chapter 19: protists text...they decompose dead organisms. however, unlike fungi, funguslike...

Activities/FeaturesObjectivesSection

Chapter 19 OrganizerChapter 19 Organizer

The World of ProtistsNational Science EducationStandards UCP.1, UCP.2,UCP.5; A.1, A.2; C.1, C.4,C.5, C.6; F.1, F.4, F.5 (1 ses-sion, 1 block)

Algae: Plantlike ProtistsNational Science EducationStandards UCP.1, UCP.2,UCP.5; A.1, A.2; C.1, C.4,C.5, C.6; F.1, F.4, F.5 (2 ses-sions, 1 block)

Slime Molds, WaterMolds, and DownyMildewsNational Science EducationStandards UCP.1, UCP.2,UCP.4, UCP.5; A.1, A.2; C.1,C.3-5, C.6; F.1, F.4, F.5; G.1-3(2 sessions, 1/2 block)

1. Identify the characteristics of KingdomProtista.

2. Compare and contrast the four groupsof protozoans.

3. Compare and contrast the variety ofplantlike protists.

4. Explain the process of alternation ofgenerations in algae.

5. Contrast the cellular differences and lifecycles of the two types of slime molds.

6. Discuss the economic importance of thedowny mildews and water molds.

MiniLab 19-1: Observing Ciliate Motion, p. 522Inside Story: A Paramecium, p. 523Problem-Solving Lab 19-1, p. 524

MiniLab 19-2: Going on an Algae Hunt, p. 527Problem-Solving Lab 19-2, p. 530Design Your Own BioLab: How doParamecium and Euglena respond to light? p. 538

Problem-Solving Lab 19-3, p. 534Social Studies Connection: The Irish PotatoFamine, p. 540

MATERIALS LIST

BioLabp. 538 microscope, microscope slides,coverslips, dropper, metric ruler, indexcards, scissors, toothpicks, methyl cellu-lose solution, Euglena culture,Paramecium culture

MiniLabsp. 522 Paramecium culture, wheatseeds, microscope, microscope slide,coverslip, dropper

p. 527 microscope, microscope slide,coverslip, dropper, pond water, paper,pencil

Alternative Labp. 534 microscope, sterile agar plate,oat cereal flakes, plasmodium stage ofPhysarum polycephalum

Need Materials? Contact Carolina Biological Supply Company at 1-800-334-5551or at http://www.carolina.com

Section 19.2

Section 19.1

Section 19.3

Products Available FromGlencoeTo order the following products,call Glencoe at 1-800-334-7344:CD-ROMNGS PictureShow: The Cell

Products Available FromNational Geographic SocietyTo order the following products,call National Geographic Societyat 1-800-368-2728:VideoProtists: Threshold of Life

Index to NationalGeographic MagazineThe following articles may beused for research relating to thischapter:“Slime Mold: The Fungus ThatWalks,” by Lee Douglas, July1981.

Teacher’s Corner

518B518A

ProtistsProtists

TransparenciesReproducible MastersSection

The World ofProtists

Algae: PlantlikeProtists

Slime Molds,Water Molds, andDowny Mildews

Section 19.1

Section 19.2

Section 19.3

Teacher Classroom Resources

Reinforcement and Study Guide, p. 83Critical Thinking/Problem Solving, p. 19BioLab and MiniLab Worksheets, p. 89Laboratory Manual, pp. 133-136Content Mastery, pp. 93-94, 96

Reinforcement and Study Guide, pp. 84-85BioLab and MiniLab Worksheets, p. 90Laboratory Manual, pp. 137-140Tech Prep Applications, pp. 27-28Content Mastery, pp. 93, 95-96

Reinforcement and Study Guide, p. 86Concept Mapping, p. 19BioLab and MiniLab Worksheets, pp. 91-92Content Mastery, pp. 93, 95-96 L1

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Section Focus Transparency 45Basic Concepts Transparency 30Reteaching Skills Transparency 29Reteaching Skills Transparency 30

Section Focus Transparency 46Basic Concepts Transparency 28Basic Concepts Transparency 30

Section Focus Transparency 47Basic Concepts Transparency 29Basic Concepts Transparency 30

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Assessment Resources Additional ResourcesSpanish ResourcesEnglish/Spanish AudiocassettesCooperative Learning in the Science ClassroomLesson Plans/Block Scheduling

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Chapter Assessment, pp. 109-114MindJogger VideoquizzesPerformance Assessment in the Biology ClassroomAlternate Assessment in the Science ClassroomComputer Test BankBDOL Interactive CD-ROM, Chapter 19 quiz

Refer to pages 4T-5T of the Teacher Guide for an explanation of the National Science Education Standards correlations.

Key to Teaching StrategiesKey to Teaching Strategies

Level 1 activities should be appropriatefor students with learning difficulties.Level 2 activities should be within theability range of all students.Level 3 activities are designed for above-average students.ELL activities should be within the abilityrange of English Language Learners.

Cooperative Learning activitiesare designed for small group work.These strategies represent student prod-ucts that can be placed into a best-workportfolio.These strategies are useful in a blockscheduling format.

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The following multimedia resources are available from Glencoe.

Biology: The Dynamics of LifeCD-ROM

Exploration: The World of ProtistsBioQuest: Biodiversity ParkVideo: ProtistsVideo: Kelp ForestsVideo: Slime Mold

Videodisc ProgramProtistsKelp ForestsSlime Mold

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http://www.carolina.com

Section

What Is a Protist?Kingdom Protista contains the

most diverse organisms of all thekingdoms. Protists may be unicellularor multicellular, microscopic or verylarge, and heterotrophic or auto-trophic. In fact, there is no suchorganism as a typical protist. Whenyou look at different protists, youmay wonder how they could begrouped together. The characteristicthat all protists share is that, unlikebacteria, they are all eukaryotes,which means that most of their meta-bolic processes occur inside theirmembrane-bound organelles.

Although there are no typical pro-tists, some resemble animals in theirmethod of nutrition. The animal-like

protists are called protozoa (prohtuh ZOH uh) (singular, protozoan).Unlike animals, though, all proto-zoans are unicellular. Other protistsare plantlike autotrophs, using pho-tosynthesis to make their food.Plantlike protists are called algae (AL

jee) (singular, alga). Unlike plants,algae do not have organs such asroots, stems, and leaves. Still otherprotists are more like fungi becausethey decompose dead organisms.However, unlike fungi, funguslikeprotists are able to move at somepoint in their life and do not havechitin in their cell walls.

It might surprise you to learn howmuch protists affect other organisms.Some protists cause diseases, such asmalaria and sleeping sickness, that

19.1 THE WORLD OF PROTISTS 519

In just a few drops of pond water,you can find an amazing collectionof protists. Some protists will be

moving, perhaps searching for food.Others will be using photosynthesis tomake food. Still others will be decom-posing organic matter in the pondwater. In this section, you will readabout the great diversity of protists,and why, in spite of this diversity,biologists group them together inKingdom Protista.

SECTION PREVIEW

ObjectivesIdentify the character-istics of KingdomProtista.Compare and contrastthe four groups of protozoans.

Vocabularyprotozoanalgaepseudopodiaasexual reproductionflagellateciliatesporozoanspore

19.1 The World of Protists

A Stylonchia searching for food

OriginWORDWORD

protozoaFrom the Greekwords protos, mean-ing “first,” and zoa,meaning “animals.”Protozoa are ani-mal-like protists.

Magnification: 770�

519

Section 19.1

BIOLOGY: The Dynamics of Life SECTION FOCUS TRANSPARENCIES

Use with Chapter 19,Section 19.1

What life characteristic is each of these organisms exhibiting?

How are these organisms alike and different?

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This Amoeba is surrounding its food. The Didinium is feeding on a Paramecium.

This Euglena moves by whipping its flagellum. Beating cilia draw food into the mouthof this Stentor.

PrepareKey ConceptsThis section first presents thegeneral characteristics of protists.Then, it discusses protozoans anddetails the characteristics of arepresentative organism fromeach of the four protozoan phyla.

Planning■ Gather cotton and toothbrush

bristles for MiniLab 19-1.

1 FocusBellringer Before presenting the lesson, display Section Focus Trans-parency 45 on the overhead pro-jector and have students answerthe accompanying questions.

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518 PROTISTS

Protists

What You’ll Learn■ You will differentiate among

the major groups of protists.■ You will recognize the ecolo-

gical niches of protists.■ You will identify some human

diseases and the protists re-sponsible for them.

Why It’s ImportantBecause protists are responsiblefor much of the oxygen in theatmosphere, and are the basefor most food chains in aquaticenvironments, most other or-ganisms depend on protists toexist.

Observing ProtistsView a slide of protists to ob-serve their variety. How are theprotists similar? How do theydiffer?

To find outmore about

the protists, visit the GlencoeScience Web Site.www.glencoe.com/sec/science

19

GETTING STARTEDGETTING STARTED

ChapterChapter

Desmids are plantlike pro-tists that produce much ofthe oxygen you breathe. TheSpirostomum ambiguum(inset) is an animal-like protist.

Magnification:475�


518

Theme DevelopmentThe theme of unity withindiversity is evident throughoutthe chapter in discussions of thecharacteristics of protists. Thetheme of homeostasis is promi-nent in discussions of how thedifferent protists carry out theirlife functions.

Chapter 19Chapter 19

MultipleLearningStyles

Look for the following logos for strategies that emphasize different learning modalities.

Kinesthetic Meeting IndividualNeeds, pp. 520, 522, 528, 531;

Project, p. 527; Activity, p. 528Visual-Spatial Activity, p. 520;Quick Demo, pp. 521, 536; Pro-

ject, p. 521; Check for Understanding, p. 524; Tech Prep, p. 523; Reinforce-ment, p. 528; Extension, p. 536

Intrapersonal Portfolio, p. 520

Linguistic Biology Journal, pp. 524, 536; Portfolio, p. 529;

Meeting Individual Needs, p. 533Logical-Mathematical Activity,p. 525Naturalist Getting StartedDemo, p. 518; Biology Journal,

p. 526; Check for Understanding, p. 536; Reteach, p. 536

GETTING STARTED DEMOGETTING STARTED DEMO

Naturalist Have students observe slides containing

a variety of living amoebas, ciliates, and flagellates. Askthem to compare and contrast the organisms. Students shouldobserve that the organisms areunicellular and move differ-ently.

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If time does not permit teach-ing the entire chapter, use theBioDigest at the end of theunit as an overview.

