Download Preassessment Report on the Circulatory System

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Part 1a: Explanation of Content
It is valuable for students to understand how the human body works
because it is knowledge that can constantly be applied to their own healthcare, or
that of their family. The awareness of the basic functions of and interactions
between the organ systems is a necessary foundation for the study of in-depth
topics, such as illnesses, effects of medicine, exercise and diet. Knowing the
path of blood through the circulatory system and the exchange of gases in the
circulatory and respiratory systems are key concepts for the understanding of the
maintenance of the human body.
The path of a red blood cell is dependent upon the needs of the somatic
cells, since the primary function of the blood is to transport materials to those
cells. When the nervous system receives the indication that a certain part of the
body needs oxygen or nutrients, blood is sent to that area. The blood travels
through blood vessels that branch into over forty billion microscopic capillaries,
the smallest vessels (Fox, 1999, p. 390). These are in “beds” that have
sphincters to control the amount of blood flowing to that area. The capillary walls
are only one cell thick, allowing for rapid exchange of materials between the
blood and tissue.
After blood leaves the capillary bed, it moves into the venous system.
This transports blood carrying carbon dioxide to the right atrium, or top chamber,
of the heart. Next, the blood moves through a valve into the right ventricle, or
bottom chamber, and out of the heart to a pulmonary artery. This vessel carries
blood to the lungs. Each alveolus [in the lungs] is covered with a cobweb of
capillaries (Ratcliff, 1975, p. 84). Here, through the process of diffusion, carbon
dioxide is exchanged for oxygen. Then, the oxygenated blood moves from the
lungs, through the pulmonary veins, and back to the left atrium of the heart. The
heart sends blood from the left atrium through a valve to the left ventricle. The
left ventricle pumps blood through a final valve into the aorta, a large elastic
artery. From the aorta, blood moves through the arterial system, and back to the
capillary beds surrounding cells that need oxygen and other materials.
Erythrocytes, or red blood cells, are the part of blood that carries oxygen.
Each erythrocyte contains approximately 280 million hemoglobin molecules (Fox,
1999, p. 366). The iron portion of the hemoglobin molecule chemically combines
with four molecules of oxygen. These oxygen molecules are picked up in the
lungs and dropped off at cells that need oxygen for cellular respiration, which is
one of the processes by which cells make energy.
When there is an increase in carbon dioxide, a waste product of cellular
respiration, in the blood, the pH of the blood lowers. This increase also lowers
the pH of the cerebrospinal fluid. Chemoreceptor neurons in the medulla
oblongata are triggered by the pH difference. Since the medulla oblongata is the
area of the brain that controls basic body functions, when the neurons receive
the message that there is too much carbon dioxide in the blood, the medulla
oblongata stimulates breathing.
Upon inhalation, oxygen enters the lungs. Since the concentration of
oxygen is greater in the alveoli of the lungs than in the blood, the oxygen
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molecules diffuse into the blood and attach onto the hemoglobin on the
erythrocytes. The opposite process occurs with carbon dioxide.
Part 1b: Relevant Standards
The topic of the circulatory system is addressed in the National Education
Standards (NES) under the life science section as content standard C. In the
“Structure and Function in Living Systems” list, one of the fundamental concepts
stated is “The human organism has systems for digestion, respiration,
reproduction, circulation, excretion, movement, control, and coordination, and for
protection from disease. These systems interact with one another.” The other
principles in this portion discuss cells, which also apply to the circulatory system
due to its function as the “delivery system” to the body’s cells.
In the “Developing Student Understanding” part, it is expressed that “In the
middle-school years, students should progress from studying life science from
the point of view of individual organisms to…developing understandings about
the cellular dimensions of living systems.” Emphasis is placed on the
enhancement of the study of cells by the use of light microscopes. It is also
stated that “Middle school students can develop the understanding that the body
has organs that function together to maintain life. Teachers should introduce the
general idea of structure-function in the context of human organ systems working
together.”
The New Jersey state science standards address similar concepts in
standard 5.5 A, #1 and 2.
Part 1c: Relevant Research
In past assessments, researchers have found that there are many
misconceptions of the circulatory system at all educational levels. As Pelaez,
Boyd, Rojas and Hoover (2005) stated, “Since the 1980s, a number of important
studies have confirmed that a student’s prior ideas can pose an obstacle to
learning when those ideas conflict with the science content taught in class.”
