Chapter 24: Reproduction in Plants€¦ · 652 REPRODUCTION IN PLANTS Reproduction in Plants What You’ll Learn You will compare and con-trast the life cycles of mosses, ferns, and

Chapter 24 OrganizerChapter 24 Organizer

Activities/FeaturesObjectivesSection

MATERIALS LIST

BioLabp. 678 microscope, microscope slide(2), coverslips (2), dropper, water, sin-gle-edged razor blade, colored pencils(red, green, and blue), hand lens,flower (complete)

MiniLabsp. 654 potato, garlic clove, carrot, testtube, petri dish, beaker, toothpicks,water, paper, pencilp. 677 microscope, corn kernels andbean seeds (germinating and ungermi-nated), paper towels, plastic zipperbags, single-edged razor blade

Alternative Labp. 674 canned kidney beans, papercup, water, dried kidney beans, waxpaper, labels, tetrazolium solution,dropper bottle

Quick Demosp. 657 photomicrographs of gameto-phytes, metric rulerp. 662 flower (rose or daffodil)p. 668 peanutp. 672 tomato, peach

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

652A

Teacher Classroom Resources

Assessment Resources Additional Resources

Products Available From GlencoeTo order the following products, call Glencoeat 1-800-334-7344:CD-ROMNGS PictureShow: What It Means to Be GreenCurriculum KitGeoKit: PlantsTransparency SetNGS PicturePack: What It Means to Be GreenVideodiscSTV: Plants

Teacher’s Corner

652B

Reproduction in PlantsReproduction in Plants

TransparenciesReproducible MastersSection

Life Cycles ofMosses, Ferns,and Conifers

Flowers andFlowering

The Life Cycle ofa Flowering Plant

Section 24.1

Section 24.2

Section 24.3

Teacher Classroom Resources

Reinforcement and Study Guide, pp. 105-106Concept Mapping, p. 24BioLab and MiniLab Worksheets, p. 109Content Mastery, pp. 117-118, 120

Reinforcement and Study Guide, p. 107Content Mastery, pp. 117, 119-120Inside Story Poster

Reinforcement and Study Guide, p. 108Critical Thinking/Problem Solving, p. 24BioLab and MiniLab Worksheets, pp. 110-112Laboratory Manual, pp. 171-178Content Mastery, pp. 117, 119-120 L1

P

LS

L2

P

LS

L2

P

LS

L3

P

LS

L2

P

LS

P

ELL

LS

L1

P

LS

L2

P

LS

L1

P

LS

L2

P

LS

P

ELL

LS

L3

P

LS

L2

P

LS

Section Focus Transparency 58Basic Concepts Transparencies 38, 39, 40

Reteaching Skills Transparencies 35, 36

Section Focus Transparency 59Basic Concepts Transparencies 41, 42, 43

Reteaching Skills Transparency 37

Section Focus Transparency 60

P

ELL

LS

L1

P

LS

P

ELL

LS

L1

P

LS

P

ELL

LS

L2

P

LS

P

ELL

LS

L1

P

LS

P

ELL

LS

L1

P

LS

P

ELL

LS

L2

P

LS

P

ELL

LS

L1

P

LS

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

COOP LEARN

LS

P

ELL

LS

P

ELL

LS

Chapter Assessment, pp. 139-144MindJogger VideoquizzesPerformance Assessment in the Biology ClassroomAlternate Assessment in the Science ClassroomComputer Test BankBDOL Interactive CD-ROM, Chapter 24 quiz

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

Life Cycles of Mosses,Ferns, and ConifersNational Science EducationStandards UCP.1, UCP.2,UCP.3, UCP.5; A.1, A.2; C.1,C.5 (1 session)

Flowers and Flowering National Science EducationStandards UCP.1, UCP.2,UCP.5; A.1, C.4-6 (1 session,1/2 block)

The Life Cycle of aFlowering PlantNational Science EducationStandards UCP.1, UCP.2,UCP.3, A.1, A.2; C.1, C.4-6;E.1, E.2; F.3, F.6; G1-3 (2 sessions, 1 block)

1. Review the steps of alternation of generation.

2. Describe the life cycles of mosses, ferns, and conifers.

3. Identify the structures of a flower.4. Examine the influence of photo-

periodism on flowering.

5. Describe the life cycle of a floweringplant.

6. Outline the processes of seed and fruitformation and seed germination.

MiniLab 24-1: Growing Plants Asexually, p. 654Problem-Solving Lab 24-1, p. 659BioTechnology: Hybrid Plants, p. 680

Problem-Solving Lab 24-2, p. 663Inside Story: Parts of a Flower, p. 665Investigate BioLab: Examining theStructure of a Flower, p. 678

Careers in Biology: Greens Keeper, p. 673MiniLab 24-2: Looking at GerminatingSeeds, p. 677

Section 24.2

Section 24.1

Section 24.3

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.

L1

P

LS

L2

P

LS

L3

P

LS

P

ELL

LS

P

COOP LEARN

LS

PP

LS

P

LS

The following multimedia resources are available from Glencoe.

Biology: The Dynamics of LifeCD-ROM

Animation: Life Cycle of a MossVideo: Fern DevelopmentAnimation: Life Cycle of a PineExploration: AngiospermVideo: Blooming Flowers

Videodisc ProgramDouble FertilizationFruit FormationSeed DispersalGermination

P

LS

P

ELL

LS

http://www.carolina.com

Section

Alternation ofGenerations

As you learned earlier, plants gothrough an alternation of generationsduring their life cycles. Rememberthat the two phases of the plant lifecycle are the gametophyte stage andthe sporophyte stage.

The cells of the sporophyte are alldiploid. Certain cells of the sporo-phyte undergo meiosis and producehaploid spores. These spores grow,by mitotic division, into the gameto-phyte. The multicellular gameto-phyte that is formed is composed ofhaploid cells. Some cells of the game-tophyte will differentiate and formhaploid gametes. The female gameteis the egg, and the male gamete is thesperm. When a sperm fertilizes anegg, a diploid zygote is formed. Thiszygote divides by mitosis, producinga tiny sporophyte or embryo. Thedevelopment of the embryo into a

mature sporophyte allows the lifecycle to begin again. Figure 24.1illustrates alternation of generations.

653

You may have seen the fine yellow dustthat covers everything when pine treesrelease their pollen. As annoying as

this pollen may seem, it has a valuable func-tion. It is an important stage in the life cycleof pine trees. Other plants have even moredramatic stages of their life cycles, such asexploding moss capsules and fern sporangia.

SECTION PREVIEW

ObjectivesReview the steps ofalternation of genera-tion.Describe the life cyclesof mosses, ferns, andconifers.

Vocabularyvegetative reproductionprotonemamegasporemicrosporemicropyle

24.1 Life Cycles of Mosses,Ferns, and Conifers

Male pine conereleasing pollen

Figure 24.1 All plants exhibit an alternation of generations.The gametophyte (n) stage produces gametes.The sporophyte (2n) produces spores.

GAMETOPHYTE (n)

Spores (n)

Meiosis

SPOROPHYTE (2n)

Mitosis

Fertilization

Femalegamete (n)

Malegamete (n)

653

Section 24.1

BIOLOGY: The Dynamics of Life SECTION FOCUS TRANSPARENCIES

Use with Chapter 24,Section 24.1

Transparency Fern Life Cycle58 SECTION FOCUS

Cop

yrig

ht ©

Gle

ncoe

/McG

raw

-Hill

, a d

ivis

ion

of T

he M

cGra

w-H

ill C

ompa

nies

, Inc

.

Which generation is dominant in the life cycle of this fern?

How does this compare with the life cycle of mosses?

11

22

Sporophyte

Fern Moss

New sporophyte

Gametophyte

PrepareKey ConceptsAlternation of generations is re-viewed and the life cycles of mosses,ferns, and conifers are presented.

Planning■ Purchase garlic, carrots, and

potatoes for MiniLab 24-1.■ Locate pictures of moss, fern,

and conifer reproductive struc-tures for Getting Started Demo.

■ Locate pictures of moss, fern,and conifer gametophytes forthe Quick Demo.

1 FocusBellringer Before presenting the lesson, display Section Focus Trans-parency 58 on the overhead pro-jector and have students answerthe accompanying questions.

P

ELL

LS

L1

P

LS

652 REPRODUCTION IN PLANTS

Reproduction in Plants

What You’ll Learn ■ You will compare and con-

trast the life cycles of mosses,ferns, and conifers.

■ You will sequence the lifecycle of a flowering plant.

■ You will describe the charac-teristics of flowers, seeds, andfruits.

Why It’s Important Plants are essential to Earth’sbiosphere. The fruits and seedsproduced by flowering plantsare a major food source forhumans and animals, and criticalfor the survival of many species.

Looking at Flowers Look closely at two differentflowers. How are they similar?How are they different?

To find outmore about

plants, visit the Glencoe ScienceWeb Site.www.glencoe.com/sec/science

24

GETTING STARTEDGETTING STARTED

ChapterChapter

Animals often play animportant role in polli-nating flowering plants.Insects, including bees,transport pollen fromflower to flower. Mostnonflowering plants,such as mosses, rely onwind or water for the dis-persal of spores.

652

Theme DevelopmentUnity within diversity is ex-plored in this chapter as the dif-ferent reproductive strategies ofmajor plant divisions are present-ed. The theme of systems andinteractions is stressed in thestudy of the life cycles of variousplants. Evolution is a theme thatoccurs throughout the chapter,especially as it relates to thecoevolution of pollinators andflowers.

Chapter 24Chapter 24

MultipleLearningStyles

Look for the following logos for strategies that emphasize different learning modalities.Kinesthetic Meeting IndividualNeeds, p. 662; Building a Model,

p. 669; Tech Prep, p. 675; Portfolio, p. 676

Visual-Spatial Biology Journal, p. 657; Meeting Individual Needs,

pp. 658, 665, 672; Reteach, p. 660;Display, p. 664; Discussion, p. 666;Quick Demo, p. 668; Reinforcement, p. 668; Microscope Activity, p. 668;

Portfolio, p. 670; Tech Prep, p. 672;Enrichment, p. 673

Intrapersonal Enrichment, p. 664; Project, p. 664Linguistic Meeting IndividualNeeds, p. 655; Portfolio, pp. 656,

662; Biology Journal, pp. 663, 668;Extension, p. 666

Logical-Mathematical QuickDemo, p. 657

GETTING STARTED DEMOGETTING STARTED DEMO

Show students pictures ofreproductive structures ofmosses, ferns, and conifers.Have students discuss waysthey are similar.

P

LS

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

Assessment PlannerAssessment PlannerPortfolio Assessment

Assessment, TWE, p. 657Portfolio, TWE, pp. 656, 662, 670, 676Alternative Lab, TWE, p. 675

Performance AssessmentMiniLab, SE, pp. 654, 677MiniLab, TWE, pp. 654, 676Problem-Solving Lab, TWE, pp. 659, 663Assessment, TWE, pp. 666, 676, 677

Alternative Lab, TWE, pp. 674-675BioLab, SE, pp. 678-679

Knowledge AssessmentSection Assessment, SE, pp. 660, 666, 677Assessment, TWE, p. 669BioLab, TWE, p. 679Chapter Assessment, SE, pp. 681-683

Skill AssessmentAssessment, TWE, p. 662

Resource ManagerResource Manager

Section Focus Transparency 58and Master

P

ELL

LS

L1

P

LS

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

Meiosis

Mitosis

Fertilization

Sporophyte (2n)

Developingsporophyte

Gametophyte (n)

Capsule

Germinatingspores

Sperm

Egg

Zygote (2n)

ProtonemaFemalegametophyte(n)

Malegametophyte(n)

Open capsule

ArchegoniumAntheridium

SPOROPHYTEGENERATION

2n

GAMETOPHYTEGENERATION

n

Rhizoids

form a structure called a protonema.The protonema (proht uh NEE muh)is a small green filament of cells thatdevelops into either a male or afemale gametophyte. In somemosses, the gametophyte can pro-duce both kinds of reproductivestructures. Remember that thearchegonium is the female reproduc-tive structure in which eggs are pro-duced and that sperm are producedin the antheridium.

The motile sperm are released fromthe antheridium and swim through acontinuous film of rainwater or dew tothe archegonium. The sperm fertilizesthe egg inside the archegonium, form-

ing a diploid zygote. The zygotedivides by mitosis to form a newsporophyte. The sporophyte is a stalkwith a capsule at the top. It grows outof the archegonium and remainsattached to the gametophyte. Thesporophyte receives much of its nutri-tion from the gametophyte. Meioticdivision within the capsule produceshaploid spores.

The capsule ripens, bursts, andreleases the spores, which can be car-ried great distances by air currents. Ifthe spore lands in a favorable envi-ronment, it germinates, completingthe life cycle. Review the moss lifecycle as you examine Figure 24.3.

24.1 LIFE CYCLE OF MOSSES, FERNS, AND CONIFERS 655

Figure 24.3 The leafy green gametophyte of amoss produces gametes that fuseto form a zygote. The zygotedevelops into the sporophyte. The sporophyte produces spores. The spores germi-nate and grow into a gametophyte, com-pleting the life cycle of a moss.

655

Revealing MisconceptionsStudents learned in previouschapters that the process of meio-sis forms gamete cells. This is truefor animals. However, in plants,spores are produced directlythough meiosis and then gametesare formed through mitosis ofthese haploid cells.

Why the difference betweenplants and animals? Actually,there is no difference. Plants justhave an added stage or step thatresults from alternation of gener-ations. In this process, meiosisstill forms haploid spore cells—the gametophyte generation—that remain haploid. The gameto-phyte is equivalent to one largemale or female animal gamete.

Visual LearningFigure 24.3 To reinforce theconcept of diploid versus haploid,ask students to assign a specificchromosome number to eachstage in Figure 24.3. Explain thatthe diploid number for thisspecies is 18. L2

P

LS

Growing Plants Asexually Plants are capable of reproduc-ing asexually. Reproductive cells such as egg or sperm are notneeded in asexual reproduction. Plants are able to use structuressuch as roots, stems, and even leaves to produce new offspring.

Procedure! Prepare three different plant parts for study using diagrams

A, B, and C as a guide. @ Observe any changes that occur to your plants over the

next two weeks.# Design a data table that will provide enough room for

diagrams of your observations, the number of days since the start of the experiment should be included.

$ Make your initial diagrams of the plant parts today and label these diagrams as “Day 1.”

% Observations should be made every three days. Replace any lost water as needed.

Analysis 1. What experimental evidence do you have that:

a. plants use a variety of structures for asexual reproduc-tion?

b. asexual reproduction is a rapid process?c. asexual reproduction requires only one parent?

2. Describe several advantages of asexual reproduction in plants.

MiniLab 24-1MiniLab 24-1 Experimenting

even seen a female gametophyte of aflowering plant. Botanists usually referto the bigger, more obvious plant asthe dominant generation. The domi-nant generation lives longer and cansurvive independently of the othergeneration. In most plant species thesporophyte is the dominant plant.

Asexual reproductionMost plants can also reproduce by

a process called vegetative reproduc-tion. Vegetative reproduction isasexual reproduction in plants wherea new plant is produced from anexisting vegetative structure. Forinstance, liverworts produce asexualstructures called gemmae that falloff and develop into new plants,Figure 24.2. The new plants havethe same genetic make-up as theoriginal plant, as if they werecloned. You can learn more aboutasexual reproduction in the MiniLabshown here.

