integrating concept mapping and the learning cycle to teach diffusion and osmosis concepts to high...

Integrating Concept Mappingand the Learning Cycle to TeachDiffusion and Osmosis Conceptsto High School Biology Students

ARTHUR L. ODOMScience Education, University of Missouri-Kansas City, Kansas City, MO 64110, USA

PAUL V. KELLYPark Hill High School, Kansas City, MO 64110, USA

Received 27 April 1999; revised 7 August 2000; accepted 5 October 2000

ABSTRACT: This study explores the effectiveness of concept mapping, the learningcycle, expository instruction, and a combination of concept mapping/learning cycle inpromoting conceptual understanding of diffusion and osmosis. Four high school biologyclasses were taught diffusion and osmosis concepts with the aforementioned treatments.Conceptual understanding was assessed immediately and seven weeks after instructionwith the Diffusion and Osmosis Diagnostic Test (DODT). The results indicated the conceptmapping/learning cycle and concept mapping treatment groups significantly outperformedthe expository treatment group in conceptual understanding of diffusion and osmosis.There was no significant difference among the learning cycle group and other treatments.C© 2001John Wiley & Sons, Inc.Sci Ed85:615–635, 2001.

INTRODUCTION

Improving science achievement through the use of more effective instructional strategies,promoting the active role of the learner, and promoting the facilitative role of the teacher haslong been an aspiration of science educators. To this end, two predominant teaching methodsthat have long histories of use remain widespread in the science education community:concept mapping (e.g., Arnaudin et al., 1984; Cullen, 1990; Jones, Carter, & Rua, 2000;Novak, 1993; Okebukola, 1992; Slotte & Lonka, 1999; Wandersee, 1990), and the learningcycle (e.g., Bergquist, 1991; Gang, 1995; Lawson, 2000; Marek & Methven, 1991; Renner,1986; Trifone, 1991). Concept mapping has over a 20-year history, growing from work byNovak and his graduate students at Cornell University (Novak, 1990). The learning cyclehas over a 30-year history, with its present structure being attributed to Dr. Robert Karplusand the persons who developed the materials of the Science Curriculum Improvement Study(Renner & Marek, 1988).

Semblance aside, concept mapping and the learning cycle are deeply rooted in twodistinct theories of cognitive development: Ausubel’s theory of verbal learning and Piaget’s

Correspondence to:A. L. ODOM; e-mail: [email protected]

C© 2001John Wiley & Sons, Inc.

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developmental theory. Both theories bring a unique epistemology to learning and haveproven to provide a better understanding of the learner and the learning process.

PURPOSE

The purpose of this study is to explore the effectiveness of concept mapping and thelearning cycle in promoting understanding of diffusion and osmosis in high school biology.Although several studies have explored the effectiveness of concept mapping (Christianson& Fisher, 1999; Gagged, Alaiyemola, & Okebukola, 1990; Wallace & Mintzes, 1990) and thelearning cycle (Marek & Mothven, 1991; Schneider & Renner, 1980), none have exploredthe effectiveness of concept mapping and the learning cycle combined. We hypothesizeconcept mapping and learning cycle lessons combined over diffusion and osmosis contentwill provide a more complete framework for knowing than concept mapping, learning cycle,or expository instruction alone because the use of a single methodology will provide onlya partial framework for knowing.

Diffusion and osmosis were selected as topics for this study because:

1. Diffusion and osmosis content can be easily modified to fit concept mapping andlearning cycle formats.

2. A diffusion and osmosis assessment instrument was readily available.3. Diffusion and osmosis are key to understanding many important life processes.4. Previous studies have indicated students have difficulty learning diffusion and osmo-

sis and more effective teaching strategies are needed.

Specifically, diffusion is the primary method of short distance transport in a cell and cellularsystems. An understanding of osmosis concepts is required to understand water intake byplants, water balance in land and aquatic creatures, turgor pressure in plants, and transportin living organisms. In addition, diffusion and osmosis are closely related to concepts inphysics and chemistry, such as permeability, solutions, and the particulate nature of matter(Friedler, Amir, & Tamir, 1987).

There have been several studies that have explored the difficulties students have withlearning diffusion and osmosis. These studies suggest that more effective methods arerequired to teach these concepts. Johnstone and Mahmoud (1980) surveyed high schoolbiology students on their perceived difficulty of isolated biology topics and reported thatosmosis and water potential were regarded by students and teachers as being among themost difficult biological concepts to understand. Odom (1995) administered the Diffusionand Osmosis Diagnostic Test (DODT) to 116 secondary biology students, 123 college non-biology majors, and 117 biology majors. Misconceptions were detected in five of the sevenconceptual areas measured by the test: the particulate and random nature of matter, con-centration and tonicity, the influences of life forces on diffusion and osmosis, the processof diffusion, and the process of osmosis. There was no significant difference found be-tween secondary and nonbiology majors’ understanding of diffusion and osmosis concepts.However, there was a significant difference between biology majors and secondary/non-biology majors.

Zuckerman (1993) identified 12 accurate conceptions and 8 inaccurate conceptions aboutosmosis held by high school science students. She reported that misconceptions about osmo-sis blocked problem solving of osmosis-related questions. Of the 12 accurate conceptions,two were especially important in enabling problem solvers to generate correct answers (i.e.,the rate of osmosis is constant; the concentrations of water across the membrane must beequal at osmotic equilibrium).

CONCEPT MAPPING AND LEARNING CYCLE 617

Theoretical Framework: Ausubel’s Theory of Verbal Learningand Concept Mapping

The key to Ausubel’s theory of verbal learning is the emphasis on meaningful learning.According to Ausubel (1968), meaningful learning is defined as the nonarbitrary, substantiverelating of new ideas or verbal propositions into cognitive structure. For meaningful learningto occur, the new ideas must have potential meaning and the learner must possess relevantconcepts that can anchor new ideas. The learner must also consciously relate the new ideasor verbal propositions to relevant aspects of their current knowledge structure in a consciousmanner.

Meaningful learning occurs by the process of subsumption when potentially meaning-ful propositions are subsumed under more inclusive ideas in existing cognitive structure.The new propositional meanings are hierarchically organized with respect to the level ofabstraction, generality, and inclusiveness. The process of meaningful learning can be im-proved by concept mapping. During concept mapping, the learner graphically representsconcepts in a hierarchically arranged structure and begins to progressively differentiateamong concepts. Progressive differentiation refers to the learning process in which learnersdifferentiate between concepts as they learn more about them. During the process of inte-grative reconciliation, the learner recognizes relationships between concepts and does notcompartmentalize them (Novak, 1990).