Assessment PlannerAssessment PlannerPortfolio Assessment

Portfolio, TWE, pp. 520, 529Assessment, TWE, pp. 521, 531MiniLab, TWE, p. 522Problem-Solving Lab, TWE, p. 530BioLab, TWE, pp. 538-539

Performance AssessmentMiniLab, SE, pp. 522, 527Problem-Solving Lab, TWE, pp. 524, 534MiniLab, TWE, p. 527

Alternative Lab, TWE, pp. 534-535Assessment, TWE, p. 535BioLab, SE, pp. 538-539

Knowledge AssessmentAssessment, TWE, pp. 525, 532, 537Alternative Lab, TWE, pp. 534-535Section Assessment, SE, pp. 525, 532, 537Chapter Assessment, SE, pp. 541-543

Skill AssessmentAssessment, TWE, p. 528

Internet Address Book

NoteInternet

addresses that you find usefulin the space below for quickreference.

Resource ManagerResource Manager

Section Focus Transparency 45and Master

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http://www.glencoe.com/sec/science

Figure 19.3Foraminiferans (a)and radiolarians (b)are amoebas thatextend pseudopodiathrough tiny holes intheir shells. Pseudo-podia act like stickynets that trap food.

Although most amoebas live insaltwater, there are freshwater onesthat live in the ooze of ponds, in wetpatches of moss, and even in moistsoil. Because amoebas live in moistplaces, nutrients dissolved in thewater around them can diffusedirectly through their cell mem-branes. However, because freshwateramoebas live in hypotonic environ-ments, they constantly take in water.Their contractile vacuoles collect andpump out excess water.

Two groupings of mostly marineamoebas, the foraminiferan and radi-olarian shown in Figure 19.3, haveshells. Foraminiferans, which are

abundant on the sea floor, have hardshells made of calcium carbonate.Fossil forms of these protists helpgeologists determine the ages ofsome rocks and sediments. Unlikeforaminiferans, radiolarians haveshells made of silica. Under a micro-scope, you can see the complexity ofthese shells. In addition, radiolariansare an important part of marineplankton—an assortment of micro-scopic organisms that float in theocean’s photic zone and form thebase of marine food chains.

Most amoebas commonly repro-duce by asexual reproduction, inwhich a single parent produces one or


Nucleus Cytoplasm

Contractilevacuole

Food vacuole

PseudopodiaFigure 19.2An amoeba feedson small organismssuch as bacteria.

a


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As an amoeba approachesfood, pseudopodia formand eventually surroundthe food.

AA The food becomesenclosed in a foodvacuole.

BB Digestive enzymes breakdown the food, and thenutrients diffuse into thecytoplasm.

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Portfolio Ask students tomake a table that summarizes thedifferences between amoebas,foraminiferans, and radiolarians.

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AssessmentAssessment

result in millions of human deathsthroughout the world every year.Unicellular algae produce much ofthe oxygen in Earth’s atmosphere andare the basis of aquatic food chains.Slime molds and water molds decom-pose a significant amount of organicmaterial, making the nutrients avail-able to living organisms. Protozoans,algae, and funguslike protists playimportant roles on Earth. Look atFigure 19.1 to see some protists.

What Is a Protozoan?If you sat by a pond, you might

notice clumps of dead leaves at thewater’s edge. Under a microscope, apiece of those wet decaying leavesreveals a small world, probably inhab-ited by animal-like protists. Althougha diverse group, all protozoans areunicellular heterotrophs that feed onother organisms or dead organic mat-ter. They usually reproduce asexually,and some also reproduce sexually.

Diversity of ProtozoansMany protozoans are grouped

according to the way they move.Some protozoans use cilia or flagellato move. Others move and feed bysending out cytoplasm-containingextensions of their plasma mem-branes. These extensions are calledpseudopodia (sewd uh POHD ee uh).Other protozoans are groupedtogether because they are parasites.There are four main groups of proto-zoans: the amoebas (uh MEE buz), theflagellates, the ciliates, and the sporo-zoans (spor uh ZOH unz).

Amoebas: Shapeless protistsThe phylum Rhizopoda includes

hundreds of species of amoebas andamoebalike organisms. Amoebas haveno cell wall and form pseudopodia to move and feed. As a pseudopodforms, the shape of the cell changesand the amoeba moves. Amoebas formpseudopodia around their food, as youcan see in Figure 19.2.

520 PROTISTS

Figure 19.1Members of KingdomProtista are animal-like, plantlike, andfunguslike.

OriginWORDWORD

pseudopodiaFrom the Greekwords pseudo, mean-ing “false,” andpodos, meaning“foot.” An amoebauses psuedopodia to obtain food.


During part of their life cycle,funguslike protists resemblesome types of fungi.

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Plantlike protistsare photosyntheticautotrophs andmay be unicellularor multicellularlike this one.

BB

Animal-like protists are unicellular heterotrophsthat move in a varietyof ways.

AA

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2 TeachActivity

Visual-Spatial After studentshave read about the charac-

teristics of protists, have themdiagram a generalized protist cell.They should draw their diagramsto scale and label the cellorganelles. Then have studentsdraw and label a bacterial cell forcomparison. Although this activ-ity will be difficult, it should initi-ate a useful discussion about thecharacteristics of protists.

Tying to PreviousKnowledgeAsk students to compare andcontrast the terms in the wordpairs that follow: eukaryotes andprokaryotes, heterotrophs andautotrophs, and motile and non-motile. Eukaryotes have membrane-bound organelles; the prokaryotes lack membrane-bound organelles.Heterotrophs take in food from theenvironment; autotrophs producetheir own food. A motile organismcan move; a nonmotile organismcannot move.

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PortfolioPortfolio

A Moving AnalogyIntrapersonal Have the studentsdescribe or draw some everyday

items that are analogous in structure,appearance, or function to protozoanstructures, such as cilia, flagella, andpseudopodia.

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MEETING INDIVIDUAL NEEDS MEETING INDIVIDUAL NEEDS

Visually ImpairedKinesthetic Ask students to buildtactile models to demonstrate the

difference between cilia and flagella. Vel-cro can model cilia, and pieces of stringtaped to a ball can simulate flagella.

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Quick DemoQuick Demo

Visual-Spatial Have stu-dents observe prepared

slides of amoebas, foraminif-erans, and radiolarians anddraw a labeled diagram of eachorganism they see, indicatingthe magnification at which theyview each organism. Then askthem to describe the functionof each labeled structure.

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P R O J E C TComparing the Speeds of Protists

Visual-Spatial Pair up students. Haveone student in each pair observe a slide

containing a variety of living protists underthe low-power magnification. While the ob-server watches a protozoan move across thediameter of the field of view, the partnershould use a stopwatch to time the event as

the observer describes it. Instruct students todivide the number of seconds the protisttakes to travel across the field of view by thefield of view size (usually 1.5 mm). The resultis speed in millimeters per second. Have stu-dents repeat the process for each differentprotist they see and make a table of theirresults.

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VIDEODISCSTV: The CellAmoeba Changing

Shape

Amoeba With Pseudopodia

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CD-ROMBiology: The Dynamicsof Life

Exploration: The World ofProtists, Disc 3BioQuest: Biodiversity ParkDisc 3, 4 Video: Protists, Disc 3

Fullvacuole

Empty vacuoleCanals

Canals takeup water fromcytoplasm

Pore opens andvacuole contracts

Pore


A Paramecium

Paramecia are unicellular organisms, but their cellsare quite complex. Within a paramecium are many

organelles and structures that are each adapted to carryout a distinct function.

Critical Thinking How might the contractile vacuoles ofa paramecium respond if the organism were placed in adilute salt solution?


Paramecium caudatum

INSIDESSTORTORYY

INSIDE

Cilia The cell is encased by anouter covering called a pelliclethrough which thousands oftiny, hairlike cilia emerge. Theparamecium can move bybeating its cilia.

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Oral groove Parameciafeed primarily on bacteriathat are swept into thegullet by cilia that linethe oral groove.

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Contractile vacuole Becausea paramecium lives in a fresh-water, hypotonic environment,water constantly enters its cellby osmosis. A pair of contrac-tile vacuoles pump out theexcess water.

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Anal pore Wastematerials leave thecell through theanal pore.

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Micronucleus and macronucleus Thesmall micronucleus playsa major role in sexualreproduction. The largemacronucleus controlsthe everyday functions of the cell.

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Gullet Food moves into thegullet, becoming enclosed atthe end in a food vacuole.Enzymes break down thefood, and the nutrients diffuse into the cytoplasm.

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IINSIDENSIDESSTORTORYY

INSIDE

Purpose Students learn about the role ofParamecium’s organelles.

Teaching Strategies■ Ask students to explain theaction of the contractile vacuoles.

Visual Learning■ Have students describe the

location, shape, and functionof each organelle.

■ Have students make a tablewith the headings Functionand Organelle. Beneath theFunction head, have studentslist: Digestion, Locomotion,Protection, Excretion, Hom-eostasis, and Reproduction.Instruct the students to use thediagram to complete theirtables.

Critical ThinkingBecause less water would moveinto the cell if it were in a dilutesalt solution, the contractile vac-uoles would collect less water andcontract less frequently.

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Observing Ciliate Motion Thecilia on the surface of a parame-cium move so that the cell nor-mally swims through the waterwith one end directed forward.But when this end bumps into anobstacle, the paramecium respondsby changing direction.

Procedure! Observe a Paramecium culture that

has had boiled, crushed wheat seeds in it for several days.@ Carefully place a drop of water containing wheat seed

particles on a microscope slide. Gently add a coverslip.# Using low power, locate a paramecium near some wheat

seed particles. CAUTION: Use caution when working witha microscope, glass slides, and coverslips.

$ Watch the paramecium as it swims around among theparticles. Record your observations of the organism’sresponses each time it contacts a particle.

Analysis1. Describe what a paramecium does when it encounters an

obstacle. 2. How long does the paramecium’s response last? 3. Describe any changes in the shape of the paramecium as it

moved among the particles.

MiniLab 19-1MiniLab 19-1

more identical offspring by dividinginto two cells. When environmentalconditions become unfavorable, sometypes of amoebas form cysts that cansurvive extreme conditions.

522 PROTISTS

Figure 19.4The flagellated pro-tozoans (a) that livein the guts of ter-mites (b) produceenzymes that digestwood, making nu-trients available totheir hosts.

Observing Paramecium

Observing and InferringFlagellates: Protozoans with flagella

The phylum Zoomastigina consistsof protists called flagellates, whichhave one or more flagella. Flagellatedprotists move by whipping their fla-gella from side to side.

Some flagellates are parasites thatcause diseases in animals, such asAfrican sleeping sickness in humans.Other flagellates are helpful. Forexample, termites like those you seein Figure 19.4 survive on a diet ofwood. Without the help of a certainspecies of flagellate that lives in theguts of termites, some termites couldnot survive on such a diet. In a mutu-alistic relationship, flagellates convertcellulose from wood into a carbohy-drate that both they and their termitehosts can use.