(Pelaez, Boyd, Rojas & Hoover, 2005). These misconceptions develop from
students’ prior experiences, alternative belief systems, use of analogies by
students, and confusion between the scientific meaning of a term and its
common meaning (Pelaez et al., 2005).
The embedding of these misconceptions in students’ learning throughout
their lives makes it difficult to change their ideas. Even after students had taken
courses including the study of the circulatory system, many could not explain the
correct answers to basic questions about circulation. For example, in the final
interview of the Pelaez et al. (2005) study of elementary education majors, the
error that blood travels from the body to the lungs without first returning to the
heart was still recorded after multiple assessments.
In the Arnaudin and Mintzes study (1985), answers provided about the
path of blood were assorted among all educational levels, and only a small
percentage of subjects answered correctly with an indication of both pulmonary
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and systemic circulations. At the junior high level, approximately seven percent
of students chose the correct “double circulation” option (Arnaudin & Mintzes,
1985, p. 728). With almost thirty percent of the subjects choosing it, the most
popular response was one that involved only systemic circulation. Around
twenty-five percent of the students noted that the lungs were part of circulation,
but chose the answer in which blood flowed directly to the toe from the lungs
instead of returning to the heart prior to systemic circulation.
The question “Where does the air go after it enters your body?” was also
posed to subjects at many educational levels. On the junior high level, only
around one-fourth of the students answered correctly that blood “tubes” carry air
to the heart (Arnaudin & Mintzes, 1985, p. 728). However, the most popular
answer (around thirty-five percent of students) chose that air tubes carry air from
the lungs to the heart. Twenty percent of answers described no distribution of
air, and the rest were divided between the idea that air tubes carry air from the
lungs to the body, and the response “none.” To summarize, over half of the
students recognized that a vessel was involved in the distribution of air, but only
one quarter of them knew what type of vessel transported oxygenated blood to
the heart.
Another shocking discovery in the Arnaudin and Mintzes study was that
only ten percent of students chose the accurate response that the circulatory
system is “closed,” meaning that it does not leave the blood vessels (1985, p.
729). The most frequent answer to this question was the “partially open” one.
Finally, there were two other misconceptions held by junior high students
about the circulatory system. Almost an equal number of students in the study
chose three-chambered or four-chambered heart answers (Arnaudin & Mintzes,
1985, p. 727). While other organisms have three parts of their hearts, the
appropriate response to this question for humans would be the four-chambered
heart option. Also, when asked “Why is blood important to your body?” the
majority of the students responded with a general, vitalistic answer (Arnaudin &
Mintzes, 1985, p. 725). This indicates that they were aware of the importance of
blood in the body, but were unsure of why it is essential.
Part 2a: Description of the class
The pre-assessment was administered to two of my seventh-grade
science classes. One class had twenty-two students, and the other had twentythree. Both classes contained heterogeneously grouped students. Out of the
forty-five students assessed, there were twenty-five females and twenty males.
The majority of the students was Caucasian and come from middle to high
economic status families. Of the forty-five students, seven have IEPs. .
Originally, I had left the assessment with a substitute for the students to
complete while I was not in school. However, the teacher did not understand the
purpose of the questionnaire, and decided to tell the students what to write on
their papers. Therefore, the original set of information was not considered, since
it was not the true knowledge of the students.
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A few days after this first attempt, I administered the assessment myself.
Preceding the distribution of the questions, I explained verbally to the students
that their responses would be used by me to gauge their prior knowledge of the
circulatory system before we would discuss it in class in the spring. Emphasis
was placed on the importance of their honesty in answering, since I would base
my instruction topics on how much they already knew about the concepts. I also
informed them that the assessment would not be part of their grade, and it was
acceptable if they were unsure of the correctness of their answers. I requested
that if the students were truly unaware of the content, they should indicate that at
the end of their response.
The students were told that they should write as much as they could about
the questions for at least ten minutes. If they needed additional time, they could
continue. Most students completed within fifteen minutes, with the longest time
spent being twenty minutes. A few students, especially the highest achieving
students seemed concerned, and made statements such as, “I really don’t know
anything about this.” I told them to think about what they know about blood, and
to do the best they could. Some students commented that the previous year,
during student research projects on the human body, someone in their class
presented the circulatory system as a topic. Others stated that they never
learned this content the year before.
