SCOPE,
SEQUENCE,
COORDINATION
and
A National Curriculum Project for High School Science Education
This project was funded in part by the National Science
Foundation. Opinions expressed are those of the authors
and not necessarily those of the Foundation. The SS&C
Project encourages reproduction of these materials for
distribution in the classroom. For permission for any other
use, please contact SS&C, National Science Teachers
Association, 1840 Wilson Blvd., Arlington, VA 22201-3000.
Copyright 1996 National ScienceTeachers Association.
SCOPE, SEQUENCE,
and
COORDINATION
SS&C Research and Development Center
Gerry Wheeler, Principal Investigator
Erma M. Anderson, Project Director
Nancy Erwin, Project Editor
Rick McGolerick, Project Coordinator
Arlington, Va., 703.312.9256
lowa School Sites and Lead Teachers
Pleasant Valley H.S., William Roberts
North Scott H.S., Mike Brown
North Carolina Coordination Center
Evaluation Center
Charles Coble, Center Co-Director
Jessie Jones, School Coordinator
East Carolina University, 919.328.6172
Frances Lawrenz, Center Director
Doug Huffman, Associate Director
Wayne Welch, Consultant
University of Minnesota, 612.625.2046
North Carolina School Sites and Lead Teachers
Tarboro H.S., Ernestine Smith
Northside H.S., Glenda Burrus
Houston SS&C Materials Development
and Coordination Center
Puerto Rico Coordination Center*
Linda W. Crow, Center Director
Godrej H. Sethna, School Coordinator
University of Houston-Downtown, 713.221.8583
Manuel Gomez, Center Co-Director
Acenet Bernacet, Center Co-Director
University of Puerto Rico, 809.765.5170
Houston School Sites and Lead Teachers
Jefferson Davis H.S., Lois Range
Lee H.S., Thomas Ivy
Jack Yates H.S., Diane Schranck
Puerto Rico School Site
UPR Lab H.S.
* * * * * * * * * * * *
California Coordination Center
Tom Hinojosa, Center Coordinator
Santa Clara, Calif., 408.244.3080
California School Sites and Lead Teachers
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Sacramento H.S., Brian Jacobs
Pilot Sites
Site Coordinator and Lead Teacher
Fox Lane H.S., New York, Arthur Eisenkraft
Georgetown Day School, Washington, D.C.,
William George
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Clinton H.S., New York, John Laffan*
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University of Iowa, 319.335.1189
*not part of the NSF-funded SS&C Project.
Advisory Board
Project Associates
Dr. Rodney L. Doran (Chairperson),
University of Buffalo
Bill G. Aldridge
SciEdSol, Henderson, Nev.
Dr. Albert V. Baez, Vivamos Mejor/USA
Dorothy L. Gabel
Indiana University
Dr. Shirley M. Malcom, American Association
for the Advancement of Science
Dr. Shirley M. McBay, Quality Education for Minorities
Dr. Paul Saltman, University of California-San Diego
Dr. Kendall N. Starkweather, International
Technology Education Association
Dr. Kathryn Sullivan, Ohio Center of
Science and Industry
Stephen D. Druger
Northwestern University
George Miller
University of California-Irvine
National Science Education Standard—Life Science
Biological Evolution
Natural selection and its evolutionary consequences provide a scientific
explanation for the fossil record of ancient life forms, as well as for the
striking molecular similarities observed among the diverse species of
living organisms.
The millions of different species of plants, animals, and microorganisms that live on Earth today are related by descent from common ancestors.
Teacher Materials
Learning Sequence Item:
1003
Structural Factors in Evolution
May 1996
Adapted by: William T. George and Linda W. Crow
Natural Selection and Its Evolutionary Consequences. Students should review examples of homologous, analogous,
and vestigial structures. They should distinguish between divergent and convergent evolution as they relate to natural
selection. They should also examine phyletic trees of major groups of plants and animals and the isolating mechanisms
that cause speciation. (Biology, A Framework for High School Science Education, p. 108.)
Contents
Matrix
Suggested Sequence of Events
Lab Activities
1. Uncommon Relatives!
2. The Nuts and Bolts of Phyletic Tree Making
3. Life on Earth
4. Human Variation with Possible Adaptive Value
Assessments
1. Homologies
2. Phyletic Trees
3. Adaptations, I
4. Adaptations, II
This micro-unit was adapted by William T. George (Georgetown Day School, Washington, D. C.) and
Linda W. Crow (University
3 of Houston-Downtown)
1003
Natural Selection and Its Evolutionary Consequences. Students should review examples of
homologous, analogous, and vestigial structures. They should distinguish between divergent and
convergent evolution as they relate to natural selection. They should also examine phyletic trees of
major groups of plants and animals and the isolating mechanisms that cause speciation. (Biology, A
Framework for High School Science Education, p. 108.)
Learning Sequence
Science as Inquiry
Science in Personal
and Social Perspectives
Science and Technology
Uncommon Relatives!
