Biology Vista
Biological Evolution
NOTES
Overview
Students investigate biological changes in species and the results of natural
selection by observing characteristics and behaviors of organisms and by
engaging in explorations of natural selection, variation, biodiversity, and
adaptation.
General Time Frame
9–10 lessons (50 minutes each)
Background Information for the Teacher
The Nature of Science and Scientific Theories
Science is a method of explaining the natural world. It assumes that anything
that can be observed or measured is amenable to scientific investigation.
Science also assumes that the universe operates according to regularities that
can be discovered and understood through scientific investigations. The testing
of various explanations of natural phenomena for their consistency with
empirical data is an essential part of the methodology of science. Explanations
that are not consistent with empirical evidence or cannot be tested empirically
are not a part of science. As a result, explanations of natural phenomena that
are not based on evidence but on myths, personal beliefs, religious values,
and superstitions are not scientific. Furthermore, because science is limited
to explaining natural phenomena through the use of empirical evidence, it
cannot provide religious or ultimate explanations.
The most important scientific explanations are called “theories.” In ordinary
speech, “theory” is often used to mean “guess” or “hunch,” whereas in
scientific terminology, a theory is a set of universal statements that explain
some aspect of the natural world. Theories are powerful tools. Scientists seek to
develop theories that
•
are firmly grounded in and based upon evidence;
•
are logically consistent with other well-established principles;
•
explain more than rival theories; and
•
have the potential to lead to new knowledge.
The body of scientific knowledge changes as new observations and discoveries
are made. Theories and other explanations change. New theories emerge, and
other theories are modified or discarded. Throughout this process, theories are
formulated and tested on the basis of evidence, internal consistency, and their
explanatory power.
The Charles A. Dana Center at UT Austin
1
Evolution as a Unifying Concept
NOTES
Evolution in the broadest sense can be defined as the idea that the universe
has a history: that change through time has taken place. If we look today at
the galaxies, stars, the planet Earth, and the life on planet Earth, we see that
things today are different from what they were in the past: galaxies, stars,
planets, and life forms have evolved. Biological evolution refers to the scientific
theory that living things share ancestors from which they have diverged; it is
called “descent with modification.” There is abundant and consistent evidence
from astronomy, physics, biochemistry, geochronology, geology, biology,
anthropology, and other sciences that evolution has taken place.
As such, evolution is a unifying concept for science. The National Science
Education Standards recognizes that conceptual schemes such as evolution
“unify science disciplines and provide students with powerful ideas to help
them understand the natural world” (p. 104) and recommends evolution as
one such scheme. In addition, Benchmarks for Science Literacy from AAAS’s
Project 2061, as well as other national calls for science reform, all name
evolution as a unifying concept because of its importance across the disciplines
of science. Scientific disciplines with a historical component, such as
astronomy, geology, biology, and anthropology, cannot be taught with integrity
if evolution is not emphasized.
There is no longer a debate among scientists about whether evolution has
taken place. There is considerable debate about how evolution has taken
place: What are the processes and mechanisms producing change, and what
has happened specifically during the history of the universe? Scientists often
disagree about their explanations. In any science, disagreements are subject
to rules of evaluation. Scientific conclusions are tested by experiment and
observation, and evolution, as with any aspect of theoretical science, is
continually open to and subject to experimental and observational testing.
The importance of evolution is summarized as follows in the National
Academy of Sciences publication Teaching about Evolution and the Nature of
Science: “Few other ideas in science have had such a far-reaching impact on
our thinking about ourselves and how we relate to the world” (p. 21).
Creationism and Other Non-Scientific Views
The National Science Education Standards note that, “[e]xplanations of how
the natural world changes based on myths, personal beliefs, religious values,
mystical inspiration, superstition, or authority may be personally useful and
socially relevant, but they are not scientific” (p. 201). Because science limits
itself to natural explanations and not religious or ultimate ones, science
teachers should neither advocate any religious interpretation of nature nor
assert that religious interpretations of nature are not possible.
The word “creationism” has many meanings. In its broadest meaning,
creationism is the idea that the universe is the consequence of something
transcendent. Thus to Christians, Jews, and Muslims, God created; to the
Navajo, the Hero Twins created; for Hindu Shaivites, the universe comes to
exist as Shiva dances. In a narrower sense, “creationism” has come to mean
“special creation”: the doctrine that the universe and all that is in it was
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Biology Institute – Fall 2004
created by God in essentially its present form, at one time. The most common
variety of special creationism asserts that
•
the Earth is very young;
•
life was created by God;
•
life appeared suddenly;
•
kinds of organisms have not changed since the creation; and
•
different life forms were designed to function in particular settings.
NOTES
This version of special creation is derived from a literal interpretation of
Biblical Genesis. It is a specific, sectarian religious belief that is not held by all
religious people. Many Christians and Jews believe that God created through
the process of evolution. Pope John Paul II, for example, issued a statement in
1996 that reiterated the Catholic position that God created and affirmed that
the evidence for evolution from many scientific fields is very strong.
“Creation science” is a religious effort to support special creationism through
methods of science. Teachers are often pressured to include it or other related
nonscientific views such as “abrupt appearance theory,” “initial complexity
theory,” “arguments against evolution,” or “intelligent design theory” when
they teach evolution. Scientific creationist claims have been discredited by
the available scientific evidence. They have no empirical power to explain
the natural world and its diverse phenomena. Instead, creationists seek
out supposed anomalies among many existing theories and accepted facts.
Furthermore, “creation science” claims do not lead to new discoveries of
scientific knowledge.
Legal Issues
Several judicial decisions have ruled on issues associated with the teaching of
evolution and the imposition of mandates that “creation science” be taught
when evolution is taught. The First Amendment of the Constitution requires
that public institutions such as schools be religiously neutral; because “creation
science” asserts a specific, sectarian religious view, it cannot be advocated in
the public schools.
When Arkansas passed a law requiring “equal time” for “creation science” and
evolution, the law was challenged in Federal District Court. Opponents of
the bill included the religious leaders of the United Methodist, Episcopalian,
Roman Catholic, African Methodist Episcopal, Presbyterian, and Southern
Baptist churches, along with several educational organizations. After a full trial,
the judge ruled that “creation science” did not qualify as a scientific theory
(McLean v. Arkansas Board of Education, 529 F. Supp. 1255 [ED Ark. 1982]).
Louisiana’s equal time law was challenged in court, and eventually reached
the Supreme Court. In Edwards v. Aguillard [482 U.S. 578 (1987)], the court
determined that “creation science” was inherently a religious idea and to
mandate or advocate it in the public schools would be unconstitutional. Other
court decisions have upheld the right of a district to require that a teacher
teach evolution and not teach “creation science” (Webster v. New Lennox
School District #122, 917 F.2d 1003 [7th Cir. 1990]; Peloza v. Capistrano
Unified School District, 37 F.3d 517 [9th Cir. 1994]).
The Charles A. Dana Center at UT Austin
3
NOTES
Some legislators and policy makers continue attempts to distort the teaching
of evolution through mandates that would require teachers to teach evolution
as “only a theory” or that require a textbook or lesson on evolution to be
preceded by a disclaimer. Regardless of the legal status of these mandates,
they are bad educational policy. Such policies have the effect of intimidating
teachers, which may result in the de-emphasis or omission of evolution. As
a consequence, the public will only be further confused about the nature of
scientific theories. Furthermore, if students learn less about evolution, science
literacy itself will suffer.
-- Adopted by the NSTA Board of Directors
July 2003
References
American Association for the Advancement of Science (AAAS), Project 2061.
(1993). Benchmarks for science literacy. New York: Oxford University Press.
Edwards v. Aguillard, 482 U.S. 578 (1987).
McLean v. Arkansas Board of Education, 529 F. Supp. 1255 (ED Ark. 1982).
National Academy of Sciences (NAS). (1998). Teaching about evolution and
the nature of science. Washington, DC: Steering Committee on Science and
Creationism, National Academy Press.
National Research Council. (1996). National science education standards.
Washington, DC: National Academy Press.
Peloza v. Capistrano Unified School District, 37 F.3d 517 (9th Cir. 1994).
Webster v. New Lennox School District #122, 917 F.2d 1003 (7th Cir. 1990).
Additional Resources
Laudan, Larry. (1996). Beyond positivism and relativism:Theory, method, and
evidence. Boulder, CO: Westview Press.
National Academy of Sciences (NAS). (1999). Science and creationism: A view
from the National Academy of Sciences, Second Edition. Washington, DC: National
Academy Press.
Ruse, Michael. (1996). But is it science:The philosophical question in the creation/
evolution controversy. Amherst, NY: Prometheus.
Skehan, James W., S.J., and Nelson, Craig E. (1993). The creation controversy and
the science classroom. Arlington,VA: National Science Teachers Association.
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Biology Institute – Fall 2004
Materials
Printed Materials included in this Vista:
NOTES
Biological Evolution Vista TEKS Correlation Chart
A Natural Selection investigation pages
Reptile line drawing
Horse Evolution for cards and sequence
Constructing an Electrophoresis Chamber
Investigating Electrophoresis investigation pages
Evolution Terminology Cards
Evolution Scenarios
The Lost Diversity of Easter Island investigation pages
Arthropods and More Arthropods investigation pages
What a Beak investigation pages
The Best Bess Beetles investigation pages
DNA Sequences for Hardware Fasteners
Nailing Evolution investigation pages
A Bear Branch in the Tree of Life investigation pages
Cats and Birds Assessment Task pages
Materials for the Teacher to Gather:
Each learning experience has a list of necessary equipment and materials.
However, it is not the intention of TEXTEAMS to dictate the types and
quantities of materials/equipment to use for the learning experiences. All the
materials/equipment that are listed in the learning experiences are suggestions.
Teacher’s notes give specific instructions for areas where the author has
experienced the need for a specific item. Substitutions for materials/
equipment should be based on local budgets, availability, and facilities.
Position Statement on the
Teaching of Evolution from the
National Science Teachers Association
Introduction
The National Science Teachers Association (NSTA) strongly supports the
position that evolution is a major unifying concept in science and should
be included in the K-12 science education frameworks and curricula.
Furthermore, if evolution is not taught, students will not achieve the level
of scientific literacy they need. This position is consistent with that of the
National Academies, the American Association for the Advancement of
Science (AAAS), and many other scientific and educational organizations.
NSTA also recognizes that evolution has not been emphasized in science
curricula in a manner commensurate to its importance because of official
policies, intimidation of science teachers, the general public’s misunderstanding
of evolutionary theory, and a century of controversy. In addition, teachers
The Charles A. Dana Center at UT Austin
5
NOTES
are being pressured to introduce creationism, “creation science,” and other
nonscientific views, which are intended to weaken or eliminate the teaching
of evolution.
Declarations
Within this context, NSTA recommends that
•
Science curricula, state science standards, and teachers should
emphasize evolution in a manner commensurate with its importance
as a unifying concept in science and its overall explanatory power.
•
Science teachers should not advocate any religious interpretations of
nature and should be nonjudgmental about the personal beliefs of
students.
•
Policy makers and administrators should not mandate policies
requiring the teaching of “creation science” or related concepts, such
as so-called “intelligent design,” “abrupt appearance,” and “arguments
against evolution.” Administrators also should support teachers against
pressure to promote nonscientific views or to diminish or eliminate
the study of evolution.
•
Administrators and school boards should provide support to teachers
as they review, adopt, and implement curricula that emphasize
evolution. This should include professional development to assist
teachers in teaching evolution in a comprehensive and professional
manner.
•
Parental and community involvement in establishing the goals of
science education and the curriculum development process should
be encouraged and nurtured in our democratic society. However,
the professional responsibility of science teachers and curriculum
specialists to provide students with quality science education should
not be compromised by censorship, pseudoscience, inconsistencies,
faulty scholarship, or unconstitutional mandates.
•
Science textbooks shall emphasize evolution as a unifying concept.
Publishers should not be required or volunteer to include disclaimers
in textbooks that distort or misrepresent the methodology of science
and the current body of knowledge concerning the nature and study
of evolution.
-- Adopted by the NSTA Board of Directors
July 2003
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Biology Institute – Fall 2004
Position Statement on the
Teaching of Evolution from the
National Science Teachers Association
NOTES
As stated in The American Biology Teacher by the eminent scientist
Theodosius Dobzhansky (1973), “Nothing in biology makes sense except in
the light of evolution.” This often-quoted declaration accurately reflects the
central, unifying role of evolution in biology. The theory of evolution provides
a framework that explains both the history of life and the ongoing adaptation
of organisms to environmental challenges and changes.
While modern biologists constantly study and deliberate the patterns,
mechanisms, and pace of evolution, they agree that all living things share
common ancestors. The fossil record and the diversity of extant organisms,
combined with modern techniques of molecular biology, taxonomy, and
geology, provide exhaustive examples of and powerful evidence for current
evolutionary theory. Genetic variation, natural selection, speciation, and
extinction are well-established components of modern evolutionary theory.
Explanations are constantly modified and refined as warranted by new
scientific evidence that accumulates over time, which demonstrates the
integrity and validity of the field.
Scientists have firmly established evolution as an important natural process.
Experimentation, logical analysis, and evidence-based revision are procedures
that clearly differentiate and separate science from other ways of knowing.
Explanations or ways of knowing that invoke non-naturalistic or supernatural
events or beings, whether called “creation science,” “scientific creationism,”
“intelligent design theory,” “young earth theory,” or similar designations, are
outside the realm of science and not part of a valid science curriculum.
The selection of topics covered in a biology curriculum should accurately
reflect the principles of biological science. Teaching biology in an effective
and scientifically honest manner requires that evolution be taught in a
standards-based instructional framework with effective classroom discussions
and laboratory experiences.
NABT endorses the following tenets of science, evolution, and biology
education. Teachers should take these tenets into account when teaching
evolution.
The Nature and Methods of Science
•
Scientists do science by asking questions, proposing and testing
hypotheses, and designing empirical models and conceptual
frameworks for research about natural events. Scientists use both
observations and inferences to gather evidence and draw conclusions
respectively; inferences are logical conclusions based on observations.
Conclusions generate additional hypothesis testing, which yields
further observations and inferences. Theories are ultimately proposed
to explain observations and inferences, predict consequences, and
solve scientific problems.
The Charles A. Dana Center at UT Austin
7
•
In science, a theory is an extensive explanation developed from welldocumented, reproducible sets of experimentally-derived data from
repeated observations of natural processes. Science does not base
theories on untestable dogmatic proposals or beliefs.
•
Scientific theories can be—and often are—modified and improved
as new empirical evidence is uncovered. Science is a constantly selfcorrecting endeavor to understand nature and natural phenomena.
•
The scientific study of evolution has both contemporary and
historical aspects. Scientists study contemporary processes directly
through observation and experiment. Scientists infer past processes
though the study of the historical record (for example, fossils and rock
strata) and contemporary results (for example, inferring past evolution
from the features of modern organisms.)
•
Evolutionary theory holds a unique prominence in biology and
science for its unifying properties and predictive features, the clear
empirical testability of its models, and the richness of new scientific
research it fosters.
NOTES
Essential Concepts of Biological Evolution
•
The diversity of life on earth is the outcome of biological evolution—
an unpredictable and natural process of descent with modification that
is affected by natural selection, mutation, genetic drift, migration and
other natural biological and geological forces.
•
Natural selection is the primary mechanism for evolutionary changes
and can be demonstrated both in the laboratory and in the wild. A
differential survival and reproduction of some genetic variants within
a population under an existing environmental state, natural selection
has no discernable direction or goal, including survival of a species.
•
Biological evolution refers to changes in populations, not individuals.
Changes must be successfully passed on to the next generation. This
means evolution results in heritable changes in a population across
many generations. In fact, evolution can be defined as any change in
the frequency of alleles within a gene pool from one generation to the
next.
Evolution in the Classroom
8
•
Evolution should be a recurrent theme throughout biology courses.
•
Teaching the principles and mechanisms of evolution across the
biology curriculumÅ\from molecular and cellular to organismal and
ecological levelsÅ\promotes a rational and coherent scientific account
of biology.
•
Science and religion differ in significant ways that make it
inappropriate to teach religious beliefs in the science classroom. To
contrast science with religion is not the role of science or science
education.