Part 2b: Questions asked / Rationale for questions asked
The questions I used were derived from an assessment of the knowledge
of elementary education majors (Pelaez et al., 2005). Upon reading the common
misconceptions of college students, I decided that these mistaken ideas were,
more than likely, set in the subjects’ heads at an earlier age. According to Yip
(1998), these notions may have been implanted by teachers who did not
thoroughly understand the topics themselves. When receiving instruction on the
topics, the subjects’ confusion or preconceived ideas may have never been
clarified throughout their education.
Since middle school is the first time students learn about the details of the
human body, I thought it would be appropriate to address misconceptions about
the circulatory system right from the beginning of their learning. The National
Education Standards state that “This period of development in youth lends itself
to human biology.”
The first question I used was based on the Pelaez et al. (2005) and
Arnaudin and Mintzes (1986, p. 49) studies of the circulatory system
misconceptions of students at various educational levels. In the Arnaudin and
Mintzes assessment, illustrated descriptions of the path of blood after it leaves
the heart were presented to subjects as a multiple choice question. However,
similar to the Pelaez et al. (2005) study, my research question was presented as
an open-ended response. The students were directed to draw, using arrows to
show direction, the path of blood from the heart to the toe, and back to where it
began. They were also asked to give a detailed explanation of the path and what
was happening at each point. This open-ended response provided the
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opportunity for students to show a visual representation of their ideas, as well as
verbally explaining them. The intention of using both types of assessment was to
have students reflect on their answers. It also permitted the results to be
checked by two methods.
The Pelaez et al. (2005) assessment also used the second question
posed in my research. This question was also based on the misconceptions
involving gas exchange and blood. Students were asked to explain as much as
possible about the process by which oxygen is added to the blood, and the
location where this addition takes place. An open-ended question was chosen to
provide the opportunity to analyze the vocabulary used in the answers.
Part 2c: Analysis of findings
Table One: Data from question one
First Question: Description of path of a drop of blood through the
circulatory system
Response
Number of students
Percent of whole group
responding with this
(45 students)
answer
responding with this
answer
Heart to heart path with
no indication of
involvement of lungs
Whole body path before
returning to heart
Path that mentions
involvement of lungs
One-way trip to
destination in body
18
40%
12
26.7%
10
22.2%
5
11.1%
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Table Two: Data from question two
Second Question: Explanation of how oxygen is added to the blood
Response
Number of students
Percent of whole group
responding with this
(45 students)
answer
responding with this
answer
Indication of lungs as
location of oxygenation,
but no detail of process
provided
Lungs send oxygen to
blood
Heart adds oxygen to
blood
Skin / Wound adds
oxygen to blood
No answer
Breathing adds oxygen,
but no detail or mention
of lungs
21
46.6%
9
20%
7
15.6%
3
6.7%
3
2
6.7%
4.4%
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Table 3: Various data from both questions
Combination of both questions: Various common responses
Response
Number of students
Percent of whole group
responding with this
(45 students)
answer
responding with this
answer
Mentioned veins
Mentioned arteries
Mentioned capillaries
Referred to different
sides of the heart
Used the term “chamber
of heart” in description
Indicated involvement of
“flaps” in heart
Specifically mentioned
that blood travels through
the brain on its path
Referred to oxygen being
“absorbed” into the blood
Mentioned a color
change in blood
Wrote that the process
repeats
13
5
1
3
28.9%
11.1%
2.2%
6.7%
1
2.2%
1
2.2%
5
11.1%
3
6.7%
4
8.9%
7
15.6%
Of the forty-five students assessed, none of them drew the correct
pulmonary/systemic path of circulation. The most frequently mentioned path
(forty percent) was one in which the blood traveled from the heart to the toe and
back to the heart. Approximately twenty-six percent of students responded that a
drop of blood travels around the entire body, including through the brain,
stomach, etc. prior to returning to the heart. Only approximately twenty-two
percent of students mentioned the lungs as part of the system. Finally, five of the
students thought that blood traveled on a one-way trip from the heart to the toe.