DEVELOPMENTAL THEORY AND THE LEARNING CYCLE

According to Lawson, Abraham, and Renner (1989), there are basically two fundamentaltypes of knowledge: declarative and procedural. Declarative knowledge is basically “knowthat,” and procedural knowledge is “knowing how.” The acquisition of declarative knowl-edge is very much a constructive process that makes use of procedural knowledge. Studentscan learn by memorization, but such learning will not improve procedural knowledge.The reason we should improve procedural knowledge is that when students participate inthe constructive process, the learning of declarative knowledge becomes more meaningfuland retention more complete. This, in turn, will give students the tools to better under-standing and the ability to explain the world by being able to generate and test their ownideas.

This process of constructing knowledge usually will begin with an observation and ques-tion. For example, an interesting question may arise or can be introduced by the teacherwhen observing osmosis in Elodea, “Suppose you kill the plant cells, would osmosis con-tinue?” This question may lead to predictions and hypotheses. If the observations fit theexpected outcomes, then the observations are assimilated into the current mental structure.If, however, observations do not fit the expected outcomes, disequilibrium results and ac-commodation is needed. As a consequence of accommodation, alternative mental structuresare selected or constructed, driven by disequilibrium, until a good match between expectedand actual outcomes occurs to restore equilibrium (Lawson, 1995). The ability to generatedeclarative knowledge depends on procedural knowledge, which is dependent on the abilityto generate and test hypotheses.

The learning cycle is a methodology that provides students with experiences in generatingboth declarative and procedural knowledge and is grounded in Piaget’s theory of cognitivedevelopment (Lawson, 1988). The learning cycle incorporates the Piagetian approach intoa succinct methodology of learning: experiencing the phenomena or concept (ExplorationPhase), applying terminology to the concept (Concept Introduction), and application of theconcepts into additional conceptual frameworks (Application).

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During exploration, students learn through their own actions and reactions to a newsituation. Exploration allows students to begin to develop the declarative and proceduralknowledge with the development of their hypothesis creation and testing skills. They explorenew materials and new ideas with minimal guidance. The new experience can raise questionsor complexities that they cannot resolve with their accustomed ways of thinking. This canspark debate and analysis of reasons for their ideas. The analysis leads to alternative waysto test ideas though the generation of predictions. The gathering and analysis of ideas maythen lead to the rejection of some ideas and retention of other ideas in the cyclic pattern ofself-regulation (Lawson, 1995).

The second phase of the learning cycle is sometimes referred to as concept introductionor term introduction. Terms and concepts are used to refer to the pattern observed duringexploration. The terms may be introduced with lectures, assigned readings, or other means.The key is to allow students to sufficiently explore the phenomenon prior to introducingterminology.

The last phase is referred to as concept application, where students organize the conceptjust learned with other related phenomena. The previously learned concepts are extended tonew situations and new contexts. Without a variety of applications, the concept’s meaningmay remain restricted to the examples used at the time it was initially defined and discussed.Without the application phase, many students may fail either to abstract the concepts fromits concrete examples or to generalize it to other situations (Lawson, 1995).

The main idea is that the learning cycle provides opportunities for students to exploretheir belief systems, which may result in argumentation, prediction, and hypothesis testing,resulting in self-regulation and knowledge construction.

A UNION OF CONCEPT MAPPING AND THE LEARNING CYCLE

Hypotheses about diffusion and osmosis are not created in a vacuum and depend on recallof previous knowledge, previous experience, and creativity. This would include knowledgeand experiences with the plant cells, processes of diffusion and osmosis, concentration,permeability, and solutions. In order for learning to be meaningful, the learner must possessconcepts relevant to the new learning. However, with many new ideas, there will be a limitednumber, or no relevant concepts in students’ cognitive structure, to serve to anchor the newlearning. In order to construct meaning of diffusion and osmosis, one must make senseof technical concepts (e.g., solution, solute, solvent, molecular movement, net movement,and direction of movement); many of which are difficult to detect or simulate in laboratorysituation.

We believe both the learning cycle and concept mapping provide a unique approach tolearning that can help students construct knowledge. The learning cycle can help promoteself-regulation and provide experiences to help students construct relevant declarative andprocedural knowledge that can provide the foundation to anchor learning of the complexprocesses associated with diffusion and osmosis. However, with the learning cycle there isno formal mechanism to make connections between numerous concepts and activities. Theapplication phase can be used to allow students to apply concepts to new situations andcontexts, but diffusion and osmosis involve many complex processes that require multiplelearning cycles. The learning cycle does not provide a mechanism to make connectionsbetween the many lessons. It is only possible to teach one lesson at a time even in a spiralcurriculum. There is not a formal mechanism to connect the many concepts learned frommultiple learning cycle lessons.

Concept mapping provides a mechanism to assist students to make connections betweenconcepts. Students provided with a series of labs, lectures, or textbook readings can construct


concept maps related to all of these activities. Students make many connections betweenmultiple concepts learned from multiple lessons. Concept mapping alone does not pro-vide opportunities for students to observe phenomena that may lead to the self-regulatoryprocess that results from disequilibrium. There is not an opportunity for assimilation and ac-commodation that results from questions, predictions, and hypothesis testing of observablephenomena.

We believe the combination of learning cycles and concept mapping provide experienceswith observable phenomena and hierarchically organized cognitive structure, both of whichare required for meaningful learning to occur.

DESIGN AND PROCEDURES

Sample

A total of 108 secondary students (grades 10–11) enrolled in four different sections ofcollege preparatory biology, formed the sample for the study. Each of the four sections wererandomly assigned to a treatment group (concept mapping,n= 26; learning cycle,n= 28;expository,n= 27; and concept mapping/learning cycle,n= 27). The same teacher taughteach of the four classes.

Test Administration

Pretest data was not collected about students’ understandings of diffusion and osmosisto cut down on potential test boredom, redundancy, and test learnedness. The researcherswanted to reduce the chance of students learning test items that could be recalled dur-ing instruction. They also wanted to reduce the chance of the teacher seeing the test andpotentially teaching to specific items on the test.

The test was administered immediately after instruction and 7 weeks after instruction toassess retention. The data collected immediately after instruction provided baseline datafor comparison. None of the students received formal instruction about diffusion and os-mosis by the instructor prior to the study. The researchers assumed the students had littleprior knowledge or understanding of diffusion and osmosis, as indicated in previous studies(Odom, 1995; Zuckerman, 1993). All of the students who participated in the study were en-rolled in college-bound biology courses and met the same GPA criteria for math and science.To provide homogeneity of treatment group students, students were classified according totheir level of formal reasoning. The students were classified as preformal or formal withthe Logical Reasoning Test (LRT) and guidelines provided by Popejoy and Burney (1990).The data was used as a covariate to correct differences among groups. Similarly, Odom andSettlage (1994) administered the Diffusion and Osmosis Diagnostic Test and the LogicalReasoning Test (Popejoy & Burney, 1990) to 116 high school biology students. They re-ported that there were significant differences between levels of cognitive development andunderstanding of diffusion and osmosis where formal outperformed preformal students.