Life Cycle of MossesMosses belong to one of the few

plant divisions in which the gameto-phyte plant is the dominant genera-tion. A haploid spore germinates to


Figure 24.2Small cups filled with tiny gemmae haveformed on the thallus of this liverwort.

Water

Beaker

Potato with eye(stem & buds)

Toothpick

Carrot(root)Water

Water

Test tube

Garlic clove(storage leaves)

AA BB CC

The basic pattern of this life cycleis the same for all plants. However,there are many variations on this pat-tern within the plant kingdom. Forinstance, recall that in mosses thegametophyte is bigger than the sporo-phyte. In others, such as floweringplants, the gametophyte is tiny, evenmicroscopic. Most people have never

654

2 Teach

Purpose Students will use several differentplant parts to demonstrate theability of plants to form newplants via asexual reproduction.

Process Skillsexperiment, analyze information,collect data, compare and con-trast, draw a conclusion

Teaching Strategies■ Have students work in smallgroups to conserve materials.■ Make sure that the originalroot end (blunt end) of the garlicclove is immersed in water. Onegarlic head should supply enoughcloves for an entire class.■ Both garlic and potato may besuspended over water usingtoothpicks as bracing. Small jars(baby food jars, plastic bathroomcups) may be used in place ofbeakers or test tubes.■ Make sure that students iden-tify their plants by placing labelson the jars and/or dishes.■ Tell students to replace anylost water from the containers.■ Some potatoes are chemicallytreated to inhibit growth of eyes.This may account for either slowor no new growth appearingwithin the two-week period.

Expected ResultsAll plant tissues will produce newgrowth. The garlic clove willshow new root and stem/leafgrowth. The carrot will show newleaves. The potato will show newstems and leaves.

Analysis1. a. The experimental proce-

dure demonstrates that different plant parts can gen-erate new growth.

b.The appearance of newgrowth occurred withinseveral days.

c. Only one plant was usedfor each experimental setup.

P

LS

MiniLab 24-1MiniLab 24-1

MEETING INDIVIDUAL NEEDS MEETING INDIVIDUAL NEEDS

English Language Learners/Learning Disabled

Linguistic Have students reviewterms associated with alternation

of generations by reinforcing the correla-tion between the name of each generationand its function. For example, sporophytesform spores, while gametophytes formgametes.

P

LSP

ELL

LS

L1

P

LS

2. Student answers may vary; they mayinclude faster growth and that all off-spring are identical to parent.

Performance Provide students with aplant called Kalanchoe (available in most gar-den shops). Have them use leaves from theplant to grow new plants asexually. Have stu-dents conduct an experiment to determine

AssessmentAssessment

what conditions stimulate the appearance ofnew plants along the leaf’s edge. Use thePerformance Task Assessment List for Carry-ing Out a Strategy and Collecting Data inPASC, p. 25. L3

P

LS

Resource ManagerResource ManagerBioLab and MiniLab Worksheets,

p. 109Basic Concepts Transparency 38 and

MasterReteaching Skills Transparency 35

and Master

P

ELL

LS

L1

P

LS

P

ELL

LS

L2

P

LS

L2

P

LS

CD-ROMBiology: The Dynamicsof Life

Animation: Life Cycle of a MossDisc 3

VIDEODISCBiology: The Dynamicsof Life

Life Cycle of a Moss (Ch. 17)Disc 1, Side 2, 1 min. 3 sec.

!8rÜ"

Meiosis

Meiosis

Spores (n)

Rhizome

Fronds

Sporophytes(2n)

Sporangium

Pinna

Sorus

Roots


2n


2n

Fertilization

Mitosis

Sperm

Rhizoids

Archegonia

Archegonium

Egg

Antheridia

Antheridium

Zygote

once the sporophyte produces itsgreen fronds, it can carry on photo-synthesis and survive on its own. Theprothallus disintegrates as the sporo-phyte matures, producing a strongrhizome that can support the fronds.If pieces of rhizome break away, new

fern plants will develop from them byvegetative reproduction. New spo-rangia develop on the pinnae of thefronds, spores will be released, andthe cycle will begin again. The lifecycle of the fern is summarized inFigure 24.5.

24.1 LIFE CYCLE OF MOSSES, FERNS, AND CONIFERS 657

Figure 24.5In the life cycle of afern, the sporophytegeneration becomesindependent of thegametophyte.

657

Chalkboard ActivityWrite the following terms on thechalkboard: spore, zygote, egg,sporophyte, and sperm. Havestudents identify whether eachstructure is haploid or diploid.

Portfolio Have studentsprepare a biological key that willenable others to identify mosses,ferns, and conifers based on fea-tures of the plant life cycle,including reproductive parts. L2

P

LS


L2

P

LS

Figure 24.4Fern sporophytes are easily seen by a hikerwalking through a forest. However, only thevery observant person would be able to finda fern gametophyte.

Most fern sporophytesgrow 25 cm or taller.

AA The heart-shapedfern gametophyteis usually less thana centimeter across.

CC

The clusters of sporangia on theunderside of a fern frond arecalled sori. Each sporangium con-tains spores that are released,sometimes in dramatic fashion.

BB

Some mosses also reproduce asex-ually by vegetative reproduction.They can break up into pieces whenthe plant is dry and brittle. With thearrival of wetter conditions, thesepieces each become a whole plant.

Life Cycle of FernsUnlike mosses, the dominant stage

of the fern life cycle is the sporo-phyte plant. The fern sporophytesinclude the familiar fronds you see inFigure 24.4. The fronds of the ferngrow from the rhizome, which is theunderground stem. On the undersideof some fronds are the sori, which areclusters of sporangia. Meiotic divi-

sion within the sporangia producesthe spores. When environmentalconditions are right, the sporangiaburst to release haploid spores.

A spore germinates to form aheart-shaped gametophyte called aprothallus, as shown in Figure 24.5.The prothallus produces botharchegonia and antheridia on its sur-face. The flagellated sperm releasedby the antheridium swim through afilm of water to the archegoniumwhere the egg is fertilized. Thediploid zygote that is the product ofthis fertilization develops into thesporophyte. Initially, this developingsporophyte depends upon the game-tophyte for its nutrition. However,


656

Revealing MisconceptionsStudents frequently think the soripresent on the underside of fernfronds are some kind of insectinfestation. Explain that thesestructures produce spores.

Chalkboard ActivityHave students write a simplemoss life cycle sequence on theboard. Help them get started byshowing them what the cycle maylook like by providing them withthis sample: sporophyte ⇒ sporesby meiosis ⇒ protonema ⇒ etc.

PortfolioPortfolio

Chemistry in BiologyLinguistic Have students do researchand prepare a report about the role

of chemotaxis in moss and fern reproduc-tion.

P

LS

PP

LS

L3

P

LS

Quick DemoQuick Demo

Logical-Mathematical

Give students pictures ofmoss, fern, and conifer game-tophytes that have the magni-fication noted on the photo.Have them calculate the size ofeach gametophyte. The size ofthe drawing (in millimeters)divided by the magnificationequals the size of the originalgametophyte (in millimeters).Students will then be able tocompare the size of the game-tophytes.

P

LS

L3

P

LS

BIOLOGY JOURNAL BIOLOGY JOURNAL

Fern Life CycleVisual-Spatial Have students dia-gram the stages of the fern life cycle

in their journals for review. Encouragestudents to divide the diagram so that all sporophytes are on one side and allgametophytes are on the other. Have them label the diagram Sporophyte stages,Gametophyte stages.

P

LSP

ELL

LS

L1

P

LS


Video: Fern DevelopmentDisc 3


Fern Development (Ch. 18)Disc 1, Side 2, 17 sec.

!8|á"


Concept Mapping, p. 24

Basic Concepts Transparency39 and Master

P

ELL

LS

L2

P

LS

P

ELL

LS

L3

P

LS

What traits do mosses, ferns, and conifers share?Sometimes it helps to organize information in a table. Theadvantage of a table is that it summarizes traits and showssimilarities and differences in a simple format.

AnalysisCopy the following data table. Complete the table using

“yes” and “no” answers.

Thinking Critically1. Which two plant groups share the most characteristics?

Which two share the fewest?2. While on a woodland trail, would you easily observe:

a. A pine gametophyte? Sporophyte? Explain.b. A fern gametophyte? Sporophyte? Explain.

3. Using information from your table, summarize the repro-ductive similarities and differences among mosses, ferns,and conifers.

Problem-Solving Lab 24-1Problem-Solving Lab 24-1 Making and Using Tables

female cone. The pollen grainadheres to a sticky drop of fluid thatcovers the opening of the ovule. Asthe fluid evaporates, the pollen grainis drawn closer to an opening of theovule called the micropyle (Mi kruhpile). Although pollination hasoccurred, fertilization will not takeplace for at least a year. The pollengrain and the female gametophytewill mature during this time.

As the pollen grain matures, it pro-duces a pollen tube that grows throughthe micropyle and into the ovule. Asperm cell from the male gametophyteis transported by the pollen tube tothe egg, where fertilization occurs.The zygote, which is nourished bythe female gametophyte, developsinside the ovule into an embryo withseveral cotyledons. The cotyledonsnourish the developing sporophyte.The ovule provides the seed coat asthe mature seed is produced.

The seed is released when thefemale cone opens. When conditionsare favorable, the seed germinatesinto a new, young sporophyte—apine tree seedling, Figure 24.7. Seeif you can identify the stages of thelife cycle in Figure 24.8. Use theProblem-Solving Lab on this page tofurther explore the life cycles ofmosses, ferns, and conifers.

659

Figure 24.7Conifer seeds germinateinto new, young sporo-phytes such as the pinetree seedling shown here.

Trait ConiferFernMoss

Has alteration of generations

Film of water needed for fertilization

Dominant gametophyte

Dominant sporophyte

Sporophyte is photosynthetic

Produces seeds

Produces sperm

Produces pollen grains

Produces eggs

Data Table

659

Purpose Students will identify and catego-rize the similarities and differ-ences among mosses, ferns, andpines by completing a chart.

Process Skillscompare and contrast, think criti-cally, analyze information, applyconcepts, predict

Teaching Strategies■ You may wish to photocopythe chart and pass out the copiesto your students.■ Review the meaning of anyterms used in the chart that maybe unfamiliar to students.■ Allow students to work insmall groups to complete thechart. Make sure they use theirtext as a reference to aid in verifi-cation of answers.■ Review student answers on thechart prior to them answering thequestions.Answers going down each columnof the table.Moss: yes, yes, yes, no, yes, no, yes,no, yesFern: yes, yes, no, yes, yes, no, yes, no,yesConifer: yes, no, no, yes, yes, yes, yes,yes, yes

Thinking Critically

1. Mosses and ferns share themost characteristics. Mossesand conifers share the least.

2. Both ferns and mossesrequire a film of water forfertilization. Therefore, bothwould most likely be foundgrowing in damp or moistenvironments.

3. All three have alternation ofgenerations and producesperm and eggs. Both mossesand ferns need water for fer-tilization; conifers do not.Mosses have a dominantgametophyte; ferns andconifers have a dominantsporophyte. Conifers producepollen grains and seeds;Mosses and ferns do not.

P

LS

Problem-Solving Lab 24-1Problem-Solving Lab 24-1The Life Cycle of Conifers

The dominant stage in conifers isthe sporophyte generation. One ofthe more familiar conifer sporo-phytes is shown in Figure 24.6. Theadult conifer produces male andfemale cones on separate branches ofthe tree. The cones contain spore-producing structures, or sporangia,on their scales. The female cones,which are larger than the male cones,develop two ovules on the upper sur-face of each cone scale. Each ovulecontains a sporangium with a diploidcell that produces, by meiosis, fourmegaspores. A megaspore is afemale spore that eventually becomesthe female gametophyte. One of thefour megaspores will survive andgrow by mitotic cell divisions into

the female gametophyte. The femalegametophyte consists of hundreds ofcells but is still dependent on thesporophyte for protection and nutri-tion. Within the female gametophyteare two or more archegonia, eachcontaining an egg. The male coneshave sporangia that undergo meiosisto produce male spores calledmicrospores. Each microspore willdevelop into a male gametophyte, orpollen grain. Each pollen grain, withits hard, water-resistant outer cover-ing, is a male gametophyte. Look atFigure 24.6 to see examples of maleand female conifer gametophytes.

In conifers, pollination is thetransfer of the pollen grain from themale cone to the female cone.Pollination occurs when a wind-borne pollen grain falls near theopening in one of the ovules of the


Figure 24.6In conifers, the sporo-phyte is immensecompared with themicroscopic gameto-phytes.

OriginWORDWORD

micropyleFrom the Greekwords mikros,meaning “small,”and pyle, meaning“gate.” The micro-pyle is the smallopening at one endof the embryo sac.

This pine sporophytecan grow more than25 meters tall.

AA

The femalegametophytein this pineovule is lessthan 0.01 mmlong.

BB

A pollen grainis so small itcan be carriedby the wind.

CC

658

Using Scientific TermsChallenge students to use theirknowledge of the prefixes micro-and mega- to describe the relativesizes of microspores and megas-pores. Microspores are smaller thanmegaspores. Have students specu-late why it is important formicrospores to be small. Theydevelop into pollen grains that mustbe light enough to be dispersed bywind.

Visual Learning■ Have students identify the

haploid structures in Figure24.8. microspores, megaspores,pollen grains, egg

■ Have students identify thestructures that make up thesporophyte and gametophytegenerations. Cones and embryoare sporophytes; all other struc-tures are gametophytes.

P

ELL

LS

L2

P

LS


Learning DisabledVisual-Spatial Prepare individualcards with a drawing on each show-

ing one single stage of the life cycle of thepine. Provide a packet of cards to studentswho are learning disabled. Have studentsarrange the cards in proper sequence toillustrate the complete life cycle for a typi-cal pine.

P

LSP

ELL

LS

L1

P

LS


Animation: Life Cycle of a PineDisc 3


Life Cycle of a Pine (Ch. 20)Disc 1, Side 2, 1 min. 37 sec.

!9,Ä"

Resource ManagerResource ManagerReinforcement and Study Guide,

pp. 105-106Content Mastery, p. 118Basic Concepts Transparency 40 and

MasterReteaching Skills Transparency 36

and Master

P

ELL

LS

L1

P

LS

P

ELL

LS

L2

P

LS

L1

P

LS

L2

P

LS

Performance Have students attemptto grow fern gametophytes from spores.Instructions and spores are available throughbiological supply houses. Use the Perform-ance Task Assessment List for Carrying Out a Strategy and Collecting Data in PASC, p. 25.

P

ELL

LS

L3

P

LS


3 AssessCheck for UnderstandingAsk students to explain the rela-tionships of the following wordpairs.

a. gametophyte—sporophyteb. antheridium—spermc. archegonium—eggd. megaspore—microspore

ReteachVisual-Spatial Divide theclass into small groups and

assign different groups the task ofmaking flowcharts of the lifecycles of mosses, ferns, andconifers. Have them put theirflowcharts on the chalkboard orposter board for class discussion.

ExtensionHave students research whichanimals use the cones of conifersas a food source.

Knowledge Have studentsexplain the role of water in moss,fern, and conifer reproduction.

