First-Year University Students' Understanding of Photosynthesis, Their Study Strategies
&Learning Context
Author(s): Elizabeth Hazel and Michael Prosser
Source: The American Biology Teacher, Vol. 56, No. 5 (May, 1994), pp. 274-279
Published by: University of California Press on behalf of the National Association of Biology
Teachers
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First-Year University Students'
Understanding
of Photosynthesis,
Strategies &
Their
Study
Learning
ElizabethHazel
O
VER
the last decade, researchon student
learning has increasingly focused on the development of students' conceptual knowledge (West & Pines 1985). There have been moves
away from views of the student as an empty jug into
which knowledge is poured and moves toward recognition of the effects of prior knowledge on students' subsequent learning (Ausubel, Novak & Hanesian 1978; Entwistle & Ramsden 1983). Advice on
study skills has moved from focusing on techniques
for aiding recallto emphasizing reflectionon learning
and acknowledging different contexts (Entwistle &
Ramsden 1983).
In this paper, we focus on students' learning of the
concept of photosynthesis-the importanceof which
is reflected in its being taught at all levels of the
education system. In studies on students' views of
photosynthesis it has been found that although most
students appreciated that light was involved, few
grasped the notion of an energy transfer, the role of
the chemical energy produced, the role of water or
the idea of energy storage (Wandersee1983;Bell 1984;
Bishop, Roth & Anderson 1985;Hegarty-Hazel1985;
Haslam & Treagust 1987;Barker& Carr1989). There
was some confusion about the respective roles of
carbon dioxide and oxygen. Many students were
unable to link photosynthesis with other physical and
chemical processes such as water uptake and respiration.
Most of the biochemical reactions of photosynthesis found in curricularscience belong to the domain
of symbolic knowledge, whereas notions such as
plant food are part of a student's intuitive knowledge
(West & Pines 1985).
Students' notions of plant food may be affectedby
packets seen on supermarketshelves and may not be
Elizabeth Hazel is Associate Professor at the Centre for Learning
and Teaching at the Universityof Technology, Sydney, P.O. Box
123, Broadway 2007 NSW, Australia, and Michael Prosser is a
Professor at La Troke University,Bunorora Vic 3083 Australia.
Context
Michael Prosser
compatiblewith scientists' views of photosynthesis.
The discrepancies between the students' and scientists' views as mediated via the curriculumremained
remarkably intractable in the face of successive
rounds of teaching, though diminished somewhat in
the final years of secondary schooling or in the first
year at a university. For example, Barkerand Carr
(1989) found that hardly any 13-year-olds used the
concept of energy storage and only about 15% of
17-year-oldsand first year university students did so.
However, correspondingresponses for the concept of
carbohydrateproduction were higher (20%rising to
45%and to 65-70%).
Barrass(1984), discussing the written work of students who had passed school examinations in biology, noted common misconceptions: Respirationoccurs in animals and photosynthesis occurs in green
plants; green plants photosynthesize in sunlight and
respire at night. Students did not realize that respiration occurred all the time. Barrass suggested that
the use of summary equations may cause some
students to think that respirationand photosynthesis
are alternativesand cannot occur simultaneously.
It appears that the nature of students' conceptual
development and their misconceptions is not simply
a function of the topics to which they have been
exposed by teachers and texts, or of the representation of those topics. Other important elements include students' prior knowledge and approaches to
learning. Biggs (1979)suggests that deep/meaningful
approaches to study promote meaningful learning.
He has shown that surface/roteapproaches resulted
in less complexity, whereas deep/meaningful approaches resulted in greater complexity. Novak
(1977) has explored the demands for meaningful
learning in different educational settings and has
demonstrated the crucial role of prior knowledge.
Entwistle and Ramsden (1983) linked these two aspects of student learning, showing that students'
approachesto study are affectedby their lack of prior
knowledge and by various contextual factors in the
274 THEAMERICAN
BIOLOGY
TEACHER,
VOLUME
56, NO. 5, MAY1994
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learning environment such as their perceptions of
assessment requirements.