Instrumentation

Conceptual understanding was measured with the Diffusion and Osmosis DiagnosticTest, which has previously been determined to be a good indicator of student understandingof diffusion and osmosis (Christianson & Fisher, 1999; Odom & Barrow, 1995). Items forthe diagnostic instrument were based on the two-tier multiple-choice format. The first tierconsisted of a content question with two, three, or four choices. The second tier consisted

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of four possible reasons for the first part: three alternative reasons and one desired reason.The alternative reasons were based on misconceptions detected during the multiple-choicetest with free response reason and the interview sessions.

The final version of the Diffusion and Osmosis Diagnostic Test consisted of 12 items.The conceptual areas covered by the test were: the particulate and random nature of matter,concentration and tonicity, the influence of life forces on diffusion and osmosis, the processof diffusion, and the process of osmosis (Odom & Barrow, 1995). Figure 1 offers an exampleof an item that assesses understanding of the particulate and random nature of matter.

A specification grid was constructed to determine the face validity and whether the testquestions matched all of the validated content specified by the propositional knowledgestatements for the final instrument (Figure 1). Two major questions were addressed whiledetermining face validity: (1) “Does the question assess the content as defined by thevalidated propositional knowledge statements?” (Figure 2), and (2) “Is the question at a level

As the difference in concentration between two areas increases, the rate of diffusion(a) Decreases(b) Increases

Reason

(a) There is less room for the particles to move.(b) If the concentration is high enough, the particles will spread less and the rate will be slowed.(c) The molecules want to spread out.(d) The greater likelihood of random motion into other regions.

Figure 1. Sample item on the Diffusion and Osmosis Diagnostic Test that assesses the particulate and randomnature of matter.

1. All particles are in constant motion.2. Diffusion involves the movement of particles.3. Diffusion results from the random motion and/or collisions of particles (ions or molecules).4. Diffusion is the net movement of particles as a result of a concentration gradient.5. Concentration is the number of particles per unit volume.6. Concentration gradient is a difference in concentration of a substance across a space.7. Diffusion is the net movement of particles from an area of high concentration to an area of low concentration.8. Diffusion continues until the particles become uniformly distributed in the medium in which they are dissolved.9. Diffusion rate increases as temperature increases.

10. Temperature increases motion and/or particle collisions.11. Diffusion rate increases as the concentration gradient increases.12. Increased concentration increases particle collisions.13. Diffusion occures in living and nonliving systems.14. Osmosis is the diffusion of water across a semipermeable membrane.15. Tonicity refers to the relative concentration of particles on either side of a semipermeable membrane.16. A hypotonic solution has fewer dissolved particles/per unit volume relative to the other side of the membrane.17. A hypertonic solution has more dissolved particles/per unit volume relative to the other side of the membrane.18. An isotonic solution has an equal number of dissolved particles/per unit volume on both sides of the membrane.19. Osmosis is the net movement of water (solvent) across a semipermeable membrane from a hypotonic solution

to a hypertonic solution.20. Osmosis occurs in living and nonliving systems.21. A semipermeable membrane is a membrane that selectively allows the movement of some substances across

the membrane while blocking the movement of others.22. Cell membranes are semipermeable.

Figure 2. Propositional knowledge statements required for understanding diffusion and osmosis.


of sophistication appropriate for secondary biology students?” If the aforementioned criteriawere not met, then the item was dropped. All 22 propositional knowledge statements werematched to the items on the Diffusion and Osmosis Diagnostic Test. All of the questions,except one, incorporated more than one of the propositional knowledge statements. Itemnumber 4 matched only propositional knowledge statement number 5, which was concernedwith concentration as measured by the number of particles per unit volume. The DODT wasinitially constructed to assess freshman college biology students’ understanding of diffusionand osmosis. Subsequent studies have indicated the DODT to be appropriate for secondarybiology students (Odom, 1995; Odom & Settlage, 1994).

Formal reasoning was assessed with the Logical Reasoning Test (LRT), and students werecategorized as preformal or formal (Popejoy & Burney, 1990). The LRT is a pencil and paperassessment containing 21 items. The items on the test were constructed and correlated tofive Piagetian-type tasks. The validity of the test was established by comparing test itemsto Piagetian-type tasks. Correlation between the test items and Piagetian tasks were used todetermine the cut-off scores for formal and preformal students.

Defining the Content Boundaries

The propositional knowledge statements used to define the DODT were also used todefine the boundaries of diffusion and osmosis content (Figure 2). The lessons for eachof the treatment groups were derived from the propositional knowledge statements. All 22propositional knowledge statements were addressed in each treatment group (Figure 3).

PropositionalKnowledge

Day Activities Statements

CONCEPT MAPPING TREATMENT1 *Demonstration of diffusion using open bottle of ammonia. 1, 2, 3, 4, 5, 6, 7, 8

*Demonstration of diffusion at molecular level using beads in a glass beaker.*Lecture on diffusion, concentration, kinetic motion, and concentrationgradient. Instructional input provided by chalkboard, overhead projector, andcomputer presentation tools.* Individual students constructed a concept mapwith the following terms:diffusion, kinetic motion, particles, concentration, concentration gradient, anduniform motion.

2 *Teacher lectured, worked with groups and individuals on concept maps.Students made a group map from individual maps constructed on day 1.Groups presented maps to the class on an overhead projector.

1, 2, 3, 4, 5, 6, 7, 8

3 *Demonstration of temperature’s effects of diffusion using hot and cold waterand dye.

9, 10, 11

*Lecture on temperature’s effect on diffusion and molecular rationale.Instructional input provided by chalkboard, overhead projector, and computerpresentation tools.*Homework assignment from text questions.

4 *Lecture on the effect of concentration on diffusion. Instructional inputprovided by chalkboard, overhead projector, and computer presentation tools.

11, 12, 13, 14, 20, 21,22

*Lecture on osmosis and semipermeable membranes. Instructional inputprovided by chalkboard, overheaded projector, and computer presentationtools.

Figure 3. Description of treatment groups by day, activities, and propositional knowledge statements addressedduring activity.

Continued

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5 *Lecture on tonicity. Instructional input provided by chalkboard, overheadprojector, and computer presentation tools.

15, 16, 17, 18, 19, 20,21, 22

*Demonstration of tonicity usingElodeaand a projection microscope.*Students revised their concepts mapsfrom day 1 and 2 by adding thefollowing concepts: temperature, living systems, nonliving systems,osmosis, water, semipermeable membrane, tonicity, hypertonic, hypotonic,and isotonic.

6 *Teacher lectured, worked with groups and individuals on conceptmaps. Groups consolidated their concept maps into one master map andpresented it to the class on an overhead. Students shared comments andanalyzed each map.

15, 16, 17, 18, 19, 20,21, 22

* Review of termsLEARNING CYCLE TREATMENT1 *Learning cycle lesson 1entitled Diffusion of solid in a liquid. 1, 2, 3, 4, 5, 6, 7, 8

*Demonstration of diffusion at the molecular level using glass beads in aglass beaker.*Discussion of diffusion, concentration, kinetic motion, and concentrationgradient. Instructional input provided by chalkboard, overhead projector,and computer presentation tools.