•
Teachers should respect diverse beliefs. Science teachers can, and
often do, hold devout religious beliefs, accept evolution as a valid
scientific theory, and teach the theory’s mechanisms and principles.
Students can maintain their religious beliefs and learn the scientific
foundations of evolution.
Biology Institute – Fall 2004
Legal Issues and Evolution Education
Teachers should teach good science with the acknowledged support of the
courts. For example, in Epperson v. Arkansas (1968), the U.S. Supreme Court
struck down a 1928 Arkansas law prohibiting the teaching of evolution in state
schools.
NOTES
In McLean v. Arkansas (1982), the federal district court invalidated a state
statute requiring equal classroom time for evolution and creationism. Edwards
v. Aguillard (1987) led to another Supreme Court ruling against so-called
“balanced treatment” of creation science and evolution in public schools.
Subsequent district and state court decisions in Illinois , Minnesota and
California have supported the right of a district to prohibit an individual
teacher from promoting creation science in the classroom. A Louisiana district
court has struck down a disclaimer on evolution that teachers had been
required to read to students before evolution was taught.
After the demise of “equal time” for creationism laws, teachers began to be
pressured to teach evolution and “evidence against evolution”. The “No Child
Left Behind” (NCLB) education bill signed into law in 2002 is presented by
antievolutionists as requiring that evolution be “balanced” with “weaknesses
in evolution” or “scientific evidence against evolution”. In the supporting
documentation that accompanies the bill, the NCLB contains a suggestion
that “… the curriculum should help students to understand the full range
of scientific views that exists, why such topics may generate controversy, and
how scientific discoveries profoundly affect society.” Called the “Santorum
Language” named after the Senator who proposed an earlier version of the
statement, this recommendation refers generally to controversial issues, with
evolution only presented as an example of a controversial issue. There is
nothing in NCLB that requires the teaching of any specific subject, or that
evolution or any specific subject be taught in any particular way. There is no
warrant for teaching “weaknesses in evolution” because of the NCLB.
All teachers and administrators should be mindful of these legal issues,
remembering that the law, science and NABT support them as they
appropriately include the teaching of evolution in the science curriculum.
Suggested Readings
Aguillard, D. (1999). Evolution education in Louisiana public schools: a decade
following Edwards V. Aguillard.The American Biology Teacher, 61, pp. 182-188.
Dobzhansky, T. (1973). Nothing in biology makes sense except in the light of
evolution. The American Biology Teacher, 35, pp. 125-129.
Freeman, S. and Herron, J.C. (2000). Evolutionary Analysis, 2nd ed. Englewood
Cliffs, NJ. Prentice Hall.
Futuyma, D. , Meagher, Tom, et. al. (2000) Evolution, Science, and
Society, Evolutionay Biology and the National Research Agenda. http://
www.rci.rutgers.edu/~ecolevol/fulldoc.pdf
Futuyma, D. (1998). Evolutionary Biology, 3rd ed. Sunderland, MA : Sinauer
Associates, Inc.
The Charles A. Dana Center at UT Austin
9
Futuyma, D. (1995). Science on Trial. Sunderland, MA : Sinauer Associates, Inc.
NOTES
Gillis, A. (1994). Keeping creationism out of the classroom. Bioscience, 44,
pp. 650-656.
Gould, S. (1994, October). The evolution of life on earth. Scientific American,
271, pp. 85-91.
Kiklas, K. (1997). The Evolutionary Biology of Plants. Chicago: The University of
Chicago Press.
Matsumura, M. (Ed.). (1995). Voices for Evolution. Berkeley, CA : The National
Center for Science Education.
Mayr, E. (2001). What Evolution Is. New York, NY : Basic Books.
Moore, J. (1993). Science as a Way of Knowing\The Foundations of Modern Biology.
Cambridge, MA : Harvard University Press.
Moore, R. (1999). Creationism in the United States:VII.The Lingering Threat.
The American Biology Teacher, 61, pp. 330-340. See also references therein to
earlier articles in the series.
National Academy of Sciences. (1998). Teaching About Evolution and the Nature
of Science. Washington, DC : National Academy Press.
National Academy of Sciences. (1999). Science and Creationism—A View from the
National Academy of Sciences. Washington, DC : National Academy Press.
National Center for Science Education. P.O. Box 9477 , Berkeley, CA 94709 .
Numerous publications including NCSE Reports.
National Research Council. (1996). National Science Education Standards.
Washington, DC : National Academy Press.
Pennock, R.T. (1999). Tower of Babel :The Evidence Against the New Creationism.
Cambridge, MA : MIT Press.
Weiner, J. (1994). Beak of the FinchÅ\A Story of Evolution in our Time. New
York : Alfred A. Knopf.
Zimmer, C. (2001). Evolution: The Triumph of an Idea. New York : Harper
Collins Publishers.
Adopted by the NABT Board of Directors, 1995. Revised 1997, 2000, and May
2004. Endorsed by: The Society for the Study of Evolution, 1998; The American
Association of Physical Anthropologists, 1998.
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Biology Institute – Fall 2004
Guidelines for Responsible
Use of Animals in the Classroom
NOTES
These guidelines are recommended by the National Science Teachers
Association for use by science educators and students. They apply, in particular,
to the use of nonhuman animals in instructional activities planned and/or
supervised by teachers who teach science at the precollege level.
Observation and experimentation with living organisms give students
unique perspectives of life processes that are not provided by other modes
of instruction. Studying animals in the classroom enables students to
develop skills of observation and comparison, a sense of stewardship, and
an appreciation for the unity, interrelationships, and complexity of life. This
study, however, requires appropriate, humane care of the organism. Teachers
are expected to be knowledgeable about the proper care of organisms under
study and the safety of their students. These are the guidelines recommended
by NSTA concerning the responsible use of animals in a school classroom
laboratory:
•
Acquisition and care of animals must be appropriate to the species.
•
Student classwork and science projects involving animals must
be under the supervision of a science teacher or other trained
professional.
•
Teachers sponsoring or supervising the use of animals in instructional
activities--including acquisition, care, and disposition--will adhere to
local, state, and national laws, policies, and regulations regarding the
organisms.
•
Teachers must instruct students on safety precautions for handling live
animals or animal specimens.
•
Plans for the future care or disposition of animals at the conclusion of
the study must be developed and implemented.
•
Laboratory and dissection activities must be conducted with
consideration and appreciation for the organism.
•
Laboratory and dissection activities must be conducted in a clean and
organized work space with care and laboratory precision.
•
Laboratory and dissection activities must be based on carefully
planned objectives.
•
Laboratory and dissection objectives must be appropriate to the
maturity level of the student.
•
Student views or beliefs sensitive to dissection must be considered; the
teacher will respond appropriately.
-- Adopted by the Board of Directors
July 1991
The Charles A. Dana Center at UT Austin
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Biology
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Biology Institute – Fall 2004
Biology
The Charles A. Dana Center at UT Austin
13
NOTES
A Natural Selection
Learning Experience 1
Description:
This learning experience is designed to help students understand the TEKS
concept of how adaptation may be a factor in natural selection.
Grade 6
6.11 (A)
Grade 7
7.10 (B)
Grade 8
Biology
8.11 (A)(C)
7 (A)(B)
Time Frame:
50 minutes
Materials:
Construction paper (1 sheet each of 3 different colors, see Advance
Preparation)
Hole punch (1 per teacher)
Zipper-type sandwich bags (5 per student group)
Fabric, 50 cm (1 length per student group, see Advance Preparation)
Colored pencils (3 different colors per student group to match the
construction paper)
Timer (1 per class)
Computer (1 per student group)
Peppered moth animation (http://www.utdanacenter.org/texteams/
downloads/scienceresources/pradeep_fla.swf)
Graph paper (1–2 sheets per student group)
A Natural Selection investigation pages (included in the Student Blackline
Masters at the end of this vista)
Advance Preparation:
1. Select two different patterned fabrics to simulate two different natural
environments. Each fabric should have several different colors and
intricate designs. Floral, fruit, and foliage prints work well. One fabric
should be designated as A and the other as B, with half of the student
groups receiving A and the other half receiving B.
2. Punch paper dots from 3 different colors of construction paper. The
dots represent the “organisms” in this simulation. Select dark, medium,
and light colors so that they will contrast with each other. One of the
dot colors should blend well with both fabrics. Colored rice grains,
pony beads, or aquarium gravel can replace the paper dots in this
learning experience.
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Biology Institute – Fall 2004
SAFETY: If rice, beads or gravel are used, remind students to keep them off
the floor to prevent someone from slipping.
NOTES
3. Each student group gets five sandwich bags. One bag has 20 dots
each of one color, for a total of 60 dots. Label this bag “Beginning
Population.” Three bags have 100 dots each of one color. Label these
bags “Offspring.” One bag is empty and is labeled “Survivors and
Their Offspring.”
4. The teacher may want to consider increasing or decreasing the time
interval for feeding or the number of predators.
5. Prepare a copy of the A Natural Selection investigation pages for each
student group.
Background Information for the Teacher:
Students often think that an organism adapts to its environment. Rather, an
organism possessing successful adaptations to an environment will survive,
reproduce, and become the parents of the next generation.
The process of evolution is dependent upon genetic variation within a
population as well as upon the events of natural selection. Genetic variations
are the results of changes in the genome of a population due to genetic
recombination, gene flow, and mutations. The differential survival and
reproduction of organisms is due to a variety of environmental factors, such as
predator-prey interactions, resource shortages, and changes in environmental
conditions.
A classic example dates from the 1800s when a light, speckled form of
the moth Biston betularia was found throughout England. This evidence is
confirmed in butterfly collections of that period. Around the middle of the
1800s, the first record of a dark form of the moth was found near Manchester.
With the advent of the Industrial Revolution, the rarely occurring dark moth
became increasingly abundant in the highly industrialized areas, while the light
moth dominated in unpolluted areas.
As early as 1837, E.B. Ford suggested that the coloration of the light moth
offered a selective advantage in an environment of low or no industrial
pollution. In such an environment, the light moth blended well with light
gray lichens found on the trunks of many trees. This particular advantage
of camouflage coloration allowed the light moth to avoid detection by
bird predators. However, the dark form of the moth would not enjoy this
coloration advantage (i.e., a dark moth on a light colored tree) and would be
more easily seen and thus devoured by bird predators. However, in areas highly
affected by industrial pollution, the selective advantage would change to favor
the dark form of the moth, i.e., a dark moth on a tree darkened by industrial
pollution being more difficult to detect than a light form of the moth on a
dark tree.
In the 1950s, H.B.D. Kettlewell decided to test the hypothesis that different
forms of the moth showed different levels of fitness. To test his hypothesis,
Kettlewell marked both light and dark forms of the moth and released them
The Charles A. Dana Center at UT Austin
15
NOTES
into polluted and non-polluted forests. He then recaptured the moths and
found the following results (Kettlewell, 1955; Kettlewell, 1956).
Polluted Forest
Moth Form
Released
Captured
Percent
Recaptured
Dark
447
123
27.50
Light
137
18
13.00
Moth Form
Released
Captured
Percent
Recaptured
Dark
406
19
4.68
Light
393
54
13.74
Unpolluted Forest
Based on the results of this investigation, Kettlewell asserted that the light
form of the moth enjoyed increased fitness in areas where the forests were
unpolluted, while the dark form of the moth was more fit in areas where
industrial pollution was high.
Kettlewell designed another investigation where he released light and dark
moths in polluted and unpolluted forests, and then observed birds foraging
for food such as insects and the moths. The observations were made from a
concealed structure near where the moths were released. Kettlewell found that
the birds easily detected moths that contrasted with the tree trunks but did not
easily detect moths whose coloring blended with the tree trunks.
It is important to note that while Kettlewell’s studies demonstrate how the
process of natural selection results in changing the frequencies of light and
dark moths over a period of time, it is an oversimplification to conclude
that bird predation is the only possible variable involved. After all, there are
studies that show populations of dark moths predominating in areas with no
industrial pollution. Also, most populations of moths in Britain have high or
low frequencies of light or dark coloration. Indeed, the dark form of the moth
may be physiologically more viable than the light form (Creed, et al., 1980).
According to the Creed study, once the selection process reaches a certain
point, the frequency of the dark moth changes from low to high.
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Biology Institute – Fall 2004
References
Creed, E. R., D. R. Lees, and M. G. Bulmer. “Pre-adult Viability Differences of
Melanic Biston betularia (L.) Lepidoptera.” Biological Journal of the Linnean Society
13 (1980): 25–62.
NOTES
Ford, E. B. “Problems of Heredity in the Lepidoptera.” Biological Review 12
(1937): 271–503.
Kettlewell, H. B. D. “Selection Experiments on Industrial Melanism in the
Lepidoptera.” Heredity 9 (1955): 323–342.
Kettlewell, H. B. D. “Further Selection Experiments on Industrial Melanism in
the Lepidoptera.” Heredity 10 (1956): 287–301.
Kettlewell, H. B. D. “A Survey of the Frequencies of Biston betularia (L.) (Lep.)
and its Melanic Forms in Great Britain.” Heredity 12 (1958): 51–72.
Rudge, David W. “Does being wrong make Kettlewell wrong for science
teaching?” Journal of Biological Education 35 (2000): 5–11.
Procedures:
1. Ask students to predict what will occur when predators hunt for prey
that have camouflaged coloring.
2. Have students complete the A Natural Selection investigation pages.
Formative Assessment: Monitor student responses to the investigation
pages. Be sure to reinforce that the survivors with the favorable characteristics
will survive to reproduce; over time, any adaptations that have been selected
will occur in the population.
A Natural Selection investigation pages (correct student
responses)
1. What do the dots represent in this simulation? [Prey]
2. Who were the predators? [Students]
3. What represents the natural selection pressure? [Predation]
4. What is the adaptation mechanism of the prey? [Blending into the
background and being less visible to predators; camouflage]
5. Which color of dots increased in frequency and why did this happen?
[The colors that blend in with the background are less visible to the predators.]
6. Which color of dots decreased in frequency and why did this happen?
[The colors that do not blend in with the fabric are more easily seen.]
7. If the dots were real organisms, what color would the parents of the
fifth generation most likely be? [The answer will depend upon the color
scheme of the fabric used.Those organisms that blend in with the background
and are able to hide from predators will live longer and be more likely to
reproduce.]
8. Predict what you think would happen if this simulation were to
continue for three more generations. [The most frequent dot color would
increase in frequency in subsequent generations.]
The Charles A. Dana Center at UT Austin
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NOTES
9. View the Peppered Moth Animation, complete Data Table II and
construct a graph of the changes in moth numbers.
Data Table II
18
Year
Number
of Lightcolored
Moths
Number
of Darkcolored
Moths
2
537
112
4
392
210
6
225
357
8
147
503
10
56
638
Biology Institute – Fall 2004
A Natural Selection
This investigation is designed to help you understand how adaptation is a factor in natural selection.
Materials:
One plastic sandwich bag labeled “Beginning Population,” one bag labeled “Survivors and Their Offspring,” three bags
labeled “Offspring,” fabric, three colored pencils, graph paper
Procedures:
1. Spread your fabric “habitat” on a flat surface.
2. Select a game warden and a recorder. The rest of the group will serve as predators.
3. While the predators have their backs turned, the game warden distributes the dots from the Beginning
Population bag across the habitat.
4. When the game warden says, “Go!” the predators should turn around, face the habitat, and pick up as many
prey (dots) as they can in a 10-second interval. PREDATORS CAN PICK UP ONLY ONE DOT AT A
TIME, USING ONLY ONE HAND. The game warden should monitor that no scooping or grabbing of
several dots occurs.
5. After Predation I is completed, students should gather the surviving dots and sort and count them by color.
The recorder enters the number of Surviving Predation I dots by color in Data Table I. Dots picked up during
Predation I should be returned to the Beginning Population bag.
Data Table I
Dot
Color
Beginning
Population
Surviving
Predation
I
Offspring
I
Surviving
Predation
II
Offspring
II
Surviving
Offspring III
Predation III
20
20
20
6. Place the Surviving Predation I dots in the Survivors and Their Offspring bag.
7. Simulate the reproduction of each Surviving Predation I dot by selecting from the Offspring bags one dot of
the same color as the survivors and placing them in the Survivors and Their Offspring bag. Record the total
number of each color of offspring in the Offspring I column of Data Table I.
8. While the predators turn their backs, the game warden distributes the dots from the Survivors and Their
Offspring bag across the habitat.