In our research we have explored ways in which
changes in students' conceptual knowledge of photosynthesis are related to their study strategies and
achievement and to course context. We believe that
there are useful implications for teachers who might
see ways of probing their students' understanding of
photosynthesis, and who may be encouraged to use
concept mapping as an instructionaltool. We ask that
teachers look at our findings on course context and
see ways in which their own contexts are similar or
different. There is a major role for teachers in setting
a course context that encourages students to become
personally engaged with important science concepts
like photosynthesis ratherthan learning superficially
or by rote.
The Research Study
Concept maps were used to elicit students' views
of photosynthesis before and after studying photosynthesis in a general biology course. The maps were
scored according to criteriadeveloped from an analysis of the curriculummaterials and experts' maps.
The students also completed a study strategy questionnaire with scales measuring surface, deep and
achieving study strategies. Achievements were measured by multiple-choice questions that formed part
of the students' final examination.
The general biology course did not have biology at
matriculation level as a prerequisite and so prior
knowledge at that level was not assumed. Photosynthesis was taught as a physiological process with
relatively little reference to ecological and other implications. Students attended lectures and one laboratory over a period of three weeks. Extensive notes
were provided, including a summary equation representing photosynthesis.
It was expected that success on the concept mapping task would be associated with the adoption of
deep study strategies. The relationship of both of
these with achievement on the multiple-choiceexamination was more problematic.Students participating
in the study were volunteers from among those who
had matriculatedin biology.
Study Strategies
Students completed the study strategy questionnaire developed by Biggs (1982, 1987). The items
were analyzed in terms of three scales: surface, deep
and achieving study strategies. The surface study
strategies are ones in which students try to rote learn
new material without any attempt to understand it
(for example, "I learn some things by rote, going over
and over them until I know them by heart"). Deep
study strategies are ones in which students attempt
to understand new materialand not just rote learn it
(for example, "I try to relate new material as I am
reading it, to what I already know on the topic").
Achieving study strategies are used by students to
maximize assessment grades (for example, "I summarizesuggested readings and include these as a part
of my notes on the topic").
Knowledge Structure: Concept Maps & Scoring
Schemes
A prompted, hierarchical concept mapping task
was used, based upon earlierversions developed for
use in both biology and microbiology(Hegarty 1984;
Hegarty-Hazel1985). Students were asked to map 13
concepts using a pack of cards containing one concept per card. The concepts were identified from the
analysis of the curriculum materials. The students
were asked to structurethe concepts hierarchicallyon
a page and then write a sentence or two describing
the resultantrelationsbetween the concepts. Figure1
shows an example of the way one first-yearbiology
student constructed a map using the 13 concepts.
Two sets of dimensions were used to score the
maps. The first set was a modification of an earlier
scheme in which a set of guidelines was developed
from an analysis of maps produced by experts (Hegarty 1984, based on Novak 1980, 1981):
* Proportionof CorrectProposition-refers to the
correctnessof the propositional statements.
* Number of Branches-refers to the level of differentiation between concepts and is the number of
points in the map in which branching occurs.
* Number of Cross-Links-refers to the level of
integrationwithin the map and is the number of
links between major structuresof the map.
This set of dimensions provides no explicit measure of students' qualitative understanding of the
subject matter knowledge-scores are simply shown
by totaled numbers. A second set of dimensions
(Hegarty1984)was developed with specific reference
to qualitative understanding based on a technique
developed by Champagne, Klopfer, De Sena and
Squires(1981).Measureswere developed to deal with
two of the major sections of the map, the so-called
light reactionsand darkreactions.The criteriaused to
allocateclass scores are shown in Table 1. Briefly,for
each reaction, a class score of five means that all the
primaryand secondary concepts must be shown and
correctly structured, a score of four means that the
three primary concepts and two of the secondary
concepts are shown and correctlystructured, and so
on. Division of concepts into "primary"and "secondary" contained a degree of arbitrarinessbut provided
a scheme most consistent with the expert maps.