2 *Learning cycle lesson 2entitled Effect of temperature on rates ondiffusion.

9, 10, 11, 12

*Discussion of temperature’s effect on diffusion and molecular rationale.Instructional input provided by chalkboard, overheaded projector, andcomputer presentation tools.*Learning cycle lesson 3entitled Effect of concentration gradients onrates of diffusion.

3 *Discussion of effect on concentration on diffusion. Instructional inputprovided by chalkboard, overhead projector, and computer presentationtools.

11, 12, 13, 14, 20, 21,22

*Learning cycle lesson 4entitled Diffusion through membranes.*Discussion of osmosis and semipermeable membranes. Instructionalinput provided by chalkboard, overhead projector, and computerpresentation tools.

4 *Learning cycle lesson 5entitled “Osmosis.” 15, 16, 17, 18, 19, 20,21, 22

*Learning cycle lesson 6entitled “Consequences of osmosis in closedsystems.”

5 *Discussion of osmosis and tonicity. Instructional input provided bychalkboard, overhead projector, and computer presentation tools.

15, 16, 17, 18, 19, 20,21, 22

*Learning cycle lesson 7entitled “Turgor pressure in cells.”*Discussion of diffusion and osmosis in living cells. Instructional inputprovided by chalkboard, overhead projector, and computer presentationtools.*

6 *Learning cycle lesson 8entitled “Observations of the central vacuole inElodea.”

15, 16, 17, 18, 19, 20,21, 22

*Discussion of osmosis in living cells. Instructional input provided bychalkboard, overhead projector, and computer presentation tools.

EXPOSITORY TREATMENT1 *Demonstration of diffusion using open bottle of ammonia. 1, 2, 3, 4, 5, 6, 7, 8

*Demonstration of diffusion at molecular level using beads in a glassbeaker.

Figure 3. (Continued)




*Lecture on diffusion, concentration, kinetic motion, and concentrationgradient. Instructional input provided by chalkboard, overhead projector, andcomputer presentation tools.*Reading assignment from text

2 *Demonstration of temperature’s effects of diffusion using hot and cold waterand dye.

9, 10, 11

*Lecture on temperature’s effect on diffusion and molecular rationale.Instructional input provided by chalkboard, overhead projector, and computerpresentation tools.*Homework assignment from text questions.

3 *Lecture on the effect of concentration on diffusion. Instructional inputprovided by chalkboard, overhead projector, and computer presentation tools.

11, 12, 13, 14, 20, 21,22

*Lecture on osmosis and semipermeable membranes. Instructional inputprovided by chalkboard, overhead projector, and computer presentation tools*Quiz

4 *Lecture on tonicity. Instructional input provided by chalkboard, overheadprojector, and computer presentation tools.

15, 16, 17, 18, 19, 20,21, 22

*Demonstration of tonicity usingElodeaand a projection microscope.*Homework assignment from text.

5 *Teacher lectured and reviewed homework. 11, 12, 13, 14, 15, 16,*Students made drawing of various situation of tonicity, osmosis, anddiffusion.

17, 18, 19, 20, 21, 22

6 *Teacher lectured and review of terms. 1–22*Students presentation of drawings.

CONCEPT MAPPING/LEARNING CYCLE TREATMENT1 *Learning cycle lesson 1entitled “Diffusion of solid in a liquid.” 1, 2, 3, 4, 5, 6, 7, 8

*Demonstration of diffusion at the molecular level using glass beads in a glassbeaker.*Discussion of diffusion, concentration, kinetic motion, and concentrationgradient. Instructional input provided by chalkboard, overhead projector, andcomputer presentation tools.* Individual students constructed a concept mapwith the following terms:diffusion, kinetic motion, particles, concentration, concentration gradient, anduniform motion.

2 *Concept maps were graded and discussed briefly. 9, 10, 11, 12*Learning cycle lesson 2entitled “Effect of temperature on rates on diffusion.”*Discussion of temperature’s effect on diffusion and molecular rationale.Instructional input provided by chalkboard, overhead projector, computerpresentation tools.*Learning cycle lesson 3entitled “Effect of concentration gradients on rate ofdiffusion.”

3 *Discussion of effect of concentration on diffusion. Instructional inputprovided by chalkboard, overhead projector, and computer presentation tools.

11, 12, 13, 14, 20, 21,22

*Learning cycle lesson 4entitled “Diffusion through membranes.”*Discussion of osmosis and semipermeable membranes. Instructional inputprovided by chalkboard, overhead projector, and computer presentation tools.

4 *Learning cycle lesson 5entitled “Osmosis.” 15, 16, 17, 18, 19,*Learning cycle lesson 6entitled “Consequences of osmosis in closedsystem.”

20, 21, 22

5 *Discussion of osmosis and tonicity. Instructional input provided bychalkboard, overhead projector, and computer presentation tools.

15, 16, 17, 18, 19, 20,21, 22

*Learning cycle lesson 7entitled “Turgor pressure in cells.”


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*Discussion of diffusion and osmosis in living cells. Instructional input providedby chalkboard, overhead projector, and computer presentation tools.*Students revised their concept mapsfrom day 1 and 2 by adding the followingconcepts:temperature, living systems, nonliving systems, osmosis, water,semipermeable membrane, tonicity, hypertonic, hypotonic, and isotonic.*Concept maps were graded and discussed briefly.

6 *Learning cycle lesson 8entitled “Observations of the central vacuole inElodea.” 15, 16, 17, 18, 19,*Discussion of osmosis in living cells. Instructional input provided by chalkboard,overhead projector, and computer presentation tools.

20, 21, 22


Teacher Researcher: Planned vs. Enacted Intervention

Observations or video recordings were not made during the study period. It was assumedthat the teacher research enacted the same intervention that was planned. The assumptionwas based on four factors: (1) educational background and leadership experience, (2) class-room observations prior to the study, (3) in- service workshops taught by the teacher, and(4) the detailed structure of the study that was designed by the teacher and university pro-fessor. The results were used to provide distinct differences and needed similarities amongtreatment groups.

The teacher completed three graduate courses in science education, which included ex-tensive training with concept mapping and the learning cycle. He worked as a cooperatingteacher for student teachers and was chair of the science department in which he providedin-service sessions on the learning cycle and concept mapping. The university professorobserved the teacher conduct numerous lessons using concept mapping/learning cycle. In-teractions between the teacher and university professor resulted in numerous concept map-ping/learning cycle lessons on diversity, genetics, biomolecules, and diffusion and osmosis.Reasons for selecting diffusion and osmosis for this study are discussed in the purposesection.