9. When the game warden says, “Go!” the predators should turn around, face the habitat, and pick up as many
prey (dots) as they can in a 10-second interval. PREDATORS CAN PICK UP ONLY ONE DOT AT A
TIME, USING ONLY ONE HAND. The game warden should monitor that no scooping or grabbing of
several dots occurs.
The Charles A. Dana Center at UT Austin
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10. After Predation II is completed, students should gather the surviving dots and sort and count them by color.
The recorder enters the number of Surviving Predation II dots by color in Data Table I. Dots picked up during
Predation II should be returned to the Beginning Population bag.
11. Place the Surviving Predation II dots in the Survivors and Their Offspring bag.
12. Simulate the reproduction of each Surviving Predation II dot by selecting from the Offspring bags one dot of
the same color as the survivors and placing them in the Survivors and Their Offspring bag. Record the total
number of each color of offspring in the Offspring II column of Data Table I.
13. While the predators turn their backs, the game warden distributes the dots from the Survivors and Their
Offspring bag across the habitat.
14. When the game warden says, “Go!” the predators should turn around, face the habitat, and pick up as many
prey (dots) as they can in a 10-second interval. PREDATORS CAN PICK UP ONLY ONE DOT AT A
TIME, USING ONLY ONE HAND. The game warden should monitor that no scooping or grabbing of
several dots occurs.
15. After Predation III is completed, students should gather the surviving dots and sort and count them by color.
The recorder enters the number of Surviving Predation III dots by color in Data Table I. Dots picked up during
Predation III should be returned to the Beginning Population bag.
16. Place the Surviving Predation III dots in the Survivors and Their Offspring bag.
17. Simulate the reproduction of each Surviving Predation III dot by selecting from the Offspring bags one dot of
the same color as the survivors and placing them in the Survivors and Their Offspring bag. Record the total
number of each color of offspring in the Offspring III column of Data Table I.
18. Construct a bar graph showing the changes from the original population to Offspring I, II, and III.
Discussion:
1. What do the dots represent in this simulation?
2. Who were the predators?
3. What represents the natural selection pressure?
4. What is the adaptation mechanism of the prey?
5. Which color of dots increased in frequency and why did this happen?
6. Which color of dots decreased in frequency and why did this happen?
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Biology Institute – Fall 2004
7. If the dots were real organisms, what color would the parents of the fifth generation most likely be?
8. Predict what you think would happen if this simulation were to continue for three more generations.
9. View the Peppered Moth Animation, complete Data Table II and construct a graph of the changes in moth
numbers.
Data Table II
Year
Number of
Light-colored
Moths
Number of
Dark-colored
Moths
2
4
6
8
10
The Charles A. Dana Center at UT Austin
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NOTES
Change by Chance
Learning Experience 2
Description:
This learning experience is designed to help students understand the TEKS
concept of how fossil organisms can be used to identify evidence of change in
species.
Grade 6
Grade 7
Grade 8
Biology
6.11 (A)
7.10 (A)(B)
8.11 (A)(C)
7 (B)
Time Frame:
15–50 minutes
Materials:
Timer (1 per class)
Blank white unlined paper (1 sheet per student)
Reptile line drawing (included in the Teacher Blackline Masters
at the end of this vista)
Horse Evolution and sequence cards (included in the Teacher Blackline
Masters at the end of this vista)
Advance Preparation:
1. This learning experience should be conducted in large groups
of about 5–10 students per group, but the assessment should be
completed with smaller groups.
2. Prepare a copy of the reptile drawing for each student group.
3. Prepare a set of Horse Evolution cards for each student group to use
in the assessment. Photocopy the Horse Evolution cards on heavyweight paper. Cut along the dark lines and shuffle the cards in each
set.
4. Prepare a transparency of the Horse Evolution sequence.
Procedures:
1. Arrange each student group in a line, one student behind the other.
Each student should have a blank sheet of paper and a pencil.
2. Give the first student in each row a copy of the reptile drawing. The
drawing should be face down until the signal to begin is given.
3. The teacher signals the beginning and end of each 15-second interval.
4. Give the first student in each line 15 seconds to draw, not trace, the
reptile on the blank paper. At the end of the 15 seconds, have each
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Biology Institute – Fall 2004
student pass his or her drawing to the second person in the line, and
give the original of the reptile drawing back to the teacher.
NOTES
5. Give the second student in each row 15 seconds to draw, not trace,
the first student’s reptile drawing on his or her own paper. At the end
of the 15 seconds, the second students pass their drawings to the third
students, and so on until all students in a group have had a chance to
draw the reptile.
6. Have each group label all of their drawings with a group name, mix
the order, and place them together. Collect each group’s drawings and
redistribute each set to a different group. Have groups sequence the
order of the drawings and then tape them on the wall.
7. Have original groups confirm the accuracy of the sequencing.
8. Ask: Why was sequencing the drawings difficult? How was this
experience similar to sequencing fossil records? How was this
experience different from sequencing fossil records?
Formative Assessment: This assessment should be completed by very small
groups of students. Distribute the Horse Evolution cards and have students
place the cards in an evolutionary sequence and justify their reasoning.
Explanations should include statements about changes in the shape and size of
the skull and changes in the structure of the leg. When students are finished,
show them the Horse Evolution sequence transparency.
The Charles A. Dana Center at UT Austin
23
NOTES
Investigating
Electrophoresis
Learning Experience 3
LEARNING EXPERIENCE 3
Description:
This learning experience is designed to help students understand the TEKS
concept of how DNA sequencing can be used to identify evidence of change
in species.
Grade 6
6.11 (A)
Grade 7
7.10 (B)
Grade 8
Biology
8.11 (A)(C)
7 (A)(B)
Time Frame:
50 minutes
Materials:
Agarose (1.2 g per student group)
Electrophoresis buffer (3 L per student group)
Electrophoresis chamber with power source (1 per class or student group
depending on school equipment)
Balance (1 per student group)
Flask, 250 ml (1 per student group)
Graduated cylinder, 100 ml (1 per student group)
Microwave (1 for the class)
Gloves or hot pads
Masking tape (1 roll for the class)
Gel casting tray (1 per student group)
Gel comb (1 per student group)
Microcentrifuge tubes (4 per student group)
Food coloring (1 bottle of green, blue, and red per class)
Glycerin (5 mL for the class)
Needle point pipettes (4 per student group)
Clear plastic wrap (about 15 cm square per student group)
Unlined white paper (1 page per student group)
Colored pencils (1 green, blue, and red per student group)
Metric ruler (1 per student group)
Safety Goggles (1 pair per student)
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Biology Institute – Fall 2004
Laboratory apron (1 per student)
Constructing an Electrophoresis Chamber (included in the Teacher
Blackline Masters at the end of this vista)
NOTES
Investigating Electrophoresis investigation pages (included in the Student
Blackline Masters at the end of this vista)
Advance Preparation:
1. Prepare one tube of each of the following for each student group.
•
0.5 mL red food coloring, 0.5 mL blue food coloring, and two
drops of glycerin. Shake well. The glycerin adds weight to the
sample. Label this tube “Unknown Horse.”
•
1 mL blue food coloring and two drops of glycerin. Shake well.
Label this tube “Miocene Horse.”
•
0.5 mL red food coloring, 0.5 mL blue food coloring, and two
drops of glycerin. Shake well. Label this tube “Pliocene Horse.”
•
0.5 mL blue and 0.5 ml green food coloring and two drops of
glycerin. Shake well. Label this tube “Holocene Horse.”
2. There are several options for preparing the agarose and the gels.
Students can prepare the agarose gel using the procedures in the Food
Coloring Electrophoresis investigation pages. Alternately, the agarose
can be prepared in advance with the students pouring the gels, or
the agarose can be prepared in advance and the gels poured prior to
this investigation. If so, the gels can be stored in plastic bags in a small
amount of buffer for several days in a refrigerator.
3. Prepare the buffer according to the supplier’s directions. Typically,
electrophoresis buffer is sold as a concentrate that has to be diluted. If
no buffer is available, a suitable substitute can be prepared using 0.05 g
of salt per liter of distilled water.
4. Prepare a copy of the Investigating Electrophoresis investigation pages
for each student group.
Procedures:
SAFETY: Caution students about the danger of chemical splashes. Students
must wear safety goggles and chemical-resistant aprons during this activity.
All chemicals must be disposed of properly. (See Texas Safety Standards for
Kindergarten–Grade 12).
Have students complete the Investigating Electrophoresis investigation pages.
Formative Assessment: Monitor the accuracy and reasonableness of student
responses to the Investigating Electrophoresis investigation pages.
The Charles A. Dana Center at UT Austin
25
NOTES
Investigating Electrophoresis investigation pages
(possible student responses):
1. Which horse(s) can be eliminated as being closely related to the
Unknown Horse? [2 and 3]
2. Which horse(s) cannot be eliminated as being closely related to the
Unknown Horse? [1]
3. DNA electrophoresis uses a matrix composed of a highly purified
form of agar to separate DNA molecules according to size. The DNA
molecules of organisms contain specific sites known as restriction sites
that, when exposed to restriction enzymes, will produce fragments of
DNA that vary in size. These various sized fragments of DNA separate
and appear as bands on an electrophoresis gel. The samples used in
your gel were actually food coloring rather than real DNA. How does
the separation of the mixture of the dye color molecules compare
with actual DNA separation?[The molecules in the dye separate according
to the different size of the molecules. Heavier molecules separate out first.
Similarily, the DNA fragments separate on the gel according to their size.]
4. What are some uses for electrophoresis in addition to criminal
investigations? [disorder diagnosis, paternity cases, identity cases, and research
such as establishing evolutionary relatedness]
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Biology Institute – Fall 2004
Constructing an Electrophoresis
Chamber
An electrophoresis chamber can be used to separate the molecules of a test solution and to spread them out in a distinct
pattern. The chamber holds a buffer solution and a special gel inoculated with a test solution. The gel is subjected to
an electrical field. Negatively charged molecules of the solution within the gel will move toward the positive electrode,
while positively charged molecules will move toward the negative electrode. The patterns the molecules make are used
to compare unknown substances to a known substance.
Materials:
1 pint rectangular plastic container (3” X 6”)
10 gauge wire
2 alligator clips
Plexiglas® – cut to fit inside container
Clear silicone
5 9-volt batteries
Electrical tape
Drill and 1/8-inch drill bit
Procedures:
1. Drill a 1/8-inch hole below and a little to the side of each handle at the ends of the container.
2. Cut 2 six-inch lengths of wire and strip two inches off one end of each length.
3. Insert the two inches of stripped wire into the drilled holes and secure with silicone.
The Charles A. Dana Center at UT Austin
27
4. Attach the alligator clips to the opposite ends of the wires.
5. Place the piece of pre-cut Plexiglas® onto several drops of silicone on the bottom ends of the container.
6. Connect the five batteries + to - and tape together.
7. When ready to run a gel, connect one of the alligator clips to the battery’s positive terminal and the other
alligator clip to the negative terminal.
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Biology Institute – Fall 2004
A Horse—of Course:
Investigating Electrophoresis
This investigation is designed to help you understand how DNA sequencing can be used to identify evidence of
change in species.
The Problem
While on an archeological field investigation at the La Brea Tar Pits in California, you discover the partial remains of
an animal. One scientist suggests that the remains are from a prehistoric horse. His colleague disagrees. She suggests that
the remains were not buried deep enough to be that of a prehistoric horse and is probably related to modern horses.
The university’s lab contains samples of DNA from several prehistoric horses as well as a modern horse. The scientists
have assigned you the task to determine how related the Unknown Horse is to the other horses.
The DNA sample from the remains will be placed in a special gel and subjected to an electric field. The parts of
the sample bearing a negative charge will move toward the positive electrode while the parts of the sample bearing
a positive charge will move toward the negative electrode. This separation creates a distinctive pattern that can be
matched to known samples. Thus, you will compare the results from the Unknown Horse sample to the DNA samples
of the known horses.You can also tell the size of molecules because of the distance they move. Larger molecules move
more slowly; therefore, less distance. Smaller molecules move more quickly and over a greater distance. This helps to
match patterns in the gel.
Electrophoresis is often used in forensic investigations because it can provide useful genetic information in criminal
cases. Samples of blood, skin, and hair can be analyzed through this technique. It is also used in the diagnosis of
disorders, paternity cases, and a variety of research areas. For example, evolutionary biologists use this type of
information to compare similarities and differences among species.
Materials:
1.2 g agarose, 3 L electrophoresis buffer, electrophoresis chamber, balance, 250 mL flask, 100 ml graduated cylinder,
microwave, gloves or hot pads, masking tape, gel casting tray, gel comb, samples from Pliocene Horse, Miocene horse,
Holocene Horse, Unknown Horse, needle point pipettes, power source, plastic wrap, unlined white paper, colored
pencils, metric ruler, safety goggles, laboratory aprons
Procedures:
SAFETY: Caution students about the danger of chemical splashes. Students must wear safety goggles and chemicalresistant aprons during this activity. All chemicals must be disposed of properly. (See Texas Safety Standards for
Kindergarten–Grade 12).
1. Prepare the gel by combining 1.2 grams of agarose and 98.8 mL of buffer solution in a 250 mL flask. Swirl the
flask to dissolve any lumps. Heat the mixture in the microwave until it comes to a boil. Using gloves or hot
pads, open the microwave and swirl the flask without removing it from the microwave. After swirling, remove
the flask and look at the contents. If you can see clear agarose particles in the solution, return the flask to the
microwave and repeat the boiling and swirling process until you can no longer see the agarose particles.
2. Cool the agarose until you can comfortably touch the flask.
The Charles A. Dana Center at UT Austin
29
3. Pressing firmly, place the masking tape on both ends of the casting tray to hold the liquid agarose in place as it
solidifies. Then place the comb in its slots on the casting tray.
4. Pour the cooled agarose into the tray. The agarose should come at least two-thirds of the way up the comb
teeth. Small pockets, called wells, will form where the comb is inserted in the agarose. The samples of DNA will
be placed in these pockets.
5. When the agarose has solidified, the comb and the tape should be gently removed.
6. Measure 5 microliters of each DNA sample into the tip end of the needlepoint pipette, being sure to use a fresh
pipette each time. Load the 5 microliter samples into separate wells on the gel, skipping a well between each of
the samples.
7. Record the order of the DNA samples by sketching the gel in the drawing below and labeling the wells with
the names of the samples.
8. Pour enough buffer in the electrophoresis chamber to fill the chamber and completely cover the gel. Place
the gel on the platform inside the electrophoresis chamber. Check the buffer level and add additional buffer
if needed to completely submerse the gel. Make sure that the filled wells are closest to the negative (black)
electrode.
9. Place the lid on the electrophoresis chamber and connect the black lead of the power source to the negative
terminal and the red lead to the positive terminal. Turn on the power supply and adjust the voltage to 100-125
volts.
10. After the gel has run for 5-10 minutes, remove the lid and observe the samples. The separation of colors should
have started. Replace the lid and allow the gel to run for a total of 10-15 more minutes. After the gel has run
for 20-25 minutes, turn off the power supply, disconnect the electrode leads, and remove the chamber lid.
Remove the gel from the casting tray and place it on a piece of clear plastic wrap that is laying on top of a piece
of white unlined paper.
11. Observe the color separation. Measure the distance that each color has migrated from its origin. Record your
observations by sketching them onto the gel diagram below. Be sure to label which sample is which and include
your measurements.
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Biology Institute – Fall 2004
Discussion:
1. Which horse(s) can be eliminated as being closely related to the Unknown Horse?
2. Which horse(s) cannot be eliminated as being closely related to the Unknown Horse?
3. DNA electrophoresis uses a matrix composed of a highly purified form of agar to separate DNA molecules
according to size. The DNA molecules of organisms contain specific sites known as restriction sites that, when
exposed to restriction enzymes, will produce fragments of DNA that vary in size. These various sized fragments
of DNA separate and appear as bands on an electrophoresis gel. The samples used in your gel were actually food
coloring rather than real DNA. How does the separation of the mixture of the dye color molecules compare
with actual DNA separation?
4. What are some uses for electrophoresis in addition to criminal investigations?
The Charles A. Dana Center at UT Austin
31
NOTES
Evolution Terminology
XPERIENCE
Learning Experience 4
Description:
This learning experience is designed to help students use terms associated
with biological evolution appropriately and apply them to real world
situations.