4 CloseBiology Journal Have students compare the game-tophyte and sporophyte gener-ations of mosses, ferns, and coni-fers. L2

P

LS

L2

P

LS


L3

P

LS

P

COOP LEARN

LS

L2

P

LS

P

ELL

LS

L2

P

LS

Section AssessmentSection AssessmentSection Assessment1. Vegetative reproduction is when a new

plant is produced from an existing veg-etative structure. An example would bethe growth of liverworts from the gem-mae that fall off a parent plant.

2. The sporophyte depends upon thegametophyte for support and most ofits nutrition.

3. The sporangia within the male pineconeproduce microspores. The microsporesdevelop into the male gametophyte orpollen grain.

4. The gametophyte is dominant in mosses,whereas the sporophyte is dominant inferns. In ferns, the sporophyte can existindependently of the gametophyte butin mosses the sporophyte remains

dependent upon the gametophyte.5. The sporophyte generation alternates

with the gametophyte generation inthe life cycle.

6. Prothallus ⇒ forms egg and sperm ⇒fertilization of egg by sperm forms ayoung sporophyte ⇒ sporophyte pro-duces spores ⇒ spores germinate toeach form a prothallus.660

Section

24.2 FLOWERS AND FLOWERING 661

What Is a Flower?The process of sexual reproduction

in flowering plants takes place in theflower, which is a complex structuremade up of several parts. Some partsof the flower are directly involved infertilization and seed production.Other floral parts have functions inpollination. There are probably asmany different shapes, sizes, colors,and configurations of flower parts asthere are species of flowering plants.In fact, features of the flower areoften used in plant identification.

The structure of a flowerEven though there is an almost

limitless variation in flower shapesand colors, all flowers share a simple,basic structure. A flower is usuallymade up of four kinds of organs:sepals, petals, stamens, and pistils.The flower parts you are probablymost familiar with are the petals.Petals are leaflike, usually colorfulstructures arranged in a circle aroundthe top of a flower stem. Sepals arealso leaflike, usually green, and encir-cle the flower stem beneath thepetals.

How would you choose flowersfor a garden or a bouquet?Perhaps you would start with

fragrant roses, jasmine, or gardenias.You might add color with tall spikes ofgladioli, cushions of marigolds, brightdaisies, or irises. Grasses would con-tribute a graceful shape, though theirflowers may be so small they are easyto overlook. All of these flowers are beautiful to look at and some have delicate scents as well. In what other ways are all of these flowers alike?

SECTION PREVIEW

ObjectivesIdentify the structuresof a flower.Examine the influenceof photoperiodism onflowering

Vocabularypetalssepalsstamenantherpistilovaryphotoperiodismshort-day plantlong-day plantday-neutral plant

24.2 Flowers and Flowering

Flowers display a varietyof shapes and colors.

661

Section 24.2

PrepareKey ConceptsFlower anatomy and modifica-tions are discussed in this section.The role of photoperiodism inanthophyte reproduction is ex-plained.

Planningn Locate flowers for the Quick

Demo.n Purchase flowers for the Bio-

Lab.n Locate flower model for Meet-

ing Individual Needs.n Collect pictures of different

flowers for the CLOSE activity.


P

ELL

LS

L1

P

LS



How does the structure of each seed make it suitablefor its method of dispersal?

Why is seed dispersal important?

11

22

Transparency Seed Dispersal59 SECTION FOCUS

Cop

yrig

ht ©

Gle

ncoe

/McG

raw

-Hill

, a d

ivis

ion

of T

he M

cGra

w-H

ill C

ompa

nies

, Inc

.

A.

C. D.

B.

Internet Address Book

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

DECODEGl /M G Hill

Male cone

Megaspores

Ovule Microspores

Microspore mother cells

Female cone

Pollengrain

Pollen grain

Femalegametophyte

Egg

Two archegoniawith egg cells

Sperm nucleus

Seed

Cotyledons

Youngseedling

Adultsporophyte

Seed coat

Embryo

Storedfood

Malegametophyte

Germinating pollen

One egg is fertilized


2n


n

Fertilization

Meiosis


Figure 24.8The life cycle of a coniferincludes the productionof two types of spores bythe sporophyte. Thesespores develop into the male and female gametophytes.

Section AssessmentSection Assessment

Understanding Main Ideas1. Explain how vegetative reproduction can pro-

duce a new plant. Provide an example.2. In what way is the sporophyte generation of a

moss dependent on the gametophyte generation?3. Describe the formation of the male gametophyte

in a conifer.4. What are two differences between the life cycle

of a fern and that of a conifer?

Thinking Critically5. Why is the term alternation of generations

appropriate to describe the life cycle of a plant?

6. Sequencing Sequence the events in the life of afern, beginning with the prothallus. For morehelp, refer to Organizing Information in the SkillHandbook.

SKILL REVIEWSKILL REVIEW

How do flowers differ? There is considerable variation inflower shape. This variation occurs when certain flower partsare fused together, parts are rearranged, or when parts maybe totally missing. However, with all the variation seen inflower shape, there are certain general patterns. Almost alldicot plants will have flower parts that are in fours or fives ormultiples of these numbers. For example, a plant havingeight or ten petals, sepals, and stamens would be a dicot.Almost all monocot plants have flower parts in threes or mul-tiples of three.

AnalysisDiagram A shows a flower with all of its parts labeled.

Imagine that the flower has been cut along the dashed line.Diagram B is a diagrammatic cross-section view seen whenlooking down onto the cut edge of the bottom half. DiagramB is shown a little larger than A so that any details can bemore clearly seen. The flower is from a dicot plant becausethere are five sepals, petals, and stamens.

Thinking Critically1. Diagrams C, D, and E are diagrammatic cross-section views

of flowers. Determine if diagram:a. C is a monocot or dicot. Explain.b. D is a monocot or dicot. Explain.c. E is a monocot or dicot. Explain.

2. Do diagrams A, C, D, and E show flowers that are com-plete or incomplete? Explain. Note: Complete flowershave sepals, petals, stamens, and pistils whereas incom-plete flowers lack one or more of these parts.

3. Which flowers are capable of self-pollination? Explain.4. Which flowers require cross-pollination? Explain.

Problem-Solving Lab 24-2Problem-Solving Lab 24-2 Interpreting ScientificIllustrations

Plants such as sweet corn that areadapted for pollination by windrather than animal pollinators haveno petals. Figure 24.9 shows someexamples of the variety in flowerforms. Study the structure of a typi-cal flower in the Inside Story. You canexplore flower adaptations further inthe Problem-Solving Lab shown here.

There is an amazing amount ofdiversity in the structures of antho-phyte flowers, seeds, fruits, and vege-tative structures. Anthophytes aredivided into different divisions andclasses based on these differences.The relationships among the differ-ent classes and divisions of antho-phytes are shown in Figure 24.10.See if you can recognize any of thedifferent divisions of plants.

PhotoperiodismThe relative length of day and

night has a significant effect on therate of growth and the timing offlower production in many species offlowering plants. For example,chrysanthemums produce flowersonly during the fall, when the daysare getting shorter and the nightslonger. A grower who wants to pro-duce chrysanthemum flowers in themiddle of summer drapes black clothover the plants to artificially increasethe length of night. The response offlowering plants to the difference inthe duration of light and dark periodsin a day is called photoperiodism.

Plant biologists originally thoughtthat day length controlled flowering.However, they now know that it is thelength of the night, or dark period,that controls flowering. Plants can beplaced in three categories dependingon the conditions they require forflower production. Plants are eithershort-day plants, long-day plants, orday-neutral plants.


AA BBPistil

Stamen

Petal

Sepal

CC DD EE

663

Purpose Students will study and interpretdiagrams of flower cross sections.

Process Skillsthink critically, compare and con-trast, interpret scientific illustra-tions

Teaching Strategies■ Review the basic anatomy of a flower before this activity.■ Make sure that studentsunderstand the differencesbetween complete and incom-plete flowers.■ Review the characteristics ofmonocots and dicots.■ Provide examples of flowershaving floral structures in multi-ples of three, four, and five.■ Illustrate a “cross-section” cutusing a cucumber as an example.

Thinking Critically

1. a. monocot; flower parts inthrees

b.dicot; flower parts in fouror multiples of four

c. dicot; flower parts in foursor multiples of four

2. A and C are complete flowersas all flower parts are present.D and E are incomplete flow-ers as D is missing sepals andE is missing a pistil.

3. A, C, and D as they haveboth stamens and pistils.Both male and female flowerparts are needed for self-fertilization

4. E requires cross-pollinationas it does not have a pistil.

Performance Have stu-dents make a sketch of dia-grams C through D and label theflower parts. Have them make a cross-section diagram of the female flower of E. Use the Per-formance Task Assessment Listfor Scientific Drawing in PASC,p. 55.

P

ELL

LS

L2

P

LS


P

LS

Problem-Solving Lab 24-2Problem-Solving Lab 24-2Inside the circle of petals are thestamens. A stamen is the male repro-ductive structure of a flower. At thetip of the stamen is the anther. Theanther produces pollen that containssperm.

At the center of the flower,attached to the top of the flowerstem, lie one or more pistils. Thepistil is the female structure of theflower. The bottom portion of thepistil enlarges to form the ovary, astructure with one or more ovules,each containing one egg. As you readin the previous section, the femalegametophyte develops inside theovule. You can learn more about

floral structure and practice your labskills in the BioLab at the end of thischapter.

Modifications in flower structureA flower that has all four organs—

sepals, petals, stamens, and pistils—iscalled a complete flower. The morn-ing glory and tiger lily shown inFigure 24.9 are examples of com-plete flowers. A flower that lacks oneor more organs is called an incom-plete flower. For example, squashplants have separate male and femaleflowers. The male flowers have sta-mens but no pistils; the female flow-ers bear pistils but no stamens.


Figure 24.9The diversity offlower forms is evi-dence of the successof flowering plants.

The male flowers of the walnuttree form long catkins.

BB

The petals of the morningglory are fused together toform a bell shape.

CC

Thistles bearclusters of tiny,tubular flowerswithin a massof spiny bracts.

DD

The location of corn tasselsat the top of the plant aidsin wind pollination.

EE

The spotted petals ofthe tiger lily curl awayfrom the reproductivestructures at the cen-ter of the flower.

AA

662

2 Teach

Skill Have students con-struct a chart that summarizesflower structures and the functionof each part. Their chart shouldinclude petals, sepals, pistil, andstamens. L2

P

LS



Display a flower such as a roseor daffodil. Elicit the functionof the flower. It is a reproduc-tive structure. Ask if grass alsoreproduces through flowers.Most students will answer no.Explain that grass is a flower-ing plant but is often not rec-ognized as such because itsflowers do not have showypetals.

P

LS


Visually ImpairedKinesthetic Purchase or borrow alarge flower model. Allow visually

impaired students to manipulate themodel as you name and describe the func-tion of each part. Have the student thentell you if the part is male, female, or nei-ther in terms of flower function.P

LSP

ELL

LS

L1

P

LS

PortfolioPortfolio

Flower ModificationsLinguistic Have students collectpictures of flowers showing differ-

ent structural modifications. Next toeach picture have the students write abrief paragraph describing the adaptivevalue of the modification.P

LS

PP

LS

L2

P

LS


Keeping a Plant DiaryLinguistic Have students imagine thatthey are a chrysanthemum. It is spring-

time and they have just started growing.Ask them to describe what they look like,explain why they are not forming flowers,and indicate the relative lengths of day andnight. Have students repeat the process foreach of the other seasons.

P

LS

L1

P

LS

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

INVESTIGATEINVESTIGATE


Exploration: AngiospermDisc 3

Resource ManagerResource ManagerReteaching Skills Transparency 37

and Master Basic Concepts Transparency 41 and

MasterSection Focus Transparency 59 and

Master

P

ELL

LS

L1

P

LS

P

ELL

LS

L2

P

LS

P

ELL

LS

L1

P

LS


Parts of a Flower

Of the four major organs of a flower, only two—the stamens and pistils—are fertile structures directly

involved in seed development. Sepals and petals supportand protect the fertile structures and help attract pollina-tors. The structure of a typical flower is illustrated here bya phlox flower.

Critical Thinking How are different flower shapesimportant to a plant’s survival?

Blue phlox

INSIDESSTORTORYY

INSIDE

Petals These are usually brightly coloredand often have perfume or nectar at their bases to attract pollinators. In many flowers, the petal also provides a surface for insect pollinators to rest on while feeding. Petals may be fused to form a tube, or shaped in ways that make the flower more attractive to pollinators.

11

Stigma At the top of thepistil is this sticky or featherysurface on which pollengrains land and grow. Thestyle is the slender stalk ofthe pistil that connects thestigma to the ovary. Thepollen tube grows down thelength of the style to reachthe ovary. The ovary, whichwill eventually become thefruit, contains the ovules.Each ovule, if fertilized, willbecome a seed.

22

Stamen The pollen-producinganther at the tip and a thin fila-ment that attaches the antherto the flower stem make up thestamen. When the pollen grainsdeveloping inside the antherreach maturity, the anther splitsopen to release them.

44Sepals A ring of sepals makes up the outermost portion of the flower. The sepals serve as a protective coveringfor the flower bud, helping to protect itfrom insect damage and prevent it fromdrying out. Sepals sometimes are colored and resemble petals.

33

Ovary

Style

Pistil

Ovule

Stigma

Stamen

Filament

Corolla

Sepals

Calyx

Petals

Anther

Pollengrains

665

IINSIDENSIDESSTORTORYY

INSIDE

Purpose To describe flower anatomy andidentify the role flower parts playin reproduction.

Teaching Strategies■ Ask students to explain whystamens and pistils are describedas the fertile structures in aflower. These structures areinvolved in the production of egg andsperm. Elicit what role is playedby flower organs that are notimportant in fertilization. Theseorgans attract pollinators or protectyoung or immature fertile flowerparts.

Visual Learning■ Ask students to use the cap-

tions to explain how the fol-lowing pairs of terms arerelated: (a) sepals and calyx; (b)petals and corolla; (c) stamenand anther; (d) stigma andstyle; (e) ovary and ovule.

Critical ThinkingThe shape of a flower may promote different pollinationmethods. For example, tubularflowers are probably pollinated byanimals.

Chalkboard ActivityWrite the following phrases onthe chalkboard: contains chloro-phyll, contains anthocyanin,where meiosis takes place, con-tains gametophyte, is part of thesporophyte, contains diploid cells,forms spores, forms microspores,forms megaspores. Ask studentsto identify the flower organ ororgans described by each phrase.L2

P

LS

L1

P

LS

L2

P

LS

P

LS


PRESENT CENOZOIC PALEOZOIC PRECAMBRIANMESOZOIC

OrchidOrchidaceae

GrassPoaceae

LilyLiliaceae

PalmPalmae

RaspberryRosaceae

ColeusLamiaceae

CarawayApiaceae

ChicoryAsteraceae

CocoaSterculiaceae

CactusCactaceae

MagnoliaMagnoliaceae

OakFagaceae

MilkweedAsclepiadaceae

Dicots

Protists

Monocots

Figure 24.10There are two classes of antho-phytes—monocots and dicots. Withineach class there are many differentfamilies, which show a great amountof variation in their vegetative andreproductive structures.

PLANTS

664

EnrichmentIntrapersonal Advise stu-dents that the light that

triggers flower production doesnot have to reach the plant’sflower buds, but must reach andbe detected by the leaves. Havestudents design an experiment toprove that it is the leaf that mustbe stimulated by light for theplant to achieve flowering.Suggest that it is possible to placeparts of the plant behind lightbarriers while other parts of thesame plant are exposed to light.