Ciliates: Protozoans with ciliaThe roughly 8000 members of the

protist phylum Ciliophora, known asciliates, use the cilia that cover theirbodies to move. Use the MiniLab onthis page to observe a typical ciliate’smotion. Ciliates live in every kind ofaquatic habitat—from ponds andstreams to oceans and sulfur springs.What does a typical ciliate look like?To find out, look at the Inside Storyon the next page.

a


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Purpose Students will discover how Para-mecium responds when it contactsa solid object.

Process Skillsobserve and infer, draw a conclu-sion

Teaching Strategies■ Using methyl cellulose to slowthe protists interferes with Para-mecium’s normal response.■ Toothbrush bristles or smallpieces of cotton may be used toblock the path of Paramecium.■ Remind students to use cau-tion when working with micro-scopes, slides, and coverslips.■ Have students wash theirhands after handling cultures.

Expected ResultsParamecium typically reverses thedirection in which its cilia arebeating and backs away from asolid object that it contacts.

Analysis1. It backs up, then proceeds

forward in a new direction.2. briefly 3. The cell turned on its long

axis, and it folded.

Portfolio Have studentsdraw what occurs when Para-mecium encounters solid objectsand write captions for the events.Use the Performance TaskAssessment List for ScientificDrawing in PASC, p. 55.PP

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MMEETING EETING IINDIVIDUAL NDIVIDUAL NNEEDS EEDS MEETING INDIVIDUAL NEEDS

GiftedKinesthetic Ask students to place atermite on a glass slide, grasp its head

with a forceps, and gently pull to separatethe head and intestines from the body. Havestudents add a few drops of Ringer’s solu-tion or water to the termite intestines, add a coverslip, and press gently on the coverslipto squash the intestines. Remind them to

handle glass microscope slides and coverslipscarefully and to use special care when view-ing slides under high power. Then, ask stu-dents to observe the slide under low- andhigh-power magnification, looking for thetermite’s intestinal flagellates. Ask them todiagram and label the flagellates they seeand place their drawings in their portfolios.

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BioLab and MiniLabWorksheets, p. 89

Reteaching Skills Trans-parency 29 and Master

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Charting Protist DiseasesVisual-Spatial Have students use anencyclopedia to make a table about the

causal agents and symptoms of the followingdiseases: malaria, sleeping sickness, Chagas

disease, giardiasis, and amoebic dysentery.Ask them to use the column headings:Kingdom, Phylum, Means of locomotion,Method of transmission, Parasitic or free-liv-ing, and Disease symptoms.

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VIDEODISCSTV: The CellCilia on Paramecium,

SEM Image

Macro- and MicronucleusIdentified

!7QÜ$#"

!7QÜ.$"

Gametes

Zygote Gut wallof mosquito

Mosquito feedson infected person

Human host

Sporozoites

Until World War II, the drug qui-nine was used to treat malaria. Today, acombination of the drugs chloroquineand primaquine are most often usedto treat this disease because they cause

few serious side effects in humans.But, some species of Plasmodium havebegun to resist these drugs. There-fore, quinine is once again being usedto treat the resistant strains.


Figure 19.6The life cycle ofPlasmodium involvestwo hosts—mosqui-toes and humans.

Section AssessmentSection Assessment

Understanding Main Ideas1. Describe the characteristics of the organisms

called protists. Then compare the characteristicsof the four major groups of protozoans. How iseach group of protozoans animal-like?

2. How do amoebas obtain food?3. Explain any differences that exist between cili-

ates and flagellates.4. What makes a sporozoan different from other

protozoan groups?

Thinking Critically5. What role do contractile vacuoles play in helping

freshwater protozoans maintain homeostasis?

6. Sequencing Trace the life cycle of a Plasmodiumthat causes human malaria. Identify all forms ofthe sporozoan and the role each plays in the disease. For more help, refer to OrganizingInformation in the Skill Handbook.

SKILL REVIEWSKILL REVIEW

Spores of Plasmodium enter the mosquito frominfected human blood and produce a zygote. Inthe mosquito’s gut, the zygote develops andeventually releases cells called sporozoites.

AA

Sporozoites enter themosquito’s salivary gland,and are injected into themosquito’s human host.

BB

The blood cells rupture,releasing both toxinsand new spores thatinfect more red bloodcells and multiply.

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The sporozoites reproduce asexuallyin the human’s liver, forming spore-like cells that enter the human’s redblood cells and multiply rapidly.

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ReteachHave students list five generalprotist traits and then make a second list of protozoan-specifictraits.

ExtensionHave students research the phy-lum of the organism Trypanosomacruzi. Ask them to draw and labelthis protist.

Knowledge Have studentsidentify the unrelated word ineach of the following groups:amoeba, foraminiferan, Para-mecium, radiolarian; pseudopodia,cilia, oral groove, pellicle; dysen-tery, AIDS, sleeping sickness,Chagas disease.

4 CloseActivity

Logical-Mathematical Makefive sets of ten index cards

with one of the following wordson each card: locomotion, cilia,pseudopodia, flagella, sarcodines,asexual reproduction, cyst, micro-nucleus, spore, sexual reproduc-tion. Give a set of cards to each offive student groups, telling themto logically sequence the cardsand then explain their sequences.L2

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Section AssessmentSection AssessmentSection Assessment1. Protists are eukaryotes without tissues.

Protozoans are unicellular, heterotrophicprotists. Rhizopods have pseudopodia,Ciliophorans have cilia, and flagella pro-pel Mastigophorans. Sporozoans are par-asites.

2. Pseudopodia entrap prey.3. Flagellates have long, whiplike flagella.

Ciliates have many short, hairlike cilia.

4. All are parasitic, many produce spores,and some cannot move.

5. Contractile vacuoles pump out excesswater that enters the cell by osmosis.

6. Student answers should include the infor-mation in Figure 19.6. Both the humanand mosquito hosts and the forms thatPlasmodium take in each host should bedistinquished.

How do digestive enzymes function in paramecia?Paramecia ingest food particles and enclose them in food vacuoles. Each food vacuole circulates in the cell as the food is digestedby enzymes that enter the vacuole. Digested nutrients areabsorbed into the cytoplasm.

Analysis1. Some digestive enzymes function best at high pH levels,

while others function best at low (more acidic) pH levels.2. Congo red is a pH indicator dye; it is red when the pH is

above 5 and blue when the pH is below 3 (very acidic).3. Yeast cells that contain Congo red can be produced by

adding dye to the solution in which the cells are growing.4. When paramecia feed on dyed yeast cells, the yeast is visi-

ble inside food vacuoles.5. Examine the drawing above. The appearance of a yeast-

filled food vacuole over time is indicated by the coloredcircles inside the paramecium. Each arrow indicates move-ment and the passing of time.

Thinking CriticallyWhat happens to the pH in the food vacuole over time?

Explain what sequence of digestive enzymes might functionin a paramecium.

Problem-Solving Lab 19-1Problem-Solving Lab 19-1 Drawing a ConclusionMany structures found in ciliates’

cells may work together to performjust one important life function. Forexample, Paramecium uses its cilia,oral groove, gullet, and food vacuolesin the process of digestion. Use theProblem-Solving Lab on this page toexplore how a paramecium digeststhe food in a vacuole.

A paramecium usually reproducesasexually by dividing crosswise andseparating into two daughter cells, asyou can see in Figure 19.5. When-ever their food supplies dwindle ortheir environmental conditions change,paramecia usually undergo a form ofconjugation. In this complex process,two paramecia join and exchangegenetic material. Then they separate,and each divides asexually, passing onits new genetic composition.

Sporozoans: Parasitic protozoansProtists in the phylum Sporozoa are

often called sporozoans because mostproduce spores. A spore is a repro-ductive cell that forms without fertil-ization and produces a new organism.

All sporozoans are parasites. Theylive as internal parasites in one or morehosts and have complex life cycles.Sporozoans are usually found in a partof a host that has a ready food supply,such as an animal’s blood or intestines.Plasmodium, members of the sporo-zoan genus, are organisms that causethe disease malaria in humans andother mammals and in birds.

Sporozoans and malariaThroughout the world today, more

than 300 million people have malaria,a serious disease that usually occurs inplaces that have tropical climates. ThePlasmodium that mosquitoes transmitto people cause human malaria. Asyou can see in Figure 19.6, malaria-causing Plasmodium live in bothhumans and mosquitoes.

524 PROTISTS

Figure 19.5A paramecium isdividing into twoidentical daughtercells.


524

Purpose Analyze the role of digestiveenzymes in Paramecium.

Process Skillsobserve and infer, interpret sci-entific illustrations, recognizecause and effect

Teaching Strategies■ Review pH. Inform studentsthat there are both liquid andpaper pH indicators.

Thinking CriticallyIt varies. The pH in a food vac-uole forming at the end of thegullet is above 5. As digestionbegins, the pH drops to below 3and changes again as digestionprogresses. As digestion nearscompletion, the pH increasesuntil it is above 5 again. There aremany digestive enzymes involvedin Paramecium digestion, and theywork at acidic and basic pHs.

Performance Give stu-dents liquids with different pHs.Have them use pH paper to findwhich liquids match the pH inParamecium’s food vacuole at thestart and end of digestion. Usethe Performance Task AssessmentList for Carrying Out a Strategyand Collecting Data in PASC,p. 25.

3 AssessCheck for Understanding

Visual-Spatial Have studentsmake a concept map show-

ing Kingdom Protista’s three sub-groups. Ask them to expand theirmaps to include the four proto-zoan phyla. L2

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Problem-Solving Lab 19-1Problem-Solving Lab 19-1

BIOLOGY JOURNAL BIOLOGY JOURNAL

Malaria and Sickle-Cell AnemiaLinguistic Have students use refer-ences to report about the correlation

between the genetic disease sickle-cellanemia and the protist disease malaria.They should include the evolutionary sig-nificance of such a relationship.

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Resource ManagerResource ManagerCritical Thinking/Problem Solving,

p. 19Laboratory Manual, pp. 133-136 L2

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Reinforcement and StudyGuide, p. 83

Content Mastery, p. 94 L1

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Nucleus

Chloroplast

Mitochondrion

Eyespot

FlagellumPellicle

Contractile vacuole

Going on an Algae Hunt Pond water may be teeming withorganisms. Some are macroscopic organisms, but the majorityare microscopic. Some may be heterotrophs, and othersautotrophs. How can you tell them apart?

Procedure! Copy the data table.

@ Place a drop of pond water onto a glass slide and add acoverslip. CAUTION: Use caution when working with amicroscope, glass slides, and coverslips.

# Observe the pond water under low magnification of yourmicroscope, and look for algae that may be present. Algaefrom a pond will usually be green or yellow-green in color.

$ Diagram several different species of algae in your datatable and indicate if each is motile or nonmotile. Indicateif the algae are unicellular or multicellular.

Analysis1. What characteristic distinguished algae from any proto-

zoans that may have been present?2. Explain how the characteristic in question 1 categorizes

algae as autotrophs.3. Did you observe any relationship between movement and

size? Explain your answer.