Some other various features were suggested by the subjects. Almost
twenty-nine percent used the term “vein” in their answer. In most cases, the
word was used as a general term for all blood vessels. An example of this is an
answer that stated “[Blood] travels down the veins…to the foot.” Only five
students referred to arteries, and the word capillary was used only once. Three
assessments included a statement regarding the blood leaving and returning to
different sides of the heart, while only one student wrote the term “chambers.”
One essay mentioned “flaps” in the heart that cause the sound of a heart beat.
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Among those that chose the “whole body” circulation option, two subjects
emphasized that kidneys filter the blood, and five subjects made a notation that
blood travels through the brain. One piece of a student response was “[Blood]
goes to the brain first because the brain…tells your blood where to go.” It is also
noted that only approximately fifteen percent of students declared that the
process repeats.
In the second question, the majority (48.8%) of pupils described the lungs
as the location of blood oxygenation, but gave no detail about the process. Nine
students indicated that the oxygen that had been inhaled moved into the blood,
but only one suggested the idea that there were blood vessels within the lungs.
An example of a typical response was “The lungs trade for new healthy blood.”
Fifteen and a half percent of the students wrote that the heart added oxygen to
the blood. Three students answered that “air” was added through the skin, such
as in a wound. Two pupils responded that oxygen is obtained during breathing,
but did not mention the lungs.
None of the students described the process of diffusion or differences in
concentration of gases in their answers. The response that was the closest to
the true answer was that oxygen was being “sucked” from the blood. Three
students stated that oxygen was absorbed into the blood. A few others used
expressions such as “refreshed,” “refueled,” “picked up,” and “combined.”
Also, seven students described a difference in color when oxygen was
added. Most of these indicated that oxygen changed from a bluish/purplish color
to red when oxygen was added. The correct fact is that blood changes from a
darker red to a bright red color when oxygen is added. The reason that blood
appears blue in the veins of fair-skinned people is because redder wavelengths
of light penetrate deeper into the skin than blue wavelengths. As a result, when
veins are between .02 and .08 inches below the surface of the skin, they look
blue (Huskey, 2000).
Part 2d: Discussion of findings
Many of the misconceptions discussed in prior research were similar to
those recorded in this assessment. Although some students had stated that they
had previously learned about human anatomy, not a single student correctly
answered either question. A few had provided pieces, such as terms, that could
serve as the foundation of an accurate answer.
With regard to the path of circulation, the most popular response for this
assessment was the same as the most popular one in the Arnaudin and Mintzes
(1985) research. The majority of students in both this and the Arnaudin and
Mintzes (1985, p. 728) sets of middle school groups thought that blood travels
from the heart to an area in the body and returns to the heart, with no mention of
the lungs. It seems that the reason for this mistaken idea is that prior to middle
school, the body is viewed as a network of cells functioning together (NES,
science standard C). Most students lack the understanding that each cell, like a
whole organism, constantly creates wastes and requires materials, but cannot
function alone. Therefore, it is not likely that a person would realize that a
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“delivery system” between cells is necessary to transport materials, and would
not recognize that the blood functions as this delivery system between the lungs
and the body’s cells.
A second reason for the absence of the association between the
circulatory and respiratory systems in the knowledge of many people is that in
daily conversations, the two systems are not usually linked together. Research
shows that “Students come to school with their own ideas about how things in the
natural world work, ideas that are not always consistent with the conceptions of
experts in the field” (Krajick, Czerniak & Berger, 2003, p. 21). Among college
nonbiology majors, there were a large number that did not think that blood was
responsible for transporting both oxygen and nutrients (Arnaudin & Mintzes,
1985, p. 725). Since this selection of subjects is the closest to typical adults, it
can be assumed that most parents have the same misconceptions as their
children. These unclear ideas are also indirectly reinforced by adults in society.
For example, there are many television programs, computer games, etc. that
emphasize the necessity of breathing and the flow of blood, but very few connect
the two ideas. Therefore, this overly generalized impression of the importance of
blood flow and breathing has been established and reinforced since early
developmental years, with no justification provided as to why they are vital
processes or how they are linked.
