Download Exposing Student Misconceptions about Cellular Structure

Journal of Virginia Science Education
v4, n2
Exposing Student Misconceptions about Cellular Structure: A Curriculum Topic Study
Abbie Martin, M.Ed.
Curriculum topic study allows teachers to investigate a specific concept in math or science by summarizing
resources, such as national standards, state standards, and research-based instructional methods. In this
action research study, the teacher researcher utilized the curriculum topic study approach to uncover
student misconceptions in the area of cellular structure and function. The researcher utilized a formative
assessment probe to find out what high school students believe about the structure of cells and
macromolecules prior to teaching a cell unit. The findings identify clear misconceptions concerning the
nature of macromolecules and their relationship to cellular structure.
Introduction
Research has shown that students have difficulty making the connection between
molecular and cellular organization (Driver, et. al., 1994). Students seem to understand that both
atoms and cells are made up of smaller parts, including the nucleus. However, they struggle to
conceptualize the foundational principal that all matter, including cells, is made of atoms. This
misunderstanding seems to perpetuate beyond differentiation between cells and atoms, and into
their understanding of the structure and function of macromolecules. This action research study
aims to expose these misunderstandings and identify the underlying cause for them.
Curriculum Topic Study Background Research
Curriculum topic study is a novel approach to pedagogy developed by Keeley (2005).
The process provides teachers access to a variety of science content and curriculum development
resources they can use to make pedagogical decisions with the goal of reducing student
misconceptions. The teacher researcher begins by investigating the state and national
benchmarks for the topic that will be studied.
The learning goals set by the American Association for the Advancement of Science
(1994) for the topic of cell structure and function for grades 9-12 include understanding that cell
structure affects function and understanding that living cells are made of chemical elements.
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Additionally, the Virginia Standards of Learning for Biology (2003) include understanding the
structure and function of macromolecules (BIO 3.b) and learning key differences between
prokaryotic and eukaryotic cells (BIO 4.a). These standards help shape the curriculum for high
school biology in Virginia, and make up a continuous theme throughout the course.
According to the American Association for the Advancement of Science (1994), students
should experience a progression of their understanding of cell structure and function as they
move through the grade levels. As elementary students, they should have an understanding that
some parts of organisms must be seen through a magnifying glass, and then as they enter the
upper elementary grades they should begin to form the concept of a cell as the basic unit of life.
Finally, as they exit middle school students should have a clear understanding of basic cell
function. By the end of the 12th grade, students should have knowledge and understanding of
the nature and function of proteins and the specialization of organelles within the cell, including
the cell membrane.
Driver, et al. (1994), a leader in misconception research, has discovered that students
often confuse the concepts of molecules and cells. Often times, students have a very general
concept of molecules and cells, both of which contain a nucleus and are surrounded by other
small things. This confusion seems to stay with children though the teenage years. Also,
students at the high school level tend to think that larger macromolecules, such as proteins and
carbohydrates, are made of cells rather than atoms. They did not understand the difference
between cells and molecules. More confusion has been found in students’ ability to differentiate
the sizes of cells and atoms. Many students at the high school level believe that cells and
molecules of protein are the same size. Driver, et al.’s (1994) research also found that students
believe single-celled organisms contain intestines and lungs.
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Method
Action research was chosen for this project due to its ease of use and effectiveness for the
classroom teacher. The researcher was able to collect data, create and teach lessons, and analyze
the results from her own classroom. Qualitative and quantitative data were collected, and quasistatistics were used to identify trends within the data set. Qualitative methods of open coding
were utilized to organize the data.
Research Questions
The researcher aims to answer the following questions:
1. What do science standards and current research say 10th grade students should know and
understand about cell structure and function?
2. What commonly held ideas and understandings do 10th grade students in Advanced
Biology at a suburban high school in southeastern Virginia have about cell structure and
function?
3. What experiences have led these students to their ideas and understandings of cell
structure and function?
Classroom Context
The students in this study were from a suburban high school in southeastern Virginia.
There were 20 student participants from an Advanced Biology course. Nine student participants
were 9th graders, and the remaining 11 student participants were 10th graders. Most students
were generally highly involved in extra-curricular activities. They all had a strong background
in science and were recommended to the advanced biology course by previous science teachers
and guidance counselors. The class consisted of 1 African-American student, and the remaining
students were Caucasian.
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Data Collection
The researcher started probing the misconceptions by administering a simple formative
assessment, or probe, designed to identify student ideas and understandings of cell structure and
function (Appendix A). The probe aimed to uncover misconceptions that may be held
concerning the difference between molecules and cells, and the function and structure of plant
and animal cells. The probe was used as a pre-assessment tool prior to the beginning of a unit on
cells.
The probe was designed with two columns of items containing names of organelles,
molecules, organs, and elements. The students were asked to place a letter B if the items are
found in both plant and animal cells, a letter A if the items are found in only animal cells, a letter
P if the items are found in only plant cells, and a letter N if the items are found in neither cell
type. The students were then asked to describe the process they used to sort through the items.
Finally, students were asked to draw and label an example of a plant and animal cell with as
many details as they were able to.
From the results of the probe, the researcher was able to clearly delineate several
commonly held misconceptions. These misconceptions mirrored those identified in the research
by Driver, et.al. (1994). The unit plan was designed to combat these misconceptions and aid
students into a clearer understanding of the structure of cells as it relates to their function and
position within a multicellular organism.