The diffusion and osmosis lessons were field tested prior to this study by the teacher.The university professor participated in learning cycle/concept mapping workshops ledby the teacher and the teacher wrote a booklet based on the field-tested lessons entitled,“The union of the learning cycle and concept mapping for meaningful learning: Diffu-sion and osmosis.” The booklet contained learning cycle lessons on diffusion and osmo-sis, instructions on when to introduce concepts for mapping, concept cutouts for conceptmapping, criterion map for assessment, and a materials list. The diffusion and osmosisbooklet was used to teach workshops at both the St. Louis and New Orleans NationalScience Teachers Association National Conventions (Kelly & Odom, 1996, 1997). Theuniversity professor participated in these workshops. The content covered in the bookletwas the same content that defined this study and the Diffusion and Osmosis Diagnos-tic Test. Based on the four previous assumptions, there was no reason to conclude thatthe lessons taught during the field tests, observations, workshops, or detailed plans ofeach treatment group were significantly different than the lessons taught during the study.Variations on other treatment groups were met by eliminating learning cycle lessons orconcept mapping activities. Greater detail on the treatment group is discussed in the nextsection.


Treatment: Concept Mapping and Expository

Concept mapping was defined as a graphical tool to aid in visually representing hier-archies of generalization and expressing propositional linkages within a system of relatedconcepts (Cliburn, 1986). Students in all four treatment groups were taught concept mappingaccording to the guidelines provided by Novak and Gowin (1984) and had engaged in con-cept mapping activities for two months prior to this study. Concept mapping was an integralpart of this teacher’s classroom. Concept maps were routinely assessed for course credit,using procedures similar to those suggested by Novak and Gowin (1984). The assessed con-cept maps were not used as a part of this study. After the concepts maps were assessed, theywere returned to students as part of the everyday class routine. Only the concept mapping(CM) and concept mapping/learning cycle (CM/LC) treatment groups engaged in conceptmapping activities during this study. However, students in other treatment groups couldhave constructed concept maps independent of the unit requirements.

Expository (EX) teaching was defined as an organized lecture supplemented by slides,overheads, charts, and demonstrations to illustrate concepts and ideas. The teacher providedexpository lessons to the CM and EX treatments. The concept mapping and expository treat-ment groups received lessons on diffusion and osmosis content via expository instruction.The lessons for each group were the same, with the exception of concept mapping activitiesfor the CM treatment. The timing of the presentation of the diffusion and osmosis contentvaried slightly from day to day. However, both groups received 6 days of instruction over theexact same content. Following is a general description of the CM and EX treatments. A moredetailed description of the treatments, along with the propositional knowledge statementsaddressed, is reported in Figure 3.

Day One—After expository instruction, individual students in the CM treatment groupwere asked to construct concept maps over the day’s lesson and were given the followingterms to include in their maps: diffusion, kinetic motion, particles, concentration, concen-tration gradient, and uniform motion. The EX treatment was given a diffusion and osmosisreading assignment from the textModern Biology(Towle, 1989).

Day Two—The teacher lectured about the day’s content. Students in the CM treatmentgroup broke into small groups and made a group map from individual maps constructedfrom Day One. The teacher assisted with groups and individuals during the construction ofthe maps. The group maps were presented to the class on an overhead projector. The EXtreatment group received a lecture and were given text questions as a homework assignment.

Days Three, Four, and Five—Both the CM and EX treatment groups received a varietyof demonstrations, lectures, and text homework assignments. In addition, on Day Five,the CM treatment group revised their concept maps constructed from Days 1 and 2 byadding the following concepts: temperature, living system, nonliving system, osmosis,water, semipermeable, membrane, tonicity, hypertonic, hypotonic, and isotonic.

Day Six—Both the CM and EX treatment groups received a variety of demonstrationsand lectures. The CM treatment students consolidated their maps into a master group mapand presented it to the class on an overhead. The EX treatment students reviewed terms andpresented diffusion and osmosis drawings they had made.

Treatment: Learning Cycle and Concept Mapping/Learning Cycle

The characteristics of the learning cycle as used in this study are outlined in Barman (1989)and Abraham and Renner (1986). Generally, we used the following sequence of three specificphases: (1) exploration phase, (2) concept introduction phase, and (3) application phase.A brief description of each day’s activities and a sample learning cycle lesson follows. A

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more detailed description of treatments, along with the propositional knowledge statementsaddressed, are reported in Figure 3.

The LC and CM/LC treatment groups received instruction with eight learning cyclelessons. In addition to the learning cycle lessons, the CM/LC treatment group engaged inconcept mapping activities using the same terms and time line as the CM treatment group.

The learning cycle lessons for the LC and CM/LC treatment groups were exactly thesame. Following is an example of a learning cycle lesson from Day Two.

Exploration phase—Groups of students were given two beakers of water. One of thebeakers contained hot water and the other contained cold water. Green dye was added toeach of the beakers and students recorded their observations.

Concept introduction phase—The teacher and the students discussed observations andthe relationship between rate of diffusion and temperature. In groups, students were askedto verbalize and write statements that described the relationship between rate of diffusionand temperature.

Application phase—Agar blocks containing phenolphthalein were placed in 1% sodiumhydroxide at 0◦C and 25◦C. Students measured the thickness of the pink band that resultedfrom sodium hydroxide diffusing into the agar blocks. Differences in thicknesses of thepink bands were discussed in the groups and as a class. Students were allowed to verbalizeand write statements that described their experiences and the relationship between rateof diffusion and temperature. A whole class discussion followed group activities. Allapplicable propositional knowledge statements (Figure 3) were integrated into the lessonduring concept introduction and after the completion of the lessons. Following instruction,the Diffusion and Osmosis Diagnostic Test was administered to each treatment group.The results and content on the test were not discussed. Seven weeks after instructionwas complete the Diffusion and Osmosis Diagnostic Test was administered again. Theseven-week time period was selected because this was the maximum time allowed beforethe groups switched teachers and sections.

DATA ANALYSIS AND RESULTS

The data for the study were analyzed using a SYSTAT statistical software package.Two separate analyses of covariance were performed on DODT scores for the post (dayafter) and post-post (seven weeks after instruction) assessments. The independent vari-able was instructional treatment (concept mapping, learning cycle, expository, and conceptmapping/learning cycle). Scores on the Logical Reasoning Test were the covariate. By con-vention, a 0.05 alpha was selected (Ferguson & Takane, 1989; Hopkins, Glass, & Hopkins,1987). After adjustment by the logical reasoning covariate (p < .05), DODT scores werenot statistically significant among treatment groups the day after instruction (p > .05). Thescores were statistically significant seven weeks after instruction, as summarized in Table 1(p < .01). The results reflected a moderate to good association between treatments andadjusted DODT scores seven weeks after instruction,R2= 0.33 (Tabachnich & Fidell,1989).

The post (day after) and post-post (seven weeks after instruction) adjusted DODT meansare displayed in Table 2. The post (day after instruction) means were 60.2%, 52.1%, 49.4%,and 57.8% for the CM, LC, EX, and CM/LC groups, respectively. For the post-post (sevenweeks after instruction) scores, the CM/LC treatment group had the highest adjusted meanscore on the DODT (56.8%), followed by the CM treatment group (53.5%), the LC treatmentgroup (48.1%), and the EX treatment group (40.6%).