MiniLab 19-2MiniLab 19-2 ObservingEuglenoids: Autotrophs and heterotrophs

Hundreds of species of euglenoids(yoo GLEE noydz) make up the phy-lum Euglenophyta. Euglenoids areunicellular, aquatic protists that haveboth plant and animal characteristics.Unlike plant cells, they lack a cell wallmade of cellulose. However, they dohave a flexible pellicle made of pro-tein that surrounds the cell mem-brane. Euglenoids are plantlike inthat most have chlorophyll and pho-tosynthesize. However, they are alsoanimal-like because, when light is notavailable, they can ingest food in waysthat might remind you of some pro-tozoans. In other words, euglenoidscan be heterotrophs. In Figure 19.7,you can see a typical euglenoid.

Euglenoids might also remind youof protozoans because they have oneor more flagella to move. They usetheir flagella to move toward light orfood. In the BioLab at the end of thischapter you can learn more abouthow a euglenoid responds to light.

Diatoms: The golden algaeDiatoms (DI uh tahmz), members of

the phylum Bacillariophyta, are uni-cellular photosynthetic organisms with

Figure 19.7Notice the eyespot in this Euglena gracilis. Itshades a light-sensitive receptor that helps E.gracilis orient itself toward light.

Diagram Unicellular/MulticellularMotile/Nonmotile

Data Table

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2 Teach

PurposeStudents will examine pond waterfor evidence of algae.

Process Skillsapply concepts, classify, compareand contrast, observe and infer

Teaching Strategies■ Collect pond water or scrapealgae from the inside of a fishtank and stir into water.■ Remind students to wear a labapron, gloves, and goggles, tohandle slides carefully, and towash their hands after their work.

Expected ResultsStudents will find many algae.

Analysis1. Algae are green in color.2. Autotrophs contain chloro-

phyll for photosynthesis.3. The smaller the algae the

more likely they are motile.

Performance Have stu-dents use fertilizers to aid algalgrowth. Use the PerformanceTask Assessment List for Carry-ing Out a Strategy and CollectingData in PASC, p. 25.

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Section

526 PROTISTS

What Are Algae?Photosynthesizing protists are

called algae. All algae contain up tofour kinds of chlorophyll as well asother photosynthetic pigments.These pigments produce a variety ofcolors in algae, including purple,rusty-red, olive-brown, yellow, andgolden-brown, and are a way of clas-sifying algae into groups.

Algae include both unicellular andmulticellular organisms. The photo-synthesizing unicellular protists,known as phytoplankton (fite uhPLANK tun), are so numerous thatthey are one of the major producersof nutrients and oxygen in aquaticecosystems in the world. It’s been

estimated that algae produce morethan half of the oxygen generated byEarth’s photosynthesizing organisms.Although multicellular algae maylook like plants because they arelarge and sometimes green, they haveno roots, stems, or leaves. Use theMiniLab on the next page to observesome algae.

Diversity of AlgaeAlgae are classified into six phyla.

Three of these phyla—the eugle-noids, diatoms, and dinoflagellates—include only unicellular species.However, in the other three phyla,which are the green, red, and brownalgae, most species are multicellular.

Each time you inhale, youbreathe in oxygen, much ofwhich is being produced by

plantlike protists. The algae areimportant in the world of livingthings. Just about every liv-ing thing depends eitherdirectly or indirectlyon these protists foroxygen and food.

SECTION PREVIEW

ObjectivesCompare and contrastthe variety of plantlikeprotists.Explain the process of alternation of generations in algae.

Vocabularythalluscolonyfragmentationalternation of

generationsgametophytesporophyte

19.2 Algae: Plantlike Protists

Kelp forest (above) and algae growing in afreshwater pond (inset)

526

Section 19.2

PrepareKey ConceptsIn this section, the diversity ofalgae is explored by focusing onthe characteristics and adapta-tions of members of the six algaephyla. Finally, alternation of gen-erations in algae is discussed.

Planning■ Collect pond water or fish tank

scum for MiniLab 19-2.■ Buy algae for students to taste.


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The large plantlike organism in the picture is giant kelp, a typeof protist called a brown alga. What role does the kelp play inthis ecosystem?

How might the loss of the kelp affect this ecosystem?

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Protozoans and AlgaeNaturalist Have students preparea table that compares and con-

trasts protozoans and algae. Suggestthat they use the headings Similaritiesand Differences. The rows can includetopics such as Cell organization, Nutri-tion, and Cell structures.

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P R O J E C TCulturing Euglena

Kinesthetic Have students establish aculture of Euglena in the following

way. Add 20 rice grains and 5 mL skim milkto 1 L of spring water. Boil for 5 minutes ona hot plate in a glass container. Remind thestudents to wear heat protective gloves oruse tongs to lift heated objects. Add 3 L ofspring water and allow the mixture to cool

overnight. Add 100 mL of a Euglena cultureyou purchased. Students can maintain the cul-ture in a well-lit area without direct sunlightwhile they design an experiment to deter-mine how the numbers of Euglena changeover time. After getting your approval fortheir designs, ask the students to carry outtheir procedures.P

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Resource ManagerResource ManagerBioLab and MiniLab Worksheets,

p. 90Section Focus Transparency 46 and

Master

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VIDEODISCSTV: The CellMagnified View of

Euglenas (1)

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The BioLab at theend of the chaptercan be used at thispoint in the lesson.

YOUR OWNDESIGN

YOUR OWNDESIGN

When diatoms die, their shells sinkto the ocean floor. The deposits ofdiatom shells—some of which aremillions of years old—are dredged ormined, processed, and used as abrasivesin tooth and metal polishes, or addedto paint to give the sparkle that makespavement lines more visible at night.

Dinoflagellates: The spinning algae

Dinoflagellates (di nuh FLAJ uhlayts), members of the phylumDinoflagellata, have cell walls thatare composed of thick celluloseplates. They come in a great varietyof shapes and styles—some evenresemble helmets, and others looklike suits of armor.

Dinoflagellates contain chloro-phyll, carotenoids, and red pigments.They have two flagella located ingrooves at right angles to each other.The cell spins slowly as the flagellabeat. A few species of dinoflagellateslive in freshwater, but most aremarine and, like diatoms, are a majorcomponent of phytoplankton. Manyspecies live symbiotically with jelly-fishes, mollusks, and corals. Some

free-living species are biolumines-cent, which means that they emitlight.

Several species of dinoflagellatesproduce toxins. One toxin-producingdinoflagellate, Pfiesteria piscicida, thatsome North Carolina researchersdiscovered in 1988 has caused a num-ber of fish kills in the coastal areas ofNorth Carolina.

Another toxic species, Gonyaulaxcatanella, produces an extremelystrong nerve toxin that can be lethal.In the summer, these organisms maybecome so numerous that the oceantakes on a reddish color as you cansee in Figure 19.10. This populationexplosion is called a red tide. In somered tides, there can be as many as 40to 60 million dinoflagellates per literof seawater.

The toxins produced during a redtide may make humans ill. Duringred tides, the harvesting of shellfish isusually banned because shellfish feedon the toxic algae and the toxins con-centrate in their tissues. People whoeat such shellfish risk being poisoned.You can learn more about the causesand effects of red tides in the

19.2 ALGAE: PLANTLIKE PROTISTS 529

Figure 19.10Red tides, such as the one shownhere (a), are often caused bydinoflagellates such as this onecalled Gonyaulax (b).

a

b


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Using Science TermsTell students that the prefix dinomeans “whirling” and the suffixflagellate means “whip.” Ask themwhy the name dinoflagellates isappropriate for these algae. Theyspin as their flagellas propel themthrough water.

Concept DevelopmentDescribe coral as a heterotrophand ask students to explain therole of dinoflagellates and coralwhen they live symbiotically.Dinoflagellates make food for thecorals, and the coral reef helps safe-guard dinoflagellates from predators.

ReinforcementCheck that students know themeaning of shellfish, biolumines-cent, and toxins. Discuss why theterm shellfish is a misnomer.Shellfish are not classified as fishes,but as arthropods (shrimp and crabs)or mollusks (clams and squid).

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shells composed of silica. They areabundant in both marine and freshwa-ter ecosystems, where they are a largecomponent of the phytoplankton.

The delicate shells of diatoms, likethose you see in Figure 19.8, mightremind you of boxes with lids. Eachspecies has its own unique shape,decorated with grooves and pores.

Diatoms contain chlorophyll as wellas other pigments called carotenoids

(KER uh teen oydz) that usually givethem a golden-yellow color. The foodthat diatoms make is stored as oilsrather than starch. These oils givefishes that feed on diatoms an oilytaste. They also give diatoms buoy-ancy so that they float near the surfacewhere light is available.

When diatoms reproduce asexu-ally, the two halves of the box sepa-rate; each half then produces a newhalf to fit inside itself. This meansthat half of each generation’s off-spring are smaller than the parentcells. When diatoms are about one-quarter of their original size, theyreproduce sexually by producinggametes that fuse to form zygotes.The zygote develops into a full-sizeddiatom, which will divide asexuallyfor a while. You can see both theasexual and sexual reproductiveprocesses of diatoms in Figure 19.9.

528 PROTISTS

Asexual reproduction

Sexual reproduction

Zygote

Mitosis

Meiosis

Wall formationaround cell

Gametes

Fusion of gametes

Spermreleased

Figure 19.8Diatom shells havemany shapes.


Figure 19.9Diatoms reproduceasexually for severalgenerations before reproducing sexually.

528


Visually ImpairedKinesthetic Allow students to hold apetri dish and explain that its halves

fit together in a manner similar to that ofa diatom’s halves.

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PortfolioPortfolio

Algal NamesLinguistic Although algae areoften called “seaweed, scum, and

sea moss,” none of these terms are scien-tifically correct. Have students find themeaning of each term and then explainwhy it is scientifically incorrect.

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Skill Have the studentsobserve, draw, and label preparedslides of Euglena gracilis. Then,ask them to estimate the size ofthe organism, using the SkillHandbook if they need help.

Reinforcement Visual-Spatial Have studentsmake a concept map that

shows how the six algae phyla arerelated. Ask them to use the fol-lowing terms: plantlike protists,autotrophic, unicellular, mostlymulticellular, diatoms, eugle-noids, dinoflagellates, greenalgae, brown algae, red algae.Have them share their maps onoverhead transparencies.

ActivityKinesthetic Have studentsprepare wet mounts of dia-

tomaceous earth and diagram thediatoms’ shapes. For a source ofdiatoms, scrape the inside of a fishtank. Remind students to handlemicroscopes, slides, and coverslipscarefully.

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VIDEODISCBiology: The Dynamicsof Life

Protists (Ch. 12)Disc 1, Side 2, 26 sec.