ReinforcementExplain to students that lily grow-ers get their greenhouse plants toflower early in spring by subject-ing the plant to artificial lightingthat simulates longer days andshorter nights. Ask students iflilies are short-day plants or long-day plants. long-day

DisplayVisual-Spatial Using Figure24.10 as a guide, have stu-

dents create a giant fan diagramon the wall or on a bulletinboard. Ask them to bring in pic-tures of monocots and dicots toadd to the display.

P

ELL

LS

L2

P

LS

L3

P

LS

P R O J E C TAre Bees the Best?

Intrapersonal Members of theBrassica genus can be pollinated

with cotton swabs, paint brushes, anddried bees. Have students design anexperiment to determine whether ornot bees are the most efficient pollina-tors.

P

LS

L3

P

LS


English Language Learners/Learning Disabled

Visual-Spatial Have students createa table with the heads Male, Female,

Neither male nor female. Ask students tolist the following structures beneath theappropriate head: stamen, pistil, anther,calyx, corolla, ovary, stigma, petal, sepal,pollen, egg, ovule, style.

P

LSP

ELL

LS

L1

P

LS


Video: Blooming FlowersDisc 3


Blooming Flowers (Ch. 21)Disc 1, Side 2, 26 sec.

!96Å" Resource ManagerResource ManagerReinforcement and Study Guide,

p. 107Content Mastery, p. 119 L1

P

LS

P

ELL

LS

L2

P

LS

Short-day plants are induced toflower by exposure to a long night.These are plants that usually formflower buds in the fall when the daysare getting shorter and the nights arelong, as shown in Figure 24.11A.Flowering occurs in the spring, as incrocuses, or in the fall as in strawberryplants. Long-day plants flower whendays are longer than the nights, asshown in Figure 24.11B. Examples ofthese are carnations, petunias, potatoes,

and garden peas. Most plant speciesare day-neutral plants, which meanstemperature, moisture or environ-mental factors other than day lengthcontrol their flowering times, asshown in Figure 24.11C. The pho-toperiodism of flowers may ensurethat a plant produces its flowers at atime when there is an abundant popu-lation of pollinators. This is importantbecause pollination is a critical eventin the life cycle of a flowering plant.



Understanding Main Ideas 1. Compare and contrast sepals and petals.2. Describe the male and female parts of a flower.3. Explain why squash flowers are considered

incomplete flowers.4. How does photoperiodism influence flowering?

Thinking Critically5. In the middle of the summer a florist receives a

large shipment of short-day plants. What mustthe florist do to induce flowering?

6. Comparing and Contrasting Explain why thestructure of wind-pollinated flowers is often dif-ferent from that of insect pollinated flowers. Formore help, refer to Organizing Information inthe Skill Handbook.


Figure 24.11Photoperiodism refers to aplant’s sensitivity to thechanging length of night.

OriginWORDWORD

photoperiodismFrom the Greekwords photos, mean-ing “light,” andperiodos, meaning “a period.” Theflowering responseof a plant to periodsof dark and light isphotoperiodism.

Short-day plants, such as pansies(above) and goldenrod, flower inlate summer and fall or early spring.

AA

Spinach and lettuce(above) are long-day plants thatflower in midsum-mer.

BB

Most plants are day-neutral.Flowering in cucumbers (above),tomatoes, and corn is not influ-enced by a dark period.

CC

666

3 AssessCheck for UnderstandingAsk students to explain the rela-tionships of the following wordgroups.

a. stamen—antherb. pistil—stigma—ovaryc. ovary—ovule

ReteachObtain a flower model. As youpoint out structures on themodel, have students name eachstructure and explain its function.

ExtensionLinguistic Have studentsdetermine the meaning of

the terms androecium, gynoe-cium, and perianth. Have themassign the term sterile or non-sterile to each flower part.

Performance Provide stu-dents with a diagram of a typicalflower. Have them label the partsof the flower and identify repro-ductive parts.

4 CloseDiscussion

Visual-Spatial Show studentspictures of flowers with dif-

ferent structural modifications.Have them point out the differ-ent flower parts and speculate asto the advantage of the modifica-tion. L2

P

LS

L1

P

LS


L3

P

LS

L1

P

LS

P

ELL

LS

L2

P

LS

Section AssessmentSection AssessmentSection Assessment1. Both are leaflike structures. Petals are

bright colors. Sepals are usually green.2. The male part is the stamen, which consists

of the anther and filament. The femalepart is the pistil, which contains the ovaryand ovules.

3. Squash flowers are incomplete becausethey do not have both pistils and stamens.

4. Flowering is controlled by photoperiodism.For example, short-day plants flower whenthe days are short and nights are long.

5. The florist should cover the greenhousewith tarps each afternoon to shorten theday and lengthen the night.

6. Wind-pollinated flowers are small and lack petals. Insect-pollinated flowers havebrightly colored petals and nectar.

Section

The Life Cycle of an Anthophyte

The life cycle of flowering plantsis similar to that of conifers in manyways. In both coniferophytes andanthophytes, the gametophyte gen-eration is contained within thesporophyte. Many of the reproduc-tive structures are also similar.However, anthophytes are the onlyplants that produce flowers andfruits. Figure 24.12 summarizes thelife cycle of flowering plants.

Development of the female gametophyte

In anthophytes, the female game-tophyte is formed in the ovule within

the ovary. In the ovule, a cell under-goes meiosis, producing haploidmegaspores. One of these mega-spores will produce the female game-tophyte. The other three spores die. In most flowering plants, the megaspore divides by mitosis threetimes, producing eight nuclei. Theseeight nuclei are the embryo sac orfemale gametophyte. Six of the nucleiare contained within six haploid cells,one of which is the egg cell. The tworemaining nuclei, which are calledpolar nuclei, are both in one cell.This cell, the central cell, is locatedat the center of the embryo sac. Theegg cell is near the micropyle. Theother five cells are arranged as shownin Figure 24.13.

24.3 THE LIFE CYCLE OF A FLOWERING PLANT 667

Transferring pollen from anther tostigma is just one step in the life cycleof a flowering plant. How does polli-

nation lead to the development of seeds encasedin fruit? How do sperm cells in the pollengrain reach the egg cells in the ovary? Thesesteps in the reproductive cycle of anthophytestake place without water—anevolutionary step thatenabled flowering plants tooccupy nearly every envi-ronment on Earth.

SECTION PREVIEW

ObjectivesDescribe the life cycleof a flowering plant.Outline the processesof seed and fruit formation and seed germination.

Vocabularypolar nucleidouble fertilizationendospermdormancygerminationradiclehypocotyl

24.3 The Life Cycle of aFlowering Plant

Bee orchid Ophrysspeculum and ovary of a flower (inset)

667

Section 24.3

PrepareKey ConceptsThe formation of anthophytegametophytes, pollination, anddouble fertilization are presented.Seed and fruit development arethen discussed. The section endswith an explanation of seed dis-persal and seed germination.

Planning■ Purchase peanuts for the Quick

Demo.■ Find flowers for Assessment.■ Purchase bean seeds for the

Tech Prep.■ Purchase beans and tetrazoli-

um chloride for the AlternativeLab.

■ Purchase tomato and peach forthe Quick Demo.

■ Purchase corn and bean seedsfor MiniLab 24-2.


P

ELL

LS

L1

P

LS



The Brazilian birthwort gives off a scent that often resemblesrotting flesh. How would this aid the plant in reproduction?

What other characteristics of this plant may help attract organisms for the purpose of aiding in reproduction?

11

22

Transparency Pollination60 SECTION FOCUS

Cop

yrig

ht ©

Gle

ncoe

/McG

raw

-Hill

, a d

ivis

ion

of T

he M

cGra

w-H

ill C

ompa

nies

, Inc

.Resource ManagerResource ManagerSection Focus Transparency 60 and

Master

P

ELL

LS

L1

P

LS

Development of the male gametophyte

The formation of the male gameto-phyte begins in the anther, as seen inFigure 24.14. Haploid microsporesare produced by meiosis within theanther. The microspores each divideinto two cells. A thick, protective wallsurrounds these two cells. This two-celled structure is the immature malegametophyte, or pollen grain. The

cells within the pollen grain are thetube cell and the generative cell.When the pollen grains are maturethe anther splits open. Depending onthe type of flower, the pollen may becarried to the pistil by wind, water, oranimals.

PollinationIn anthophytes, pollination is the

transfer of the pollen grain from the


Female gametophy

Ovule

Embryo sac

Central cell

Egg cell

Micropyle

Figure 24.13 The eight nuclei produced by themegaspore form the femalegametophyte of anthophytes.

MEIOSIS

Microsporemother cell (2n)

Tubenucleus

Generativecell

Pollen grain(male gametophyte)

Microspores(n)

ANTHER

Pollen sac

Figure 24.14 Meiotic division ofeach of many cellswithin the anther produces fourmicrospores. Thesemicrospores developinto the male gameto-phyte or pollen grain

669

Building a ModelKinesthetic Use a plasticsandwich bag to represent a

female gametophyte. Place threesmall balls of clay of the samecolor within the bag and explainthat each ball represents a hap-loid nucleus. (One is the egg andthe other two are the centralcell.) Introduce two small balls ofclay of a different color to thebag. Explain that each ball repre-sents the two sperm nuclei thatenter the female gametophyte.Fuse one sperm with the egg andexplain that this represents thezygote, which is now diploid.Fuse the other three nuclei.Explain that this represent thetriploid nucleus that formsendosperm. Point out thattogether the fusing of the clayillustrates double fertilization.

Knowledge Show studentsa flower pistil that has been cutopen to reveal the ovary. Ask themto point to where the followingoccur: growth of pollen tube,development of female gameto-phyte, and double fertilization.L2

P

LS


P

LS

L1

P

LS


n


2n

Fertilization

Meiosis

Flowers

Youngseedling

Germinatingseed

Seed

Fruit

Pollen tube

Adultsporophyteplant

Zygote

Endospermnucleus

Pollentube

Doublefertilization

Egg

Tubenucleus

Sperm

Malegametophyte

Microsporesin fours

Ovule withmegasporemother cell

Anther Pollen sacwith microsporemother cellsOvary

Fourmegaspores

Female gametophytewith four nuclei


Figure 24.12In the life cycle of a flowering plant, the sporophyte gener-ation nourishes and protects the developing gametophyte.After fertilization, the new sporophyte, which is containedin a seed or fruit, is released from the parent plant.

668

ReinforcementVisual-Spatial Provide stu-dents with a black line

drawing of the life cycle of aflowering plant. Using coloredpencils, have them shade in thegametophyte stage and thesporophyte stage in two differentcolors.

Microscope ActivityVisual-Spatial Have studentsview prepared slides of

Lilium ovaries. Ask students todraw and label an ovule.P

LS

L1

P

LS

P

ELL

LS

L1

P

LS


Visual-Spatial Show stu-dents the tiny sporo-

phyte inside a peanut. It is thestructure with two tiny leaves.CAUTION: Do not allow stu-dents to eat the peanuts assome students may be allergicto them.

P

LS


Flowering Plant Life CycleLinguistic Have students write aparagraph in their journal outlining

the steps of a flowering plant’s life cycle.Encourage them to illustrate the conceptswith drawings.

P

LS

L2

P

LS


Basic Concepts Trans-parency 42 and Master

P

ELL

LS

L2

P

LS


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

food. By producing nectar andattracting animal pollinators, animal-pollinated plants are able to promotepollination without producing largeamounts of pollen.

Some nectar-feeding pollinators areattracted to a flower by its color orscent or both. Some of the bright,vivid flowers attract pollinators such asbutterflies and bees. Some of theseflowers have markings that are invisi-ble to the human eye but are easilyseen by insects. Flowers that are polli-nated by beetles and flies have a strongscent but are often dull in color.

Many flowers have structural adap-tations that favor cross-pollination.This results in greater genetic varia-tion because the sperm from oneplant fertilizes the egg from another.For example, the flowers of certainspecies of orchids resemble femalewasps. The male wasps visit theflower and attempt to mate with itand become covered with pollen,which is deposited on orchids it mayvisit in the future.

FertilizationOnce a pollen grain has reached

the stigma of the pistil, several eventstake place before fertilization occurs.Inside each pollen grain are two hap-loid cells, the tube cell and the gener-ative cell. The tube cell nucleusdirects the growth of the pollen tubedown through the pistil to the ovary,as shown in Figure 24.16. The gen-erative cell divides by mitosis, pro-ducing two haploid sperm cells. Thesperm cells are transported by thepollen tube through a tiny opening inthe ovule called the micropyle.

Within the ovule is the femalegametophyte, composed of eight hap-loid cells. One of the sperm unites withthe egg cell forming a diploid zygote,which begins the new sporophytegeneration. The other sperm cell fuseswith the central cell, which containsthe polar nuclei, to form a cell with atriploid (3n) nucleus. This process, inwhich one sperm fertilizes the egg andthe other sperm joins with the centralcell, is called double fertilization.


Pollen grain

Stigma

Style

Ovary

Central cell(2n)

Ovule

Egg nucleus

Two spermnuclei

Pollen tube

Tube nucleus

Double Fertilization

One spermfertilizes thecentral cell(3n)

One spermfertilizes theegg cell (2n)

Figure 24.16In flowering plants,the male gameto-phyte grows throughthe pistil to reach thefemale gametophyte.Double fertilizationinvolves two spermcell nuclei. One sperm cell uniteswith the egg nucleusand the other spermcell uniteswiththediploid central cell of the female gametophyte.

671

Revealing MisconceptionsStudents may believe that “hayfever” is an allergy to hay.However, hay fever is an allergicreaction to the protein present inpollen. Often, the pollen is pro-duced by plants that bloom in theearly fall or spring.

EnrichmentThere are many different mecha-nisms to ensure pollination. Tellstudents about the carrion flowersthat have a fragrance similar torotting flesh that attracts its polli-nators—flies and beetles. Onespecies of aquatic plant releases itspollen in a “pollen boat” thatfloats on the water’s surface untilit slides down the dimple createdby the surface tension aroundnearby flowers.

Concept DevelopmentCorn has male and female flowersfound on different parts of thesame plant. Have students explainwhat a corn tassel is, where thefemale corn flower is located, andwhat corn silk is. The corn tassel iscomposed of all the stamens of manymale flowers. The corn silk is com-posed of all the styles of many femaleflowers. The corn kernels on the cobare fertilized fruits of the plant.

anther to the pistil. Plant reproduc-tion is most successful when the pol-lination rate is high, which meansthat the pistil of a flower receivesenough pollen of its own species tofertilize the egg in each ovule. Manyanthophytes have elaborate mecha-nisms that help ensure that pollengrains are deposited in the right placeat the right time. Some of these areshown in Figure 24.15. Although itmay seem wasteful for wind-polli-nated plants to produce such largeamounts of pollen, it does help

ensure pollination. Most anthophytespollinated by animals produce nectar,which serves as a valuable, highlyconcentrated food for visitors to theflowers. Nectar is a liquid made up ofproteins and sugars. It usually col-lects in the cuplike area at the base ofthe petals. Animals such as insectsand birds brush up against theanthers while trying to get to thenectar. The pollen that attaches tothem can be carried to anotherflower, resulting in pollination. Someinsects also gather pollen to use as


Figure 24.15The shape, color, and size ofa flower reflect its relation-ship with a pollinator.