TABLE 1Analysis of Covariance of Instructional Treatments

Source of Variance Adjusted SS df MS F

(Day after instruction)Instructional treatment 34.8 3 11.6 2.3∗

Formal reasoning 209.6 1 209.1 42.1Error 512.7 103

(Seven week after instruction)Instructional treatment 69.7 3 23.2 5.4∗∗

Formal reasoning 154.9 1 154.9 35.9Error 433.5 103

∗p > .05.∗∗p < .01.

A Tukey post-hoc comparison (Ferguson & Takane, 1989) of the seven weeks after in-struction treatments indicated concept mapping/learning cycle and concept mapping treat-ments were significantly different from the expository treatment (p < .01 and p < .05,respectively). The learning cycle treatment was not significantly different from the othertreatments and concept mapping/learning cycle and concept mapping treatments were notsignificantly different from each other (p > .05). Table 3 is a summary of responses to theDODT categorized by treatment, item number, and conceptual area. The CM/LC treatmenthad the top score on 9 of 12 items, while the CM treatment had the top score on 3 of 12items. The CM/LC treatment had the top scores on all items covering the particulate andrandom nature of matter, influence of life forces on diffusion and osmosis, membranes,process of diffusion, kinetic energy of matter, and half the items covering concentration andtonicity. The CM treatment had the top score on the items covering the process of diffusionand half of the items covering concentration and tonicity. Low scores were scattered amongthe CM, LC, and EX treatments. EX had the largest number of low scores (7/12), followedby LC (3/12) and CM (2/12).

DISCUSSION

There is potential bias when using one teacher for all treatment groups. The teacher in thisstudy was aware of this potential and took every precaution to give equal treatment to each

TABLE 2Least-square Mean Scores on the DODT

Least Square Mean Score on the DODT

Treatment n Day After (7) weeks After

Concept mapping 26 60.2 53.5∗

Learning cycle 28 52.1 48.1Expository 27 49.4 40.6Concept mapping/learning cycle 27 57.8 56.8∗∗

Significantly different from expository.∗p < .05.∗∗p < .01.

628 ODOM AND KELLY

TABLE 3Mean Score on the DODT (Seven) Weeks after Instruction

Treatment

Conceptual Area Assessed Item CM LC EX CM/LC

The particulate and random 2 34.2 32.6 32.8 52.3∗

nature of matter 3 58.0 64.9 43.8 66.4∗

6 90.4 88.0 68.0 90.8∗

Concentration and tonicity 4 34.6 47.4 39.7 59.3∗

9 64.4∗ 47.5 47.0 49.0Influence of life forces on 11 27.6 21.5 11.0 47.5∗

diffusion and osmosisMembrances 12 81.9 81.8 63.4 84.1∗

Process of diffusion 1 44.7∗ 23.1 13.1 23.65 29.8∗ 1.1 9.9 8.3

Process of osmosis 8 28.6 31.1 23.4 39.1∗

10 56.4 40.8 42.9 60.5∗

Kinetic energy of matter 7 91.8 97.0 92.0 100∗

∗Top score among treatment groups. CM = Concept mapping; LC= Learning cycle;EX=Expository; CM/LC=Concept mapping/Learning cycle.

group. Four different sections of college prep high school biology classes were selected forthe study. A copy of the DODT was not available prior to teaching each treatment. The exactfield-tested laboratories used during learning cycle lessons were used as demonstrationsduring CM and EX treatments. Lectures were attempted to be reproduced, verbatim, duringEX and CM treatments with scripted notes. We believe we reduced the probability of teacherbias with all of the aforementioned precautions.

The study set out to investigate the effectiveness of concept mapping, the learning cy-cle, expository, and concept mapping/learning cycle instructional strategies on enhancingachievement in diffusion and osmosis content. The results seem to suggest that both theCM/LC and CM strategies enhance learning of diffusion and osmosis concepts more effec-tively than expository teaching. However, the two treatments (CM and CM/LC) were notsignificantly different from the LC treatment.

The next section will focus on possible reasons for the difficulties with diffusion and os-mosis, by examining each item on the Diffusion and Osmosis Diagnostic Test. According toGilbert (1977), if a multiple choice item has four to five distractors, understanding is consid-ered satisfactory if more than 75% of the students answer the item correctly. With a typicalmultiple-choice test having four possible selections, there is a 25% chance of guessing thecorrect answer. With a two-tier item having two selections on the first tier and four selectionson the second tier, there is a 12.5% chance of guessing the correct answer combination. Wewill use Gilbert’s criteria to discuss each treatment group and item on the DODT.

Kinetic Energy of Matter

The kinetic energy of matter concept was examined through item 7. Analysis of responsesrevealed few misconceptions. Over 90% of the students in each treatment group selectedthe correct content and reason answer. In the question, green dye was added to two differentbeakers, one containing water at 25◦C (beaker 1) and the other containing water at 35◦C(beaker 2). Students were asked to determine which beaker would become light green first.


Each treatment group got to see the movement of dye after it was added to hot and coldwater. The CM and EX groups viewed the activity as a demonstration. The CM/LC andLC groups conducted the experiment. The reason each treatment group scored high maybe because the concept is directly observable and the test item was specifically addressedwith the activity.

The Particulate Nature and Random Motion of Matter

The particulate nature and random motion of matter was examined through items 2, 3, and6 of the DODT. These items assessed students’ understandings of the movement of matterat the molecular level. Students either conducted experiments or observed demonstrationsof diffusion, such as the diffusion of potassium permanganate in water and the diffusionof sodium hydroxide as a result of both temperature and concentration gradients into agarblocks with phenolphthalein. Molecular movement was simulated with red beads shakenin a container of white beads.

The desired response to item 2 was “during the process of diffusion, particles will gener-ally move from high to low concentrations” because “particles in areas of greater concen-tration are more likely to bounce toward other areas.” The CM/LC group had an averagescore of 52.3% for this item; 20 percent points above the other groups. All of the treatmentgroups scored below 75% on this item, suggesting an unsatisfactory understanding.

A common alternative response may have been due to a misunderstanding of termi-nology. For example, many students selected “particles generally move from high to lowconcentration because particles tend to move until the two areas are isotonic and then theparticles stop moving.” These students may have memorized the prefix “iso-” which means“the same” and interpreted this item to mean that particles would continue to move untilthey are “the same” concentration throughout. It is possible that these students had a partialunderstanding of diffusion, because an end result of the process of diffusion is a uniformdistribution of particles (or, the particles are “the same” throughout).

The second portion of the alternative response suggests that particles stop moving. Stu-dents may have interpreted “stop moving” as equivalent to “no net movement,” therebydemonstrating a partial understanding of kinetic theory of matter. Another common alter-native selection for item 2 was that “there are too many particles crowded into one areaand therefore they move to an area with more room.” This selection could represent ananthropomorphic view of matter; that is, the need for molecules to move into another area.