Activity 1
Human Variation with
Possible Adaptive Value
Activity 4
The Nuts and Bolts of
Phyletic Tree Making
Activity 2
Life on Earth
Activity 3
Homologies
Assessment 1
Phyletic Trees
Assessment 2
Adaptations, I
Assessment 3
Adaptations, II
Assessment 4
4
History and Nature
of Science
Suggested Sequence of Events
Event #1
Lab Activity
1. Uncommon Relatives (45 minutes)
Event #2
Lab Activity
2. The Nuts and Bolts of Phyletic Tree Making (45 minutes)
Alternative or Additional Activities
3. Life on Earth (1 hour)
Event #3
Lab Activity
4. Human Variation with Possible Adaptive Value (45 minutes)
Event #4
Readings from Science as Inquiry, Science and Technology, Science in Personal and Social Perspectives, and History and Nature of Science
Suggested readings:
Asimov, Isaac, “Classifying Life,” A Short History of Biology, Garden City, N.Y.:
The Natural History Press, 1964, pp. 31–37.
Campbell, Neil A., “The Evolutionary History of Biological Divsersity,” Biology,
3rd Ed., Redwood City, Calif.: The Benjamin/Cummings Publishing Co., Inc.,
pp. 500–503.
Preiser, Rachel, “Evolution Watch,” Discover Magazine, Vol. 17, No. 5, March
1996, p. 30.
Zimmer, Carl, “Evolution Watch,” Discover Magazine, Vol. 17, No. 3, March 1996,
p. 34.
Assessment items are at the back of this volume.
5
Assessment Recommendations
This teacher materials packet contains a few items suggested for classroom assessment. Often, three
types of items are included. Some have been tested and reviewed, but not all.
1. Multiple-choice questions accompanied by short essays, called justification, that allow teachers to
find out if students really understand their selections on the multiple choice.
2. Open-ended questions asking for essay responses.
3. Suggestions for performance tasks, usually including laboratory work, questions to be answered,
data to be graphed and processed, and inferences to be made. Some tasks include proposals for
student design of such tasks. These may sometimes closely resemble a good laboratory task, since
the best types of laboratories are assessing student skills and performance at all times. Special
assessment tasks will not be needed if measures such as questions, tabulations, graphs, calculations,
etc., are incorporated into regular lab activities.
Teachers are encouraged to make changes in these items to suit their own classroom situations and to
develop further items of their own, hopefully finding inspiration in the models we have provided. We
hope you may consider adding your best items to our pool. We also will be very pleased to hear of
proposed revisions to our items when you think they are needed.
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Activity 1
Teacher Sheet
Science as Inquiry
Uncommon Relatives!
How do the bones of animal limbs compare?
Overview:
The purpose of this activity is to focus on how homologous structures support the theory of common decent.
Students will examine homologous bone structures found in a frog arm, a chicken wing and a human arm.
Materials:
Per lab group:
chicken wing (fresh from grocery store)
dissecting pan
forceps
frog, preserved
gloves, disposable, 1 pr
scalpel
scissors
skeleton, human (model or chart)
Procedure:
Fresh frog legs (but not arms) are often available in grocery
stores. These fresh legs may be useful to you to avoid the problems of
preserved specimens. Do to the nature of this activity, it is not
suggested to catch living frogs and use them for this procedure.
Strippng the Skin from the Arm. Using a scalpel and a dissecting pan, students cut the skin around the base of the frog’s arm where
it joins the body.
Instruct them to grasp the edge of the skin with forceps and pull
the skin down the arm toward the digits. If this procedure seems
difficult, it sometimes help to pull the frog’s arm upward toward the
head, extending it as far as possible. It is very similar to removing the
skin from a piece of chicken before cooking.
Removing Arm from Shoulder. Using scissors, students cut the
muscle around the base of the arm to expose the bone. Warn them to
be careful doing this part of the procedure and to proceed slowly. If they do not they may lose part of
what they want to see. At this point they will have the bones of the shoulder and arm exposed. Next, they
loosen the arm from the shoulder by rotating the arm in a circular fashion and pulling it backward. Some
connective tissues may have to be cut to completely free the arm from the shoulder.
Revealing the Skeletal System of Arm. With the arm successfully removed from the shoulder,
students cut away the muscles, trying not to disturb the skeletal system. Suggest that they gently scrap
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Activity 1
the bones to move as much muscle and connective tissue as possible.
Finally have them draw this dissected arm, showing the arrangements of
bones in the frog arm. Detail is important so encourage them to show as
much as possible.
Chicken Wing. Repeat this process using a chicken wing. Since the wing
is already removed from the shoulder, Students need only strip the skin and
remove the muscular tissue. Again have them draw the arrangement of the
bones in the chicken wing.
Upon completion of both of these dissections, have students compare the frog arm, chicken wing and
human arm (using a chart or model). In each case students will need to determine the total number of
bones, point out any similarities in structure of the limbs, similarities in the shape of the bones and
similarities in the arrangement of the bones.
In a large group discussion, discuss these similarities using the illustrations of bone structures.
Introduce the terms—homologous and vestigial structures.