The butterfly uses itslong proboscis to sipnectar that bees andflies cannot reach.

AA

Flowers polli-nated by hum-mingbirds areoften tubular andcolored bright redor yellow but mayhave little scent.

DD

Bats sip nectarfrom night-blooming flow-ers with astrong, mustyodor, such asbananas andsome cacti.

CC

The ultraviolet markings ofsome flowers guide insectsto a flower’s nectar.

EE

The wind-pollinated flowersof this ragweed plant aresmall and green and lackstructures that would blockwind currents.

BB

670

ReinforcementAsk students to explain how aplant can reproduce sexually if itsflowers are incomplete. Pollenfrom the male flower can be car-ried to the female flower by wind,insects, or other animals.

Tying to PreviousKnowledgeAsk students to answer the fol-lowing questions. (a) Why ispollen needed for fertilization? Itcontains sperm cells. (b) Why mustthe pollen that fertilizes a flowerbe from the same species as thefemale flower? Chromosome num-bers and alleles must be identical forfertilization to occur. (c) What willhappen if pollen lands on thewrong species of flower? No pollentube will form and fertilization willnot occur.

PortfolioPortfolio

Cross- and Self-PollinationVisual-Spatial Have students pre-pare a series of drawings that explain

the concepts of cross-pollination and self-pollination. Instruct students to includeproper labels and titles for the drawings.Non-artistic students may be provided witha flower outline that they can trace fortheir diagrams.

P

LS

PP

LSP

ELL

LS

L2

P

LS


Exploration: PollinationDisc 3

VIDEODISCSTV: PlantsWhat is a Seed?

Unit 4, Side 3, 3 min.Germination

!7gb/Q~Ö"

VIDEODISCBiology: The Dynamics of LifeDouble Fertilization (Ch. 24)

Disc 1, Side 2, 49 sec.

CD-ROMBiology: The Dynamics of LifeAnimation: Double Fertilization

Disc 3

!9TÑ"

CAREERS IN BIOLOGY

Greens Keeper

Do you like to work outside? Is golfyour favorite sport? Then you

already know the value of a velvetygreen fairway, which is the firstrequirement in becoming a greenskeeper.

Skills for the JobA greens keeper maintains both

the playing quality and the beauty of agolf course. Beginning keepers usually learnon-the-job and spend their days mowing the greens. Greenskeepers who want to manage large crews will need a two- orfour-year degree in turf management and a certificate ingrounds management. They must be thoroughly familiarwith different types of grasses and know how weather andwear affect them so they can keep fairways smooth and per-fectly green. Other careers in turf management including car-ing for the grounds of shopping centers, schools, sports play-ing fields, cemeteries, office buildings, and other locations.

For more careers in related fields, be sureto check the Glencoe Science Web Site.

www.glencoe.com/sec/science

Fruit formationAs the seeds develop, the sur-

rounding ovary enlarges andbecomes the fruit. A fruit is the struc-ture that contains the seeds of ananthophyte. Figure 24.17 shows howthe fruit of a blueberry develops fromthe ovary inside the flower.

A fruit is as unique to a plant as itsflower, and many plants can be identi-fied by examining the structure oftheir fruit. You are familiar withplants that develop fleshy fruits, suchas apples, grapes, melons, tomatoes,and cucumbers. Other plants developdry fruits such as peanuts, sunflower“seeds,” and walnuts. In dry fruits, theovary around the seeds hardens as thefruit matures. Some plant foods thatwe call vegetables or grains are actu-ally fruits, as shown in Figure 24.18.Can you think of any vegetables thatare actually fruits? For example,tomatoes are fleshy fruits that areoften referred to as vegetables.


Figure 24.18 A fruit is the ripened ovary of aflower that contains the seeds orseed of the plant. The mostfamiliar fruits are those we con-sume as food.

Fleshy fruits develop a juicy fruitwall full of water and sugars.

BB

Dry fruits have dry fruit walls. The ovary wallmay start out with a fleshy appearance, as inhickory nuts or bean pods, but when the fruitis fully matured, the ovary wall is dry.

AA

673

Career PathCourses in high school:biology, botany, chemistry,

mathematicsCollege: two- or four-year degreeto become a crew supervisorOther education sources: on-the-job training

Career IssueWith so many issues and prob-lems in today’s world, ask studentsif they think anyone should beconcerned about the quality of agolf course. Have them explainthe reasons for their opinions.

For More InformationFor more information on becom-ing a greens keeper, students canwrite to:

Professional Grounds Management Society

120 Cockeysville Road, Suite 104Hunt Valley, MD 21031

EnrichmentVisual-Spatial Have studentsresearch the type of fruits:

cypsela, berry, pome, follicle,legume, capsule, and aggregate.Ask them to create a visual thatdefines each fruit type and showsexamples of each. L3

P

LS

Ovules

Ovary

Sepals

Fusedpetals

Stamens

Fruit

Double fertilization is unique toanthophytes and is illustrated inFigure 24.16. The triploid nucleuswill divide many times, eventuallyforming the endosperm of the seed.The endosperm is food storage tis-sue that supports development of theembryo in anthophyte seeds.

Many flowers contain more thanone ovule. Pollination of these flowersrequires that at least one pollen grainland on the stigma for each ovule con-tained in the ovary. In a watermelonplant, for example, hundreds of pollengrains are required to pollinate a sin-gle flower if each ovule is to be fertil-ized. You are probably familiar withthe hundreds of watermelon seedsthat are the result of this process.

Seeds and FruitsThe embryo contained within a

seed is the next sporophyte genera-tion. The formation of seeds and thefruits that enclose them help ensurethe survival of the next generation.

Seed formationAfter fertilization takes place, most

of the flower parts die and the seedsbegin to develop. The wall of the ovulebecomes the hard seed coat, whichmay aid in dispersal and helps protectthe embryo until it begins growinginto a new plant. Inside the ovule, thezygote divides and grows into theplant embryo. The triploid centralcell develops into the endosperm.


Figure 24.17A fruit consists of the seeds andthe surrounding mature ovary ofa flowering plant.

OriginWORDWORD

endospermFrom the Greekwords endon, mean-ing “within,” andsperma, meaning“seed.” The endo-sperm is storage tissue found in theseeds of manyanthophytes.

When the eggs in the ovules ofa blueberry flower have beenfertilized, the petals, stamens,and stigma wither and fallaway.

AA

The wall of the ovary in ablueberry becomes fleshyand grows up and around theovary as the seeds develop.

BB

The remains of thesepals and some driedstamens usually canbe seen at the top.

CC

672


Show students a tomato and apeach. Ask how the two plantparts are alike and how theydiffer. Students may suggestthat both have seeds but thatone is a fruit and one is a veg-etable. Ask students to providedefinitions for fruit and veg-etable. Use their definitions topoint out that a tomato is afruit. If students are still notsure of the relationship, askhow the seeds got inside thetwo structures and what waspresent on the plant beforethe tomato or peach appeared.P

LS


English Language LearnersVisual-Spatial Have students preparea table with the heads Haploid, Dip-

loid, and Triploid across the top. Ask themto group the following terms, phrases, ornumbers beneath their correct head:sperm, 3n, pollen tube nucleus, egg, n,endosperm, central cell, fertilized egg, 2n.P

LSP

ELL

LS

L1

P

LS

Fruits and FiberVisual-Spatial Have students preparea chart comparing the amount of

fiber in five fruits. They should explain whya high fiber diet is considered beneficial.L2

P

LS

CAREERS IN BIOLOGY

Concept DevelopmentShow students an apple. Explainthat an apple is a “false fruit.”Explain that unlike most fruits,which form from the ovary wall,the fleshy part of an apple formsfrom the swollen receptacle.


Animation: Fruit FormationDisc 3


Fruit Formation (Ch. 25)Disc 1, Side 2, 39 sec.

!9^Ö"

Cultural DiversityThe History of ChocolateTheobroma cacao is a native tree from CentralAmerica. After flowering, it produces largepods that contain about 40 cacao beans.Because of its seeds, cacao was domesticatedby the Mayas and Aztecs who turned the

seeds into a rich brown drink called choco-late. Researchers are suspicious that thechemicals in chocolate, theobromine andmethylxanthin, may have an addictive qual-ity. This may explain why some individualscrave chocolate and chocolate products.


growth and development of the newplant. This period of inactivity in amature seed is called dormancy. Thelength of time a seed remains dor-mant can vary from one species toanother. Some seeds, such as willow,magnolia, and maple remain dor-mant for only a few weeks afterthey mature. These seeds cannotsurvive harsh conditions for longperiods of time. Other plantsproduce seeds that can remaindormant for remarkably long peri-ods of time, Figure 24.20. Evenunder harsh conditions, the seeds ofdesert wildflowers and some coniferscan survive dormant periods of 15 to20 years. Scientists discoveredancient seeds of the East IndianLotus, Nelumbo nucifera, in China,which they have radiocarbon dated tobe more than a thousand years old.Imagine their amazement when theseseeds germinated!

Requirements for germinationDormancy ends when the seed is

ready to germinate. Germination isthe beginning of the development ofthe embryo into a new plant. Theabsorption of enough water and thepresence of oxygen and favorabletemperatures usually end dormancy,but there may be other requirements.Water is important because it acti-vates the embryo’s metabolic system.Once metabolism has begun, the seedmust continue to receive water or itwill die. Just before the seed coatbreaks open, the plant embryo beginsto respire rapidly. Many seeds germi-nate best at temperatures between25°C and 30°C. Arctic species germi-nate at lower temperatures than dotropical species. At temperaturesbelow 0°C or above 45°C, most seedswon’t germinate at all.

Some seeds have special require-ments for germination, Figure 24.21.

For example, some germinate morereadily after they have passedthrough the acid environment of ananimal’s digestive system. Othersrequire a period of freezing tempera-tures, as do apple seeds, extensivesoaking in saltwater, as do coconutseeds, or certain day lengths. Recallthat the seeds of some conifers willnot germinate unless they have beenexposed to fire. The same is true of

Figure 24.20Seeds can remaindormant for longperiods of time.Lupine seeds likethese may germinateafter remaining dor-mant for decades.

Figure 24.21The seeds of thedesert tree Cercidiumfloridum have hardseed coats that mustbe cracked open inorder to germinate.This occurs when theseeds tumble downrocky gullies in suddenrainstorms.

use care when working with chemicals.Analysis

1. Tetrazolium indicates cell respiration when itturns pink. Which seed treatment carried oncell respiration? Why? Uncanned seeds aregerminating and require energy; cannedseeds are dead.

2. The darker the pink color, the greater therate of respiration. Which seed part carrieson the greatest rate of respiration? Why?Embryo; rapid growth requires more energy.

Portfolio Design an experimentto determine how many seeds in a seedpacket are alive. Use the PerformanceTask Assessment List for Designing anExperiment in PASC, p. 23. L3

P

LS


675

Seed dispersalA fruit not only protects the seeds

inside it, but also may aid in dispersingthose seeds away from the parent plantand into new habitats. The dispersalof seeds, Figure 24.19, is importantbecause it reduces competition forsunlight, soil, and water between theparent plant and its offspring. Animalssuch as raccoons, deer, bears, and birdshelp distribute many seeds by eatingdry or fleshy fruits. They may carrythe fruit some distance away from theparent plant before consuming it andspitting out the seeds. Or they may eatthe fruit, seeds and all. Seeds that areeaten may pass through the digestivesystem unharmed and are depositedin the animal’s wastes. Squirrels,birds, and other nut gatherers maydrop and lose some of the seeds theycollect, or even bury them only toforget where. These seeds can thengerminate far from the parent plant.

Plants, such as water lilies andcoconut palms that live in or nearwater produce fruits or seeds with air

pockets in the walls, which enablethem to float and drift away from theparent plant. The ripened fruits ofmany plants split open to releaseseeds designed for dispersal by thewind or by clinging to animal fur.Orchid seeds are so tiny that theyresemble dust grains or feathers andare easily blown about by the wind.The fruit of the poppy flower forms aseed-filled capsule that releases sprin-kles of tiny seeds like a salt shaker asit bobs about in the wind. Tumble-weed seeds are scattered by the windas the whole plant rolls along theground.

Seed germinationAt maturity, seeds are fully formed.

The seed coat dries and hardens,enabling the seed to survive condi-tions that are unfavorable to the par-ent plant. The seeds of some plantspecies must germinate immediatelyor die. However, the seeds of someplant species can remain in the soiluntil conditions are favorable for


Figure 24.19A wide variety of seed-dispersal mechanismshave evolved amongflowering plants.

The ripe pods of violets snap openwith a pop, which sends a showerof small seeds in all directions.

AA

Clinging fruits, likethose of the cockle-bur and burdock,are covered byhooks that stick tothe fur or feathersof passing animalsor the clothes ofpassing humans.

BB

Wind-dispersedseeds have adapta-tions that enablethem to be heldaloft while theydrift away fromtheir parent.

CC

Tying to PreviousKnowledgeAsk students to define the termpolyploidy. Explain that it is esti-mated that between 35 and 50%of all flowering plants are poly-ploid. The most common poly-ploid condition is tetraploid or4n. Tetraploids are often biggeror more vigorous that the diploidplant and thus are more desirablefor agriculture and/or horticul-ture.

Alternative LabRespiring Seeds

Purpose To compare the rate of respiration in ger-minating and nongerminating seeds.

P

LS

Materialscanned kidney beans, paper cup, water,dried kidney beans, wax paper, labels,tetrazolium solution in dark dropper bot-tles (add 1 g of 2,3,5-triphenyl tetrazoliumchloride to 100 mL distilled water)ProcedureGive the following directions to students.

1. Soak ten kidney bean seeds overnightin water. The next day, split each seedin half. Split ten canned kidney bean

seeds in half.2. Place all seeds split-side up onto two

sheets of wax paper. Mark each paperwith a label indicating seed treatments.

3. Add a drop of tetrazolium to each cutsurface. Wait 20-30 minutes. Record inwhich seeds and where in the seeds apink color appears. Note: Tetrazoliumcan be diluted and discarded down thesink, but the bean seeds cannot be dis-carded in the sink. Caution students to674

Water and SeedGermination

Kinesthetic Water mustbe absorbed by seeds

prior to germination in aprocess called imbibition. Thevolume change that occursduring imbibition can be mea-sured through water displace-ment.

Place 50 mL of water in agraduated cylinder. Add 10bean seeds. The new level ofwater less the original volumeequals the volume of the 10seeds. Remove the seeds fromthe cylinder and soak them inwater overnight. The followingday, add 50 mL of water to thegraduated cylinder. Add thesoaked beans and calculatetheir new volume. Have stu-dents use the water-displace-ment technique to calculatethe percent of volume changethat occurs through imbibition.P

LSP

ELL

LS

L2

P

LS


Animation: Seed DispersalDisc 3


Seed Dispersal (Ch. 26)Disc 1, Side 2, 1 min. 9 sec.

!9hÜ"


Basic Concepts Trans-parency 43 and Master

Laboratory Manual, pp. 171-178 L2

P

LS

P

ELL

LS

L2

P

LS


Video: GerminationDisc 3


Germination (Ch. 27)Disc 1, Side 2, 25 sec.