In item 3, students were asked to determine the rate of diffusion as a result of a concen-tration gradient. The desired response was that “as the difference in concentration betweentwo areas increases, the rate of diffusion increases,” because of “the greater likelihood ofrandom motion into other regions.” The average score for the CM/LC group was 66.4%,followed by 64.9% for the LC group, 58.0% for the CM group, and 43.8% for the EX group.None of the treatment groups scored above 75.0% on this item, suggesting an unsatisfactoryunderstanding.

The most common alternative response for item 3 was “the molecules want to spread out.”This is another anthropomorphic view of matter. Another common alternative response was“the rate of diffusion will decrease because if the concentration is high enough, the particleswill spread less and the rate will be slowed.” It is reasonable that students were imagining acramped area, like a large number of people having difficulty moving in a crowded room. Itis equally possible that the students had no appreciation of the random motion of molecules.

In item 6, students were to determine what would happen to blue dye molecules after theyhad been evenly distributed throughout a large container of clear water. The desired responsewas “that molecules of dye continue to move around randomly” (rather than stop moving),

630 ODOM AND KELLY

because “molecules are always moving.” Three of the treatments, CM/LC, CM, and LM,respectively, had an average score of 90.8%, 90.4%, and 88.0%, suggesting a satisfactoryunderstanding. Each group either observed or participated in an experiment where dye wasplaced in water, which may explain the high scores. The EX group had an average score of68.0%. The EX group observed the experiment but was not given the opportunity for activeknowledge construction that was provided to the other groups, possibly explaining the lowscores.

Many in the EX group selected that “if dye stopped moving it would settle to the bottom ofthe container.” This may be because students believed that movement is necessary to opposegravity. Another alternative response for item 6 was that “the dye and water are liquids,therefore, their molecules would continue to move randomly; if it were solid the moleculewould stop moving.” It is possible that students had an understanding of the underlyingprocesses and were confused by the wording of the alternative response; that is, whetherthe response was referring to the macro- or micro-level. There is relatively little molecularmovement in solids compared to liquids. Furthermore, students may believe liquids havemolecular motion because the shape of liquids can be easily manipulated. Thus, the shapesof solids are not as easily manipulated.

Concentration and Tonicity

These concepts were examined through items 4 and 9. Again, students observed or partic-ipated in activities with sodium hydroxide diffusing into agar blocks with phenolphthalein,and the osmosis of water as a result of a concentration gradient with dialysis tubing, syrup,and an egg in food coloring.

In item 4, the desired pair of responses was a glucose solution that can be made moreconcentrated by “adding more glucose,” because “it increases the number of dissolvedparticles.” The CM/LC group had the highest average on item 4, followed by the LC, EX,and CM groups (59.3%, 47.4%, 39.7%, and 34.6%, respectively). None of the groups hadan average score above 75%, suggesting unsatisfactory understanding. The most commonalternative response for increasing the concentration of a glucose solution was “addingmore glucose,” because “the more water there is, the more glucose it takes to saturatethe solution.” While the reason is true standing alone, it is an incorrect reason for thephenomenon described in the item.

Item 9 assessed students’ understanding of the concept of tonicity. A diagram on thetest showed two columns separated by a semipermeable membrane. Side 1 contained 10%salt water and side 2 contained 15% salt water. The desired answer combination to theitem was side 1 is “hypotonic” to side 2 because “there are fewer dissolved particles onside 1.” The CM group had the highest average score followed by the CM/LC, LC, andEX groups (64.4%, 49.0%, 47.5%, and 47.0%, respectively). None of the groups had anaverage score above 75.0%, suggesting unsatisfactory understanding. Item 9 involves theprefixes “hypo-,” “hyper-,” and “iso-.” Each refers to the relative concentration of dis-solved particles in solutions separated by a membrane. The most common alternative re-sponse was “hypotonic” because “water moves from a high to a low concentration.” It ispossible that students memorized the terms with little understanding of the concept. An-other common alternative response was side 1 is “hypertonic” to side 2 because “watermoves from a high to a low concentration.” Water moving from high to low concen-tration is a possible result of two different solutions being separated by a membrane,but it is not the reason one solution has a greater tonicity than the other. This selectionmay represent at least a partial understanding of the process of osmosis (net direction ofmovement).


The Influence of Life Forces on Diffusion and Osmosis

Students observed or participated in diffusion and osmosis activities with both nonlivingand living systems. Nonliving system activities involved observing osmosis with dialysistubing. The living system involved observing osmosis in potato slices and Elodea cells. Thisconcept was examined through item 11. In this item, a plant cell was killed and placed in25% salt water, then the question was asked whether diffusion and osmosis would continue.The desired response combination was “diffusion and osmosis would continue,” because“the cell does not have to be alive.” The CM/LC group had the highest score, followed bythe CM, LC, and EX groups (47.5%, 27.6%, 21.5% and 11.0%, respectively), suggestingunsatisfactory understanding. The most common alternative response was diffusion andosmosis would stop after a plant cell was killed because the cell was no longer functioning.It is reasonable that students would compare a cell with a living organism such as a person.When a person dies, many observable physiological functions stop, such as the heartbeatand breathing. At the macro-level, when an organism dies it stops functioning; but at themicro-level, processes may continue for hours or days. Activities were designed to helpstudents make connections between nonliving and living systems.

Membranes

The activities students participated in relation to membranes included a balloon filledwith anise seed, osmosis with dialysis tubing, and osmosis in Elodea. This concept wasexamined through item 12. Students were asked about the permeability of a cell membrane.Over 80% of the students in the CM/LC, CM, and LC groups characterized cell membranesas semipermeable because they allow some substances to pass, suggesting a satisfactoryunderstanding. The EX had an unsatisfactory average score of 63.4%. Each student in theCM/LC and LC groups was able to smell the anise seed through the balloon, which couldexplain the high scores. The CM students were provided an opportunity to connect theideas from multiple experiences during mapping activities. Again, the EX groups containedpassive participants and were not given the opportunity to formally tie together the multipledemonstrations.

The Process of Diffusion

The students either conducted experiments or observed demonstrations of diffusion,such as the diffusion of potassium permanganate in water and the diffusion of sodiumhydroxide as a result of both temperature and concentration gradients into agar blocks withphenolphthalein. Molecular movement was simulated with red beads shaken in a containerof white beads. Students also observed the movement of dye in water.

This concept was examined through items 1 and 5. In item 1, a drop of blue dye is placein a container of clear water and over time the dye becomes evenly distributed throughoutthe water. The desired response was “the process responsible for blue dye becoming evenlydistributed in the water is “diffusion” because “there is movement of particles betweenregions of different concentrations. The average score for the CM group was 44.7%, followedby 23.6% for the CM/LC group, 23.1% for the LC group, and 13.1% for the EX group.None of the treatment groups scored above 75.0% on this item, suggesting an unsatisfactoryunderstanding.