The misunderstandings of the process of gas exchange within the body
can also be attributed to the aforementioned issues. Without an appreciation for
the knowledge of the cellular level of the human body, the primary function of the
blood as a “delivery system” cannot be realized. As Yip (1998) states, “It is
argued that for certain areas in biology, particularly those that are concerned with
more complex or abstract phenomena, such as…mechanism of circulation,
children are less likely to come into immediate and direct contact with them in
daily life”. While it is easy to see blood flow in other areas of the body due to
cuts or the ability to see veins, students rarely see the pulmonary arteries and
veins since they are protected beneath the ribcage and are only visible in cases
of surgery or severe injury. Also, focus in everyday life is placed on the major
organs as opposed to the vessels that connect them. Unless students are
continually exposed to the ideas that blood is responsible for transporting
materials to the body and the fact that the circulatory system serves as a method
of connection between all body parts, it will be difficult for students to remember
that these are the true functions of them. Also, “For biological science, it is also
well documented that children develop their informal ideas from an early age in
certain areas such as…respiration, [and] gas exchange” (Yip, 1998).
Consequently, it can be more challenging for students to restructure their ideas
after they have already created them, as opposed to being exposed to the
circulatory system for the first time in middle school.
Diffusion and the differences in concentration as the method by which
materials are transferred was not referred to in any of the responses. More than
likely, students have not learned this concept in their previous education, which
would explain the reason why they did not know to include it in their answers.
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The second most popular response to the circulatory path question was
that a drop of blood travels throughout the entire body prior to returning to the
heart. This mistaken belief may be the result of a faulty assumption that because
blood is located throughout the body and blood also flows to and from the heart,
students may think that blood travels through the whole body prior to its return to
the heart. If this notion was never challenged by either educational topics or
everyday life, students may not be aware of the inaccuracy in their beliefs.
Other false impressions revealed in this assessment can be attributed to
various sources. The idea that blood cells change color when oxygen is added
may come from instructional diagrams that use blue and red as representative
colors for deoxygenated and oxygenated blood, respectively. This may be
considered one of the “faulty mental models” detected by Pelaez et al. when it
was affirmed that “Many need help interpreting stylized textbook diagrams that
seemed clear to an expert” (2005). Another reason for the error in believing that
blood transforms from blue to red is the phrase “blue-blooded,” which refers to
noble birth. This supports Yip’s (1998) idea that “naïve ideas [arise] from
everyday experiences and language usage of the learners”.
The language usage issue may also be responsible for the application of
the word “vein” to represent all types of blood vessels. Since the bluish color of
the veins allows them to be seen more easily than arteries or capillaries, many
people mistakenly believe that these are the only blood vessels within the body.
Therefore, they use the term loosely whenever they refer to the circulatory
system.
Part 2e: Implications
Through my assessment and the research of past scientists, it was made
clear that there are many misconceptions that both middle school students and
adults have about the circulatory system. The reason that adults continue to
have misunderstandings about the human body is more than likely that at a
younger age, they were either misinformed by an adult or never received
clarification on their questionable ideas. According to Arnaudin and Mintzes,
(1985, p. 729), “In a number of instances, the relative frequencies of alternative
conceptions common to elementary school students remained stable at the
secondary and college levels…[and] students preconceptions tend to be
‘amazingly tenacious and resistant to extinction’”.
In order for this pattern of misunderstanding to cease, teachers must
begin to address the erroneous beliefs of their students, and adjust their teaching
by designing lessons that will assist in the reconstruction of their thinking. It is
stated “Poor instruction and shallow development of science concepts in
elementary and middle school grades are often at fault for persistent, inaccurate
beliefs about scientific phenomena” (Krajick et al., 2003, p. 21).
An excellent way for teachers to begin to tackle the job of rebuilding
students’ knowledge bases of the circulatory system is to conduct frequent
assessments to analyze the most prominent mistakes within their classes.
Open-ended questions, concept maps, interviews, and diagrams have all been
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utilized in research to discover the thoughts of students prior to discussion of the
topic in classes. As Minstrell avowed, “…I had two ears, but only one mouth, and
[I] use[d] them in that proportion…My critical questions as a teacher became:
What is the understanding of my students?” (Feldman & Minstrell, “What is
Action Research). He also states that “…if about 10 percent or more of my
students exhibit a similar sort of thinking, then I need to acknowledge and
describe the conceptions and reasoning they are using, and I need to design
instruction to address that thinking” (Feldman & Minstrell, “What is Action
Research). If all teachers adapted this approach, it may reduce the number of
students leaving middle school with inaccurate belief systems.
