Scalpel Mouse ?
OR
A Statistical Comparison
of Real & Virtual Frog Dissections
T I N A R. C R O S S
P
rior to the 1980s, it was common for students to
dissect preserved and live specimens in the laboratory. Both high school and college students commonly dissected frogs and cats. College laboratory
instructors commonly handed students live frogs, with
instructions to “pith” the frogs, and then dissect them.
Pithing consisted of holding the live frog while inserting
a probe down the spinal column, then reversing the
probe and inserting it into the brain while rotating it to
destroy all nervous tissue. That allowed the student to
cut the frog open and observe the heart beating, lungs
inflating, and other processes.
PETA (People for the Ethical Treatment of Animals)
objects strongly to the dissection of animals on the basis
that is violates animal rights (Lewis, 2001). Additionally,
many students object strongly to dissecting animals.
TINA R. CROSS, Ph.D., is lead science teacher at Carver High
School, Integrated Math/Science/Technology Magnet Program,
Columbus, GA 31906; e-mail: crosst@ldl.net. Her son, VICTOR E.
CROSS, is a student at Central High School, Phenix City, AL
36867; e-mail: crosst@ldl.net.
408 THE AMERICAN BIOLOGY TEACHER, VOLUME 66, NO. 6, AUGUST 2004
V I C TO R E. C R O S S
Orlans (1988) and Russo (1997) point out that there
has always been a controversy over the dissection of animals. Several states have enacted legislation that protects the students right to not dissect. School districts
have the right to enact students’ rights policies, which
enable students to choose whether or not they dissect
or not (Lewis, 2001).
Lewis (2001) points out that virtual dissection is
beneficial in many ways. Students have a model that is
clearly labeled, and which, after use it is not too damaged to use again. Additionally, dissection is expensive,
which in these times of limited funds has often resulted
in students completing high school having never dissected an organism.
Velle and Hall (1999) reported that a study was
conducted using 64 ninth grade students in Wisconsin.
Two classes, led by different teachers, were utilized. The
class of Teacher A dissected real frogs, while the class of
Teacher B performed the virtual dissection. Students in
both classes followed the same lab outline and turned
in the same lab report. At the end of the lab, both classes were given two tests. One test was virtual; the other
test used organic frogs. The results in this study indicated that students who had completed the virtual dissection performed better on both tests. It should be noted,
however, that the teacher conducting the virtual dissection was a veteran of 20 years in the classroom, while
the teacher working with the students who were dissecting the organic frogs was a first year biology intern.
Additionally, the method by which the performances
were judged was not indicated.
Dave McNeely (2000) is Professor of Biology at the
University of Texas. In an online chat room, his reply to
the question of whether virtual dissections should be
adopted in place of traditional organic dissections was:
The trend toward eliminating actual experiences
for students, instead substituting some pseudoexperience is really troubling me. They aren’t
doing the dissection to learn that a pig has a gall
bladder, or even that it is found in the underside of
one lobe of the liver. They’re doing the dissection so
that they will have handled and seen the inside of
a real animal in a disciplined way, and will have
some basis in experience for the next time having
had the experience might prove useful. Please
reconsider abandoning dissections in favor of pictures, whether the pictures come packaged with a
computer or not. What’s already lacking in biology classes is hands-on experience.
On the other hand, Kinzie (1993a) reported that a
frog dissection from an interactive video disc (IVD) was
at least as effective as the dissection of an organic frog in
promoting learning of both frog anatomy and dissection
procedure. He also said that the students who were pretaught with the IVD had better understanding of the
material than students who received no pre-preparation.
Kinzie followed this report with a second paper (1993b)
in which he reported that students who used a computer-based frog dissection to prepare for an organic dissection improved their performance and comprehension during organic frog dissections.
The inspiration for this study originated when a
site license for a computer dissection program was
awarded as a prize at a national science teachers meeting. After researching the topic, it was discovered that,
basically, experts disagree strongly about the efficacy
of computer-based dissections when compared with
organic dissections. As a result, this study was
designed to test whether students in a high school AP
Biology class performed equally well using both methods, or whether one method was more efficient in promoting student learning than the other. The null
hypothesis was that there would be no significant difference (.01 level) in the performance of the students
regardless of the method of dissection. The alternative
hypothesis was that students who dissected organic
frogs would perform significantly better on the labo-
ratory practical than students who dissected the virtual frogs.