Grade 6
Grade 7
Grade 8
Biology
6.11 (A)
7.10 (A)(B)
8.11 (A)(C)
7 (A)
Time Frame:
50 minutes
Materials:
Evolution Terminology Cards (included in the Teacher Blackline Masters
at the end of this vista)
Evolution Scenarios (included in the Student Blackline Masters at the end
of this vista)
Advance Preparation:
1. Prepare a set of Evolution Terminology Cards for each student group.
Photocopy the cards on heavy-weight paper. Cut along the dark lines
and shuffle the cards in each set.
2. Prepare a copy of the Evolution Scenarios for each student group.
Background Information for the Teacher:
Terms used in understanding evolution and its related processes can be
confusing to students. Listed below are the evolution-related terms used in this
vista.
Adaptation.
The alteration of a body structure, behavior, or function
that makes an organism more successful in surviving to
reproduce.
Biodiversity.
The variety and number of species in a biological
community.
Evolution.
The changes seen in life forms over long periods of
time.
Extinction.
The dying out of a species.
Natural Selection. Differential reproductive success of phenotypes resulting
from interaction with the environment. (Phenotypes
favored by the environment are successful in producing
offspring.)
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Biology Institute – Fall 2004
Phylogeny.
The evolutionary history of a species.
Speciation.
The evolving of new species.
Species.
A group of individuals with similar anatomical
characteristics who are capable of interbreeding to
produce fertile offspring.
Variation.
The differences in characteristics among individuals of a
species.
NOTES
Procedures:
1. Distribute the Evolution Terminology Cards and have students
assemble the puzzle. The puzzle pieces fit together to match either the
evolutionary term and its definition, or the evolutionary term and an
example.
2. When students have had sufficient time to assemble their puzzles, ask
them to describe their process.
3. Have students complete the Evolution scenarios using their assembled
Evolution Terminology cards.
Formative Assessment: Monitor students as they assemble their puzzles and
redirect them as needed. Monitor students’ responses to the Scenarios; since
other accurate responses are possible. However, students should give reasonable
explanations.
Word Wall:
Students can create Verbal-Visual Word Association Cards for each of the
vocabulary terms from the activity.
Teacher note: Verbal-Visual Word Association Card directions:
1.
Divide a sheet of paper or a note card into four sections.
2.
Write the vocabulary word in the top left-hand corner and its
definition in the bottom left-hand corner.
3.
Draw a picture associated with a personal connection in the top
right-hand corner.
4.
Provide a non-example or sentence using the word in the
bottom right-hand corner.
The Charles A. Dana Center at UT Austin
33
34
WORD
PICTURE
DEFINITION
NON-EXAMPLE
Biology Institute – Fall 2004
Adaptation
Extinction
Example: The length of the
abdomen in adult beetles
vaires an average of 1.5 mm.
Evolution
Example: The dodo bird
(Raphus cucullatus).
A group of individuals with similar
anatomical characteristics and
capable of interbreeding to produce
fertile offspring.
Biodiversity
Adaptation
Natural Selection
Biodiversity
Coming to an end or dying out
of a species or other taxon.
Evolution
Phylogeny
Number and relative abundance of
species in a biological community
Species
Differences in characteristics
among individual species.
Speciation
Biodiversity
Adaptation
35
Extinction
Variation
Any alteration of structure,
behavior, or function that makes an
organism more reproductively
successful.
Variation
Extinction
Species
The evidence of new species
evolving.
The evolutionary history of a
species.
Species
Natural Selection
Changes in life forms
over time.
The Charles A. Dana Center at UT Austin
Variation
Example: Seven species of
grass plants in the same prairie.
Extinction
Differential reproductive
success of phenotypes
resulting from interaction
with the environment.
Natural Selection
Variation
Evolution Terminology Cards
NOTES
Evolution Scenarios (correct student responses):
Each of the scenarios below describes one of the following evolutionary
terms: Adaptation, Biodiversity, Evolution, Extinction, Natural Selection,
Phylogeny, Species, Speciation, or Variation. Read and discuss each scenario.
Use your understanding of these terms to select the one that best relates to
each scenario. When your group has more than one response for each scenario,
explain your reasoning.
Extinction
1. There are only about 1,000 giant pandas left in the
wild. An effective captive-breeding program is critical to the animal’s
survival. Scientists are racing against time to understand panda biology
and behavior in an effort to gain insights that will help this species
survive in the wild.
Natural Selection 2. Scientists have studied the guppy populations in two
pools of Trinidad’s Aripo River system. Guppies in pool #1 are preyed
upon by cichlids that tend to eat larger guppies. Guppies in pool #2
are preyed upon by killifish that tend to eat smaller guppies. Guppies
in pool #1 have larger broods, reproduce at a younger age, and are
smaller at maturity than those in pool #2. If guppies from pool #1
are placed in a pool with killifish predators, the average size of mature
guppies increases over time.
3. The land snails of the species Cepaea nemoralis have
Variation
shells that differ in color and number of stripes. Snails with lightcolored, striped shells are found mainly in well-lighted areas, and darkcolored snails lacking stripes are found in shady places. Shell color
serves as camouflage for the snails.
Species
4. The Monterey pine and the Bishops pine inhabit the
same area of central California, but do not interbreed to produce
fertile offspring due to the fact that one releases its pollen in February
and the other in April.
Adaptation
5. The long beak of the hummingbird fits easily into the
slender neck of the blossom of a flowering plant.
6. A deciduous forest in West Virginia contains
Biodiversity
the following types of trees: yellow poplar, sassafras, black cherry,
cucumber magnolia, red maple, red oak, butternut, shagbark hickory,
American beech, and sugar maple.
7. Studies of shared dental and skeletal characteristics
Phylogeny
indicate that domestic cats and lions are more closely related to
each other than they are to horses. Fossil evidence also supports this
relationship.
8. The Basilosaurus sp. is a prehistoric ancestor of
Evolution
the modern baleen whale. A comparison of the skeletons of the
Basilosaurus sp. and the baleen reveals evidence of a hind leg on the
Basilosaurus sp. that is not found in the skeleton of a baleen whale.
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Biology Institute – Fall 2004
Evolution Scenarios
Each of the scenarios below describes one of the following evolutionary
terms: Adaptation, Biodiversity, Evolution, Extinction, Natural Selection,
Phylogeny, Species, Speciation, or Variation. Read and discuss each scenario.
Use your understanding of these terms to select the one that best relates to
each scenario. When your group has more than one response for each scenario,
explain your reasoning.
NOTES
_____________1. There are only about 1,000 giant pandas left in the
wild. An effective captive-breeding program is critical to the animal’s
survival. Scientists are racing against time to understand panda biology
and behavior in an effort to gain insights that will help this species
survive in the wild.
_____________2. Scientists have studied the guppy populations in two
pools of Trinidad’s Aripo River system. Guppies in pool #1 are preyed
upon by cichlids that tend to eat larger guppies. Guppies in pool #2
are preyed upon by killifish that tend to eat smaller guppies. Guppies
in pool #1 have larger broods, reproduce at a younger age, and are
smaller at maturity than those in pool #2. If guppies from pool #1
are placed in a pool with killifish predators, the average size of mature
guppies increases over time.
______________3. The land snails of the species Cepaea nemoralis have
shells that differ in color and number of stripes. Snails with lightcolored, striped shells are found mainly in well-lighted areas, and darkcolored snails lacking stripes are found in shady places. Shell color
serves as camouflage for the snails.
______________4. The Monterey pine and the Bishops pine inhabit
the same area of central California, but do not interbreed to produce
fertile offspring due to the fact that one releases its pollen in February
and the other in April.
______________5. The long beak of the hummingbird fits easily into the
slender neck of the blossom of a flowering plant.
______________6. A deciduous forest in West Virginia contains the
following types of trees: yellow poplar, sassafras, black cherry,
cucumber magnolia, red maple, red oak, butternut, shagbark hickory,
American beech, and sugar maple.
______________7. Studies of shared dental and skeletal characteristics
indicate that domestic cats and lions are more closely related to
each other than they are to horses. Fossil evidence also supports this
relationship.
______________8. The Basilosaurus sp. is a prehistoric ancestor of
the modern baleen whale. A comparison of the skeletons of the
Basilosaurus sp. and the baleen reveals evidence of a hind leg on the
Basilosaurus sp. that is not found in the skeleton of a baleen whale.
The Charles A. Dana Center at UT Austin
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NOTES
The Lost Diversity of
Easter Island
Learning Experience 5
Description:
This learning experience is designed to help students understand the TEKS
concept of how the process of natural selection results in the diversity of
organisms.
Time Grade
Frame:
6
6.11 (A)
50 minutes
Grade 7
7.10 (B)
Grade 8
Biology
8.11 (A), 8.14 (B)
7 (B)
Materials:
Mixed seed (1 bag per student group)
The Lost Diversity of Easter Island investigation pages (included in the
Student Blackline Masters at the end of this vista)
Advance Preparation:
1. Prepare a sandwich bag of mixed seeds for each student group. These
can be a mixture of vegetable, (e.g., corn, peas, and peppers) and
flower seeds. Be sure each bag has a mixture of species that represent a
variety of species. The total number of seeds should be about 50.
2. Prepare a copy of The Lost Diversity of Easter Island investigation
pages for each student group.
3. Locate a drawing of the Easter Island statues to show to students
(included in Teacher Blackline Masters at the end of this vista).
Procedures:
Have students complete The Lost Diversity of Easter Island investigation pages.
Formative Assessment: Monitor student responses to the investigation
pages. As you discuss their responses to the questions, be certain that students
understand biodiversity and have provided reasonable responses to the
investigation pages.
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Biology Institute – Fall 2004
The Lost Diversity of Easter Island investigation pages
(correct student responses)
NOTES
1. In what ways were the native plants on the island used by the original
voyagers? [Palm trees were used to make canoes; hauhau plants were used to
make ropes and as fuel for cooking; toromino shrubs were also used as fuel.]
2. How did the non-native plants compete with the native plants on
the island? [Native plants were cleared in farming practices and other human
endeavors.]
3. Describe the difference between the number of different kinds
of plants in 350 and in 1722. This difference is called a loss of
biodiversity. [The once lush and abundant plant populations of 350 AD
were reduced to a few grasses and shrubby plants by 1722 AD.]
4. How did the loss of biodiversity have an impact on the island
dwellers? [The loss of food-producing native plants meant that the islanders
had to depend on farming to produce food. The extensive farming caused a loss
of soil fertility, which reduced crop yields and resulted in a lack of food.]
5. How might the loss of biodiversity been prevented? [Students will
propose various responses regarding the changes in human behavior that
could have prevented the loss in plant variety, which directly impacts animal
variety.]
6. Examine the seeds in the small bag. About how many seeds are in the
bag? Guess how many different kinds of seeds, or species, are in the
bag. Number of Seeds [Answers will vary] Number of Species of Seeds
[Answers will vary]
7. Open the bag, count the total number of seeds, and then separate the
seeds into different species. How many different kinds of seeds are in
the bag? Number of Seeds [Answers will vary] Number of Species of
Seeds [Answers will vary]
8. Did everyone in your group agree on the number of species? [Answers
will vary]
9. Was it relatively easy to distinguish each species? Why or why not?
[Some species are easily distinguished based on physical appearance, while
others are very similar and less easily distinguished.]
10. Examine the seeds and select the two species that are most different.
Place them on opposite sides of your work area and name one Seeds
A, and the other Seeds B. Arrange the remaining seeds in order of
similarity from Seeds A to Seeds B. What criteria did your group use
in arranging the seeds? [Answers will vary]
11. As the teacher directs, observe the arrangements of other groups.
How was their arrangement different from or similar to your group’s
arrangement? [Answers will vary]
12. Which species of seeds do you believe is the most important to
humans? Why do you think so? [Answers will vary]
13. Name each species of seeds. Construct a graph of the number
of individuals in each species of seeds. This graph represents the
biodiversity of the seeds in your bag. [Answers will vary]
The Charles A. Dana Center at UT Austin
39
The Lost Diversity of Easter Island
This activity is designed to help you understand how the loss of diversity within an ecosystem can affect the survival of
organisms.
Scenario
Around 350 AD, voyagers from the Marqueasas islands landed on the small island now known as Easter Island. This small
island, a 64-square mile eastern outpost of Polynesia, was a lush paradise containing dense palm tree forests, toromino
and other shrubs, hauhau plants, and many kinds of grasses. The arriving voyagers cut down the palm trees to build long
canoes to fish for food and cut down the hauhau plants to make ropes from their fibers. The toromino shrubs were used
for their fuel source. The native palm forest and grasslands were also cut down to farm the banana, sugar cane, taro, and
sweet potato plants they had brought with them to supplement their fish and dolphin diet.
By 1400, almost 15,000 people lived on the island. They had a structured society that saw to the allocation of the island’s
resources. But intensive farming had depleted the farm land, native birds had been hunted to near extinction, and
the palm trees had almost all been cut down to build ever-bigger canoes to fish farther out to sea. In desperation, the
islanders began appealing more dramatically to their gods and erected numerous large stone statues around the island.
In 1550, war broke out over the dwindling food supply and decreasing space on the island. By this time, the hauhau
plants had become extinct, having been used to cook the island rats that were farmed in the struggle for survival. With
the palms gone and the fishing waters depleted, the islanders began to consume the only remaining source of protein on
the island—one another.
The once highly structured society crumbled as warring gangs took over. The remaining grasslands were burned to
destroy any hideouts. The winners ate the losers. By 1722, only 100 or so islanders remained, living in the caves of this
now barren island, stripped of its trees and maintaining only a few grasses and a few shrubs. In 1774, when Captain
James Cook visited the island, there were only four canoes that leaked badly and had to be continuously bailed to
remain afloat. Many of the stone statues had been tipped over or destroyed.
Discussion:
1. In what ways were the native plants on the island used by the original voyagers?
2. How did the non-native plants compete with the native
plants on the island?
3. Describe the difference between the number of different kinds of plants in 350 and in 1722. This difference is
called a loss of biodiversity.
4. How did the loss of biodiversity have an impact on the
island dwellers?
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Biology Institute – Fall 2004
5. How might the loss of biodiversity been prevented?
6. Examine the seeds in the small bag. About how many seeds are in the bag? Guess how many different kinds of
seeds, or species, are in the bag.
Number of Seeds_______________
Number of Species of Seeds______________
7. Open the bag, count the total number of seeds, and then separate the seeds into different species. How many
different kinds of seeds are in the bag?
Number of Seeds_______________
Number of Species of Seeds______________
8. Did everyone in your group agree on the number of species?
9. Was it relatively easy to distinguish each species? Why or why not?
10. Examine the seeds and select the two species that are most different. Place them on opposite sides of your work
area and name one Seeds A, and the other Seeds B. Arrange the remaining seeds in order of similarity from
Seeds A to Seeds B. What criteria did your group use in arranging the seeds?
11. As the teacher directs, observe the arrangements of other groups. How was their arrangement different from or
similar to your group’s arrangement?
12. Which species of seeds do you believe is the most important to humans? Why do you think so?
13. Name each species of seeds. Construct a graph of the number of individuals in each species of seeds. This graph
represents the biodiversity of the seeds in your bag.
The Charles A. Dana Center at UT Austin
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NOTES
Arthropods and More
Arthropods
Learning Experience 6
Description:
This learning experience is designed to help students understand the TEKS
concept that adaptations in organisms may provide an advantage for survival
during the natural selection process.
Grade 6
6.10 (C)
Grade 7
7.10 (B)
Grade 8
Biology
7 (A)(B)
Time Frame:
50 minutes
Materials:
Arthropod specimens (1 of each selected type per student group)
Petri dish (1 per arthropod specimen)
Dissecting microscope (1 per student group)
Probe (1 per student group)
Metric ruler (1 per student group)
Arthropods and More Arthropods investigation pages (included in the Student
Blackline Masters at the end of this vista)
Advance Preparation:
1. Select a variety of arthropods to use during this learning experience,
such as crickets, grasshoppers, mayflies, crayfish, pill bugs, or millipedes.
They can be obtained from biological supply companies, pet stores,
or bait shops. Hand lenses can be substituted for dissecting scopes;
however, microscopes enable students to view small body parts such as
mandibles and gills.
