingchlorophyll, caretenoids, and red pigments. Marineblooms of dinoflagellates can cause toxic red tides.

Red AlgaeMembers of the phylum Rhodophyta are multi-

cellular marine algae. Because of their red andblue pigments, some species can grow at depths of100 meters.

Brown AlgaeAbout 1500 species of algae are classified in

phylum Phaeophyta and all contain a brown pig-ment. Thelargest brownalgae are thegiant kelpsthat can growto about 60meters inlength.

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Magnification: 8�

Euglenas use oneor two flagella tomove.

The shells ofdiatoms containsilica.

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Mycorrhizae

Fungal hyphae can growamong a plant’s root cells.

Hyphae offungus Plant cell

552

A chocolate slime mold

Some plants live in association with mutualistic fungi. These rela-tionships, called mycorrhizae (my kuh RHY zuh), benefit both the

fungi and the plants. The hyphae of the fungus are entwined withthe roots of the plant, and absorb sugars and other nutrients fromthe plant’s root cells. In turn, the fungus increases the surface areaof the plant’s roots, allowing the roots to absorb more water andminerals.

The relationship enables the fungus to obtain food and the plantto grow larger. Some plants have grown so dependent on their mych-orrhizal relationships that they cannot grow without them.

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VIRUSES, BACTERIA, PROTISTS, AND FUNGI 553


These mushrooms have gills containing basidia on theunderside of their caps.

Ascomycota, such as this scarlet cup, produce sporesinside cup-shaped sacs.

Imperfect fungi, such as this Penicillium mold, areclassified in phylum Deuteromycota. Sexual repro-duction has never been observed in imperfect fungi.

Green AlgaeThe green algae in the phylum Chlorophyta,

may be unicellular, colonial, or multicellular. Themajor pigment in their cells is chlorophyll, andsome also have yellow pigments.

Funguslike ProtistsFunguslike protists include the slime molds,

water molds, and downy mildews. They are sap-rophytes, decomposing organic material to obtainits nutrients.

FungiMembers of Kingdom Fungi are mostly multicel-

lular, eukaryotic organisms that have cell wallsmade of chitin. The structural units of a fungus arehyphae. Fungi secrete enzymes into a food sourceto digest the food and then absorb the digestednutrients.

Fungi may be saprophytes, parasites, or mutual-ists. They play a major role in decomposingorganic material and recycling Earth’s nutrients.

Club FungiClub fungi include mushrooms, puffballs, and

bracket fungi, and all are members of phylumBasidiomycota. Club fungi have club-shaped struc-tures called basidia in which their sexual sporesare produced.

Zygospore-Forming FungiMembers of phylum Zygomycota produce

thick-walled, sexual spores called zygospores.Zygomycotes also form many asexual spores insporangia.

Sac FungiFungi that produce sexual spores called asco-

spores in saclike structures called asci are classifiedin phylum Ascomycota. Sac fungi produce asexualspores, called conidiospores, which develop inchains or clusters from the tips of elongatedhyphae called conidiophores.

LichensA lichen is a symbiotic association of a mutual-

istic fungus and a photosynthetic alga or cyano-bacterium. Lichens live in many inhospitable areas,such as cold climates and high altitudes, but theyare sensitive to pollution and do not grow well inpolluted areas.

Some of this bread mold’s hyphae (HI fee) form a matcalled a mycelium that is anchored in the food source byother hyphae called rhizoids.

(t)Vaughan Fleming/Science Photo Library/Photo Researchers, (cl)Matt Meadows, (cr)Mark Steinmetz, (b)A. McClenaghan/Science Photo Library/Photo Researchers


554 UNIT 6 STANDARDIZED TEST PRACTICE

Multiple Choice

1. The core of a virus contains ________.A. phospholipids C. amino acidsB. nucleic acids D. proteins

2. Photosynthetic bacteria include ________.A. cyanobacteria C. methanogensB. anaerobes D. chemoautotrophs

3. The most likely place to find archaebacteriawould be in ________.A. foodB. a DNA labC. a hot sulfur springD. a fast flowing stream

4. The bacterial name associated with a rodshape is ________.A. bacillusB. coccusC. spirillumD. nucleic acid

5. A key enzyme utilized by an RNA virus is________.A. reverse transcriptaseB. provirusC. attachment proteinD. capsid

6. Penicillin kills bacteria by interfering with the enzymes that link the sugar chains in the________.A. nucleusB. cell wallC. plasmidD. capsule

7. In the ________ cycle, viruses use the cell’senergy and raw materials to copy themselves,then burst from the cell.A. cellB. lysogenicC. plasmidD. lytic

8. In the illustration of a diatom above, the shellis made of ________.A. proteinB. silicaC. carbohydrateD. lipid

9. A population explosion of dinoflagellates that produces a strong nerve toxin is________.A. only possible in freshwaterB. Pfiesteria piscicidaC. a red tideD. rare in warm, polluted waters

10. A student finds a species of autotrophic algae with a long filament that propels itthrough the water. The filament is a________.A. flagellumB. pseudopodC. ciliumD. microtubule

11. The major pigment of green algae is________.A. redB. caroteneC. chlorophyllD. a chloroplast

InvestigateAsk what kinds of questions to expect on thetest. Ask for practice tests so that you canbecome familiar with the test-taking materials.

1c

1c

1c

1c

Standards Practice The assessed California standard appears next to the question.


UNIT # STANDARDIZED TEST PRACTICE 555

12. Mushrooms are classified in phylum________.A. BasidiomycotaB. ZygomycotaC. AscomycotaD. Deuteromycota

13. Cell walls of fungi contain ________.A. cellulose C. hyphaeB. spores D. chitin

14. A puffball is a type of ________.A. sac fungus C. lichenB. club fungus D. imperfect fungus

15. Lichens are sensitive to ________.A. pollution C. droughtB. cold D. predators

Use the information below and your knowledge of science to answer questions 16–19.

16. The organism pictured is ________.A. prokaryoticB. eukaryoticC. multicellularD. not a living organism

17. The component designated as C is most com-monly found in ________.A. disease causing virusesB. harmless virusesC. disease causing bacteriaD. harmless bacteria

18. Component F is a ________.A. ribosomeB. pilusC. nucleusD. plasmid

19. The physical law that best explains why component G causes the organism to move is ________.A. Newton’s first law of motionB. Newton’s third law of motionC. Ohm’s lawD. Boyle’s law

AB

C

D

EF

G

UNIT 6 STANDARDIZED TEST PRACTICE 555

Constructed Response/Grid In

Record your answers on your answer document.

20. Open Ended Compare and contrast the structures and functions of viruses to those of cells. Why areviruses not considered to be living?

21. Open Ended In agricultural regions where farmers use large amounts of nitrogen fertilizers in theirfields, local ponds and lakes often develop a thick, green scum containing algae in late summer.Hypothesize why this happens.

22. Open Ended Both fungi and animals are heterotrophs. Contrast the interactions of fungi and plantswith the interactions of animals and plants.

23. Open Ended Describe some vastly different characteristics among organisms in the Kingdom Protista.What common characteristics link them as protists?

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chapter 20: fungi - coconinohighschool · decomposer: organism that breaks ... types of fungi, all...

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