!9rá"

Looking at Germinating Seeds Seeds are made up of a plant embryo, a seed coat, and in some plants, a food-storage tissue. Monocot and dicot seeds differ in their internal structures.

Procedure! Obtain from your teacher a soaked,

ungerminated corn kernel (monocot), a bean seed (dicot), and corn and bean seeds that have begun to germinate.

@ Remove the seed coats from each of the ungerminatedseeds, and examine the structures inside. Use low-powermagnification. Locate and identify each structure of theembryo and any other structures you observe.

# Examine the germinating seeds. Locate and identify thestructures you observed in the dormant seeds.

Analysis1. Diagram the dormant embryos in the soaked seeds, and

label their structures.2. Diagram the germinating seeds, and label their structures.3. List at least three major differences you observed in the

internal structures of the corn and bean seeds.

MiniLab 24-2MiniLab 24-2cotyledons and the plant’s first leaves.As the stem grows larger and theleaves turn green, the plant can pro-duce its own food through photosyn-thesis. To learn more about germinat-ing seeds, try the MiniLab shown here.

Vegetative reproductionThe roots, stems, and leaves of

plants are called vegetative structures.When these structures produce a newplant, it is called vegetative reproduc-tion. Vegetative reproduction is com-mon among anthophytes. Some mod-ified stems of anthophytes, such aspotato tubers, can produce a newplant. Potatoes will grow new stemsfrom their “eyes” or buds. Farmersmake use of this feature when theycut potato tubers into pieces andplant them. The buds on these sec-tions grow new shoots that produceentire new plants.

Although cloning animals is a rela-tively new phenomenon, gardenershave relied for years on cloning toreproduce plants. Using vegetativereproduction to grow numerous plantsfrom one plant it is frequently referredto as vegetative propagation. Someplants, such as geraniums, can bepropagated by planting cuttings, whichare pieces of the stem or a leaf thathas been cut off another plant. Evensmaller pieces of plants can be used

to grow plants by tissue culture. Tinypieces of plants are placed on nutri-ent agar in test tubes or petri dishes.The plants produced by cuttings andtissue cultures contain the samegenetic makeup as the original plants.Therefore, they are botanical clones.



Understanding Main Ideas1. What is the relationship between the pollina-

tion of a flower and the production of one ormore seeds?

2. What part of an anthophyte flower becomesthe fruit?

3. Describe the process of double fertilization inanthophytes.

4. Explain how the production of nectar couldenhance the pollination of a flowering plant.

Thinking Critically5. Describe the formation of the female gameto-

phyte in a flowering plant.

6. Making and Using Tables Make a table thatindicates whether each structure of a flower isinvolved in pollination, fruit formation, seed pro-duction, or seed dispersal. For more help, refer toOrganizing Information in the Skill Handbook.


Corn seed germination

Observing3 AssessCheck for UnderstandingHave students explain how thewords in each of the followingpairs are related.

a. pollen tube—double fertiliza-tion

b. epicotyl—hypocotylc. dormancy—germination

ReteachHave students indicate when orwhere in the life cycle each termin the Check for Understandingapplies.

ExtensionHave students research themechanism responsible for rootsgrowing down and stems growingup.

Performance Provide stu-dents with a sliced peach or cher-ry half and a sliced open flower.Have them locate and name thefollowing structures: ovule beforeand after fertilization, ovarybefore and after fertilization,embryo.

4 CloseDiscussionWatermelons have numerousblack seeds and some small whiteseeds. Ask students to speculatewhat the small white seeds foundin a watermelon might be. Theyare unfertilized ovules. L2

P

LS

L1

P

LS


L3

P

LS

L2

P

LS

L2

P

LS


Figure 24.23Germination of a bean seed is stimulated bywarm temperatures and water, which softensthe seed coat.

Figure 24.22Many wildflowers require fire for their seeds to germinate.This is especially true in prairie environments where firesare periodically set to induce the germination of prairiewildflower seeds.

certain wildflower species, includinglupines and gentians, Figure 24.22.

The germination of a typical dicotembryo is shown in Figure 24.23.Once the seed coat has been softenedby water, the embryo starts toemerge from the seed. The first partof the embryo to appear is theembryonic root called the radicle(RAD ih kul). The radicle grows downinto the soil and develops into a root.The portion of the stem nearest theseed is called the hypocotyl (HI pohkaht ul). In some plants, the first partof the stem to push above ground isan arched portion of the hypocotyl.As the hypocotyl continues growing,it straightens, bringing with it the

The hypocotylis the first partof the stem toappear.

BB

As new leavesmature, thecotyledonswither andfall away.

DDAs the hypocotylstraightens, theplant’s first leaves,the cotyledons, are exposed to sunlight.

CC

The radicle willbecome the pri-mary root.

AA Radicle

Cotyledon

Seed coat

Primary root

Secondaryroots

Hypocotyl

Epicotyl

Cotyledon

Withered cotyledons

Hypocotyl

676

Purpose To compare dormant and germi-nating monocot and dicot seedembryos.

Process Skillsobserve and infer, compare andcontrast

Safety PrecautionsAdvise students to use cautionwith razor blades and always tocut away from the body.

Teaching Strategies■ Soak some seeds 24 hours andothers 72 hours prior to use.After the 72-hour seeds havebeen soaking for 24 hours, wrapthem in moist paper towels andplace them in sealed plastic bags.■ Advise students to lay the cornon its flat side while cutting.

Expected ResultsGerminating seeds have largerembryos.

Analysis1. Labels should include cotyle-

don(s), embryo.2. Diagrams of dicot should

include cotyledons, embryo,epicotyl, radicle, plumule,and hypocotyl. Diagrams ofmonocot should include onlycotyledon and embryo.

3. Monocot has one cotyledon,small embryo, is slow to ger-minate, and its embryo partsare hard to differentiate.Dicot seed has two cotyle-dons, larger embryo, and eas-ily seen embryo parts.

Performance Provide stu-dents with seeds. Have studentsclassify each seed after removingthe seed coat. Use the Perform-ance Task Assessment List forMaking and Using a ClassificationSystem in PASC, p. 49. L2

P

LS


P

LS

MiniLab 24-2MiniLab 24-2

PortfolioPortfolio

Modeling Seed DispersalKinesthetic Provide students with a strip of Velcro, a piece of fabric,

cotton batting, tape, string, clay, stiffpaper, and scissors. Have them use thematerials to prepare models that showdifferent means of seed dispersal. Modelsmay imitate attaching to animal fur orfloating in air.

P

LSP

ELL

LS

L1

P

LS

Resource ManagerResource ManagerReinforcement and Study Guide,

p. 108BioLab and MiniLab Worksheets,

p. 110Content Mastery, pp. 117, 119-120

L1

P

LS

L2

P

LS

P

ELL

LS

L2

P

LS

Section AssessmentSection AssessmentSection Assessment1. Pollination transports sperm to the

female gametophyte. Inside the ovule,the sperm cells are involved in doublefertilization. One pollen grain is re-quired for the production of each seed.

2. the ovary wall3. Double fertilization occurs when one

sperm unites with the egg cell, formingthe 2n zygote and the other sperm cell

fuses with the central cell to form a 3ncell.

4. Nectar is a source of nutrition for ani-mal pollinators such as insects and bats;they get pollen on them as they try toreach the nectar. As these animals trav-el from flower to flower, they cross-pol-linate the flowers.

5. In the ovule, meiosis produces four hap-

loid megaspores. One of these megas-pores will undergo three mitotic divisions, producing eight nuclei. Theseeight nuclei make up the embryo sac orfemale gametophyte.

6. pollination: anther, stamen, stigma;fruit formation: ovary, and ovule; seedproduction: ovule, egg; seed dispersal:ovary 677

pollen-filled anther on the tip.Note the number of stamens.

3. Locate the pistil. The stigma atthe top of the pistil is often sticky.The style is a long, narrow struc-ture that leads from the stigma tothe ovary.

4. Place an anther from one of thestamens onto a microscope slideand add a drop of water. Cut theanther into several pieces withthe razor blade. CAUTION:Always take care when using arazor blade.

5. Examine the anther under lowand high power of your micro-scope. The small, dotlike struc-tures are pollen grains.

6. Slice the ovary in half length-wise with the razor blade.Mount one half, cut side fac-ing up, on a microscopeslide.

7. Examine the ovary sectionwith a hand lens or stere-omicroscope. Themany, small, dotlikestructures that fill thetwo ovary halves areovules. Each ovulecontains an eggcell that is notvisible under lowpower. A tinystalk connects eachovule to the ovary wall.

8. Identify the ovary and ovules.9. Make a diagram of the flower,

labeling all its parts. Color thefemale reproductive parts red.Color the male reproductive partsgreen. Color the remaining partsblue.


1. Observing How many stamens arepresent in your flower? How manypistils, ovaries, sepals, and petals?

2. Comparing and ContrastingMake a reasonable estimate of thenumber of pollen grains in theanther and the number of ovules inan ovary of your flower.

3. Interpreting Data Which pro-duces more? Pollen grains by oneanther? Ovules produced by oneovary? Give a possible explanationfor your answer.

ANALYZE AND CONCLUDEANALYZE AND CONCLUDE

Going FurtherGoing Further

Project Use a field guide to identify com-mon wildflowers in your area. Most fieldidentifications are made on the basis ofcolor, shape, numbers, and arrangement offlower parts. If collecting is permitted, pick afew common flowers to press and makeinto a display of local flora.

To find out more aboutflowers, visit the Glencoe

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


1. Stamens, petals, and sepalswill be in multiples of 3 if amonocot, multiples of 4 or 5if a dicot. One pistil andovary will be present.

2. thousands of pollen grains, 10to 100 ovules

3. Yes; the flower increases theprobability of a pollen celllanding on the correct stigmaby producing and releasing alarge number of pollengrains.

Knowledge Provide stu-dents with diagrams of a flowerother than that used in thisBioLab. Have them label andindicate the general function of allimportant structures. Use thePerformance Task AssessmentList for Making Observations andInferences in PASC, p. 17. L1

P

LS


ANALYZE AND CONCLUDEANALYZE AND CONCLUDE

679

■ If necessary, review proper use of thestereomicroscope.

Data and ObservationsStudent diagrams, when colored properly,should show the petals and sepals as blue,pistil as red, and stamens as green.

Going FurtherGoing Further

Provide students with a compo-site flower such as a sunfloweror daisy. Have them determinethe locations of the individualflorets and their various flowerparts. L2

P

LS

Examining the Structure of a Flower

F lowers are the reproductive structures of anthophytes. Seeds thatdevelop within the flower are carried inside a fruit. Seeds provide

an extremely important form of reproduction in flowering plants.Flowers come in many colors and shapes. Often their colors or shapes arerelated to the manner in which pollination takes place. The major organsof a flower include the petals, sepals, stamens, and pistils. Some flowersare incomplete, which means they do not have all four kinds of organs.You will study a complete flower.


microscope 2 coverslipssingle-edged dropper

razor blade water

Safety Precautions Always wear goggles in the lab.

Handle the razor blade with extremecaution. Always cut away from you.Use caution when working with amicroscope and slides. Wash yourhands with soap and water after han-dling plant material.

Skill HandbookUse the Skill Handbook if you need

additional help with this lab.

PREPARATIONPREPARATION

1. Examine your flower. Locate thesepals and petals. Note theirnumbers, size, color, and arrange-ment on the flower stem.

2. Remove the sepals and petalsfrom your flower by gentlypulling them off the stem. Locatethe stamens, each of which con-sists of a thin filament with a

PROCEDUREPROCEDURE

ProblemWhat do the parts of a flower look

like? How are they arranged?

ObjectivesIn this BioLab, you will:■ Observe the structures of a flower.■ Identify the functions of flower parts.

Materialsflower—any complete flower that is

available locally, such as phlox, lily,or tobacco flower

hand lens (or stereomicroscope)colored pencils (red, green, blue)2 microscope slides

678


Time Allotment One class period

Process Skillsobserve and infer, use the micro-scope, compare and contrast,interpret data

Safety Precautions■ Some students may be allergic

to the chemicals used in pre-served specimens.

■ Caution students against rub-bing their eyes with theirhands because of the preserva-tive. Always have studentswash their hands thoroughlyafter handling preserved speci-mens.

■ Handle the razor blade withextreme caution. Always cutaway from the body.

Alternative Materials■ Do not use composite species

of flowers such as sunflower,daisy, or dandelion.

■ Preserved slides that showeggs within the ovule are avail-able from supply houses.

■ Preserved flowers are availableat any time of the year frombiological supply houses. Adisadvantage to such flowers isthat the preservative tends todiscolor flower parts, espe-cially petals and sepals, whichwill appear dull green.

PREPARATIONPREPARATION

P

LS

678

PROCEDUREPROCEDURE

Teaching Strategies■ When preparing the anther wet mount,it may be helpful for students to squash thepreparation using their thumb and a pieceof lens paper over the coverslip. Advise stu-dents to press down firmly to avoid crack-ing the coverslip, or use plastic coverslipsfor this wet mount.■ Eggs will not be visible; students should

not attempt to observe ovules under themicroscope in order to observe egg cells.■ Students can work in groups of two tothree for this BioLab.■ Show students how to remove the petalsand sepals.■ You may wish to appoint certain students aslab helpers. These students can be called uponby their classmates for help and guidance.

Resource ManagerResource ManagerBioLab and MiniLab Worksheets,

pp. 111-112 L2

P

LS


Chapter 24 AssessmentChapter 24 Assessment

SUMMARYSUMMARY

Section 24.1

Section 24.2

Section 24.3

Main Ideas■ In mosses, a gametophyte forms archegonia and

antheridia. The gametophyte is dominant.■ In ferns, the prothallus forms archegonia and

antheridia. The sporophyte is dominant.■ In conifers, cones produce spores that form

male or female gametophytes. The pollen grainproduces sperm, which fertilizes the egg. Theembryo is protected by a seed.

Vocabularymegaspore (p. 658)micropyle (p. 659)microspore (p. 658)protonema (p. 655)vegetative reproduction

(p. 654)

Main Ideas■ Flowers are made up of four organs: sepals,

petals, stamens, and pistils.■ Photoperiodism affects the timing of

flower production.

Vocabularyanther (p. 662)day-neutral plant (p. 666)long-day plant (p. 666)ovary (p. 662)petals (p. 661)photoperiodism (p. 663)pistil (p. 662)sepals (p. 661)short-day plant (p. 666)stamens (p. 662)

CHAPTER 24 ASSESSMENT 681

1. Pollen and nectar produced by flowers pro-vide ________ for butterflies and bees.a. protection c. shelterb. food d. fruit

UNDERSTANDING MAIN IDEASUNDERSTANDING MAIN IDEAS2. Flowers that are dull in color and have no

nectar yet have a strong scent might be polli-nated by ________.a. bees c. beetlesb. butterflies d. hummingbirds

Life Cycles ofMosses, Ferns,and Conifers

Flowers andFlowering

Main Ideas■ The male gametophyte is produced by a

microspore in the anther. The female gameto-phyte is produced by a megaspore in the ovule.

■ Sperm are transported by a pollen tube to theovule, where fertilization takes place.

■ In double fertilization, one sperm joins with theegg to form a zygote. The second sperm joinsthe central cell to form endosperm.

■ The ovary wall becomes the fruit.■ Fruits and seeds are modified for dispersal.■ Seeds can stay dormant for long periods of time.