2. Prepare a copy of the Arthropods and More Arthropods investigation
pages for each student group.
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Biology Institute – Fall 2004
Procedures:
Have students complete the Arthropods and More Arthropods investigation
pages.
NOTES
ANIMAL SAFETY: Remind students that arthropods are living organisms and
must be handled with care and respect.
SAFETY: Caution students to keep their fingers away from the crayfish claws.
Students should wash their hands after handling the arthropod specimens.
Formative Assessment: Have students discuss their responses to the
investigation pages. Confirm that students have accurately identified how the
functions of the body parts are the result of adaptations.
Arthropods and More Arthropods investigation pages
(correct student responses)
1. Based on your data, which arthropods are best equipped for
swimming? Explain your answer. [Any arthropod with a long abdomen
and swimmerets]
2. Based on your data, which arthropods are best equipped for crawling
or burrowing? Explain your answer. [Any arthropod with a short
abdomen and large claws]
3. Look at the number of jointed appendages for each specimen. Is this
characteristic common to all arthropods? [Jointed appendages are common
to all arthropods; however, the number for each specimen varies.]
4. How are crayfish adapted for a watery environment? [They breathe with
gills and have swimmerets.]
5. Like crayfish, pill bugs are also crustaceans. What type of respiratory
organs do pill bugs have? Why do these organisms need to be in close
proximity to water? [Pill bugs have gills that must be kept moist in order to
absorb oxygen from water.]
The Charles A. Dana Center at UT Austin
43
NOTES
44
6. The largest arthropods are aquatic. Hypothesize as to why this is so.
[The larger an arthropod grows, the heavier the exoskeleton will become. Land
arthropods do not have the advantage of support from their watery environment
as the aquatic arthropods do.]
Biology Institute – Fall 2004
Arthropods and More Arthropods
This activity is designed to help you understand characteristics in organisms by observing and analyzing arthropod
adaptations.
Background Information:
The Phylum Arthropoda includes many familiar classes of animals, such as insects, crustaceans, arachnids, millipedes, and
centipedes. The huge varieties of animals that make up this phylum live in almost every habitat of the world. They serve
many functions within their specific ecosystems and are a significant part of almost all food webs.
Arthropods are diverse but do share the following characteristics: an exoskeleton, a head, a thorax (or a fused
cephalothorax), an abdomen, and pairs of jointed appendages. These animals are distinguished from each other based
on differences in body structures and eating habits. The differences help the animals adapt to their niches and flourish
there.
Materials:
Arthropod specimens contained in petri dishes, dissecting microscope, probe, metric ruler
Procedures:
ANIMAL SAFETY: Arthropods are living organisms and must be handled
with care and respect.
SAFETY: Keep your fingers away from the crayfish claws.Wash your hands
after handling the arthropod specimens.
Observe all of the arthropod specimens with the naked eye and with the dissecting scope. Complete the Arthropod
Characteristics chart for each specimen.
The Charles A. Dana Center at UT Austin
45
Arthropod Characteristics
Characteristic
Specimen
1
Specimen
2
Specimen
3
Specimen
4
Specimen
5
Number of
body regions
Length of
head
Length of
thorax
Length of
abdomen
Description
of legs and
swimmerets
Number of
antennae
Description of
eyes
Description of
mouth parts
Location of
respiratory
organs
Other body
parts
Discussion:
1. Based on your data, which arthropods are best equipped for swimming? Explain your answer.
2. Based on your data, which arthropods are best equipped for crawling or burrowing? Explain your answer.
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Biology Institute – Fall 2004
3. Look at the number of jointed appendages for each specimen. Is this characteristic common to all arthropods?
4. How are crayfish adapted for a watery environment?
5. Like crayfish, pill bugs are also crustaceans. What type of respiratory organs do pill bugs have? Why do these
organisms need to be in close proximity to water?
6. The largest arthropods are aquatic. Hypothesize as to why this is so.
7. What is the likely food source of each specimen?
8. Draw a food web containing at least 10 organisms and including at least five types of arthropods.
The Charles A. Dana Center at UT Austin
47
NOTES
What a Beak
Learning Experience 7
Description:
This learning experience is designed to help students understand the TEKS
concept that speciation may result during the natural selection process.
Grade 6
Grade 7
Grade 8
6.10 (C)
7.10 (B)
8.11 (A)
Biology
7 (B)
Time Frame:
50 minutes
Materials:
Zipper-type sandwich bags (3 per student group)
Timer (1 per class)
Spoon (1 per student group)
Slotted spoon (1 per student group)
Ice cream shop tasting spoon (1 per student group)
Wooden craft spoon (1 per student group)
Felt square (1 per student group)
Rice grains (small handful per student group)
Raisins (30 per student group)
Marbles (30 per student group)
What a Beak investigation pages (included in the Student Blackline
Masters at the end of this vista)
Advance Preparation:
1. Prepare three sandwich bags for each student group: one containing
a small handful of rice grains, one bag containing 30 raisins; and one
bag containing 30 marbles.
2. Prepare a copy of the What a Beak investigation pages for each
student group.
Procedures:
Have students complete the What a Beak investigation pages.
Formative Assessment: Monitor the reasonableness of students’ data tables
and graphs. Through discussion of the story, confirm that students understand
the process of speciation.
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Biology Institute – Fall 2004
What a Beak investigation pages
(correct student responses)
NOTES
1. What is a species? [A group of similar organisms]
2. Define speciation. [Formation of a new group of similar organisms that
cannot interbreed with the original species.]
3. What type of beak would a bird have if its main source of food were
snails? [Flat and wide]
4. Predict how a mutation in beak size and shape could lead to
speciation in a group of birds that become isolated from the original
population. [A mutation that increased beak size would result in an ability
to eat things other than seeds, such as nuts and insects, thereby increasing the
chance of survival.]
5. How can variation in bird beaks lead to speciation? [Organisms become
isolated by their feeding patterns, changes are introduced and passed down
through generations, and the new birds can no longer interbreed with the
original birds.]
The Charles A. Dana Center at UT Austin
49
What a Beak
This investigation is designed to help you understand how variations within a species lead to speciation.
Background Information:
Some scientists think that organisms within the same species can undergo enough changes over time to prevent
interbreeding between some populations. This transformation leads to the formation of another distinct species and is
called speciation. Speciation may occur when a group of one species of organisms becomes isolated from their own
population. As natural selection chooses the fittest individuals to survive and reproduce, their traits are passed on to their
offspring. Scientists think this slow process of change causes these isolated organisms to differ distinctly from the original
population from which they came.
Charles Darwin (while on his research adventure around the world during the 1830’s) made observations that led many
biologists to theorize about speciation. Darwin drew sketches and collected many specimens of birds while visiting the
Galapagos Islands near South America. He noticed that these birds had similar characteristics to birds on the mainland,
but their beak shapes and sizes were very different. Upon his return to England, zoologists informed him that the birds
he thought were wrens, warblers and blackbirds were actually all finches. The differences in the beaks began Darwin
thinking about how a bird’s beak may allow it to eat different types of food more efficiently. If a mutation allowed a bird
to become more fit by obtaining more food, then it would pass on these characteristics to its offspring. Over time, these
changes would eventually be passed down to other generations, and these “new” birds would no longer interbreed with
the “original” birds. Thus, you would have a different species.
Darwin made observations of birds, their beaks, and their food sources. He noticed that the size and shape of a bird’s
beak was specifically designed for eating specific types of food. Looking at a bird’s beak can help you determine the
types of foods different birds eat. Short, thick beaks are good for cracking and opening seeds. Narrow, pointed beaks
help birds dig insects out of small cracks. Powerful, hooked beaks are suited for tearing or gripping prey such as mice.
Long, spear-like or wide beaks help some birds catch fish. Broad, flat beaks are good for straining mud and water for
food.
In this investigation, you will determine how the variation in the size and shapes of beaks allow a bird species to take
advantage of food sources. Being able to utilize a food source and survive to reproduce allows a bird to pass its traits on
to its offspring.
Materials:
Timer, spoon, slotted spoon, wooden craft spoon, taster spoon, felt squares, rice-grain maggots, raisin-grubs,
marble-snails
Procedures:
1. Spread the felt square on a flat surface. Each student selects a type of spoon to use as a “beak.”
2. Sprinkle the rice-grain maggots across the felt square.
3. When the teacher calls the time, all students should use their “beak” to feed for 30 seconds. Food can be picked
up with the beak only one piece at a time.
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Biology Institute – Fall 2004
4. Construct a data table to record the number of pieces of food eaten by each beak.
5. Repeat steps 1–3 for the raisin-grubs and then for the marble-snails. Then add the results of numbers eaten to
the data table.
6. Construct a bar graph of the data in your table.
Discussion:
1. What is a species?
2. Define speciation.
3. What type of beak would a bird have if its main source of food were snails?
4. Predict how a mutation in beak size and shape could lead to speciation in a group of birds that become isolated
from the original population.
5. How can variation in bird beaks lead to speciation?
The Charles A. Dana Center at UT Austin
51
NOTES
The Best Bess Beetles
Learning Experience 8
LEARNING EXPERIENCE 8
Description:
This learning experience is designed to help students understand the TEKS
concept that behavior of organisms may provide an advantage for survival
during the natural selection process.
Grade 6
Grade 7
Grade 8
Biology
7 (B)
Time Frame:
50 minutes
Materials:
Petri dish (1 bottom per student group)
Metric ruler (1 per student group)
Balance (1 per student group)
Bess beetles (1 per student group)
Small, clear plastic cup (1 per student group)
Pennies or small washers (15 per student group)
Unscented, unwaxed wide dental floss, 50 cm (1 per student group)
Paper towel, approximately 30 cm square (1 per student group)
Cellophane tape (1 roll for the class)
Hand lens (1 per student group)
The Best Bess Beetles investigation pages (included in the Student
Blackline Masters at the end of this vista)
Advance Preparation:
1. Prepare a copy of the Best Bess Beetles investigation pages for each
student group.
2. Bess beetles can be ordered from a living materials source. They
should be ordered to arrive about a week before beginning this
learning experience. Place one (1) beetle in a small, clear plastic cup
for each student group. It is important to order sufficient beetles, as
the same beetles cannot be used repeatedly due to fatigue.
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Biology Institute – Fall 2004
Background Information for the Teacher:
The short-horned stag beetle Passalus cornutus, commonly called the Bess
beetle, is found in the eastern United States and southern Texas. These large,
shiny black beetles exhibit complete metamorphosis. The adults live in pairs,
with both sexes sharing the tunneling and family care duties. Eggs are laid
in tunnels in decomposing wood. The larvae are fed finely chewed wood
chips mixed with feces by the adults. The larvae require several months for
development, and often generations will overlap. The adult stage can last
from 6 to 12 months. These beetles do not breed well in captivity, so the
establishment of a long-term colony is difficult. However, the adult beetles
from this activity could be maintained in the classroom for a few months until
they reach the end of their life cycle.
NOTES
Procedures:
ANIMAL SAFETY: Remind students that Bess beetles are living organisms
and must be handled with care and respect.
SAFETY: Caution students to keep their fingers away from the beetles’
pinchers. Students should wash their hands after handling the beetles.
1. Show students the Bess beetles. So students won’t be startled if
they hear it, tell them that adults and larvae are capable of making a
whistling noise called stridulating.
2. Have students observe their beetles. Ask: Are the beetles identical?
How are they similar? How are they different?
3. Have students complete The Best Bess Beetles investigation pages.
Provide a format for students to record group data and calculate
class averages. Using graphing calculators, students could construct
scatterplot graphs of the class data collected.
4. Have students discuss the variation in mass, length, and pulling power
found in this small sample of beetles. Use the graphs to discuss any
connection between mass or length and pulling power. Ask students to
describe the advantages and disadvantages of variation in size.You may
also want to have students discuss other factors that would have an
impact on their results, such as the placement of the pennies/washers
in the petri dish or the length of the dental floss.
Teacher note: The teacher may also want to have students prepare
a graph of the results of all classes taught throughout the day, in order
to increase the numbers of beetles being analyzed.
5. Ask students about the behavior of the beetles in response to pulling
the petri dishes.
The Charles A. Dana Center at UT Austin
53
NOTES
Teacher note: Bess beetles have a structural adaptation of small
extensions on their appendages that provide traction. This structural
adaptation enables them to exhibit the pulling behavior seen in this
learning experience and enables them to move around the leaf litter
and fallen logs found in their natural environment.
Formative Assessment: Monitor student responses to the investigation
pages. Ask students if there is any behavior that can be related to the variation
in size or mass of beetles.
Best Bess Beetles investigation pages
(correct student responses
1. Observe the beetle’s appendages with a hands lens. What anatomical
adaptation does the beetle have that allows it to exhibit the pulling
behavior? [Bess beetles have a structural adaptation of small extensions on
their appendages that provide traction.]
2. Which of the class beetles would most probably survive and reproduce
in its normal environment? [The strongest individuals in terms of the
ability to maneuver through their environment to avoid predation and find a
mate. (Actual answer will vary due to beetle sample and group names.)]
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Biology Institute – Fall 2004
The Best Bess Beetles
This investigation is designed to help you understand that behavior of organisms may provide an advantage for survival.
Background:
The short-horned stag beetle Passalus cornutus commonly called the Bess beetle, is found in the eastern United States
and in south Texas deciduous forests These large, shiny black beetles exhibit complete metamorphosis. The adults live
in pairs, with both sexes sharing the tunneling and family care duties. Eggs are laid in tunnels in decomposing wood.
The larvae are fed finely chewed wood chips mixed with feces by the adults. The larvae require several months for
development, and often generations will overlap. The adult stage can last from 6 to 12 months.
Materials:
Petri dish, ruler, balance, Bess beetle in a cup, pennies/washers, dental floss, paper towel, tape, and hand lens
Procedures:
ANIMAL SAFETY: Bess beetles are living organisms and must be handled with care and respect.
SAFETY: Keep your fingers away from the beetles’ pinchers. Wash your hands after handling the beetles.
1. Measure the mass of an empty petri dish to the nearest tenth of a gram. Record the information in
Data Table 1. Pick up the beetle by gently holding it on either side of its abdomen with your thumb and
forefinger and place it on its back in the petri dish. Measure the mass of the dish and the beetle to the nearest
tenth of a gram. Record the information in Data Table 1.
2. Calculate the mass of your beetle by subtracting the mass of the dish from the mass of the beetle and the dish,
and record your calculation in Data Table 1.
Data Table 1
Measurement
Mass of empty petri dish
Mass of beetle and petri dish
Mass of beetle
Average mass of class beetles
Difference between average mass of
class beetles and group beetle
The Charles A. Dana Center at UT Austin
55
3. Keep the beetle on its back and measure its length from tip to tip to the nearest tenth of a centimeter. Return
the beetle to the cup. Record the information in Data Table 2.
4. Weigh a penny/washer to the nearest tenth of a gram, and record your measurement in Data Table 2.
Data Table 2
Measurement
Length of group beetle
Average length of class beetles
Difference between average length of
class beetles and group beetle
Mass of one penny/washer
Average mass of class pennies/washers
Difference between average mass
of class pennies/washers and group
penny/washer
5. Describe how your beetle varies in mass and length from the average beetle.
6. How much mass do you think your beetle could pull?
7. Using the materials provided, determine the mass that can be pulled by your Bess beetle. Tape the paper towel
to a flat surface. Use the dental floss to shape a lasso and slip it over the head and body of your beetle until it fits
loosely around the middle of the body between the thorax and abdomen. Do not tie a knot in the loop around
the beetle. Tape the other end of the twine to the petri dish.
8. Place your beetle on an edge of the paper towel so that the beetle can grip the towel as it walks across the
towel. The petri dish should be on a flat and smooth surface.
9. When the beetle begins to walk and pull the petri dish, add one penny/washer at a time to the dish until the
beetle can no longer move. It may be necessary to reposition the beetle to prevent the dish from touching the
paper. Do not prod or push your beetle.
10. Once the beetle has reached the maximum weight it can pull, gently remove the dental floss from the beetle
and place the beetle in the cup.
11. Count and measure the mass of the total number of pennies/washers the beetle was able to pull. Record this
information in Data Table 3.