Methods & Materials
This experiment was conducted with four AP Biology
classes over a two-year period. The classes were designated as “A,” “B,” “C,” and “D.” Twelve copies of the computer program Biolab Frog Dissection were purchased. For
class “A,” 18 identically sized slips of paper were cut. Nine
of the slips said “Computer Dissection” and nine of the
slips said “Organic Frog Dissection.” All eighteen slips
were placed in an empty box, that was closed and shaken
thoroughly. Twenty-one preserved frogs, each approximately 15 cm long, were purchased from Carolina
Biological Supply Company, along with dissection worksheets. The dissection worksheets were assembled.
The names of the students in Class A were called in
alphabetical order. Each student reached into the box
and chose a slip of paper. If the paper said “Computer
Dissection,” the student was to complete a computer
dissection; if the paper said “Organic Frog Dissection,”
the student was to complete the dissection in the traditional manner. Each student was given a set of dissection worksheets. Students who were to use the computer program were issued a CD with the computer dissection program on it. Students who were to complete the
organic frog dissection were given the dissection sheets,
a preserved frog, dissecting scissors, dissecting pins,
and a dissecting pan. All students were instructed that
at the end of the dissections they would be given a laboratory practical using the organic frogs. The laboratory
practical would involve the students’ identification of
the organs and tissues of the dissected organic frogs,
along with the functions of the structures. The students
were given two days of class (on block scheduling) to
complete the assignment.
The procedure was repeated in exactly the same
manner for Class B, with the exception of the size of the
class. As a result, when the 23 slips of paper were prepared for the students to choose, 12 read “Computer
Dissection” and 11 read “Organic Frog Dissection.” In
all other ways, Class B was treated in exactly the same
manner as class A.
Since Class B was larger than class A, it was necessary
to set up 23 stations. Twelve slips of paper, 1.5 cm long
and 1 cm long, were cut and numbered 1-12 using a
Number 2 pencil. Dissecting pins were inserted through
the slips of paper. Each number was placed in organs in
one of 12 frogs. Each frog had a card placed next to it with
numbered questions on the card. Each number on the
index card had two questions. The questions were: Name
the organ, and What is the function of this organ? There
were also 11 stations with no frogs, but with an index card
labeled “Rest Station.” The dissecting pans containing the
FROG DISSECTION 409
B. The actual dissections were performed precisely the
same as well. However, the day after the lab practical
involving the preserved frogs, a second lab practical was
administered using the virtual dissection program. A digital projector was used to place the virtual images on a
screen, and the program highlighted the organ.
frogs were covered with Saran Wrap® to ensure that the
frogs would not dry out overnight.
At the beginning of class on the following day, the
Saran Wrap® was removed from the dissected frogs.
Each student was instructed to move to one of the 23
numbered stations. The students were instructed that
they would have two minutes at each station. When
time was called, the student was to move to the station
with the next highest number. When a student reached
station 23, he/she was to move to Station 1.
To analyze the data, a t test was used.
Results
Over a two-year period, four classes of AP Biology
students were tested, with a total of 74 students. Due to
budgetary and other restrictions, none of the students
had previously dissected a frog. The first year (two classes), students dissected either a real frog or a virtual frog,
then completed a lab practical using only real frogs. The
second year (two additional classes), students dissected
At the end of 50 minutes, the laboratory practicals
were collected and graded. The grades were recorded.
During Year Two, there were 18 students in Class C
and 15 students in Class D. Determination of who would
dissect real frogs and who would dissect virtual frogs was
handled exactly the same as it had been for Classes A and
Table 1.
Number of students tested, average class scores, and t test values (0.01 significance level) for students dissecting real and virtual frogs.