Vocabularydormancy (p. 675)double fertilization

(p. 671)endosperm (p. 672)germination (p. 675)hypocotyl (p. 676)polar nuclei (p. 667)radicle (p. 676)

The Life Cycleof a FloweringPlant

681



Chapter Assessment, pp. 139-144MindJogger VideoquizzesComputer Test BankBDOL Interactive CD-ROM, Chapter 24

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. b2. c

UNDERSTANDING MAIN IDEASUNDERSTANDING MAIN IDEAS

All ChapterAssessment

questions and answers have beenvalidated for accuracy and suitabili-ty by The Princeton Review.

For thousands of years, humans have influ-enced the breeding of plants, especially food

crops and flowers. Today’s plant breeders createhybrid strains with a variety of desired character-istics, such as more colorful or fragrant flowers,tastier fruit, higher yields, or increased resistanceto disease.

The perfect ear of corn The first step in creat-ing a hybrid is the selection of parent plants withdesirable characteristics. A breeder might select acorn plant that ripens earlier in the season or onethat can be sown earlier in the spring because itsseeds germinate well in cool, moist soil.

The next step is to grow several self-polli-nated generations of each plant to form a true-breeding line that always shows the desired char-acteristic. To do this, each plant must be pre-vented from cross-pollinating with other corn.The female flowers, called silks, grow near themiddle of the corn stalk. The breeder coverseach flower to prevent wind-borne pollen fromfertilizing it. The pollen-producing male tasselsare removed and the breeder uses their pollen tohand-pollinate each flower.

Once each true-breeding line has been estab-lished, the real experimentation begins. Breederscross different combinations of true-breedinglines to see what characteristics the resulting F1hybrids will have. These trials show which of thetrue-breeding lines reliably pass their desiredcharacteristic to hybrid offspring, and whichcrosses produce seeds that the breeder can mar-ket as a new, improved variety of corn.

Applications for the futureCell culture and genetic engineering tech-

nologies are new plant breeding techniques.Protoplast fusion removes the cell walls from the

cells of leaves or seedlings, then uses electricityor chemicals to fuse cells of two different species.Some of these fused cells have been successfullycultured in the lab and grown into adult plants,though none have produced seeds.

Recombinant DNA technology has been usedto insert specific genes into the chromosomes of aplant. This technique helps produce plants thatare resistant to frost, drought, or disease.


Hybrid Plants

If you’ve looked through any seed catalogs lately, you may have noticed phrases like “newthis season!” or “improved yield,” or “sweeter-tasting.” Sometimes the designation “F1”

is given beside the names of some plant varieties. All of these plants are hybrids thathave been produced in experiments conducted by plant breeders.

TechnologyTechnologyBIOBIO

Analyzing Concepts Why do seed companiesrecommend not saving seeds from hybrid vari-eties to plant the following year? (Hint: The off-spring of self-pollinated hybrids constitute the F2generation.)

To find out more about hybridseeds, visit the Glencoe Science

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

INVESTIGATING THE TECHNOLOGYINVESTIGATING THE TECHNOLOGY

Technician performing hybridization studies

680

Purpose Students explore old and newmethods of plant hybridization.

BackgroundSeed saver organizations encour-age home gardeners and farmersto grow open-pollinated, or non-hybrid, varieties of vegetables andflowers. These natural varieties canreliably be reproduced from seedpollinated in the wild by wind,insects, or birds. Many growerslike to raise heirloom varieties ofnonhybrids that are becomingrare because an increasing num-ber of hybrid varieties are offeredevery year. Open-pollinated vari-eties help maintain genetic diver-sity in plant populations. Seedsproduced by hybrids are eithersterile or tend to revert to unwant-ed characteristics of the parentgeneration.

Teaching Strategies■ Review with students Mendel’sexperiments with garden peasand the genetic crosses discussedin Chapter 10.■ Point out that plant breedersdon’t necessarily know whether adesired characteristic is regulatedby one gene or many genes. Thisis one reason why field trials ofmany different crosses are oftenrequired to obtain hybrid vari-eties with specific characteristics.

Investigating the TechnologyTo ensure that a new crop willhave the characteristics of thehybrid, a farmer must purchaseseeds from the plant breeder eachtime a new crop is planted. Seedfor the desired hybrid can beobtained only by cross-pollinat-ing the same line of parent plants.F1 hybrids produce offspring withvariable characteristics, not nec-essarily those of the hybrid. Forexamples, see the Punnet squaresand discussion of F2 hybrids inChapter 10.

P

LS

TechnologyTechnologyBIOBIO

Going FurtherGoing FurtherGoing Further

Ask students to compare and contrastmodern methods of creating hybrids withthe techniques used by Gregor Mendel inhis experiments with garden peas duringthe 1800s. L2

P

LS


Note Internet addressesthat you find useful in

the space below for quick reference.

VIDEOTAPEMindJogger Videoquizzes

Chapter 24: Reproduction in PlantsHave students work in groups as they playthe videoquiz game to review key chapterconcepts.




CHAPTER 24 ASSESSMENT 683

22. How does dormancy contribute to the sur-vival of a plant species in a desert ecosystem?

23. In what ways can the relationship between thegametophyte and sporophyte in seed plantsbe regarded as good for the gametophyte?

24. Explain why a scientist might hypothesizethat the eating habits of herbivorous mam-mals affected the evolution of fruits in flow-ering plants.

25. Observing and Inferring A plant speciesproduces heavy, spiked pollen grains. Whatconclusion can you draw about the plant’spollination method?

26. Comparing and Contrasting Compare andcontrast the formation of a moss sporophyteand a fern sporophyte.

27. Formulating Hypotheses Form a hypothesisthat explains why the primary root is the firstpart of the plant to emerge from a germinat-ing seed.

28. Concept Mapping Complete the conceptmap by using the following vocabulary terms:pistil, microspore, anther, stamen, ovary,megaspores.

THINKING CRITICALLYTHINKING CRITICALLY

ASSESSING KNOWLEDGE & SKILLSASSESSING KNOWLEDGE & SKILLS

The graph below provides data from anexperiment that tests the effects of ionizingradiation on the germination of seeds.

Using a Graph Use the graph to answer thefollowing questions.1. Which group of beans had the highest

percentage of germination?a. controlb. high-exposure levelc. medium-exposure leveld. low-exposure level

2. As the radiation dose increases, germi-nation ________.a. increases c. stopsb. decreases d. is not affected

3. When beans are given a low dose ofradiation, ________ germinate.a. 25 percent c. noneb. 50 percent d. 100 percent

4. When beans are given a medium dose ofradiation, ________ germinate.a. 12.5 percent c. 37.5 percentb. 25 percent d. 50 percent

5. Designing an Experiment Design anexperiment on bean plants in which thefollowing hypothesis is tested: Beanplants exposed to ionizing radiation willnot grow as tall as those that are notexposed.

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

Perc

ent g

erm

inat

ion

Control High

Exposure level

Medium Low

100

50

0

Germination of Beans After Exposure to Radiation

Flowers have

male parts

that producethat produce

in an

female parts

1.

2.

3.

4.

5.

6.

in an

683

23. The gametophyte is protectedand nourished by the sporo-phyte.

24. Mammals may have selectedonly certain fruits for their dietand thus aided in dispersal andsurvival of these species.

25. The plant is probably pollinatedby animals.

26. The moss and fern sporophytesboth develop from a diploidzygote in the archegonium ofthe gametophyte. The mosssporophyte will remain depen-dent upon the gametophyte,whereas the fern sporophytewill eventually survive on itsown.

27. The primary root anchors theseed and obtains needed waterfrom the soil for further growthand development of the plant.

28. 1. Pistil; 2. Megaspores; 3. Ovary;4. Stamen; 5. Microspores; 6. Anther

THINKING CRITICALLYTHINKING CRITICALLY


1. a2. b3. a4. a5. Bean plants that have just

emerged from the soil aredivided into four groups:one the control that is notirradiated, another givena high dose, anothergiven a medium dose, andanother a low does ofradiation. The heights ofthe plants are measuredand recorded for theduration of the experi-ment.


9. A(n) ________ is one that has all four organs:sepals, petals, stamens, and pistils.a. short-day plant c. incomplete flowerb. long-day plant d. complete flower

10. The response of flowering plants to the dif-ference in the duration of light and dark peri-ods in a day is called ________.a. photoperiodism c. pollinationb. nastic movement d. dormancy

11. A triploid cell resulting from double fertiliza-tion becomes the ________.

12. The structure marked A in the photograph is the ________.

13. The gametophyte produces ________ that arehaploid.

14. In ferns, sperm released by the ________ fer-tilize eggs in the ________.

15. Male pinecones produce ________ that willdevelop into the male gametophyte, or pollengrain.

16. The period of inactivity in a mature seed iscalled ________.

17. After pollination, a pollen tube grows down-ward through the pistil to the ________.

18. A short-day plant is more likely to flowerwhen the days are ________ and the nightsare ________.

19. During fertilization in anthophytes, the twosperm cells enter the ovule through an open-ing called the ________.

20. Growing new plants from cuttings or tissueculture is called ________.

21. You eat peas, beans, corn, peanuts, and cere-als. Why are seeds a good source of food?

APPLYING MAIN IDEASAPPLYING MAIN IDEAS

682 CHAPTER 24 ASSESSMENT

TEST–TAKING TIPTEST–TAKING TIP

Plan Your Work and Work Your Plan Set up a study schedule for yourself well in ad–vance of your test. Plan your workload so that youdo a little each day rather than a lot all at once.The key to retaining information is to repeatedlyreview and practice it.

AA

3. Moss gametophytes are ________ and formgametes by ________.a. diploid; meiosis c. diploid; mitosisb. haploid; mitosis d. haploid; meiosis

4. By eating fruit, mammals help ________.a. fertilize flowers c. photoperiodismb. nastic movement d. disperse seeds

5. While feeding, butterflies and bees carrypollen from flower to flower, causing________.a. pollination c. germinationb. dormancy d. photoperiodism

6. The heart-shaped structure formed by adeveloping fern spore is called a ________.a. protonema c. prothallusb. sporophyte d. frond

7. Which of the following plants do NOT pro-duce pollen?a. pine tree c. apple treeb. mosses d. corn

8. Which of the following is a fern gameto-phyte?a. c.

b. d.

682

3. b4. d5. a6. c7. b8. d9. d

10. a11. endosperm12. pistil13. gametes14. antheridia, archegonia15. microspores16. dormancy17. ovary18. short, long19. micropyle20. vegetative propagation

21. Seeds store food intended foruse by the embryo plant.

22. Seeds will remain alive untilwater becomes available forgermination.

APPLYING MAIN IDEASAPPLYING MAIN IDEAS



Club Mosses Club mosses are non-seed plants in the divi-

sion Lycophyta. They possess vascular tissue andare found primarily in moist environments.Species that exist today are only a few centime-ters high, but they are otherwise similar to fossilLycophytes that grew as high as 30 m and formeda large part of the vegetation of Paleozoicforests.

Ferns Ferns, division Pterophyta, are the most well-

known and diverse of the non-seed vascularplants. They have leaves called fronds that growup from an underground stem called the rhi-zome. Ferns are found in many different habitats,including shady forests, stream banks, roadsides,and abandoned pastures.

Horsetails Horsetails are non-seed vascular plants in

the division Sphenophyta. They are commonlyfound growing in areas with damp soil, such asstream banks and sometimes along roadsides.Present-day horsetails are small, but theirancestors were treelike.

Plants

Sporophyte Generation Thezygote develops into an embryo, whichgrows into the sporophyte generation ofthe moss. The sporophytes grow out of thetip of the female branches of the gameto-phyte and consist of capsule-topped stalks.Cells inside each capsule undergo meiosisto form haploid (n) spores.

685

BIODIGESTBIODIGEST

The hollow,jointed stems of horsetails are surroundedby whorls ofscalelike leaves.

As in all vascularplants, the sporo-phyte of this clubmoss is the domi-nant generation.Spores develop atthe base of specialleaves that formcone-shaped struc-tures called strobili.

Fern spores developin clustered structurescalled sori, usuallyfound on the under-sides of fronds.

Sperm

Capsule

Sporophyte

Egg

Gametophyte

AntheridiumMale reproductive

organ

ArchegoniumFemale

reproductiveorgan

The green, leafy growth of this moss is the gametophyte. The brown stalks toppedwith spore-filled capsulesare the sporophyte.

685

2 TeachMicroscope Activity

Visual-Spatial Have studentsview mosses, liverworts, and

hornworts with a stereomicro-scope. Ask students to describetheir observations orally or inwriting in their journals. If possi-ble, supply sporophytes andgametophytes with male andfemale reproductive structuresand ask students to compare thecharacteristics of these structuresand generations. L2

P

LS

BIODIGESTBIODIGEST

Non-Seed Plants Non-seed plants reproduce by forming spores.

A spore is a haploid (n) reproductive cell, pro-duced by meiosis, which can withstand harsh envi-ronmental conditions. When conditions becomefavorable, a spore can develop into the haploid,gametophyte generation of a plant. A spore willbecome either a female or male gametophyte.

Mosses, Liverworts, andHornworts

Mosses, liverworts, and hornworts are threedivisions of non-seed, nonvascular plants that livein cool, moist habitats. Because they have no

vascular tissues to move water and nutrients fromone part of the plant to another, they cannotgrow more than a few inches tall.

FOCUS ON ADAPTATIONSFOCUS ON ADAPTATIONS

The life cycle of most plant speciesalternates between two stages, or

generations. The sporophyte generationproduces spores, which develop into thegametophyte generation. The gameto-phyte produces gametes. In nonvascularplants, the gametophyte is larger andmore conspicuous than the sporophyte.In vascular plants, the sporophyte domi-nates. The gametophyte of a vascularplant is extremely small and may remainburied in the soil or inside the body ofthe sporophyte.

Gametophyte GenerationA gametophyte is haploid (n) and pro-duces eggs and sperm. In mosses, thegametophyte is the familiar soft, greengrowth that covers rotting logs or moistsoil. The tiny moss gametophytes pro-duce male and female branches. Spermcells produced by the male branchesmust swim through rain or dew to reachthe egg cells produced by the femalebranches. Fertilization takes place insidethe female reproductive organ and adiploid (2n) zygote is produced.

Alternation of Generations

684

Plants Earth is virtually covered with plants. Plants provide food

and shelter for multitudes of organisms. Through theprocess of photosynthesis, they transform the radiant energyof sunlight into chemical energy in food and release oxygento the atmosphere. All plants are multicellular eukaryotes.Plant cells are surrounded by a cell wall made of cellulose.

For a preview of the plant unit, study this BioDigest before you read the chapters.After you have studied the plant chapters, you can use the BioDigest to review the unit.

BIODIGESTBIODIGEST

VITAL STATISTICSVITAL STATISTICS

Non-Seed PlantsNumbers of species:Bryophyta—mosses, 20 000 speciesLycophyta—club mosses, 1000 speciesSphenophyta—horsetails, 15 speciesPterophyta—ferns, 12 000 speciesAnthocerophyta—hornworts, 100 speciesHepatophyta—liverworts, 6500 species

Mosses often grow inmasses that form thick

carpets

The leafy gameto-phyte is haploid.The spore stalksand capsules arediploid.