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Biology Institute – Fall 2004
Data Table 3
Measurement
Number of pennies/washers beetle
pulled
Difference between the class average
number of total pennies/washers pulled
and number pulled by group beetle
Total mass pulled by group beetle
Class average total mass pulled
Difference between the class average
mass of total pennies/washers pulled
and mass of pennies/washers pulled by
group beetle
12. Describe how your beetle varied in the number and mass of total pennies/washers pulled from the average
beetle.
13. How did your actual results compare with your predicted results given in Step 6.
14. As a class, construct a scatterplot graph of the class results for length of beetle and mass pulled. Construct
another scatterplot graph of the class results for mass of beetle and mass pulled. What do the graphs indicate? Is
there any connection between the amount of mass pulled and the length or mass of the beetle pulling?
Discussion:
1. Observe the beetle’s appendages with a hands lens. What anatomical adaptation does the beetle have that allows
it to exhibit the pulling behavior?
2. Which of the class beetles would most probably survive and reproduce in its normal environment?
The Charles A. Dana Center at UT Austin
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58
Biology Institute – Fall 2004
Nailing Evolution
NOTES
Learning Experience 9
LEARNING EXPERIENCE 9
Description:
This learning experience is designed to help students understand the TEKS
concept that natural selection produces organisms that can be grouped
according to similar characteristics (phylogeny).
Grade 6
Grade 7
Grade 8
Biology
7 (B)
Time Frame:
50 minutes
Materials:
Zipper-type sandwich bag (1 per student group)
Metric ruler (1 per student group)
Wooden peg (1 per student group)
Brass tack (1 per student group)
2” nail (1 per student group)
3” nail (1 per student group)
Screw (1 per student group)
Bolt (1 per student group)
Toggle bolt (1 per student group)
DNA Sequences for Hardware Fasteners (included in the Teacher
Blackline Masters at the end of this vista)
Nailing Evolution investigation pages (included in the Student Blackline
Masters at the end of this vista)
Advance Preparation:
1. Prepare a set of hardware devices by placing a wooden peg, brass tack,
2” nail, 3” nail, screw, bolt, and toggle bolt in a zipper-type sandwich
bag for each student group.
2. Photocopy and cut apart a set of DNA Sequences for Hardware
Fastener strips for each student group.
3. Prepare a copy of the Nailing Evolution investigation pages for each
student group.
The Charles A. Dana Center at UT Austin
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NOTES
Background Information for the Teacher:
A cladogram is an often used method for phylogenetic analysis. The basic
idea of a cladogram is to group members that share a common evolutionary
history. The members of a group are more closely related to one another than
they are to other organisms. Furthermore, each species possesses a mixture of
primitive characteristics that already existed in the common ancestor along
with the newly evolved characteristics. That is, they share unique new features
not present in distant ancestors. Scientists make three assumptions:
•
A group of organisms are related by descent from a common ancestor.
•
Populations are thought to divide into exactly two groups as the
pattern emerges.
•
Characteristics in a lineage may change over time.
Procedures:
Have students complete the Nailing Evolution investigation pages.
SAFETY: Students should be cautioned about the appropriate use of the tacks,
nails, bolts, and screws.
Formative Assessment: Monitor student responses to the investigation
pages. Confirm that students understand that the cladogram designates the
level of relatedness between organisms and not descent.
Nailing Evolution investigation pages
(correct student responses)
1. Record the names of the hardware pieces and your observations for
each in Data Table 1. (Student answers will vary.)
2. Use the information from Data Table 1 to complete the cladogram
below.
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Biology Institute – Fall 2004
Relatedness Of Fasteners
NOTES
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�
Toggle bolt
�
Screw
�
Bolt
�
3” nail
�
2” nail
Brass tack
�
�
Wooden peg
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3. Compare pairs of hardware fasteners, count any differences, and record
that number in Data Table 2.
Data Table 2
Wooden
peg
Bolt
2”
nail
Toggle
bolt
3”
nail
Brass
tack
Screw
Wooden
peg
0
4
2
4
3
1
4
Bolt
4
0
2
3
2
4
2
2” nail
2
2
0
4
1
2
4
Toggle
bolt
4
3
4
0
4
4
1
3” nail
3
2
1
4
0
3
4
Brass
tack
1
4
2
4
3
0
4
Screw
4
2
4
1
4
4
0
The Charles A. Dana Center at UT Austin
61
NOTES
62
4. Use the information recorded in Data Table 2 to infer the
evolutionary relationships among the various hardware fasteners.
For example, the DNA sequence of the wooden peg and brass tack
indicate that they are closely related. To what extent do the DNA
sequences above support the information in your cladogram? Do you
need to revise your cladogram? Why or why not? [According to the
information recorded in Data Table 2, there is only one difference between the
wooden peg and the brass tack.There are two differences between the wooden
peg and the 2” nail.There are three differences between the wooden peg and
the 3” nail. Based on this data, the brass tack is most closely related to the
wooden peg.The next most closely related hardware piece would be the 2” nail,
followed by the 3” nail.With regard to the evolutionary relationships among
the bolt, screw, and toggle bolt, one could examine the actual DNA sequence
differences that occur relative to the 3” nail, which was the most recent ancestor
identified in the above scenario. Following this line of thinking, the DNA
sequence for the bolt is most similar to that of the 3” nail (differences: AGG
and CCC), followed by the screw (differences: GCT, AGG, and CCC), and
finally the toggle bolt (differences: CCG, GCT, AGG, and CCG).]
Biology Institute – Fall 2004
DNA Sequences for Hardware Fasteners
Wooden peg
AGG CAT AAA CCA ACC GAT TAC
Brass tack
AGG CAT ATT CCA ACC GAT TAC
2” nail
AGG CCC CTT CCA ACC GAT TAC
3” nail
AGG CCC CTT CCA ACC GAT CAC
Bolt
AGG CCC CTT CCA ACC AGG CCC
Screw
AGG CCG GCT CCA ACC AGG CCC
Toggle bolt
AGG CCG GCT CCA ACC AGG CCG
The Charles A. Dana Center at UT Austin
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Nailing Evolution
This activity is designed to help you understand that natural selection produces organisms that can be grouped
according to similar characteristics.
Materials:
Ruler, wooden peg, bolt, 2” nail, toggle bolt, 3” nail, brass tack, screw
Procedures:
SAFETY: The tacks, nails, bolts, and screws should be used in an appropriate manner.
1. Record the names of the hardware pieces and your observations for each in Data Table 1. Observe as many
anatomical characteristics as possible.
Data Table 1
Characteristics
Composition
Length
Number
of threads
present
Thread width
Head type
Head size
Other
2. Use the information from Data Table 1 to complete the cladogram below. Begin by listing the wooden peg
as the most closely related hardware fastener to the Common Ancestor. Then add the next hardware fastener
that is the most closely related to the wooden peg according to the information in Data Table 1. Continue this
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Biology Institute – Fall 2004
process for numbers 3–7. Remember: According to cladistics, the greater the number of characteristics shared
by two organisms, or in this case hardware fasteners, the more closely related they are with regard to their
evolution.
Relatedness of Fasteners
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�
�
�
�
�
�
�
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3. The DNA sequences on the strips were obtained from each of the hardware fasteners. Compare pairs of
hardware fasteners, count any differences, and record that number in Data Table 2. Be sure to compare the
DNA sequences by triplets, such as CTT to GCT, which would only count as one (1) difference.
Data Table 2
Wooden
peg
Wooden
peg
Bolt
Bolt
2” nail
Toggle
bolt
3” nail
Brass tack
Screw
0
0
2” nail
Toggle
bolt
3” nail
Brass tack
Screw
The Charles A. Dana Center at UT Austin
0
0
0
0
0
65
4. Use the information recorded in Data Table 2 to infer the evolutionary relationships among the various
hardware fasteners. For example, the DNA sequence of the wooden peg and brass tack indicate that they are
closely related. To what extent do the DNA sequences above support the information in your cladogram? Do
you need to revise your cladogram? Why or why not?
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Biology Institute – Fall 2004
A Bear Branch in the
Tree of Life
NOTES
Learning Experience 9
LEARNING EXPERIENCE 10
Description:
This learning experience is designed to help students understand the
application of using DNA sequencing to show relatedness among organisms.
Grade 6
Grade 7
Grade 8
Biology
6.11 (C)
7.10 (C)
8.11 (C)
7 (B)
Time Frame:
50 minutes
Materials:
A Bear Branch in the Tree of Life investigation pages (included in the Student
Blackline Masters at the end of this vista)
Advance Preparation:
Prepare a copy of the A Bear Branch in the Tree of Life investigation pages for
each student group.
Background Information for the Teacher:
Mitochondrial DNA (mtDNA) is useful for studying the recent evolution of
closely related species and populations within species because it accumulates
mutations rapidly and it is maternally inherited. This learning experience is
derived from Teacher Enhancement materials funded by the National Science
Foundation and managed by Texas A&M University.
Procedures:
Have students complete the A Bear Branch in the Tree of Life investigation
pages.
Formative Assessment: Monitor student responses to the investigation
pages.
A Bear Branch in the Tree of Life investigation pages
(correct student responses):
1. Complete Table 1 by recording how many variations in band number
occur between any two bears.
The Charles A. Dana Center at UT Austin
67
Table 1
NOTES
Number of
different
bands in
bear-to-bear
comparisons
Polar Bear
Black Bear
Brown Bear
Polar Bear
0
6
1
Black Bear
6
0
5
Brown Bear
1
5
0
Total Number
of Bands
Number of
Different
Bands
Percent
Difference
Polar Bear/
Black Bear
10
6
60%
Black Bear/
Brown Bear
9
5
56%
Brown Bear/
Polar Bear
13
2. Complete Table 2.
Table 2
Bear
Comparison
1
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8%
3. Using the knowledge gained in the Nailing Evolution Learning
Experience and the information from Table 2, complete this
cladogram, showing the relationship of the polar bear, black bear, and
brown bear.
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�����
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4. Two of these species have been known to produce fertile hybrids
when allowed to breed with each other in captivity. Which two are
they? Why do they not mate in the wild? [The polar bear and brown
bear would be able to mate successfully; however, this will not occur in the wild
because they live in different habitats.]
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Biology Institute – Fall 2004
A Bear Branch in the Tree of Life
This activity is designed to help you understand the application of using DNA sequencing to show relatedness among
organisms.
Background Information:
Gel electrophoresis is a type of DNA analysis that can be used to determine how closely living organisms are related
to one another based on their DNA. In this procedure, a matrix composed of a highly purified form of agar is used to
separate DNA molecules according to size. The DNA molecules of organisms contain specific sites known as restriction
sites that, when exposed to restriction enzymes, will produces fragments of DNA that vary in size. These various-sized
fragments of DNA separate and appear as bands on an electrophoresis gel. Below are the results of a gel electrophoresis
for three types of bears. Analyze and compare the DNA bands shown in the diagram to determine how closely
the bears are related. The more bands that organisms have in common the more closely related they are. The bands
represent DNA fragments that result when the restriction enzyme Hind III breaks the bonds between the nucleotides
of the mitochondrial DNA of a polar bear, a black bear, and a brown bear.
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����
����
Procedures:
1. Complete Table 1 by recording how many variations in band number occur between any two bears. For
example, in examining the bands of the black and polar bears there is a difference of six (6) bands.
����������
The Charles A. Dana Center at UT Austin
��������������
������������
�������
������
������
����������
����������
69
����������
Table 1
Number of
different
bands in
bear-to-bear
comparisons
Polar Bear
Polar Bear
0
Black Bear
6
Black Bear
Brown Bear
0
Brown Bear
0
2. Complete Table 2. The number of different bands is taken from Table 1. To determine the total number of
bands, count the number of bands on the diagram for each of the bears in the pair being compared and then
add the two numbers together. To determine the percent difference, divide the number of different bands by the
total number of bands.
Table 2
Bear
Comparison
Polar Bear/
Black Bear
Total Number
of Bands
Number of
Different
Bands
Percent
Difference
10
6
60%
Black Bear/
Brown Bear
Brown Bear/
Polar Bear
3. Using the knowledge gained in the Nailing Evolution Learning Experience and the information from Table 2,
complete this cladogram, showing the relationship of the polar bear, black bear, and brown bear.
��������������������
4. Two of these species of bears have been known to produce fertile hybrids when allowed to breed with each
other in captivity. Which two are they? Why do they not mate in the wild?
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Biology Institute – Fall 2004
Cats and Birds
NOTES
Assessment Task
A population of beachcombing birds lives on an island with light-colored
sand beaches. These birds occur naturally in two colors, white and black. As
the population increases, some of the birds move to a nearby island with darkcolored sand beaches. This island has many more food sources and vegetation
for nesting, but it also has a small population of bird-eating cats, some with
extremely poor eyesight and some with normal eyesight.
1. After a period of time, the birds on the two islands are reunited but
are unable to mate. What factors and processes might account for this
change? [Answers will vary but should include speciation.]
2. Draw an illustration of how bird color can be an advantageous
adaptation. [Illustrations will vary but should show a dark-colored bird on a
dark background and a light-colored bird on a white background.]
3. Use the data in Table 1 to predict the populations of cats and birds in
year 4.
Table 1
Year
Cats with
Normal
Eyesight
Cats with
Poor Eyesight
Total Number
of Birds
1
90
30
500
2
42
12
239
3
12
2
292
4
4. Based on the data in Table 1, what will likely happen to the
population of Cats with Poor Eyesight? [Answers will vary. Students
should use data from their table to explain their responses.]
5. Cite examples of variation in this scenario. [Color of the birds; eye sight
of the cats]
6. A mutation occurs that results in some of the cats with poor eyesight
being able to make sounds similar to the mating call the birds make.
How would this behavioral adaptation be advantageous? [Larger ears
allow the cats to locate and better capture birds.]
7. Fossil evidence is discovered on the island indicating that there might
have been a third type of cat living on the island at some point in
time. Gel electrophoresis is performed with DNA taken from the cats
living on the island and from the cat fossil. The results are shown in
Table 2. Based on this data, would you conclude that these cats are of
the same species? Why or why not?
The Charles A. Dana Center at UT Austin
71
Table 2
NOTES
Cat
Comparison
Total Number
of Bands
Number of
Different
Bands
Percent
Difference
Cats with
normal
eyesight/
Fossil cat
22
10
45%
Cats with
poor eyesight/
Fossil cat
21
12
57%
22
1
5%
Cats with
normal
eyesight/Cats
with poor
eyesight
[No. According to the data, the differences between the island cat species and the
fossil cat species is too great.]
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Biology Institute – Fall 2004
Cats and Birds
Assessment Task
A population of beachcombing birds lives on an island with light-colored sand beaches. These birds occur naturally in
two colors, white and black. As the population increases, some of the birds move to a nearby island with dark-colored
sand beaches. This island has many more food sources and vegetation for nesting, but it also has a small population of
bird-eating cats, some with extremely poor eyesight and some with normal eyesight.
1. After a period of time, the birds on the two islands are reunited but are unable to mate. What factors and
processes might account for this change?
2. Draw an illustration of how bird color can be an advantageous adaptation.
3. Use the data in Table 1 to predict the populations of cats and birds in year 4.
Table 1
Year
Cats with
Normal
Eyesight
Cats with
Poor Eyesight
Total Number
of Birds
1
90
30
500
2
42
12
239
3
12
2
292
4
4. Based on the data in Table 1, what will likely happen to the population of Cats with Poor Eyesight?
5. Cite examples of variation in this scenario.
6. A mutation occurs that results in some of the cats with poor eyesight being able to make sounds similar to the
mating call the birds make. How would this behavioral adaptation be advantageous?
The Charles A. Dana Center at UT Austin
73
7. Fossil evidence is discovered on the island indicating that there might have been a third type of cat living on
the island at some point in time. Gel electrophoresis is performed with DNA taken from the cats living on the
island and from the cat fossil. The results are shown in Table 2. Based on this data, would you conclude that
these cats are of the same species? Why or why not?