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VIDEODISCSTV: The Cell: Diatom,Magnified 300 Times

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VIDEODISCThe Infinite VoyageSecrets from a Frozen

WorldThe Antarctic Peninsula: Pack Iceand Life Cycles (Ch. 6) 10 min. 30 sec.

Effects of UV Radiation onPhytoplankton (Ch. 8)4 min. 30 sec.

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keep their bodies floating near thesurface, where light is available.

The largest and most complex ofbrown algae are kelp. In kelp, thethallus is divided into the holdfast,stipe, and blade. The holdfastsanchor kelp to rocks or the sea bot-tom. Some giant kelps may grow upto 60 meters long. In some parts ofthe world, such as off the Californiacoast, giant kelps form dense, under-water forests. These kelp forests arerich ecosystems and provide a widevariety of marine organisms withtheir habitats.

Green algaeGreen algae make up the phylum

Chlorophyta. The green algae arethe most diverse algae, with morethan 7000 species. The major pig-ment in green algae is chlorophyll,but some species also have yellowpigments that give them a yellow-green color. Most species of greenalgae live in freshwater, but some livein the oceans, in moist soil, on treetrunks, in snow, and even in the furof sloths—large, slow-moving mam-

mals that live in the tropical rain for-est canopy.

Green algae can be unicellular,colonial, or multicellular in organiza-tion. As you can see in Figure 19.12,Chlamydomonas is a unicellular andflagellated green alga. Spirogyra is amulticellular species that forms slenderfilaments. Volvox is a green alga thatcan form a colony, a group of cellsthat lives together in close association.

A Volvox colony is composed ofhundreds, or thousands, of flagellatedcells arranged in a single layer form-ing a hollow, ball-shaped structure.The cells are connected by strands ofcytoplasm, and the flagella of individ-ual cells face outward. The flagellacan beat in a coordinated fashion,spinning the colony through thewater. Small balls of daughtercolonies form inside the large sphere.The wall of the large colony willeventually break open and release thedaughter colonies.

Green algae reproduce both asexu-ally and sexually. For example,Spirogyra reproduces asexually by frag-mentation. During fragmentation, an

531

Figure 19.12Chlamydomonas is a unicellularspecies of green algae (a), whileSpirogyra is a multicellular form(b). The wall of a Volvox colonycontains hundreds of cells (c). Thesmaller balls inside the sphere aredaughter colonies.

OriginWORDWORD

thallusFrom the Greekword thallos, mean-ing “green shoot.”A thallus is a plantwithout stems,roots, or leaves.

Magnification:14�

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531

Why is the number of red tides increasing? Scientistshave been aware of red tide poisoning of birds, fishes, andmammals such as whales andhumans for years. Could the risein red tide poisoning be related to human activities?

AnalysisThe following events are associated with the appearance

of red tides.The dinoflagellate toxin that causes illness and sometimesdeath in humans accumulates in the body tissues of shell-fish, such as clams and oysters.Within five weeks, 14 humpback whales died on beachesin Massachusetts. The whales’ stomachs contained mack-erel with high levels of dinoflagellate toxin.Between 1976 and 1986, the human population of HongKong increased sixfold, and its harbor had an eightfoldincrease in red tides. Human waste water was commonlyemptied into the harbor.Studies show that red tides are increasing world wide.An algal bloom occurs when algae, using sunlight andabundant nutrients, increase rapidly in number to hun-dreds of thousands of cells per milliliter of water.

Thinking Critically1. Which statement above provides evidence that supports

each of the following ideas. Explain each answer.a. Dinoflagellate poisons flow through the food chain.b. Dinoflagellates are autotrophs.c. There is a correlation between human activities and

algae growth.2. All animals equally tolerate dinoflagellate toxins. Which

statement contradicts this idea? Explain your answer.

Problem-Solving Lab 19-2Problem-Solving Lab 19-2Problem-Solving Lab on the next page.

Red algaeRed algae, members of the phylum

Rhodophyta, are multicellular marineseaweeds. The body of a seaweed, aswell as that of some plants and otherorganisms, is called a thallus andlacks roots, stems, or leaves. Redalgae use structures called holdfasts toattach to rocks. They grow in tropicalwaters or along rocky coasts in coldwater. You can see a red alga inFigure 19.11.

In addition to chlorophyll, redalgae also contain photosyntheticpigments called phycobilins. Thesepigments absorb green, violet, andblue light—the only part of the lightspectrum that penetrates water belowdepths of 100 m. Therefore, the redalgae can live in deep water wheremost other seaweeds cannot thrive.

Brown algaeAbout 1500 species of multicellular

brown algae make up the phylumPhaeophyta. Almost all of thesespecies live in salt water along rockycoasts in cool areas of the world.Brown algae contain chlorophyll aswell as a yellowish-brown carotenoidcalled fucoxanthin, which gives themtheir brown color. Many species ofbrown algae have air bladders that

530 PROTISTS

A sperm whale’s carcass

Figure 19.11This Coralline alga is only one ofabout 4000 species of red algae.Some species are popular foods inJapan and other countries.

Recognizing Causeand Effect

A

B

C

D

E

530

Purpose Students will analyze real-lifeevents associated with red tides.

Process Skillsthink critically, acquire informa-tion, draw a conclusion, recog-nize cause and effect

Teaching Strategies■ Have students work in smallgroups, discussing each eventthoroughly.■ Have groups share answers.

Thinking Critically

1. a. A or B—Toxins accumulatein shellfish that humans eat;mackerel eat dinoflagellatesand whales eat the mackerel.b. E—Autotrophs use sun-light and nutrients to grow.c. C—Human populationgrowth correlates with thefrequency of red tides.

2. A or B—Shellfish are notaffected by dinoflagellate tox-ins, but humans are; mackereldo not die from dinoflagellatetoxins, but whales do.

Portfolio Have studentsdiagram dinoflagellates they ob-serve on prepared slides. Use thePerformance Task AssessmentList for Scientific Drawing inPASC, p. 55. L1

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Purchase preserved brown andred algae for class display. Ifpossible, buy some edible algaefor students to taste.

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Cultural DiversityAlgae Harvesting in JapanInform students that people in many areasof the world, particularly Asia, eat somealgae. Point out that algae contain nutrients,such as protein, and many vitamins and min-erals. Algae are eaten fresh and boiled orfried in many Asian recipes. One edible algae

used in Japanese cooking is Porphyra, a redalga commonly called nori. Since the seven-teenth century, the Japanese have harvestednori from Tokyo Bay. Have students researchhow the Japanese harvest algae. Bring insome Japanese foods that contain algae forthe class to sample. L3

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Allow students to feel the tex-ture of agar in a petri dish.Then, display an ingredientlabel from an ice cream cartonthat lists alginate, agar, or car-rageenan, a protein found inred algae. Discuss why algalproducts are used in ice creamand agar. Encourage studentsto think of other productsthat might have a similar algaingredient.

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Visually ImpairedKinesthetic Have students make atextural circle graph that shows the

number of species in each algal phylum.Provide the following data: Euglenoids =800, Diatoms = 10 000, Dinoflagellates =2000, Red algae = 4000, Brown algae =1500, Green algae = 7000.

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Portfolio Have studentsmake a flowchart of the life cycleof Ulva and include the terms:alternation of generations, game-tophyte, sporophyte, mitosis,meiosis, zygote, and gamete.P

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Resource ManagerResource ManagerTech Prep Applications, p. 27Laboratory Manual, pp. 137-140 L2

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Video: Kelp Forests, Disc 3VIDEODISCBiology: The Dynamicsof Life

Kelp Forests (Ch. 13)Disc 1, Side 226 sec.!8JÇ"

VIDEODISCSTV: The CellVolvox With

Chloroplasts

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Malegametophyte

Gametophyte (n)

Gametophyte (n) Femalegametophyte

Gamete Gamete

Spore

Spore

Fertilization

MeiosisZygote

2n 2n 2n n

n

Sporophyte (2n)

individual breaks up into pieces andeach piece grows into a new individual.

Green algae, and some other typesof algae, have a complex life cycle.This life cycle consists of individualsthat alternate between producingreproductive cells called spores andproducing gametes.

Alternation ofGenerations

The life cycles of some algae andall plants have a pattern called alter-

nation of generations. An organismthat has this pattern alternatesbetween a haploid and a diploid gen-eration.

The haploid form of the organismis called the gametophyte because itproduces gametes. The gametes fuseto form a zygote from which thediploid form of the organism, whichis called the sporophyte, develops.Certain cells in the sporophyteundergo meiosis. Eventually, thesecells become haploid spores that candevelop into a new gametophyte. Look

532 PROTISTS


Understanding Main Ideas1. In what ways are algae important to all living

things on Earth?2. Give examples that show why the green algae

are considered to be the most diverse of the sixphyla of algae.

3. In what ways do the sporophyte and gameto-phyte generations of an alga such as Ulva differfrom each other?

4. Why are phycobilins an important pigment inred algae?

Thinking Critically5. Use a table to list the reasons why euglenoids

should be classified as protozoans and also asalgae.

6. Making and Using Tables Construct a table listing the different phyla of algae. Indicatewhether they have one or more cells, their color,and give an example of each. For more help, referto Organizing Information in the Skill Handbook.


Figure 19.13In the life cycle of the sea lettuce, thegenerations alternatebetween haploid(gametophyte) anddiploid (sporophyte).Both fungi and plantsalso alternate genera-tions.

532

3 AssessCheck for UnderstandingHave students describe brieflythree unicellular and three multi-cellular algae phyla.

ReteachHave the class develop a conceptmap of the material in this chap-ter’s first two sections.

ExtensionAsk students to compile a list offoods that contain algae.

Knowledge Make six linedrawings showing an alga fromeach of the six phyla. Give stu-dents sets of the drawings and askthem to list three facts or ideasabout each alga.

4 CloseDiscussion QuestionsHave each student prepare threequestions about algae. Collect thequestions and have the studentsanswer them. L1

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Section AssessmentSection AssessmentSection Assessment1. They are producers of oxygen and the

primary autotrophs of many food chains.2. Chlamydomonas is a unicellular example.

Volvox is a colonial form. Ulva is a multi-cellular alga.

3. Haploid gametophytes form gametesand diploid sporophytes form spores.

4. They can absorb the green, violet, andblue light that penetrates deep water.

5. Their chloroplasts are algaelike and theirlocomotion is protozoanlike.

6. Euglenophyta—one, green, euglena;Bacillariophyta—one, golden, diatom;Dinoflagellata—one, green, yellow, andred, dinoflagellate; Rhodophyta—many,red, red seaweed; Phaeophyta—many,brown, brown seaweed; Chlorophyta—one or many, green, green algae.

VIDEODISCThe Infinite Voyage The Living Clock,

Circadian Rhythm and theBiological Clock (Ch. 4)

5 min.!7KVF"


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What are FunguslikeProtists?