275
PHOTOSYNJTHESIS
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PHOTOSYNTHESIS
IN GREEN PLANTS
1
LIGHT ENERGY-PHOTONS
OF LIGHT, DIFFERENT WAVELENGTHS
1
REACTION CENTER
WATER
H 20
PIGMENTS, CHLOROPHYLLS A & B
PHOTOSYSTEMS I & II
4
HYDROGEN DONOR
REDUCING POWER
ATP
6~~~,e
02
CARBON SOURCE
CARBON DIOXIDE
CO2
REDUCED PYRIDINE
NUCLEOTIDES
8
CALVIN CYCLE
11
GLUCOSE
12
STARCH
Figure 1. A first-yearuniversity student's concept map of
photosynthesis. Propositions linking concepts in the student's map of photosynthesis follow:
1. Photosynthesis has essential components.
2. Photon of light absorbed by chlorophyllmolecule.
3. As high energy electronpassed throughelectronacceptors, ATP and NADPH2 are formed and store the
energy produced.
4. Hydrolysis of water. Splitting H20 molecule to reimburse chlorophyll molecule with electron.
5. Eventually high energy electron and hydrogen atom
end up reducing NADP.
6. Oxygen is formed as a waste product of hydrolysis of
water molecules.
7. NADPH2 enters the Calvin cycle.
8. ATP enters the Calvin cycle.
9. CO2enters the Calvin cycle.
10. ATP provides an energy source to reduce CO2.
11. C02 is transfixedinto a complex organic C6 molecule.
12. Glucose is stored in plants economicallyas starch.
Achievement: Multiple-Clhoice Questions on
Photosynthesis
Ten multiple-choice questions on photosynthesis
were included in the final examination. The questions
were designed to measure objectives of at least comprehension level, not sirmply recall of knowledge.
Several multiple-choice iexaminations were made
available to the students early in the course. Students
were encouraged to use these multiple-choice questions for self-assessment during the course. Tutors
were available for discussion.
The percentages of correct propositions increased
somewhat (t35 = 1.82, p < 0.1) but the other indicators showed little or no change. These results indicate
that students' understandingof photosynthesis could
best be described as moderate both before and after
the course.
The course context may be a decisive factor in
interpretingthis result: Students were enrolled in a
course requiring little prior knowledge. The participating students, however, had studied biology at the
matriculationlevel and may not have felt a need to
improve their knowledge of this topic. Some support
for this suggestion is found in comparisons with an
earlier study (Hegarty-Hazel 1985) where students
without matriculationbiology entered the course with
low priorknowledge that improvedover the period of
the course. It appearsthat students with matriculation
biology entered the course with substantial prior
knowledge of photosynthesis and did not change on
dimensionscoveredby the concept mapping task.
Table 3 shows the correlationmatrix for the preand posttest concept mapping variables, study strategy variablesand achievement variables.Table3 also
shows consistent negative correlationsbetween the
surface study strategy variable and each of the concept map variables and achievement. This suggests
that rote learning was associated with poor concept
maps and low achievement. Not only were the negative correlations statistically significant, they were
also quite large, and therefore of substantial educational significance. The large negative correlation
between the surface study strategy variable and
achievement variableis particularlynoteworthy.
Also shown are consistent positive correlations
between the deep study strategyvariableand the postcourse concept map indicatorsand achievement. The
size of these correlations,while substantial, was not
as large as the negative correlationswith the surface
study strategyvariable.However, the results suggest
that meaningful learning was associated with good
post-course concept maps and high achievement.
There are only small or negligible correlations between the achieving study strategy variable and the
concept map variables and achievement, suggesting
Table 1. Scoring for major structures of photosynthesislight and dark reactions.