Table 2
Cat
Comparison
Total Number
of Bands
Number of
Different
Bands
Percent
Difference
Cats with
normal
eyesight/
Fossil cat
22
10
45%
Cats with
poor eyesight/
Fossil cat
21
12
57%
22
1
5%
Cats with
normal
eyesight/Cats
with poor
eyesight
74
Biology Institute – Fall 2004
Biological Evolution
Teacher Blackline Masters
The Charles A. Dana Center at UT Austin
75
�������
76
Biology Institute – Fall 2004
The Charles A. Dana Center at UT Austin
77
�������������
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Horse Evolution
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Constructing an Electrophoresis
Chamber
An electrophoresis chamber can be used to separate the molecules of a test solution and to spread them out in a distinct
pattern. The chamber holds a buffer solution and a special gel inoculated with a test solution. The gel is subjected to
an electrical field. Negatively charged molecules of the solution within the gel will move toward the positive electrode,
while positively charged molecules will move toward the negative electrode. The patterns the molecules make are used
to compare unknown substances to a known substance.
Materials:
1 pint rectangular plastic container (3” X 6”)
10 gauge wire
2 alligator clips
Plexiglas® – cut to fit inside container
Clear silicone
5 9-volt batteries
Electrical tape
Drill and 1/8-inch drill bit
Procedures:
1. Drill a 1/8-inch hole below and a little to the side of each handle at the ends of the container.
2. Cut 2 six-inch lengths of wire and strip two inches off one end of each length.
3. Insert the two inches of stripped wire into the drilled holes and secure with silicone.
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Biology Institute – Fall 2004
4. Attach the alligator clips to the opposite ends of the wires.
5. Place the piece of pre-cut Plexiglas® onto several drops of silicone on the bottom ends of the container.
6. Connect the five batteries + to - and tape together.
7. When ready to run a gel, connect one of the alligator clips to the battery’s positive terminal and the other
alligator clip to the negative terminal.
The Charles A. Dana Center at UT Austin
79
Adaptation
Extinction
Example: The length of the
abdomen in adult beetles
vaires an average of 1.5 mm.
Evolution
Example: The dodo bird
(Raphus cucullatus).
A group of individuals with similar
anatomical characteristics and
capable of interbreeding to produce
fertile offspring.
Biodiversity
Adaptation
Natural Selection
Biodiversity
Coming to an end or dying out
of a species or other taxon.
Evolution
Phylogeny
Number and relative abundance of
species in a biological community
Species
Differences in characteristics
among individual species.
Speciation
Biodiversity
Adaptation
Biology Institute – Fall 2004
Extinction
Variation
Any alteration of structure,
behavior, or function that makes an
organism more reproductively
successful.
Variation
Extinction
Species
The evidence of new species
evolving.
The evolutionary history of a
species.
Species
Natural Selection
Changes in life forms
over time.
80
Variation
Example: Seven species of
grass plants in the same prairie.
Extinction
Differential reproductive
success of phenotypes
resulting from interaction
with the environment.
Natural Selection
Variation
Evolution Terminology Cards
DNA Sequences for Hardware Fasteners
Wooden peg
AGG CAT AAA CCA ACC GAT TAC
Brass tack
AGG CAT ATT CCA ACC GAT TAC
2” nail
AGG CCC CTT CCA ACC GAT TAC
3” nail
AGG CCC CTT CCA ACC GAT CAC
Bolt
AGG CCC CTT CCA ACC AGG CCC
Screw
AGG CCG GCT CCA ACC AGG CCC
Toggle bolt
AGG CCG GCT CCA ACC AGG CCG
The Charles A. Dana Center at UT Austin
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Biology Institute – Fall 2004
Biological Evolution
Student Blackline Masters
The Charles A. Dana Center at UT Austin
83
A Natural Selection
This investigation is designed to help you understand how adaptation is a factor in natural selection.
Materials:
One plastic sandwich bag labeled “Beginning Population,” one bag labeled “Survivors and Their Offspring,” three bags
labeled “Offspring,” fabric, three colored pencils, graph paper
Procedures:
1. Spread your fabric “habitat” on a flat surface.
2. Select a game warden and a recorder. The rest of the group will serve as predators.
3. While the predators have their backs turned, the game warden distributes the dots from the Beginning
Population bag across the habitat.
4. When the game warden says, “Go!” the predators should turn around, face the habitat, and pick up as many
prey (dots) as they can in a 10-second interval. PREDATORS CAN PICK UP ONLY ONE DOT AT A
TIME, USING ONLY ONE HAND. The game warden should monitor that no scooping or grabbing of
several dots occurs.
5. After Predation I is completed, students should gather the surviving dots and sort and count them by color.
The recorder enters the number of Surviving Predation I dots by color in Data Table I. Dots picked up during
Predation I should be returned to the Beginning Population bag.
Data Table I
Dot
Color
Beginning
Population
Surviving
Predation
I
Offspring
I
Surviving
Predation
II
Offspring
II
Surviving
Offspring III
Predation III
20
20
20
6. Place the Surviving Predation I dots in the Survivors and Their Offspring bag.
7. Simulate the reproduction of each Surviving Predation I dot by selecting from the Offspring bags one dot of
the same color as the survivors and placing them in the Survivors and Their Offspring bag. Record the total
number of each color of offspring in the Offspring I column of Data Table I.
8. While the predators turn their backs, the game warden distributes the dots from the Survivors and Their
Offspring bag across the habitat.
9. When the game warden says, “Go!” the predators should turn around, face the habitat, and pick up as many
prey (dots) as they can in a 10-second interval. PREDATORS CAN PICK UP ONLY ONE DOT AT A
TIME, USING ONLY ONE HAND. The game warden should monitor that no scooping or grabbing of
several dots occurs.
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Biology Institute – Fall 2004
10. After Predation II is completed, students should gather the surviving dots and sort and count them by color.
The recorder enters the number of Surviving Predation II dots by color in Data Table I. Dots picked up during
Predation II should be returned to the Beginning Population bag.
11. Place the Surviving Predation II dots in the Survivors and Their Offspring bag.
12. Simulate the reproduction of each Surviving Predation II dot by selecting from the Offspring bags one dot of
the same color as the survivors and placing them in the Survivors and Their Offspring bag. Record the total
number of each color of offspring in the Offspring II column of Data Table I.
13. While the predators turn their backs, the game warden distributes the dots from the Survivors and Their
Offspring bag across the habitat.
14. When the game warden says, “Go!” the predators should turn around, face the habitat, and pick up as many
prey (dots) as they can in a 10-second interval. PREDATORS CAN PICK UP ONLY ONE DOT AT A
TIME, USING ONLY ONE HAND. The game warden should monitor that no scooping or grabbing of
several dots occurs.
15. After Predation III is completed, students should gather the surviving dots and sort and count them by color.
The recorder enters the number of Surviving Predation III dots by color in Data Table I. Dots picked up during
Predation III should be returned to the Beginning Population bag.
16. Place the Surviving Predation III dots in the Survivors and Their Offspring bag.
17. Simulate the reproduction of each Surviving Predation III dot by selecting from the Offspring bags one dot of
the same color as the survivors and placing them in the Survivors and Their Offspring bag. Record the total
number of each color of offspring in the Offspring III column of Data Table I.
18. Construct a bar graph showing the changes from the original population to Offspring I, II, and III.
Discussion:
1. What do the dots represent in this simulation?
2. Who were the predators?
3. What represents the natural selection pressure?
4. What is the adaptation mechanism of the prey?
5. Which color of dots increased in frequency and why did this happen?
6. Which color of dots decreased in frequency and why did this happen?
The Charles A. Dana Center at UT Austin
85
7. If the dots were real organisms, what color would the parents of the fifth generation most likely be?
8. Predict what you think would happen if this simulation were to continue for three more generations.
9. View the Peppered Moth Animation, complete Data Table II and construct a graph of the changes in moth
numbers.
Data Table II
Year
Number of
Light-colored
Moths
Number of
Dark-colored
Moths
2
4
6
8
10
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Biology Institute – Fall 2004
A Horse—of Course:
Investigating Electrophoresis
This investigation is designed to help you understand how DNA sequencing can be used to identify evidence of
change in species.
The Problem
While on an archeological field investigation at the La Brea Tar Pits in California, you discover the partial remains of
an animal. One scientist suggests that the remains are from a prehistoric horse. His colleague disagrees. She suggests that
the remains were not buried deep enough to be that of a prehistoric horse and is probably related to modern horses.
The university’s lab contains samples of DNA from several prehistoric horses as well as a modern horse. The scientists
have assigned you the task to determine how related the Unknown Horse is to the other horses.
The DNA sample from the remains will be placed in a special gel and subjected to an electric field. The parts of
the sample bearing a negative charge will move toward the positive electrode while the parts of the sample bearing
a positive charge will move toward the negative electrode. This separation creates a distinctive pattern that can be
matched to known samples. Thus, you will compare the results from the Unknown Horse sample to the DNA samples
of the known horses.You can also tell the size of molecules because of the distance they move. Larger molecules move
more slowly; therefore, less distance. Smaller molecules move more quickly and over a greater distance. This helps to
match patterns in the gel.
Electrophoresis is often used in forensic investigations because it can provide useful genetic information in criminal
cases. Samples of blood, skin, and hair can be analyzed through this technique. It is also used in the diagnosis of
disorders, paternity cases, and a variety of research areas. For example, evolutionary biologists use this type of
information to compare similarities and differences among species.
Materials:
1.2 g agarose, 3 L electrophoresis buffer, electrophoresis chamber, balance, 250 mL flask, 100 ml graduated cylinder,
microwave, gloves or hot pads, masking tape, gel casting tray, gel comb, samples from Pliocene Horse, Miocene horse,
Holocene Horse, Unknown Horse, needle point pipettes, power source, plastic wrap, unlined white paper, colored
pencils, metric ruler, safety goggles, laboratory aprons
Procedures:
SAFETY: Caution students about the danger of chemical splashes. Students must wear safety goggles and chemicalresistant aprons during this activity. All chemicals must be disposed of properly. (See Texas Safety Standards for
Kindergarten–Grade 12).
1. Prepare the gel by combining 1.2 grams of agarose and 98.8 mL of buffer solution in a 250 mL flask. Swirl the
flask to dissolve any lumps. Heat the mixture in the microwave until it comes to a boil. Using gloves or hot
pads, open the microwave and swirl the flask without removing it from the microwave. After swirling, remove
the flask and look at the contents. If you can see clear agarose particles in the solution, return the flask to the
microwave and repeat the boiling and swirling process until you can no longer see the agarose particles.
2. Cool the agarose until you can comfortably touch the flask.
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3. Pressing firmly, place the masking tape on both ends of the casting tray to hold the liquid agarose in place as it
solidifies. Then place the comb in its slots on the casting tray.
4. Pour the cooled agarose into the tray. The agarose should come at least two-thirds of the way up the comb
teeth. Small pockets, called wells, will form where the comb is inserted in the agarose. The samples of DNA will
be placed in these pockets.
5. When the agarose has solidified, the comb and the tape should be gently removed.
6. Measure 5 microliters of each DNA sample into the tip end of the needlepoint pipette, being sure to use a fresh
pipette each time. Load the 5 microliter samples into separate wells on the gel, skipping a well between each of
the samples.
7. Record the order of the DNA samples by sketching the gel in the drawing below and labeling the wells with
the names of the samples.
8. Pour enough buffer in the electrophoresis chamber to fill the chamber and completely cover the gel. Place
the gel on the platform inside the electrophoresis chamber. Check the buffer level and add additional buffer
if needed to completely submerse the gel. Make sure that the filled wells are closest to the negative (black)
electrode.
9. Place the lid on the electrophoresis chamber and connect the black lead of the power source to the negative
terminal and the red lead to the positive terminal. Turn on the power supply and adjust the voltage to 100-125
volts.
10. After the gel has run for 5-10 minutes, remove the lid and observe the samples. The separation of colors should
have started. Replace the lid and allow the gel to run for a total of 10-15 more minutes. After the gel has run
for 20-25 minutes, turn off the power supply, disconnect the electrode leads, and remove the chamber lid.
Remove the gel from the casting tray and place it on a piece of clear plastic wrap that is laying on top of a piece
of white unlined paper.
11. Observe the color separation. Measure the distance that each color has migrated from its origin. Record your
observations by sketching them onto the gel diagram below. Be sure to label which sample is which and include
your measurements.
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Discussion:
1. Which horse(s) can be eliminated as being closely related to the Unknown Horse?
2. Which horse(s) cannot be eliminated as being closely related to the Unknown Horse?
3. DNA electrophoresis uses a matrix composed of a highly purified form of agar to separate DNA molecules
according to size. The DNA molecules of organisms contain specific sites known as restriction sites that, when
exposed to restriction enzymes, will produce fragments of DNA that vary in size. These various sized fragments
of DNA separate and appear as bands on an electrophoresis gel. The samples used in your gel were actually food
coloring rather than real DNA. How does the separation of the mixture of the dye color molecules compare
with actual DNA separation?
4. What are some uses for electrophoresis in addition to criminal investigations?
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Evolution Scenarios
Each of the scenarios below describes one of the following evolutionary terms: Adaptation, Biodiversity, Evolution,
Extinction, Natural Selection, Phylogeny, Species, Speciation, or Variation. Read and discuss each scenario. Use your
understanding of these terms to select the one that best relates to each scenario. When your group has more than one
response for each scenario, explain your reasoning.
_____________1. There are only about 1,000 giant pandas left in the wild. An effective captive-breeding program
is critical to the animal’s survival. Scientists are racing against time to understand panda biology and behavior in
an effort to gain insights that will help this species survive in the wild.
_____________2. Scientists have studied the guppy populations in two pools of Trinidad’s Aripo River system.
Guppies in pool #1 are preyed upon by cichlids that tend to eat larger guppies. Guppies in pool #2 are preyed
upon by killifish that tend to eat smaller guppies. Guppies in pool #1 have larger broods, reproduce at a
younger age, and are smaller at maturity than those in pool #2. If guppies from pool #1 are placed in a pool
with killifish predators, the average size of mature guppies increases over time.
______________3. The land snails of the species Cepaea nemoralis have shells that differ in color and number of
stripes. Snails with light-colored, striped shells are found mainly in well-lighted areas, and dark- colored snails
lacking stripes are found in shady places. Shell color serves as camouflage for the snails.
______________4. The Monterey pine and the Bishops pine inhabit the same area of central California, but do not
interbreed to produce fertile offspring due to the fact that one releases its pollen in February and the other in
April.
______________5. The long beak of the hummingbird fits easily into the slender neck of the blossom of a
flowering plant.
______________6. A deciduous forest in West Virginia contains the following types of trees: yellow poplar, sassafras,
black cherry, cucumber magnolia, red maple, red oak, butternut, shagbark hickory, American beech, and sugar
maple.
______________7. Studies of shared dental and skeletal characteristics indicate that domestic cats and lions are
more closely related to each other than they are to horses. Fossil evidence also supports this relationship.
______________8. The Basilosaurus sp. is a prehistoric ancestor of the modern baleen whale. A comparison of the
skeletons of the Basilosaurus sp. and the baleen reveals evidence of a hind leg on the Basilosaurus sp. that is not
found in the skeleton of a baleen whale.
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The Lost Diversity of Easter Island
This activity is designed to help you understand how the loss of diversity within an ecosystem can affect the survival of
organisms.
Scenario
Around 350 AD, voyagers from the Marqueasas islands landed on the small island now known as Easter Island. This small
island, a 64-square mile eastern outpost of Polynesia, was a lush paradise containing dense palm tree forests, toromino
and other shrubs, hauhau plants, and many kinds of grasses. The arriving voyagers cut down the palm trees to build long
canoes to fish for food and cut down the hauhau plants to make ropes from their fibers. The toromino shrubs were used
for their fuel source. The native palm forest and grasslands were also cut down to farm the banana, sugar cane, taro, and
sweet potato plants they had brought with them to supplement their fish and dolphin diet.
By 1400, almost 15,000 people lived on the island. They had a structured society that saw to the allocation of the island’s
resources. But intensive farming had depleted the farm land, native birds had been hunted to near extinction, and
the palm trees had almost all been cut down to build ever-bigger canoes to fish farther out to sea. In desperation, the
islanders began appealing more dramatically to their gods and erected numerous large stone statues around the island.
In 1550, war broke out over the dwindling food supply and decreasing space on the island. By this time, the hauhau
plants had become extinct, having been used to cook the island rats that were farmed in the struggle for survival. With
the palms gone and the fishing waters depleted, the islanders began to consume the only remaining source of protein on
the island—one another.