Certain groups of protists, theslime molds, the water molds, andthe downy mildews, consist of organ-isms with some funguslike features.Recall that fungi are heterotrophicorganisms that decompose organicmaterials to obtain energy. Likefungi, the funguslike protists decom-pose organic materials.

There are three phyla of fungus-like protists. Two of these phyla con-sist of slime molds. Slime molds havecharacteristics of both protozoans

and fungi and are classified by theway they reproduce. Water moldsand downy mildews make up thethird phylum of funguslike protists.Although funguslike protists are notan everyday part of human lives,some disease-causing species damagevital crops.

Slime MoldsMany slime molds are beautifully

colored, ranging from brilliant yellowor orange to rich blue, violet, and jetblack. They live in cool, moist, shadyplaces where they grow on damp,

19.3 SLIME MOLDS, WATER MOLDS, AND DOWNY MILDEWS 533

When you walk through thewoods, you might notice aspot of color on a fallen log.

Turning the log over, you uncover aglistening mass of yellow-orangeslime that fans out over the log.What you’ve found is a slime mold,one of a variety of funguslike protists.Slime molds, along with water moldsand downy mildews, obtain energy bydecomposing organic materials,and play an important rolein recycling nutrients inmany ecosystems.

SECTION PREVIEW

ObjectivesContrast the cellulardifferences and lifecycles of the two typesof slime molds.Discuss the economicimportance of thedowny mildews andwater molds.

Vocabularyplasmodium

19.3 Slime Molds, Water Molds,and Downy Mildews

A plasmodial slimemold that is feeding(above) and repro-ducing (inset)

533

Section 19.3

PrepareKey ConceptsThis section presents the charac-teristics of funguslike protists.The phyla of plasmodial slimemolds, cellular slime molds, andwater molds and downy mildewsare described. Finally, the originof protists is discussed.

Planning■ Obtain meat, string, and an

aquarium for the Quick Demo.


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The pictures show some stages of the life cycle of a cellularslime mold, a funguslike protist. During which part is the slimemold animal-like?

Why might it be difficult to classify slime molds?

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Spore-filled capsule

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English Language LearnersLinguistic Reinforce terms studentscan use to recall the three groups

of protists. For animal-like protists, useunicellular, motile, and heterotroph. Forplantlike protists, use photosynthetic,autotroph, unicellular, and multicellular. For funguslike protists, use heterotroph and decomposer.

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digesting them in food vacuoles. Atthat rate, a plasmodium would crossyour textbook page in eight hours.

A plasmodium may reach morethan a meter in diameter and containthousands of nuclei. However, whenmoisture and food become scarce inits surroundings, a plasmodiumtransforms itself into many separate,stalked, spore-producing structures.Meiosis takes place within thesestructures and produces haploidspores, which the wind disperses. Aspore germinates into either a flagel-lated or an amoeboid cell, or agamete, that can fuse with anothercell to form a zygote. The diploidzygote grows into a new plasmodium.

Cellular slime moldsUnlike plasmodial slime molds,

cellular slime molds spend part of

their life cycle as an independentamoeboid cell that feeds, grows, anddivides by cell division, as shown inFigure 19.15. When food becomesscarce, these independent cells joinwith hundreds or thousands of othersto reproduce. Such an aggregation ofamoeboid cells resembles a plasmod-ium. However, this mass of cells ismulticellular—made up of manyindividual amoeboid cells, each witha distinct cell membrane. Cellularslime molds are haploid during theirentire life cycle.


Figure 19.15The reproductive cycleof a cellular slime moldis complex (a). Singlecells clump and form astructure that resemblesa small garden slug (b).Eventually, the clumpforms a stalked repro-ductive structure thatproduces spores (c).

OriginWORDWORD

plasmodiumFrom the Greekword plassein,meaning “mold,”and the Latin wordodium, meaning“hateful.” One formof a slime mold is a plasmodium.

a

b

Cellsgather

The mass compactsand forms asluglike structure

The sluglikestructuremigrates

Spore-filledcapsule on astalk forms

SporesAmoebalikecells released

Cells feed,grow, and divide

Multicellularamoeboid likemass forms

c


ReinforcementPrepare an overview that illus-trates the relationship betweenthe phyla Myxomycota andAcrasiomycota and KingdomProtista.

Performance Have eachstudent write two questions aboutslime molds. Divide the class intopairs and have students quiz eachother. L1

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Analysis1. Describe the slime mold’s appearance

and behavior. Is it a plasmodial or cellu-lar slime mold? yellow, bloblike, stringy,moves very slowly—plasmodium

2. Describe the slime mold’s microscopicappearance and behavior. Materialflows within the slime mold, stops, thenflows in the opposite direction.

Knowledge Write a paragraphexplaining if you observed the feeding orthe reproductive stage of the slime mold.Use the Performance Task AssessmentList for Writing in Science in PASC,p. 87. L2

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535

What changes occur during a slime mold’s life cycle?Plasmodial slime molds undergo a number of different stagesduring their life cycle. The most visible stage is the plasmodialstage, where the organism looks like a slimy mass of material.The plasmodium changes into a reproductive stage that ismicroscopic and, therefore, less visible.

AnalysisExamine the life cycle of a plasmodial slime mold. The

structures below the dashed line are diploid in chromosomenumber. Based on the diagram and your understanding ofmitosis and meiosis, answer the questions below.

Thinking Critically1. What cell process, mitosis or meiosis, takes place between

F and G? Explain why. Between A and B? Explain why.2. What letter best shows fertilization occurring? Motile

spores? An embryo? Explain why in each case.3. During which stage does the slime mold feed? Explain.

Problem-Solving Lab 19-3Problem-Solving Lab 19-3 Predicting

organic matter such as rotting leavesor decaying tree stumps and logs.

There are two major types of slimemolds—plasmodial slime molds andcellular slime molds. The plasmodialslime molds belong to the phylumMyxomycota, and the cellular slimemolds make up another grouping,the phylum Acrasiomycota.

Slime molds are animal-like duringmuch of their life cycle, moving aboutand engulfing food in a way similar tothat of amoebas. However, like fungi,slime molds make spores to repro-duce. Use the Problem-Solving Lab onthis page to learn more about the lifecycle of a slime mold.

Plasmodial slime moldsPlasmodial slime molds get their

name from the fact that they form aplasmodium (plaz MOHD ee um), amass of cytoplasm that containsmany diploid nuclei but no cell wallsor membranes. This slimy, multinu-cleate mass, like the one you see inFigure 19.14, is the feeding stage ofthe organism. The plasmodiumcreeps like an amoeba over the sur-faces of decaying logs or leaves.Some plasmodiums move at the rateof about 2.5 centimeters per hour,engulfing microscopic organisms and

534 PROTISTS

Figure 19.14The moving, feedingform of a plasmodialslime mold is a multi-nucleate blob ofcytoplasm.

AB

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D

EF

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Spores

Reproductivestages

Growth stages

2 Teach

Purpose Students will relate cell divisionto a slime mold’s life cycle.

Process Skillsapply concepts, interpret scien-tific illustrations, think critically

Teaching Strategies■ Grow slime molds and havestudents observe them with astereo microscope.■ Review mitosis, meiosis, fertil-ization, and spore formation.

Thinking Critically

1. mitosis—cell growth; meio-sis—haploid gamete forma-tion (gametes form at C)

2. D—two gamete cells join;C—cells with flagella; E—itresults from fertilization.

3. growth stage—organisms usefood to grow

Performance Have stu-dents grow slime molds from pur-chased spores. Use the Perform-ance Task Assessment List forCarrying Out a Strategy andCollecting Data in PASC, p. 25.

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Alternative LabObserving Slime Mold

Purpose Allow students to observe a plasmodium-type slime mold.Materialspetri dish with plasmodium stage of

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Physarum polycephalum (Prepare subcul-tures two days in advance by cutting sec-tions from the culture, putting the pieceson plastic agar plates that contain a fewflakes of oat cereal moistened with distilledwater.); stereo microscopeProcedureGive students the following directions.

1. Wear a lab apron, gloves, and safetygoggles during this lab.

2. Observe the slime mold.

3. Design a way to determine if theorganism moves or not.

4. Record your macroscopic observations. 5. Use a stereo microscope to observe the

slime mold. Record your observationsabout its microscopic appearance andbehavior.

6. Wash your hands thoroughly when youfinish. Dispose of the slime mold asyour teacher directs.

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Video: Slime MoldDisc 3

VIDEODISCVIDEOTAPEThe Secret of Life

On the Brink: Portraits ofModern Science

VIDEODISCBiology: The Dynamicsof Life

Slime Mold (Ch. 14)Disc 1, Side 2, 14 sec.

!8TÉ"

!7@Z'ULA"


Concept Mapping, p. 19

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PRESENT PALEOZOIC PRECAMBRIANMESOZOICCENOZOIC

Oomycotes175 species

Myxomycotes450 species

Phaeophytes1500 species

Bacillariophytes10 000 species

Chlorophytes7000 species

Rhizopods11 500 species

Flagellates2500 species

Ciliates8000 species

Sporozoans3900 species

Animals

Plants

Fungi

Euglenophytes800 species

Dinoflagellates1000 species

Rhodophytes4000 species

Acrasiomycotes65 species

Figure 19.17This fanlike diagram showsthe relationships of the dif-ferent protist phyla on theGeologic Time Scale.


Understanding Main Ideas1. Describe the protozoan and funguslike charac-

teristics of slime molds.2. Why might some biologists refer to plasmodial

slime molds as acellular slime molds. (Hint: Look in Appendix B for the origins of scientificterms.)

3. How could a water mold eventually kill a fish?4. How does a plasmodial slime mold differ from a

cellular slime mold?

Thinking Critically5. In what kinds of environments would you expect

to find slime molds? Explain your answer.

6. Observing and Inferring If you know that a plasmodium consists of many nuclei within a single cell, what can you infer about the processthat formed the plasmodium? For more help,refer to Thinking Critically in the Skill Handbook.


PROTISTS

537

Knowledge Ask studentsto list several protozoanlike traitsand several funguslike traits of thefunguslike protists.

4 CloseActivityHave students list five wordsrelated to funguslike protists. Tellthem that four words must berelated to each other, and thefifth word must be unrelated.Collect the lists. Copy some listsonto the chalkboard and, in eachcase, have the class find the unre-lated word and describe how theremaining words are related. L2

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Section AssessmentSection AssessmentSection Assessment1. They are protozoanlike in that at differ-

ent stages they have flagella and theability to move like amoebas. They arefunguslike in that they produce spores,and many are saprophytic decomposers.

2. The plasmodium is a mass of cytoplasmcontaining many nuclei but no cell wallsor membranes that separate cells.

3. The mold digests its tissues.

4. Plasmodial slime molds feed as a multinu-cleated plasmodium, but cellular slimemolds feed as amoeboid cells.

5. Slime molds should live in moist environ-ments where the moisture would preventdehydration and provide the conditionstheir food supply needs to thrive.