SecondaryConcepts
PrimaryConcepts
LightReactions:
Generationof ATP
Generationof NADPH
Results
Hydrogensource
Table 2 shows descriptive statistics (means, standard deviations, medians and ranges) for each of the
pre-course and post-course concept map variables.
CO2fixed
ATPrequired
NADPHrequired
Energy from light
Reactioncenter
Generationof 02
DarkReactions:
Cumulative(Calvincycle)
Glucoseis produced
Storageproducts(e.g. starch)
56, NO. 5, MAY1994
TEACHER,
VOLUME
BIOLOGY
276 THEAMERICAN
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Table 2. Pre-courseand post-course concept map scores.
RANGE
VARIABLE
Standard
Deviation
Mean
VARIABLE
Percentageof CorrectPropositions
Pre
Post
Number of Branches
Pre
Post
Number of Cross-Links
Pre
Post
Class Score (light reactions)
Pre
Post
Class Score (dark reactions)
Pre
Post
Median
Min
Max
23
27
10
11
22
26
0
6
55
56
2.86
2.44
1.59
1.44
2.83
2.17
0
0
6
6
1.25
1.28
1.25
1.23
1.04
1.04
0
0
4
4
2.86
2.86
1.07
0.93
2.81
2.79
1
1
5
5
2.53
2.67
1.18
1.24
2.43
2.50
0
1
5
5
n = 36
ables were not. This is consistentwith a course design
that did not assume any priorknowledge.
that such strategies had little effect on students'
understanding of photosynthesis.
Some, but not all, of the post-course map variables
were positively correlated with their corresponding
pre-course concept map variables (the proportionof
correctpropositions,the numberof links and the class
score for dark reactionswere related, while the class
score for light reactionsand numberof brancheswere
not). Post-courseconceptmap variableswere positively
correlatedwith achievement, while pre-course vari-
How Do Students View Photosynthesis?
An inspection of students' concept maps revealed
some of the reasons why their understanding of
photosynthesis was only moderate. In the light reactions, students did not seem to understand that there
is an absolute requirementfor a hydrogen donor and
Table 3. Correlationsbetween the study strategy, pre-courseand post-course concept map and achievement scores.
2
StudyStrategy
1. Surface
2. Deep
3. Achieving
ConceptMap
Pre-Course
4. % CorrectPropositions
5. Number of Branches
6. Number of Cross-Links
7. Class Score (light reactions)
8. Class Score (dark reactions)
Post-CourseConceptMap
9. Proportionof CorrectPropositions
10. Number of Branches
11. Number of Cross-links
12. Class Score (light reactions)
13. Class Score (darkreactions)
Achievement
14. Multiple-ChoiceQuestions
-27
3
4
5
6
7
8
12 -38 -33 -39 -36 -41
31 -17
20
25
20
28
08
04
11
07
05
40
59
54
62
27
54
64
42
79
71
9
-30
14
-144
28
34
20
20
10
11
12
13
14
-29 -25 -30 -28 -63
52
26
47
30
24
02
10
-11 -00 -22
40
03
05 -02
43
07
-03
33
27
03
40
59
35
30
16
39
10 -08 -06
29
07
54
20 -01
39
12
01
35
50
28
81
51
23
83
60
49
32
40
38
37
Note: Decimal points omitted
r = .29, p < .05; r = .41, p < .01; r = .52, p < .001
n = 36
277
PHOTOSYNTHESIS
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that water acts in this role. There was a corresponding uncertainty as to the exact mechanism by which
oxygen is produced. Probably, the most important
problemwas lack of understanding of the centralrole
of ATP and NADPH generated by the light reactions
(as a result of the conversion of light energy to
chemical energy) and used in the so-called dark
reactions. Students lacked awareness of the role of
ATP and NADPH in fueling the Calvin cycle. The
involvement of CO2 in the Calvin cycle but not the
light reactions was not uniformly understood.