The once highly structured society crumbled as warring gangs took over. The remaining grasslands were burned to
destroy any hideouts. The winners ate the losers. By 1722, only 100 or so islanders remained, living in the caves of this
now barren island, stripped of its trees and maintaining only a few grasses and a few shrubs. In 1774, when Captain
James Cook visited the island, there were only four canoes that leaked badly and had to be continuously bailed to
remain afloat. Many of the stone statues had been tipped over or destroyed.
Discussion:
1. In what ways were the native plants on the island used by the original voyagers?
2. How did the non-native plants compete with the native
plants on the island?
3. Describe the difference between the number of different kinds of plants in 350 and in 1722. This difference is
called a loss of biodiversity.
4. How did the loss of biodiversity have an impact on the
island dwellers?
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5. How might the loss of biodiversity been prevented?
6. Examine the seeds in the small bag. About how many seeds are in the bag? Guess how many different kinds of
seeds, or species, are in the bag.
Number of Seeds_______________
Number of Species of Seeds______________
7. Open the bag, count the total number of seeds, and then separate the seeds into different species. How many
different kinds of seeds are in the bag?
Number of Seeds_______________
Number of Species of Seeds______________
8. Did everyone in your group agree on the number of species?
9. Was it relatively easy to distinguish each species? Why or why not?
10. Examine the seeds and select the two species that are most different. Place them on opposite sides of your work
area and name one Seeds A, and the other Seeds B. Arrange the remaining seeds in order of similarity from
Seeds A to Seeds B. What criteria did your group use in arranging the seeds?
11. As the teacher directs, observe the arrangements of other groups. How was their arrangement different from or
similar to your group’s arrangement?
12. Which species of seeds do you believe is the most important to humans? Why do you think so?
13. Name each species of seeds. Construct a graph of the number of individuals in each species of seeds. This graph
represents the biodiversity of the seeds in your bag.
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Arthropods and More Arthropods
This activity is designed to help you understand characteristics in organisms by observing and analyzing arthropod
adaptations.
Background Information:
The Phylum Arthropoda includes many familiar classes of animals, such as insects, crustaceans, arachnids, millipedes, and
centipedes. The huge varieties of animals that make up this phylum live in almost every habitat of the world. They serve
many functions within their specific ecosystems and are a significant part of almost all food webs.
Arthropods are diverse but do share the following characteristics: an exoskeleton, a head, a thorax (or a fused
cephalothorax), an abdomen, and pairs of jointed appendages. These animals are distinguished from each other based
on differences in body structures and eating habits. The differences help the animals adapt to their niches and flourish
there.
Materials:
Arthropod specimens contained in petri dishes, dissecting microscope, probe, metric ruler
Procedures:
ANIMAL SAFETY: Arthropods are living organisms and must be handled
with care and respect.
SAFETY: Keep your fingers away from the crayfish claws.Wash your hands
after handling the arthropod specimens.
Observe all of the arthropod specimens with the naked eye and with the dissecting scope. Complete the Arthropod
Characteristics chart for each specimen.
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Arthropod Characteristics
Characteristic
Specimen
1
Specimen 2
Specimen 3
Specimen 4
Specimen 5
Number of body
regions
Length of head
Length of thorax
Length of
abdomen
Description
of legs and
swimmerets
Number of
antennae
Description of
eyes
Description of
mouth parts
Location of
respiratory
organs
Other body parts
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Discussion:
1. Based on your data, which arthropods are best equipped for swimming? Explain your answer.
2. Based on your data, which arthropods are best equipped for crawling or burrowing? Explain your answer.
3. Look at the number of jointed appendages for each specimen. Is this characteristic common to all arthropods?
4. How are crayfish adapted for a watery environment?
5. Like crayfish, pill bugs are also crustaceans. What type of respiratory organs do pill bugs have? Why do these
organisms need to be in close proximity to water?
6. The largest arthropods are aquatic. Hypothesize as to why this is so.
7. What is the likely food source of each specimen?
8. Draw a food web containing at least 10 organisms and including at least five types of arthropods.
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What a Beak
This investigation is designed to help you understand how variations within a species lead to speciation.
Background Information:
Some scientists think that organisms within the same species can undergo enough changes over time to prevent
interbreeding between some populations. This transformation leads to the formation of another distinct species and is
called speciation. Speciation may occur when a group of one species of organisms becomes isolated from their own
population. As natural selection chooses the fittest individuals to survive and reproduce, their traits are passed on to their
offspring. Scientists think this slow process of change causes these isolated organisms to differ distinctly from the original
population from which they came.
Charles Darwin (while on his research adventure around the world during the 1830’s) made observations that led many
biologists to theorize about speciation. Darwin drew sketches and collected many specimens of birds while visiting the
Galapagos Islands near South America. He noticed that these birds had similar characteristics to birds on the mainland,
but their beak shapes and sizes were very different. Upon his return to England, zoologists informed him that the birds
he thought were wrens, warblers and blackbirds were actually all finches. The differences in the beaks began Darwin
thinking about how a bird’s beak may allow it to eat different types of food more efficiently. If a mutation allowed a bird
to become more fit by obtaining more food, then it would pass on these characteristics to its offspring. Over time, these
changes would eventually be passed down to other generations, and these “new” birds would no longer interbreed with
the “original” birds. Thus, you would have a different species.
Darwin made observations of birds, their beaks, and their food sources. He noticed that the size and shape of a bird’s
beak was specifically designed for eating specific types of food. Looking at a bird’s beak can help you determine the
types of foods different birds eat. Short, thick beaks are good for cracking and opening seeds. Narrow, pointed beaks
help birds dig insects out of small cracks. Powerful, hooked beaks are suited for tearing or gripping prey such as mice.
Long, spear-like or wide beaks help some birds catch fish. Broad, flat beaks are good for straining mud and water for
food.
In this investigation, you will determine how the variation in the size and shapes of beaks allow a bird species to take
advantage of food sources. Being able to utilize a food source and survive to reproduce allows a bird to pass its traits on
to its offspring.
Materials:
Timer, spoon, slotted spoon, wooden craft spoon, taster spoon, felt squares, rice-grain maggots, raisin-grubs,
marble-snails
Procedures:
1. Spread the felt square on a flat surface. Each student selects a type of spoon to use as a “beak.”
2. Sprinkle the rice-grain maggots across the felt square.
3. When the teacher calls the time, all students should use their “beak” to feed for 30 seconds. Food can be picked
up with the beak only one piece at a time.
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4. Construct a data table to record the number of pieces of food eaten by each beak.
5. Repeat steps 1–3 for the raisin-grubs and then for the marble-snails. Then add the results of numbers eaten to
the data table.
6. Construct a bar graph of the data in your table.
Discussion:
1. What is a species?
2. Define speciation.
3. What type of beak would a bird have if its main source of food were snails?
4. Predict how a mutation in beak size and shape could lead to speciation in a group of birds that become isolated
from the original population.
5. How can variation in bird beaks lead to speciation?
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The Best Bess Beetles
This investigation is designed to help you understand that behavior of organisms may provide an advantage for survival.
Background:
The short-horned stag beetle Passalus cornutus commonly called the Bess beetle, is found in the eastern United States
and in south Texas deciduous forests These large, shiny black beetles exhibit complete metamorphosis. The adults live
in pairs, with both sexes sharing the tunneling and family care duties. Eggs are laid in tunnels in decomposing wood.
The larvae are fed finely chewed wood chips mixed with feces by the adults. The larvae require several months for
development, and often generations will overlap. The adult stage can last from 6 to 12 months.
Materials:
Petri dish, ruler, balance, Bess beetle in a cup, pennies/washers, dental floss, paper towel, tape, and hand lens
Procedures:
ANIMAL SAFETY: Bess beetles are living organisms and must be handled with care and respect.
SAFETY: Keep your fingers away from the beetles’ pinchers. Wash your hands after handling the beetles.
1. Measure the mass of an empty petri dish to the nearest tenth of a gram. Record the information in
Data Table 1. Pick up the beetle by gently holding it on either side of its abdomen with your thumb and
forefinger and place it on its back in the petri dish. Measure the mass of the dish and the beetle to the nearest
tenth of a gram. Record the information in Data Table 1.
2. Calculate the mass of your beetle by subtracting the mass of the dish from the mass of the beetle and the dish,
and record your calculation in Data Table 1.
Data Table 1
Measurement
Mass of empty petri dish
Mass of beetle and petri dish
Mass of beetle
Average mass of class beetles
Difference between average mass of
class beetles and group beetle
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3. Keep the beetle on its back and measure its length from tip to tip to the nearest tenth of a centimeter. Return
the beetle to the cup. Record the information in Data Table 2.
4. Weigh a penny/washer to the nearest tenth of a gram, and record your measurement in Data Table 2.
Data Table 2
Measurement
Length of group beetle
Average length of class beetles
Difference between average length of
class beetles and group beetle
Mass of one penny/washer
Average mass of class pennies/washers
Difference between average mass
of class pennies/washers and group
penny/washer
5. Describe how your beetle varies in mass and length from the average beetle.
6. How much mass do you think your beetle could pull?
7. Using the materials provided, determine the mass that can be pulled by your Bess beetle. Tape the paper towel
to a flat surface. Use the dental floss to shape a lasso and slip it over the head and body of your beetle until it fits
loosely around the middle of the body between the thorax and abdomen. Do not tie a knot in the loop around
the beetle. Tape the other end of the twine to the petri dish.
8. Place your beetle on an edge of the paper towel so that the beetle can grip the towel as it walks across the
towel. The Petri dish should be on a flat and smooth surface.
9. When the beetle begins to walk and pull the petri dish, add one penny/washer at a time to the dish until the
beetle can no longer move. It may be necessary to reposition the beetle to prevent the dish from touching the
paper. Do not prod or push your beetle.
10. Once the beetle has reached the maximum weight it can pull, gently remove the dental floss from the beetle
and place the beetle in the cup.
11. Count and measure the mass of the total number of pennies/washers the beetle was able to pull. Record this
information in Table 3.
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Data Table 3
Measurement
Number of pennies/washers beetle
pulled
Difference between the class average
number of total pennies/washers pulled
and number pulled by group beetle
Total mass pulled by group beetle
Class average total mass pulled
Difference between the class average
mass of total pennies/washers pulled
and mass of pennies/washers pulled by
group beetle
12. Describe how your beetle varied in the number and mass of total pennies/washers pulled from the average
beetle.
13. How did your actual results compare with your predicted results given in Step 6?
14. As a class, construct a scatterplot graph of the class results for length of beetle and mass pulled. Construct
another scatterplot graph of the class results for mass of beetle and mass pulled. What do the graphs indicate? Is
there any connection between the amount of mass pulled and the length or mass of the beetle pulling?
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Discussion:
1. Observe the beetle’s appendages with a hands lens. What anatomical adaptation does the beetle have that
allows it to exhibit the pulling behavior?
2. Which of the class beetles would most probably survive and reproduce in its normal environment?
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Nailing Evolution
This activity is designed to help you understand that natural selection produces organisms that can be grouped
according to similar characteristics.
Materials:
Ruler, wooden peg, bolt, 2” nail, toggle bolt, 3” nail, brass tack, screw
Procedures:
SAFETY: The tacks, nails, bolts, and screws should be used in an appropriate manner.
1. Record the names of the hardware pieces and your observations for each in Data Table 1. Observe as many
anatomical characteristics as possible.
Data Table 1
Characteristics
Composition
Length
Number
of threads
present
Thread width
Head type
Head size
Other
2. Use the information from Data Table 1 to complete the cladogram below. Begin by listing the wooden peg
as the most closely related hardware fastener to the Common Ancestor. Then add the next hardware fastener
that is the most closely related to the wooden peg according to the information in Data Table 1. Continue this
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process for numbers 3–7. Remember: According to cladistics, the greater the number of characteristics shared
by two organisms, or in this case hardware fasteners, the more closely related they are with regard to their
evolution.
Relatedness of Fasteners
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3. The DNA sequences on the strips were obtained from each of the hardware fasteners. Compare pairs of
hardware fasteners, count any differences, and record that number in Data Table 2. Be sure to compare the
DNA sequences by triplets, such as CTT to GCT, which would only count as one (1) difference.
Data Table 2
Wooden
peg
Wooden
peg
Bolt
Bolt
2” nail
Toggle
bolt
3” nail
Brass tack
Screw
0
0
2” nail
Toggle
bolt
3” nail
Brass tack
Screw
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0
0
0
0
0
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4. Use the information recorded in Data Table 2 to infer the evolutionary relationships among the various
hardware fasteners. For example, the DNA sequence of the wooden peg and brass tack indicate that they are
closely related. To what extent do the DNA sequences above support the information in your cladogram? Do
you need to revise your cladogram? Why or why not?
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A Bear Branch in the Tree of Life
This activity is designed to help you understand the application of using DNA sequencing to show relatedness among
organisms.
Background Information:
Gel electrophoresis is a type of DNA analysis that can be used to determine how closely living organisms are related
to one another based on their DNA. In this procedure, a matrix composed of a highly purified form of agar is used to
separate DNA molecules according to size. The DNA molecules of organisms contain specific sites known as restriction
sites that, when exposed to restriction enzymes, will produces fragments of DNA that vary in size. These various-sized
fragments of DNA separate and appear as bands on an electrophoresis gel. Below are the results of a gel electrophoresis
for three types of bears. Analyze and compare the DNA bands shown in the diagram to determine how closely
the bears are related. The more bands that organisms have in common the more closely related they are. The bands
represent DNA fragments that result when the restriction enzyme Hind III breaks the bonds between the nucleotides
of the mitochondrial DNA of a polar bear, a black bear, and a brown bear.
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Procedures:
1. Complete Table 1 by recording how many variations in band number occur between any two bears. For
example, in examining the bands of the black and polar bears there is a difference of six (6) bands.
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105
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Table 1
Number of
different
bands in
bear-to-bear
comparisons
Polar Bear
Polar Bear
0
Black Bear
6
Black Bear
Brown Bear
0
Brown Bear
0
2. Complete Table 2. The number of different bands is taken from Table 1. To determine the total number of
bands, count the number of bands on the diagram for each of the bears in the pair being compared and then
add the two numbers together. To determine the percent difference, divide the number of different bands by the
total number of bands.
Table 2
Bear
Comparison
Polar Bear/
Black Bear
Total Number
of Bands
Number of
Different
Bands
Percent
Difference
10
6
60%
Black Bear/
Brown Bear
Brown Bear/
Polar Bear
3. Using the knowledge gained in the Nailing Evolution Learning Experience and the information from Table 2,
complete this cladogram, showing the relationship of the polar bear, black bear, and brown bear.
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4. Two of these species of bears have been known to produce fertile hybrids when allowed to breed with each
other in captivity. Which two are they? Why do they not mate in the wild?
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Cats and Birds
Assessment Task
A population of beachcombing birds lives on an island with light-colored sand beaches. These birds occur naturally in
two colors, white and black. As the population increases, some of the birds move to a nearby island with dark-colored
sand beaches. This island has many more food sources and vegetation for nesting, but it also has a small population of
bird-eating cats, some with extremely poor eyesight and some with normal eyesight.
1. After a period of time, the birds on the two islands are reunited but are unable to mate. What factors and
processes might account for this change?
2. Draw an illustration of how bird color can be an advantageous adaptation.
3. Use the data in Table 1 to predict the populations of cats and birds in year 4.
Table 1
Year
Cats with
Normal
Eyesight
Cats with
Poor Eyesight
Total Number
of Birds
1
90
30
500
2
42
12
239
3
12
2
292
4
4. Based on the data in Table 1, what will likely happen to the population of Cats with Poor Eyesight?
5. Cite examples of variation in this scenario.
6. A mutation occurs that results in some of the cats with poor eyesight being able to make sounds similar to the
mating call the birds make. How would this behavioral adaptation be advantageous?
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7. Fossil evidence is discovered on the island indicating that there might have been a third type of cat living on
the island at some point in time. Gel electrophoresis is performed with DNA taken from the cats living on the
island and from the cat fossil. The results are shown in Table 2. Based on this data, would you conclude that
these cats are of the same species? Why or why not?
Table 2
Cat
Comparison
Total Number
of Bands
Number of
Different
Bands
Percent
Difference
Cats with
normal
eyesight/
Fossil cat
22
10
45%
Cats with
poor eyesight/
Fossil cat
21
12
57%
22
1
5%
Cats with
normal
eyesight/Cats
with poor
eyesight
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