6. The process suggests mitosis without celldivision.

Water Molds and Downy Mildews

Water molds and downy mildewsare both members of the phylumOomycota. Most members of thislarge and diverse group of funguslikeprotists live in water or moist places.As shown in Figure 19.16, some feedon dead organisms and others areplant parasites.

Most water molds appear as fuzzy,white growths on decaying matter.They resemble some fungi becausethey grow as a mass of threads over afood source, digest it, and thenabsorb the nutrients. But at somepoint in their life cycle, water moldsproduce flagellated reproductivecells—something that fungi never do.This is why water molds are classifiedas protists rather than fungi.

One economically importantmember of the phylum Oomycota isa downy mildew that causes diseasein many plants. In the Social Studies

Connection at the end of the chapter,you can read about a downy mildewcalled Phytophthora infestans that hasaffected the lives of many people bydestroying their major food crop.

Origin of ProtistsHow are the many different kinds

of protists related to each other andto fungi, plants, and animals? You cansee the relationships of protists toeach other in Figure 19.17.

Although taxonomists are nowcomparing the RNA and DNA ofthese groups, there is little conclusiveevidence to indicate whether ancientprotists were the evolutionary ances-tors of fungi, plants, and animals orwhether protists emerged as evolu-tionary lines that were separate.Because of evidence from compara-tive RNA sequences in modern greenalgae and plants, many biologistsagree that ancient green algae wereprobably ancestral to modern plants.

536 PROTISTS

Figure 19.16Water molds and downy mildews live inmoist places and cause both plant andanimal diseases.

The downy mildewPhytophthorainfestans is killing this potato plant.

AA

The water mold growingon this insect is decompos-ing the insect’s tissues andabsorbing the nutrients.

BB


536

Visual LearningFigure 19.17 Review the rela-tionships among the differentprotist phyla shown in the figure.

3 AssessCheck for Understanding

Naturalist Have studentscompare and contrast the

three funguslike protist phyla.Ask them to explain why theseorganisms are classified as pro-tists and not fungi.

ReteachNaturalist Have studentgroups prepare charts that

compare and contrast the phylaMyxomycota, Acrasiomycota, andOomycota.

ExtensionVisual-Spatial Have studentsmake flowcharts of the life

cycles of Myxomycota and Acra-siomycota organisms and includethe chromosome number foreach stage. L3

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Note Internet addressesthat you find useful in

the space below for quick reference.


Origin of ProtistsLinguistic Have students write aparagraph offering their views on

the origin of and relationships amongprotists.

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Visual-Spatial Tie stringaround a piece of meat

and suspend it in the water ofan aquarium. After severaldays, remove the meat andhave students examine it bothmacroscopically and with astereo microscope and re-cordtheir observations. Have stu-dents wear a lab apron anddisposable gloves.

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Reinforcement and StudyGuide, p. 86

Content Mastery,pp. 93, 95-96 L1

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PLAN THE EXPERIMENTPLAN THE EXPERIMENT

1. Decide on an experimental pro-cedure that you can use to testyour hypothesis.

2. Record your procedure, step-by-step, and list the materialsyou will be using.

3. Design a data table in which torecord your observations andresults.

Check the PlanDiscuss all the following points

with other group members to deter-mine your final procedure.1. What variables will you have to

measure?2. What will be your control?3. What will be the shape of the

light-controlled area(s) on yourmicroscope slide?

4. Decide who will prepare mate-rials, make observations, andrecord data.

5. Make sure your teacher has ap-proved your experimental planbefore you proceed further.

6. To mount drops of Parameciumculture and Euglena culture onmicroscope slides, use a tooth-pick to place a small ring ofmethyl cellulose on a cleanmicroscope slide. Place a drop of Paramecium or Euglena culture within this ring. Place a coverslip over the ring and cul-ture. The thick consistency of methyl cellulose should slow down the organisms for easy observation.

7. Make preliminary observationsof swimming Paramecia andEuglena. Then think againabout the observation timesthat you have planned. Maybeyou will decide to allow moreor less time between yourobservations.

8. Carry out your experiment.


1. Checking Your Hypothesis Didyour data support your hypothesis?Why or why not?

2. Comparing and ContrastingCompare and contrast all the re-sponses of the Paramecium andEuglena to both light and darkness.What explanations can you suggestfor their behavior?

3. Making Inferences Can you useyour results to suggest what sort of responses to light and darknessyou might observe using other het-erotrophic or autotrophic protists?

ANALYZE AND CONCLUDEANALYZE AND CONCLUDE

Going FurtherGoing Further

Project You may want to extend this experi-ment by varying the shapes or relative sizes oflight and dark areas or by varying the bright-ness or color of the light. In each case, makehypotheses before you begin. Keep your datain a notebook, and draw up a table of yourresults at the end of your investigations.

To find out more aboutprotists, visit the Glencoe

Science Web Site.www.glencoe.com/sec/science

YOUR OWNDESIGN

YOUR OWNDESIGN

1. Answers may vary. Data mustbe used to either support orreject student hypotheses.

2. Euglena are attracted to light.Paramecium avoid brightlight. Euglena need light tomake food. Heterotrophic,Paramecium can find food indim and dark places.

3. Most autotrophs show a posi-tive response to light whereasmost heterotrophs show anegative response.

Error AnalysisAdvise students to do several tri-als for each organism. Ask themwhy this is important.

Portfolio Have studentswrite an evaluation of what theylearned in this investigation. Usethe Performance Task AssessmentList for Writing in Science inPASC, p. 87. L2

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ANALYZE AND CONCLUDEANALYZE AND CONCLUDE

539

Data and ObservationsData should indicate that Euglena areattracted to light; Paramecium are not.

Going FurtherGoing Further

Students may wish to test theresponse of these protists toother factors, such as differentconcentrations of salt solutions.

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538 PROTISTS

How do Paramecium andEuglena respond to light?

M embers of the genus Paramecium are ciliated protozoans—unicellular, heterotrophic protists that move around in search of

small food particles. Euglena are unicellular algae—autotrophic protiststhat usually contain numerous chloroplasts. In this BioLab, you’ll investigate how these two protists respond to light in their environment.

YOUR OWNDESIGN

YOUR OWNDESIGN

ProblemDo both Paramecium and Euglena

respond to light and do they respondin different ways? Among the mem-bers of your group, decide on onetype of protist activity that wouldconstitute a response to light.

HypothesesDecide on one hypothesis that you

will test. Your hypothesis might bethat Paramecium will not respond tolight and Euglena will respond, orthat Paramecium will move away fromlight and Euglena will move towardlight.

ObjectivesIn this BioLab, you will:■ Prepare slides of Paramecium and

Euglena cultures and observe swim-ming patterns in the two organ-isms.

■ Compare how these two differentprotists respond to light.

Possible MaterialsEuglena cultureParamecium culturemicroscopemicroscope slidesdroppermethyl cellulosecoverslipsmetric rulerindex cardsscissorstoothpicks

Safety PrecautionsAlways wear goggles in the lab.

Use caution when working with amicroscope, glass slides, and cover-slips. Wash your hands with soap andwater immediately after working withprotists and chemicals.

Skill HandbookUse the Skill Handbook if you need

additional help with this lab.

PREPARATIONPREPARATION

YOUR OWNDESIGN

YOUR OWNDESIGN

538

Time Allotment One class period

Process Skillsobserve and infer, experiment,form a hypothesis, identify andcontrol variables

Safety PrecautionsRemind students to be carefulwhen working with microscopes,slides, and coverslips and to usespecial care when viewing a slideunder high power. Have studentswash their hands after finishingthe lab.

■ To demonstrate how Euglenaand Paramecium respond tolight, cover a test tube con-taining Euglena with blackpaper containing a narrow,slitlike opening. Leave thetube in bright light for 12hours and then remove thepaper. Where the slit waslocated, students should ob-serve a green band of Euglena.Cover half of a test tube con-taining Paramecium with blackpaper, place the tube on itsside in bright light for 12hours. Paramecium should con-gregate in the covered side.

Possible HypothesesIf Paramecium are attracted tolight, then they will move to thelight zone on a glass slide con-taining both light and dark zones.

If Euglena are attracted tolight, then they will move to thelight zone on a glass slide con-taining both light and dark zones.

PREPARATIONPREPARATION

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Teaching Strategies■ Provide time for students to observe theorganisms’ size, speed, and mobility under amicroscope before they begin.■ Have students use low power to observeParamecium (a 5� objective works best) andhigh power to observe Euglena.■ Advise students that they must countorganisms quickly.

Possible Procedures■ Index cards can provide a light and dark

microscope zone. Cut the cards to fit overpart of the coverslip. Students shouldfocus on the edge of the card to observeeach organism’s direction of movement.If possible, use coverslips (22 � 30 mm or22 � 40 mm) that cover a large area.

■ Prepare or purchase methyl cellulose.

Resource ManagerResource ManagerBioLab and MiniLab Worksheets,

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Chapter 19 AssessmentChapter 19 Assessment

SUMMARYSUMMARY

Section 19.1

Section 19.2

Section 19.3

Main Ideas■ Kingdom Protista is a diverse group of living

things that contains animal-like, plantlike, andfunguslike organisms.

■ Some protists are heterotrophs, some are auto-trophs, and some get their nutrients by decom-posing organic matter.

■ Amoebas move by extending pseudopodia. Theflagellates use one or more flagella to move.The beating of cilia produces cilliate movement.Sporozoans live as parasites and produce spores.

Vocabularyalgae (p. 519)asexual reproduction

(p. 521)ciliate (p. 522)flagellate (p. 522)protozoan (p. 519)pseudopodia (p. 520)spore (p. 524)sporozoan (p. 524)

The World of Protists

Main Ideas■ Algae are unicellular and multicellular photo-

synthetic autotrophs. Unicellular species includethe euglenoids, diatoms, dinoflagellates, andsome green algae. Multicellular species includered, brown, and green algae.

■ Green, red, and brown algae, often called sea-weeds, have complex life cycles that alternatebetween haploid and diploid generations.

Vocabularyalternation of

generations (p. 532)colony (p. 531)fragmentation (p. 531)gametophyte (p. 532)sporophyte (p. 532)thallus (p. 530)

Algae: PlantlikeProtists

Main Ideas■ Slime molds, water molds, and downy mildews

are funguslike protists that decompose organicmaterial to obtain nutrients.

■ Plasmodial and cellular slime molds change in appearance and behavior before producingreproductive structures.