Once the misconceptions have been identified, teachers should present
activities that will help students to correct their knowledge of the subject. Yip
(1998) suggests the following instructional strategies that have previously been
effective in achieving this goal: “cognitive conflict, analogies, metacognitive
methods, as well as knowledge of the constructivist approach of teaching” . The
constructivist approach of education is the understanding that students enter a
classroom with prior knowledge, and educators should create learning
environments that expose students to a number of new experiences so that they
have multiple opportunities to reconstruct their comprehension (Krajick et al.,
2003, p. 53). For this to be successful, teachers must be open to notion that they
may have to create new ways to address an issue if the original method was not
effective.
In planning to deal with inaccuracies regarding the circulatory system, the
assessments in research have shown that more focus should be placed on
instruction of the “big picture” of the function of the circulatory system as opposed
to the typical stressing of details and vocabulary regarding the flow of blood.
Some ideas that Arnaudin and Mintzes (1986, p. 50) developed were observing
blood under a light microscope and dissecting animals to view their circulatory
systems. This would give pupils the chance to see first-hand an example of how
the inside of their bodies function. Manipulative models that allow children to
mimic the path of blood and its tasks in the body may also provide clarity about
the system. Writing assignments that require students to apply their knowledge
of the function of the circulatory system can assist teachers in pinpointing which
students truly understand the process and which need further instruction. Also,
group discussions and debates permit the sharing of ideas by peers, who may be
able to describe correct answers in ways that are more obvious to a fellow middle
school student than an educator or textbook’s explanation.
While the goal of teachers should be to dissolve the misconceptions of
their students, they should be sensitive to the self-conscious attitudes of
adolescents. If teachers do not consider this, there may be a risk that students
will be disheartened about science, and avoid it in future years. Arnaudin and
Mintzes (1985, p. 731) state “…an important element in fostering conceptual
change is the establishment of a nonthreatening environment which encourages
exchanges of ideas. Familiarity with students’ alternative conceptions may very
well aid teachers in developing such an environment by reassuring students that
their ideas, though not currently acceptable to modern science, many times have
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a long and honored tradition in the history of science, or may be valid in other
contexts.”
Middle school is considered to be an important time in students’ lives
because it is when they begin to construct their own view about the world and
become interested in science. Due to this belief, more emphasis should be
placed on delivering accurate and clear information in ways that will allow the
students to embrace the concepts permanently.
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References
Arnaudin, M.W., & Mintzes, J.J. (1985). Students' alternative conceptions of the
human circulatory system: A cross age study. Science Education, 69,
721-733.
Arnaudin, M.W., & Mintzes, J.J. (1986). The cardiovascular system: Children's
conceptions and misconceptions. Science and Children, 23/(5), 48-51.
Feldman, Allan & Minstrell, Jim. Action research as a research methodology
for the study of the teaching and learning of science.
Fox, Stuart Ira. (1999). Human Physiology. Boston: McGraw-Hill.
Huskey, Robert J. (2000, February 3). Why venous blood appears blue.
Retrieved November 29, 2005 from
http://www.people.virginia.edu/~rjh9u/blueblud.html
Krajcik, Joseph S., Czerniak, Charlene, & Berger, Carl. (2003). Teaching
Science in Elementary and Middle School Classrooms. Boston: McGraw
Hill.
National Education Standards. Retrieved October 27, 2005 from
http://www.nap.edu/readingroom/books/nses/html/3.html#tsc
Pelaez, Nancy J., Boyd, Denise D., Rojas, Jacqueline B., & Hoover, Mildred A.
(2005). Prevalence of blood circulation misconceptions among
prospective elementary teachers. Advan. Physiol. Edu. 29: 172-181,
2005; doi:10.1152/advan.00022.2004. Retrieved October 27, 2005.
Ratcliff, J.D. (1975). I Am Joe’s Body. New York: Berkley/Reader’s Digest Book.
Yip, Din Yan. (1998, September 1). Teachers’ misconceptions of the circulatory
system. Journal of Biological Education, 0021-9266, Vol. 32, Issue 3.
Retrieved October 27, 2005 from EBSCO MegaFILE database.