Implications for Teachers
This study revealed considerable stability in students' conceptual knowledge of photosynthesis over
the period of the course. There were only small
improvements in the details and overall structureof
students' knowledge.
Earlierwe found substantial improvements in the
structure of concept maps of first-year university
students who had not studied biology at matriculation level (Hegarty-Hazel 1985). In the present research, we expected that students who had studied
biology at matriculationlevel would surge ahead at
the university level, but they did not. This may be
because the level of assumed knowledge was low; the
participating students found little need to improve
their understanding (Barker& Carr1989also showed
little differencebetween the performanceof final-year
high school students and that of first-yearuniversity
students). We believe that teachers should address
the issue of having students with little prior knowledge together in class with well-prepared students.
Should more use be made of diagnostic testing?
Should class work be set at the lowest common
denominator?In what ways can flexibility be incorporated in the curriculum?In what ways can student
autonomy be fostered in settings where students
have different degrees of preparation?
The study showed that the study strategies
adopted by students were strongly related to the
structureof their conceptual knowledge and achievement. The relationships were positive with deep or
meaningful study strategies, and negative with rote
or surface study strategies. These results are in the
directionteachers would hope for. Students who use
deeper study strategies get better results on tests of
meaningful learning.
The relationships with achieving study strategies
were generally negligible. Yet it is the achieving
study strategiesthat are often included in study skills
courses and manuals, and are often associated with
rote learning (e.g. summarizing notes, learning key
words, preparing examination answers). Such
courses and manuals rarelyaddress the development
of deeper or more meaningful study strategies. This
may be because the achieving strategies can be dealt
with independently of the discipline, while the
deeper and more meaningful strategies are more
discipline-specific.
We would endorse the idea that any advice teachers might give on study skills should emphasize
reflection on learning and should explicitly acknowledge students' repertoires of study strategies and
their motives, the subject matter, the differences
between disciplines and courses, the system of rewards, and the methods of assessment (Entwistle &
Ramsden 1983).
In our study, by setting multiple-choice items at
levels higher than recall, course organizers established a context in which straight recall was not
rewarded by high achievement. But it may still be
that students' misconceptionsof the course context in
general, and the multiple-choice items in particular,
resulted in many students adopting more rote and
fewer deep study strategies, thus resulting in little
improvement in their conceptual knowledge.
While such findings might indicate that students'
misconceptions need to be directly addressed, these
findings suggest that the development of appropriate
approaches to study may be as important, or even
more so. The misconceptions may then look after
themselves. There is an obvious role for teachers to
find out about their students' approaches to study
and to foster deeper approaches when appropriate.
The results of this researchprovide furthersupport
for the use of concept maps in both research and
teaching. Numericalindicatorsbased upon an analysis of the maps were found to be related to students'
study strategies and achievement as expected. Interviews associated with our use of concept maps indicated that they could be a useful diagnostictechnique
for both teachers and students. For example, some
students responded to doing the concept maps with
phrases such as "ah ha/the penny drops" or "my
knowledge is all in bits." In attempting to introduce
concept mapping for students in two of the biological
sciences, we have found that a supportive environment was needed in which tutors were willing to
discuss students' maps on an ongoing basis. In one
course, physiology, the allocation of marks early in
the course for students' concept maps proved to be a
useful incentive. Using concept maps in one discipline (physiology) aided their introductionin another
(microbiology).
Acknowledgments
This research was funded in part by a grant from
the University of New South Wales. Thanks are due
to Professors R. Breznak and R. Uffen of Michigan
State University, and Professors D.J. Anderson and
K.C. Marshallof the University of New South Wales
278 THEAMERICAN
BIOLOGY
TEACHER,
VOLUME
56, NO. 5, MAY1994
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for help in the development of expert and criterion
concept maps. Thanks also to Associate ProfessorR.
King, Dr. M. Augee and staff of the first year Biology
Unit at the University of New South Wales for incorporating this study within their course context.
J. Moss provided research assistance.
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