The most common alternative response was that the process is “diffusion” because “thedye separates into small particles and mixes with water.” It is reasonable that students viewdye as one large particle (e.g., drop of dye), and when a drop of dye is added to water it

632 ODOM AND KELLY

breaks into small particles. Furthermore, when the “dye” is added to the water, studentsmay have been using the word “dye” at a macro-level (e.g., a bottle of “dye”) instead of atthe micro-level (e.g., “dye” molecules).

Another common alternative response was that the process is “osmosis,” because there ismovement of particles between regions of different concentrations. It is possible that thesestudents had an understanding of the underlying processes with little understanding of theterms diffusion and osmosis.

In item 5, a small amount of sugar is added to a container of water and allowed to set for avery long period of time without stirring. The desired response combination was “the sugarmolecules will be evenly distributed throughout the container,” because “there is movementof particles from a high to low concentration.” A minority of students in each group selectedthe desired answer (CM 29.3%, CM/LC 8.3%, EX 9.9%, and LC 1.1%).

The most common alternative responses were “the sugar molecules will be more con-centrated on the bottom of the container,” because “the sugar is heavier than water and willsink,” and “there will be more time for settling.” One interpretation of these results is thatstudents integrated gravity concepts into solution chemistry. Students can see sugar granulessink to the bottom of the container. If students ignored the condition (that the sugar wasallowed to set for a very long period of time), their response would describe what happenswhen sugar granules are first placed in the container.

The Process of Osmosis

Students observed or participated in osmosis experiments in many situations, includingwith dialysis tubing and Elodea cells. This concept was assessed through items 8 and 10.Analysis of responses revealed numerous alternative conceptions. In each item, studentswere asked to determine the net direction of water movement through a membrane.

In item 8, a semipermeable membrane through which only water could pass separatedthe two columns of water. Side 1 contained water and dye and side 2 contained water. Aminority of the students selected “after two hours the water level in side 1 will be higherthan side 2,” because “the concentration of water molecules is less on side 1” (LC/CM39.1%, LC 31.1%, CM 28.6%, and EX 23.4%).

The most common alternative response was the water on side 1 will be higher, because“water will move from the hypertonic to the hypotonic solution.” It is likely that studentshad memorized the tonicity terms with little understanding of their meaning. Students mayhave recalled that there is a “rule” to determine the net direction of water movement. Thecorrect rule is water moves from hypotonic to hypertonic solutions, thus students may haveremembered the rule incorrectly.

The terms for tonicity appear to be difficult for students to apply. The prefixes “hypo-,”“hyper-,” and “iso-” refer to the relative concentrations of solute. In cases of osmosis, stu-dents need to know the relative concentration of the solvent water. This knowledge cannotbe obtained from the terms for tonicity directly. For example, the prefix “hypo-” means“less” or “under.”” If a solution is hypotonic, the solution has a smaller concentrationof solute than the hypertonic solution with which it is compared. Water concentration,then, is greater in the hypotonic solution than in the hypertonic one. The tonicity termsprovide the relative concentration of the solvent that is needed to decide in which direc-tion water will diffuse so that net movement is from greater concentration to lesser con-centration.

Another alternative response for item 8 was “water moves until it becomes isotonic.”Memorization of the term isotonic with little understanding of the process of osmosiscould result in this misconception. “Iso-” means “the same,” and it is possible that students


consider osmosis as continuing until the concentrations are the same on each side, as wasthe case in item 2.

Item 10 assessed the process of osmosis in a plant cell. This item shows a picture of aplant cell that lives in freshwater, the cell was then placed in 25% salt water and studentswere asked what happened to the size of the central vacuole. The desired response was “thecentral vacuole would decrease in size” because “water will move from the vacuole to thesaltwater solution.” A minority of students determined the correct direction of water flowand the desired reason (CM/LC 60.5%, CM 56.4%, EX 42.9%, and LC 40.8%), suggestingunsatisfactory understanding.

The most common alternative response was “salt absorbs water from the central vacuole.”The meaning of “absorb” may be different in a science context than in a nonscientific context.Common everyday experiences in a nonscience context are sponges absorb water and papertowels absorb water. If “absorb” is viewed as the “taking away” of water, then studentsmay have believed that the saltwater solution absorbs the freshwater. In a scientific context,absorption is capillary action caused by adhesion. Salt solutions do not cause capillaryaction.

SUMMARY

We set out to investigate the effectiveness of concept mapping, the learning cycle, exposi-tory, and concept mapping/learning cycle instructional strategies at enhancing achievementin diffusion and osmosis content. The results seem to suggest that both the CM/LC and CMstrategies enhance some aspects of learning of diffusion and osmosis concepts more effec-tively than expository teaching. However, the two treatments (CM and CM/LC) were notsignificantly different than the LC treatment. CM/LC and CM seemed to make membranes,kinetic energy of matter, and elements of the particulate and random nature of matter easierto learn. The learning of concentration and tonicity, processes of diffusion and osmosis,life forces influence on diffusion and osmosis, and elements of the particulate and randomnature of matter were difficult even with CM/LC and CM.

It appears that CM may play a larger role than the learning cycle in helping students learndiffusion and osmosis concepts. This may be due to CM being the common factor amongthe two groups that were significantly different than EX, while LC was not significantlydifferent from the other groups. We believe additional research is needed to determine therole of the learning cycle at teaching diffusion and osmosis concepts. Even though wehave limited and somewhat conflicting data about the effectiveness of the learning cycleat teaching diffusion and osmosis, concept mapping and the learning cycle combined, andconcept mapping alone appeared to be a superior method for enhancing science learningas compared to expository instruction. We believe that the data provides some support ofour original hypothesis that concept mapping and the learning cycle provide an exceptionalcombination of strategies, because each method brings a unique epistemology to learning,although additional research is needed.

What concept mapping and the learning cycle have in common is the active role of thestudent. In both, students are actively engaged in constructing knowledge. During eachphase of the learning cycle, students are actively manipulating materials, recording data,or analyzing results. Students are encouraged to discuss findings in groups and with theclass. The teacher acts as a facilitator. Similarly, with concept mapping students are activelymaking connections between concepts. During group mapping, students debate and arguerelationships between concepts and placement of concepts on the map. Combined, thelearning cycle provides concrete experiences with the concepts, while concept mappingprovides an opportunity to makes connections between concepts.

634 ODOM AND KELLY

Each methodology has its strengths and has contributed significantly to improving scienceachievement, the promotion of the active role of the learner, and the promotion of the facil-itative role of the teacher. However, teachers’ use of a single methodology, either learningcycle or concept mapping alone without the other, provides the learner with only a partialframework of knowing. Instruction and teacher planning should reflect both Ausubel’s andPiaget’s distinct methodologies; effective instruction and meaningful learning seemingly re-quire both a verbal and a process-orientated approach. This study illustrates that the conceptmapping/learning cycle strategy can be useful in promoting science learning. We believethat this is a useful tool that should be explored by other teachers and researchers.

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