Results
The data has been divided into three tiers. The first tier consists of data from student
responses to the probe items. Students could choose from four possible answers for each item;
found in both animal and plant cells, found in neither animal nor plant cells, found in plant cells
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only, or found in animal cells only. Students indicated their answer choice using the letters B, N,
P, or A. The researcher found striking results in eight of the twenty-four items that are
delineated in Figure 1.
Figure 1. Student responses to tier 1 questioning.
Neither cell
types
40%
Animal cells
only
0%
Plant cells
only
0%
Mitochondria 35%
0%
30%
35%
Lungs
0%
60%
40%
0%
Intestines
0%
45%
55%
0%
Lipids
25%
0%
10%
65%
Carbon
40%
45%
5%
10%
DNA
60%
10%
30%
0%
Water
Molecule
55%
35%
5%
5%
Atoms
Both cell
types
60%
Student respondents were greatly divided in the location of lungs, intestines, water, and
even atoms. As illustrated in the graph in Figure 2, there is little consensus among the Advanced
Biology class about whether or not cells contain atoms, carbon, or even water. Furthermore,
many students had difficulty remembering that DNA is found in both plant and animal cells.
Tier 2 Questioning
Tier 2 questioning requested that students describe their reasoning or rule for making the
determination for each probe item. Students were able to freely respond to this question using as
much or as little written response as they felt necessary. Student responses were categorized
using an open coding method. This method involves creating new categories for each response
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type and then grouping categories into broader themes to further organize the data. Figure 3
outlines the researcher’s results.
Figure 2. Tier 2 student responses.
Prior knowledge
9
8
Guessed
7
6
Remembered from middle
school
5
4
3
Thought about what each
organism needed
2
Didn’t know
1
Remembered making a
model
0
Tier 3 Questioning
The third tier of responses required students to draw and label an example of a plant and
animal cell. These responses ranged in detail, but were all quite similar. Most students drew a
cell membrane around a nucleus for both cell types (Appendix B). Some included the cell wall
for plant cells, and some did not. The general theme of all respondents’ drawings was their
ability to remember that a cell is a container that holds smaller organelles which serve different
function for different cells. The respondents, as a whole, provided this information in sufficient
detail for their grade level and aptitude.
Discussion
Students in the advanced biology class had difficulty identifying the basic units of
structure that form cells in living things. Forty percent of respondents indicated that cells do not
contain atoms. This reveals a basic disconnect between their understanding of molecular
structure and living systems. Carbon and water also provided students with difficulty. Thirty36
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five percent of respondents indicated that water is not found in either cell type. Additionally,
45% of students believed that neither cell type contains carbon. Fifty-five percent of students
indicated that animal cells could contain intestines. This misconception is supported by Driver’s
research. Students have a very hard time organizing molecular and living systems. They do not
seem to understand that atoms, the smallest unit of matter, are the building blocks of
macromolecules and all cells.
Significance
This action research has revealed a great gap in understanding of molecular and cellular
structure for the studied group. Clear, direct instruction should be provided to students aimed at
combating these misconceptions. In addition, students should be exposed to a variety of
examples and imagery to aid them in processing and retaining the appropriate framework. It is
recommended that biology teachers begin the discussion of molecular structure with a diagram
or illustration comparing the size of the atom to that of a molecule, cell, organ, and organism. In
addition, students may find it helpful to differentiate between the atomic nucleus and the cellular
nucleus.
Teachers may also find the use of interlocking blocks as a useful tool for modeling cells.
Interlocking blocks can be put together in various shapes using distinct colors and patterns. Each
interlocking block could be modeled like an atom, and macromolecules could be modeled out of
the joining together of many blocks. Then, those model macromolecules can be placed together
to simulate the formation of cell parts or whole cells. This activity may help provide a useful
connection between the size and structure of atoms and the size and structure of cells.
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Future Research
Future research should be conducted to determine the starting point of this
misconception. Students in lower grade levels could be interviewed and probed to find their
current understanding of cellular and molecular structure. Furthermore, lessons of teachers in
the lower grades could be examined to reveal possible inconsistencies. Professional
development experiences may be necessary to provide elementary school teachers with effective
methods of describing the relationship between atoms and cells to students.
References
American Association for the Advancement of Science. (1994). Benchmarks for science literacy.
NY, NY: Oxford University Press.
National Research Council (1996). National science education standards. Washington DC:
National Academy Press.
Driver, R., et. al (1994). Making sense of secondary science: Research into children's ideas. NY,
NY: Routledge Press.
Keeley, P. (2005). Science curriculum topic study: Bridging the gap between standards and
practice. Thousand Oaks, CA: Corwin Press.
Abbie Martin is a biology teacher at Jamestown High School in Williamsburg, VA. She can be reached by
email at [email protected]
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Appendix A
Cell Type Assessment Probe
Place a mark next to items you could find in a plant cell, animal cell, both, or neither.
A=animal
P=plant
B=both
N=neither
Cell Membrane
_______
Vacuole
_______
Cell wall
_______
Complex carbohydrates
_______
Enzymes
_______
Lysosome
_______
Molecules of proteins
_______
Chromosome
_______
Nucleus
_______
Flagella
_______
Lungs
_______
DNA
_______
Atoms
_______
Intestines
_______
Golgi apparatus
_______
Lipids
_______
Virus
_______
Chemical compounds
_______
Chloroplasts
_______
Carbon
_______
Ribosome
_______
Mitochondria
_______
Water molecule
_______
Simple sugars
_______
1. Explain your thinking. How did you decide if the items could be found in a plant or animal cell?
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
2. Now, draw and label an example of a plant and animal cell. Be as detailed as you can.
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Appendix B
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