Vocabularyplasmodium (p. 534)

Slime Molds,Water Molds,and DownyMildews

CHAPTER 19 ASSESSMENT 541

1. Which organisms cause red tides?a. dinoflagellates c. green algaeb. euglenoids d. red algae

2. Which organelle in protists is able to elimi-nate excess water?a. anal pore c. contractile vacuoleb. mouth d. gullet

UNDERSTANDING MAIN IDEASUNDERSTANDING MAIN IDEAS 3. Which of the following pairs contains termsmost related to each other?a. paramecium—alternation of generationsb. asexual reproduction—gametophytec. sporozoan—ciliad. amoeba—pseudopodia

4. Producers in aquatic food chains include________.a. algae c. slime moldsb. protozoans d. amoebas

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Chapter Assessment, pp. 109-114MindJogger VideoquizzesComputer Test BankBDOL Interactive CD-ROM, Chapter

19 quiz

Main IdeasSummary statements can be used bystudents to review the major con-cepts of the chapter.

Using the VocabularyTo reinforce chapter vocabulary, usethe Content Mastery Booklet andthe activities in the Interactive Tutorfor Biology: The Dynamics of Life onthe Glencoe Science Web Site.www.glencoe.com/sec/science

1. a2. c3. d4. a

UNDERSTANDING MAIN IDEASUNDERSTANDING MAIN IDEAS

All ChapterAssessment

questions and answers have beenvalidated for accuracy and suitabil-ity by The Princeton Review.

A funguslike protist known as Phytophthorainfestans causes a disease called potato blight.

Between the years 1845–1847, the disease damaged or totally destroyed the Irish potato

crop—a primary food source for about one-thirdof the Irish population at the time. A severe

seven-year famine resulted.

The potato was first grown in Ireland in thelate 1500s and within 200 years was a wide-

spread food crop. Potatoes grew well in the tem-perate, rainy Irish climate. They were not vul-nerable to many diseases, needed no processing,and were nutritious. In addition, most Irish peo-ple were tenant farmers with farms averagingfewer than 15 acres. Enough potatoes could begrown on a few acres to support an entire familyfor a year. By 1845, the potato crop fed a largepercentage of the Irish population.

Invasion of a downy mildew Historians suggest that Phytophthora infestans arrived inIreland in 1845 on a ship that arrived fromNorth America. The wet conditions in Irelandduring July and August that year were ideallysuited for the spread of the protist, a downymildew, which is classified in the phylum

Oomycota. In addition, the wind probably widelydispersed the P. infestans spores, infecting theleaves and stems of mature potato plants. Thespores also washed into the soil and infected theunderground stems, or tubers, of the potatoes.The potato blight damaged the Irish potato cropin 1845, and it destroyed nearly the entire potatocrop in one week’s time in the summer of 1846.

Mass emigration of the Irish Many Irish people starved in the years that followed. Manyothers emigrated from Ireland. By 1855, thepopulation of Ireland had fallen from about eightmillion to four million. The Irish immigratedprimarily to four countries, the United States,England, Canada, or Australia. The large num-bers of immigrants greatly affected the socialstructure of these four countries as well as that of Ireland.

Most of the Irish quickly adapted to theirnew homes. For example, in the United States,some Irish became politically active. In fact, John F. Kennedy, who was president of theUnited States from 1960–1963, was the great-great-grandson of an Irish tenant farmer whoimmigrated to the United States in 1848.

Many Irish people who immigrated to theUnited States at the time of this famine settled in the large East Coast cities, such as New York,Philadelphia, and Boston. Their descendants arenow an integral part of American society and livethroughout the United States.

ConnectionSocial StudiesSocial Studies

Connection The Irish PotatoFamine

Today, fungicides, chemicals that prevent fungalgrowth, control outbreaks of Phytophthora infes-tans. How might this information affect researchabout the evolutionary relationships of fungus-like protists?

To find out more about the Irishpotato famine and Phytophthora,

visit the Glencoe Science Web Site.www.glencoe.com/sec/science

CONNECTION TO BIOLOGYCONNECTION TO BIOLOGY

540

Purpose Students will learn why a balancebetween humans and the organ-isms in their environment isimportant.

Teaching Strategies■ Ask what influences other thanfamine might lead to mass emi-grations? Climatic changes, partic-ularly droughts, political upheavals,wars, economic devastation.

Connection to BiologyWith fewer infestations of Phyto-phthora infestans, it is more diffi-cult to determine its evolutionaryrelationships. Outbreaks of P.infestans are minimized by the useof fungicides, but new resistantstrains have arisen that are diffi-cult to control and that destroymany crops. In addition, theoveruse of pesticides hasincreased the number of crop-damaging insects, making somecrops more susceptible to insectdestruction.

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Connection


Note Internet addresses that you find useful in the spacebelow for quick reference. VIDEOTAPE

MindJogger VideoquizzesChapter 19: ProtistsHave students work in groups as they playthe videoquiz game to review key chapterconcepts.




CHAPTER 19 ASSESSMENT 543

24. Up to the late 1800s, malaria was common inthe extreme southeastern part of the UnitedStates. In an attempt to fight the disease,ponds and wetlands were often filled in ordrained. How do you suppose this actionhelped cut down on the number of malariacases?

25. Observing and Inferring Why do you sup-pose many people who own aquariums addsnails to them?

26. Formulating Hypotheses In agriculturalregions where farmers use large amounts ofnitrogen fertilizers in their fields, local pondsand lakes often develop a thick, green scumcontaining algae in late summer. Hypothesizewhy this happens.

27. Sequencing Sequence the stages of both sexual and asexual reproduction in diatoms.

28. Concept Mapping Complete the conceptmap by using the following vocabulary terms:amoebas, sporozoans, flagellates, protozoans,ciliates

THINKING CRITICALLYTHINKING CRITICALLY

ASSESSING KNOWLEDGE & SKILLSASSESSING KNOWLEDGE & SKILLS

During a summer ecology class, a group ofhigh school students studied unicellularalgae at a site in the middle of a pond. Forthree days and nights, they measured thenumber of cells in the water at variousdepths. They produced the following graphbased on their data.

Interpreting Data Use the graph to answerthe following questions.1. At what time were the highest concen-

trations of diatoms at the surface?a. midnight c. 3 a.m.b. noon d. 6 p.m.

2. At what time were the highest concen-trations of diatoms about a meter belowthe surface?a. midnight c. 3 a.m.b. noon d. 6 p.m.

3. Which of the following is the best de-scription of the movement of diatoms inthe water column?a. 6-hour cycleb. 12-hour cyclec. 24-hour cycled. irregular cycling

4. Interpreting Data Why might the dia-toms show the pattern found by thegroup of high school students?

For additional review, use the assessmentoptions for this chapter found on the Biology: TheDynamics of Life Interactive CD-ROM and on theGlencoe Science Web Site.www.glencoe.com/sec/science

CD-ROM

Loca

tion

of h

ighe

st c

once

ntra

tion

of d

iato

ms

Times in hours

Locations of Diatoms

Surface

50 cm

100 cm12 a.m. 12 p.m. 12 a.m. 12 p.m. 12 a.m.

Animal-like protistsare called

1.

2. 3. 4.

that usecilia tomove

that usepseudopods

to move

that useflagella to

move

that producespores and

are parasites

5.

includeinclude include include

543

24. Mosquitoes breed in water. The elimination of breedinggrounds reduces the mosquitopopulation and reduces the riskof contracting malaria.

25. Snails help keep the growth ofunwanted algae in check.

26. The nitrogen fertilizers run offinto water sources, where theystimulate the growth andreproduction of algae.

27. A diatom reproduces asexuallyfor several generations, with itscell walls getting progressivelysmaller and smaller. Eventually,the cell undergoes meiosis andreleases gametes that grow anew cell with a large cell wall.Then, the new diatoms beginreproducing asexually.

28. 1. Protozoans; 2. Amoebas; 3.Ciliates; 4. Flagellates; 5.Sporozoans

THINKING CRITICALLYTHINKING CRITICALLY


1. b2. a3. c4. They are photosynthetic

and move to the surfaceto utilize sunlight duringdaylight hours.


5. Protists are classified on the basis of their________.a. nutritionb. method of locomotionc. reproductive abilitiesd. size

6. Euglenoids are unique algae because of their________.a. flagellab. ciliac. silica wallsd. heterotrophic nature

7. Which of the following is not a protist?

a. c.

b. d.

8. The algae that can survive in the deepestwater are the ________?a. brown algae c. diatomsb. red algae d. green algae

9. The largest and most complex of brown algaeare the ________.a. kelp c. sea lettuceb. Chlamydomonas d. Spirogyra

10. Which of the following are protected by ar-mored plates?a. kelp c. dinoflagellatesb. fire algae d. diatoms

11. Unlike bacteria, all protists are ________.

12. The protozoan that causes malaria is classi-fied as a ________ because it is a spore-producing parasite.

13. Volvox is an alga that lives in a ________, agroup of cells in close association.

14. What type of structure does the protist shown to the right use to move?

15. Asexual reproduction may occur when anorganism breaks into pieces in a processknown as ________.

16. Diatoms and dinoflagellates are two phyla ofprotists in the group collectively called________.

17. The haploid form of an alga that has alterna-tion of generations is known as the ________,and the diploid form is the ________.

18. Amoebas, cilliates, flagellates, and sporozoansare collectively called ________.

19. Individual cells of a cellular slime mold mayfuse to form a structure that resembles a________ and that reproduces.

20. Paramecia move about using short projec-tions called ________, but euglenas moveusing a long projection, the ________.

21. Why is it a disadvantage for a sporozoan tobe a parasite? How might a sporozoan’smethod of asexual reproduction offset thisdisadvantage?

22. In which ecosystem would a plasmodial slimemold transform itself into spore-producingstructures more frequently: a rainy forest inthe Pacific Northwest or a dry, oak forest inthe Midwest? Explain your answer.

23. Give three examples of organelles that helpprotists maintain homeostasis in their envi-ronments.

APPLYING MAIN IDEASAPPLYING MAIN IDEAS

542 CHAPTER 19 ASSESSMENT

TEST–TAKING TIPTEST–TAKING TIP

Work Weak Areas, Maintain Strong OnesIt’s sometimes difficult to focus on all the conceptsneeded for a test. So ask yourself “What’s mystrongest area?” and “What’s my weakest area?”Focus most of your energy on your weak areas. Butalso put in some “upkeep” time in your strongestareas.

542

5. a6. d7. b8. b9. a

10. c11. eukaryotes12. sporozoan13. colony14. flagellum15. fragmentation16. algae17. gametophyte; sporophyte18. protozoans19. plasmodium20. cilia; flagellum

21. Finding a suitable host; produc-ing many spores will improvethe possibility of survivalbecause some of the spores mayfind a host.

22. oak forest—dry conditions stim-ulate spore-producing struc-tures.

23. Answers will vary, but mayinclude cilia, pseudopodia, fla-gella, eyespots, contractile vac-uoles, or others.

APPLYING MAIN IDEASAPPLYING MAIN IDEAS



chapter 19: protists text...they decompose dead organisms. however, unlike fungi, funguslike...

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