N
=
Average test score on
real frog lab practical
CLASS A Hypothesis:
Ho: x>x (null)
Ha: x<x (alternative)
Real frog dissection
Virtual frog dissection
9
9
70
60
-1.999
CLASS B Hypothesis:
Ho: x>x (null)
Ha: x<x (alternative)
Real frog dissection
Virtual frog dissection
11
12
73.9
66
-1.522
CLASS C Hypothesis:
Ho: x>x (null)
Ha: x<x (alternative)
Real frog dissection
Virtual frog dissection
Real frog dissection
Virtual frog dissection
9
9
9
9
78.88
68.44
-1.258
CLASS D Hypothesis:
Ho: x>x (null)
Ha: x<x (alternative)
Real frog dissection
Virtual frog dissection
Real frog dissection
Virtual frog dissection
7
8
7
8
84
78
410 THE AMERICAN BIOLOGY TEACHER, VOLUME 66, NO. 6, AUGUST 2004
Average test score on
virtual frog lab practical
79.22
78
t = (0.01
significance level)
+0.149
-1.935
85.57
83.125
+1.04
either a real frog or a virtual frog, and, following the dissection, were tested twice. The first test was a laboratory practical using real frogs. The second test was also a
laboratory practical, but utilized the virtual frogs. A t
test was performed on all classes at the 0.01 significance
level. The results of the t tests may be found in Table 1.
for students who, for ethical or emotional reasons,
absolutely refuse to work with an organic frog.
Additionally, computer graphics are improving constantly. It may not be long before three-dimensional
images are available with the same optical quality as
organic frogs.
Conclusions & Discussion
References
The t test value for Class A was -1.999, which indicates that students dissecting the preserved frog performed significantly better on the laboratory practical utilizing the preserved frog (1% chance of the null being
true). Again, the statistical analysis for Class B indicates
that students taking the laboratory practical after dissecting the organic frogs performed significantly better than
students taking the laboratory practical following dissecting the computer frogs. Classes C and D also performed
significantly better on the laboratory practical after having dissected the preserved frogs. The null hypothesis,
that there will be no significant difference in the performance of the students regardless of the method of dissection, was therefore rejected. The alternative hypothesis,
that students who dissect organic frogs will perform significantly better on the laboratory practical than students
who dissect the computer frogs was accepted.
Kinzie, M. (1993a). The effects of interactive dissection simulations on the performance and achievement of high school
biology students. Journal of Research in Science Teaching,
30(8), 989-1000.
The data in this experiment distinctly demonstrate
that the students who used the computer program did
not score as well in the laboratory practical as the students who used the organic frogs. This is clearly opposite to those results reported by Velle and Hall (1999).
However, it should be noted that Velle and Hall worked
with ninth grade students in a biology class, while this
study involved eleventh and twelfth grade students in
AP Biology classes. Since AP Biology is much more difficult than general biology, it is possible that the computer programs are more effective for general knowledge
than for advanced skills. Another difference was the
Velle and Hall study involved two different teachers
(one using computer dissection, the other used organic
frogs), while in this study the same teacher was responsible for teaching all the students.
Kinzie, M. (1993b). Use of dissection-related courseware by lowability high school students: A qualitative inquiry. Educational
Technology, Research and Development, 41(3), 87-101.
Lewis, O. (2001). Disgusted With Dissection. Available online at:
http://radford.edu/~archive/season04/vent/stories/
peta.htm.
McNeely, D. (2000). Dissection simulation. Available online at:
http://bioww.clemson.edu/biolab/dissect.html.
Orlans, F.B. (1988). Should students harm or destroy animal
life? The American Biology Teacher, 50,6-12.
Russo, R. (1997). Virtual labs. Journal of Computers in Math and
Science Teaching, 16(4), 577-582.
Velle, S. & Hal, T. (1999). Virtual Frog Dissection—Reality Check?
Available
online
at:
http://www.ofsd.k12.wi.us/
science/study/htm.
During the second year of this study, a second laboratory practical was administered to all students in
Classes C and D. This laboratory practical was administered using the virtual dissection program. There were
no significant differences in the virtual laboratory practical test scores between students who had dissected virtually and those who had dissected the preserved frogs.
Apparently students who dissect preserved frogs are
capable of transferring information to the virtual format, but that transfer of information does not occur
from virtual frog to preserved frog.
It cannot be concluded that computer dissections
should be completely rejected. They are excellent tools
FROG DISSECTION 411