684

National Science Education StandardsUCP,.1, UCP.2, UCP.5, C.4, C.5,C.6, F.4

PreparePurposeThis BioDigest can be used as anintroduction to or an overview ofthe structures and functions ofplants. If time is limited, you maywish to use this unit summary toteach about plants in place of thechapters in the Plants unit.

Key ConceptsStudents learn about the charac-teristics of the major plant divi-sions. They are introduced to thealternation of generations; thedistinctions between non-seedand seed plants; pollination andfertilization; and the adaptivevalue of flowers, seeds, and fruits.

1 FocusBellringer

Visual-Spatial Bring anassortment of live plants

into the classroom, includingmosses, horsetails, and clubmosses, if available. Include asmall potted pine or otherconifer, and several potted flow-ering plants. Ask students toobserve each plant and make alist of its characteristics in theirjournals.

P

LS

L1

P

LS

BIODIGESTBIODIGEST

MultipleLearningStyles

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

Kinesthetic Quick Demo, p. 686; Meeting Individual

Needs, p. 686Visual-Spatial MicroscopeActivity, p. 685; Quick Demo,

p. 685; Visual Learning, p. 687Interpersonal Project, p. 688

Linguistic Visual Learning, p. 688; Extension, p. 689Naturalist Biology Journal, p. 687


Visual-Spatial If horse-tails grow in your area,

bring several stems into theclassroom. Show students thatthe stems come apart fairlyeasily at the nodes, and thatthe stems are hollow. Havethem examine the strobili, ifthese are present. Point outthat the silica in the stemsgives horsetails a scouring-padquality and is the source ofthe common name “scouringrush.”

P

LSQuick DemoQuick Demo

Visual-Spatial Show students young fern fid-

dleheads and sori on theunder-side of a fern frond. In the spring, fiddleheads aresometimes available in spe-cialty markets as a food item.If a live fern is available, showstudents the undergroundstem (rhizome) from whichroots grow down and frondsgrow up.

P

LS


Animation: Life Cycle of a MossDisc 3

Assessment PlannerAssessment Planner

Performance AssessmentAssessment, TWE, p. 687

Knowledge AssessmentAssessment, TWE, p. 688BioDigest Assessment, SE, p. 689

Skill AssessmentAssessment, TWE, p. 689

Stamen

Sepals

Petals

Stigma

Pistil Style

Ovary

Ovules

Pollen

Filament

Anther

Flowering Plants The flowering plants, division Anthophyta,

form the largest and most diverse group of plantson Earth today. They provide much of the foodeaten by humans. Anthophytes produce flowersand develop seeds enclosed in a fruit.

Monocots and Dicots The Anthophytes are classified into two

classes: the monocotyledons and the dicoty-ledons. Cotyledons, or “seed leaves,” are con-tained in the seed along with the plant embryo.Monocots have a single seed leaf that absorbsfood for the embryo. The two seed leaves ofdicots store food for the embryo.

Flowers Flowers are the organs of reproduction in

anthophytes. Sepals enclose the flower bud andprotect it until it opens; petals, which are oftenbrightly colored or perfumed, attract pollinators.Inside the circle of petals are the pistil and stamens.

Plants

Vascular Plants The stems of mostplants contain vascular tissues made up oftubelike, elongated cells through which water,food, and other materials move from one partof the plant to another. One reason vascularplants can grow larger than nonvascular plantsis because vascular tissue is a much more effi-cient method of internal transport than osmo-sis and diffusion. In addition, vascular tissuesinclude thickened fibers that can support tallerupright growth.

687

BIODIGESTBIODIGEST

Monocots (left) include grasses,orchids, and palms. Dicots(below) include many flower-ing trees and wildflowers.

An unbroken column of watertravels from the roots in xylemtissues. Sugars formed by photosynthesis travel aroundthe plant in phloem tissues.

The pistil is the female reproductive organ.Inside the ovary at the base of the pistil arethe ovules. Ovules contain the female game-tophyte generation of the plant. Femalegametes—egg cells—form in each ovule.

The stamen is the malereproductive organ of a

flower. Pollen grains con-taining male gametes

form inside the anther.

Water andsugars

Flower

Flower stalk

Leaf

Roots Sugars to sink

H2O

H2O

Sugars

CO2

687

Performance Have stu-dents collect branches or leaves oflocal trees and use field guides toidentify them. The lesson can beextended by trading botanicalspecimens with teachers in otherareas.

Visual LearningVisual-Spatial Explain tostudents that monocots have

leaves with parallel veins andflower parts in multiples of three.Dicots have leaves with nettedveins and flower parts in multi-ples of four or five. Have studentsuse these characteristics to clas-sify photographs or cut flowersbrought into the classroom.Extend the lesson by having stu-dents discuss the sizes and shapesof the flowers and their adapta-tions for pollination. L1

P

LS

L2

P

LS


BIODIGESTBIODIGEST

Seed Plants A seed is a reproductive structure that con-

tains a sporophyte embryo and a food supplyenclosed in a protective coating. The food supplynourishes the young plant during the first stagesof growth. Like spores, seeds can survive harshconditions. The seed develops into the sporophytegeneration of the plant. Seed plants includeconifers and flowering plants.

Conifers Conifers, division Coniferophyta, produce

seeds, usually in woody strobili called cones, andhave needle-shaped or scale-like leaves. Coniferseeds are not enclosed in a fruit. Most conifersare evergreen plants, which means they bearleaves all year round.

Adapted for Coldand Dry Climates

Conifers are common incold or dry habitats through-out the world. Conifer needleshave a compact shape and athick, waxy covering that helpsreduce evaporation and con-serve water. Conifer stems arecovered with a thick layer ofbark that insulates the tissuesinside. These adaptationsenable conifers to carry on lifeprocesses even when tempera-tures are below freezing.

FOCUS ON ADAPTATIONSFOCUS ON ADAPTATIONS

A ll plants probably evolvedfrom filamentous green

algae that lived in the nutrient-rich waters of Earth’s ancientoceans. An ocean-dwelling algacan absorb water and dissolvedminerals directly into its cells. Asland plants evolved, new struc-tures developed for absorbing andtransporting water and mineralsfrom the soil to all the aerial partsof the plant.

Nonvascular PlantsIn nonvascular plants, water andnutrients must travel from one cellto another by the relatively slowprocesses of osmosis and diffusion.As a result, nonvascular plants arelimited to environments whereplenty of water is available.

Moving from Water to Land

Plants

686

BIODIGESTBIODIGEST

Seeds of conifers develop at the baseof each woody scale of female cones.

Plants probably evolvedfrom filamentous

green algae.

The leaves and branches of conifersare flexible. They bend under theweight of snow and ice, allowing anybuildup to slide off before it becomesheavy enough to break the branch.


ConifersExamples: Pine, spruce, fir, larch, yew, redwood, juniper.Numbers: 400 species.Size range: Giant sequoias of central California, to 99 mtall, the most massive organisms in the world; coast red-woods of California, to 117 m, the tallest trees in the world.

686

Guest SpeakerHave a pharmacist or physi-cian visit the class to discuss

plants that are important in theproduction of medicines.

BIODIGESTBIODIGEST


Kinesthetic Bring to classand allow students to

handle several varieties ofconifer cones. Include malecones if available. Tell studentsthe common name and/or Latinname of the tree each cone isfrom. Ask students to recordtheir observations of eachspecies in their journals.P

LS

L1

P

LS


Visually ImpairedKinesthetic As part of the Bellringerdemonstration, have students with

visual impairments handle the plants.Break off small parts for them to handle.Ask them to describe what they feel aspartners write down their observations.Make sure students don’t injure them-selves by handling the plants. L1

P

LS


Identifying and ClassifyingPlants

Naturalist Have students collect pic-tures of different types of plants.

They should identify the plants and classifythem as vascular or nonvascular and non-seed or seed producing.

P

LSP

ELL

LS

L2

P

LS


Reinforcement and StudyGuide, pp. 109-110

Content Mastery, pp. 121-124 L1

P

LS

L2

P

LS


Animation: Life Cycle of a PineExploration: Classifying PinesDisc 3


Animation: Water Uptake inRootsExploration: AngiospermDisc 3

VIDEODISCSTV: Plants, What Is a Seed?Unit 4, Side 3, 13 min. 45 sec.

What Is a Seed? (In its entirety)

!7,W=9LÇ"

Stems growing up

Roots growing down

Plant Responses Plants respond to changes in

their environment such as light,temperature, and water availabil-ity. Chemicals called hormonescontrol some of these responsesby increasing cell division andgrowth.

Plants

689

BIODIGESTBIODIGEST

Roots exhibitpositive geotro-pism. Stems showa negative geo-tropic response.

The phototropicresponse shownhere is the resultof increased cellgrowth on theside of the stemaway from thelight.

BIODIGEST ASSESSMENTBIODIGEST ASSESSMENT

Understanding Main Ideas1. Which of the following is a Bryophyte?

a. moss c. club mossb. horsetail d. conifer

2. The term for a mature fern leaf is ________.a. leaf c. frondb. scale d. needle

3. Nonvascular plants would most likely befound growing ________.a. in sandy desert soilb. on an ocean beachc. on a snowy mountain sloped. in a shady, moist environment

4. Which plant group has leaves adapted forlife in cold environments?a. Anthophyta c. Pterophytab. Sphenophyta d. Coniferophyta

5. Dicots have ________.a. one cotyledonb. two cotyledonsc. needlelike leavesd. spores borne in cone-shaped strobili

6. Reproductive structures of conifers are________.a. flowers c. fruitsb. cones d. sori

7. Mosses, ferns, and club mosses are alikebecause they require ________.a. water for fertilizationb. adaptations for conserving waterc. insects for pollinationd. warm, sunny habitats

8. Lycophytes, sphenophytes, and conifero-phytes have specialized leaves that formreproductive structures known as ________.a. sori c. conesb. flowers d. strobili

9. Vascular plants do not include the ________.a. Lycophytes c. Sphenophytesb. Bryophytes d. Pterophytes

10. Which plant group produces flowers andseeds enclosed in a fruit?a. Anthophyta c. Pterophytab. Coniferophyta d. Lycophyta

Thinking Critically1. Compare the spore-bearing structures of

ferns with the seed-bearing structures ofconifers.

2. Why do vascular plants have an adaptiveadvantage over nonvascular plants?

3. Describe three ways in which seeds may bedispersed.

689

3 AssessCheck for UnderstandingHave students explain the differ-ence between the terms in each ofthe following word pairs.

a. seed—sporesb. vascular—nonvascularc. cone—fruitd. monocot—dicot

ReteachHave students name plants thatare or produce structures, listedin the word pairs of the Checkfor Understanding. Ask them toexplain why each plant is repre-sentative of the term.

ExtensionLinguistic Have studentsresearch one plant division

of their choice and present a brieforal report to the class.

Skill Have students pre-pare a chart that shows the differ-ent types of plants and their majorcharacteristics.

4 CloseActivityHave students prepare questionsabout the major characteristics ofplants and write them on thechalkboard. Have the class discusseach question.

L2

P

LS


L3

P

LS

L2

P

LS

L2

P

LS

BIODIGESTBIODIGEST

BIODIGEST ASSESSMENTBIODIGEST ASSESSMENT

Understanding Concepts1. a 4. d 7. a 9. b2. c 5. b 8. d 10. a3. d 6. b

Thinking Critically1. Ferns produce spores in sori on fronds.

Coni-fers develop seeds at the base ofscalelike leaves that form cones.

2. Vascular plants are not limited to moistenvironments because they do not haveto rely on osmosis and diffusion fortransport of water and nutrients. Also,vascular tissue provides support so theplants can grow larger.

3. Seeds may be blown away by the wind.They may be carried by water when theyfall in the ocean or in streams. They mayalso be transported by animals who eatthe fruit and discard the seeds, or by ani-mals who pass seeds through their diges-tive systems and deposit them with theirdroppings.

Pollen tube

Ovary

Sperm nuclei

Ovule

Egg nucleusand endospermnucleus

Pollen In seed plants, the sperm are enclosed in the

thick-coated pollen grains, which are the malegametophyte generation of the plant. Pollen is one of the important adaptations that hasenabled seed plants to live in a wide variety ofland habitats.

Pollinators Flowers can be pollinated by wind, insects,

birds, and even bats. Some flowers have colorfulor perfumed petals that attract pollinators.Flowers may also contain sweet nectar, as well aspollen, which provides pollinators with food.

FruitFollowing fertilization,

the ovary develops into afruit with seeds inside.Some flowering plantsdevelop fleshy fruits,such as apples, melons,tomatoes, and squash.Other flowering plantsdevelop dry fruits, such as peanuts, almonds, or sunflowers. Fruits help protect seeds until they are mature. Fruits also help scatter seeds into new habitats.

Plants

688

BIODIGESTBIODIGEST

Plants that depend on thewind to carry pollen fromanther to stigma tend tohave small, inconspicuousflowers. The flowers ofgrasses and this alder arepollinated by the wind.

In a process called double fertilization, one ofthe sperm fertilizes the egg and the other uniteswith the endosperm nucleus.

Pollen is carried to the stigma of a flower. Thepollen grain grows a tube down the style to theovary. Two sperm travel down the tube.

Plants that depend on insects for pollination may be brightlycolored and fragrant. Pollen rubsoff on the bee that visits a flower

to feed onnectar. Whenit moves to anotherflower, someof the pollenmay rub offonto thestigma.

Many plantsproduce fruitsthat are eatenby animals.

Maple tress producefruits with a winglikeshape that can becarried long distancesby the breeze.


Flowering PlantsExamples: Grasses, oaks, maples, palms,irises, orchids, roses, beans.Numbers: 230 000 species (60 000 monocots;170 000 dicots).Size range: A few millimeters to 75 m.

688

Knowledge Ask studentsto compare and contrast pollina-tion and fertilization in conifersand flowering plants. In conifers,pollen is carried by wind to thefemale cone. In flowers, pollen mayalso be transported by animals. Inflowers, the pollen is carried to thestigma. In both conifers and flowers,the pollen grows a tube throughwhich the sperm travels to reach theovary. In both, sperm and egg uniteto form a zygote that develops into aseed.

KnowledgeAfter students have observedflowers and fruits from the sameplants, ask them to discuss whichparts of the flower become whichparts of the fruit, and to identifythe parts of the flower that witheraway and do not form part of thefruit. The ovary swells to become thefruit. The ovule may be visiblearound the seeds, as in apples. Thesepals may be visible on the blossomend of the fruit. Petals, pistil, andstamen wither away.

Visual LearningLinguistic Bring into theclassroom several different

fruits, including both dry andfleshy varieties. If possible, bringfruits that develop from some ofthe flowers used in the aboveactivity. Have students examinethe exterior of each fruit, thencut it open to observe thearrangement of seeds. Ask stu-dents to describe their observa-tions in their journals. L1

P

LS


BIODIGESTBIODIGEST

P R O J E C TStreet-Tree Census

Interpersonal Have studentsconduct a street-tree census

in their community. They can analyze theresults of the census and submit a classreport to the community governmentwith suggestions on locations where addi-tional trees could be planted.

P

COOP LEARN

LS

L3

P

LS

CD-ROMBiology: The Dynamics of LifeAnimation: Double Fertilization

Animation: Fruit FormationExploration: Pollination Disc 3

Documents

Chapter 24: Reproduction in Plants€¦ · 652 REPRODUCTION IN PLANTS Reproduction in Plants What You’ll Learn You will compare and con-trast the life cycles of mosses, ferns, and