Background:
This activity has been done to point out that anatomical similarities between species will often indicate a
common descent in evolutionary terms. The same skeletal elements make up the limbs of humans, chickens,
and frogs, although these appendages are used in very different ways. These structures are referred to as
homologous because they are similar in structure but different in function. Obviously a chicken uses its wings
to fly, the frog uses its limbs to jump, and humans use their arms for grasping and pulling. All of these limbs
have different functions, but they all have similar structures as revealed by the skeletal comparisons. In fact,
some of the same bones are present although the specific design details do vary.
Some structures have similar functions but not similar structures. These structures are referred to as
analogous. The wing of a insect and the wing of a bat are both used for flying, but their structures are
very different.
A common descent hypothesis was proposed by Darwin to explain the anatomical similarities
between organisms. All vertebrate forelimbs contain the same set of bones that are organized in similar
ways. Although their functions are not similar, this structural evidence points toward a common ancestor
with a basic forelimb that was modified through an evolutionary pathway.
There are some structures that are labeled as vestigial because they are not functional. Humans have
a tailbone but no tail. Some snakes have visible (yet useless) legs. These vestigial structures provide a
glimpse of perhaps a former functional structure that is no longer useful.
At the end of this activity , it is important to introduce to the students to the terms—homologous,
analogous, vestigial—and to the theory of common descent. Have them provide examples of each of
these types of structures. There are many more than mentioned in this brief background section.
Variations:
A comparison of chick and pig embryos can also be used to provide embryological evidence of common descent. Slides of 72–96 hour chick and 8–l0 mm pig embryos are needed for this activity and the
teacher should become familiar with structural features of these embryos in order to show similarities.
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Activity 1
Bone Structures
Similar bones are shaded with
identical patterns.
Adapted from:
Biological Science Curriculum Study, Biological Science, An Ecological Approach, Kendall/Hunt
Publishing Co., 1987.
Campbell, Neil A., Biology, Benjamin/Cummings Publishing Co., 1990.
Miller, Kenneth R., and Joseph Levine, Biology, Prentice Hall, 1991.
Volpe, E. Peter, Understanding Evolution, 2nd Ed., Dubuque, Iowa: Wm. C. Brown Co. Publishers,
1970, p. 131.
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Activity 2
Teacher Sheet
Science as Inquiry
The Nuts and Bolts of Phyletic Tree Making
How can a phyletic tree be constructed?
Overview:
The purpose of this investigation is to allow students to become familiar with the techniques involved
in constructing a phyletic tree. It is assumed that in previous grade levels students have had basic experiences in classification (see Micro-Units 901, 903 and 905).
Materials:
Per lab group (2 students):
box, small (or plastic bag) containing 20 of the following items:
small springs
pencils
paper clips
cup hooks
staples
washers
Phillips-head machine screws
wing nuts
wood screws
stop nuts
l-cm square of wire screen
straight nails
picture hanging screws
slotted-head screws
metal snaps
Phillips pan-head screws
safety pins
watch gears
1-cm lengths of wire
thumbtacks
paper fasteners
drawing paper
metric ruler
Procedure:
Before class begins, prepare boxes or bags with 20 of the hardware and office supply pieces. Each
lab group will need one of these for this activity. Be sure that each one has the same 20 pieces but none
of these 20 pieces can be duplicates.
Using the drawing paper, students empty the contents of the box on top of the paper. Ask them to divide all
the objects into two groups based on some observable characteristic that is present in one group and totally absent
in the other group. For example, one characteristic that could be used is the
presence or absence of a head ( nails can have a head and nuts do not). As you
move around the room check to see if this first division is based on the total
presence or absence of the chosen characteristic. Have students place one
Observable
characteristic
group on one side of the paper and the other on the other side of the paper.
absent
present
Next students use a ruler to draw a 2-inch V using two lines at the
bottom of the paper. Have student label the upper ends of the V-head with
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Activity 2
the characteristic that is present in one group and absent
in the other group. At this point they have just established
the first evolutionary step in constructing their phyletic
tree.
Students continue the process and divide each
group into further groups. This division is always
Observable
characteristic
based on the presence or absence of an observable
characteristic. Each time they should draw their Vabsent
present
shaped lines and label the ends with the characteristic
used.
Challenge them to continue it until they only have
one item in each group. This challenge may be difficult
to achieve if the pieces are similar. If they accomplish this feat, they should have 20 different groups at
the top of their paper and each of these groups will have only one member.
Have them post their trees without the objects and review with the class the strategies used. Some things
to look for is the use of the same characteristic on each side of the tree but at different levels. Color is usually
not a good characteristic to use because of its variability. You may want to have some other pieces to introduce
at this time that can be classified using the different phyletic trees. A good
system should be able to accommodate new items. If not, the system must be
revised.
Background:
African
Impala
Oryx
Aepyceros
Red Deer
Reindeer
Oryx Cervus
Rangifer
Bovidae
Cervidae
Ass
Horse
Zebra
Equus (genus)
Equidae (family)
Ungulata (order)
Sample Tree Diagram
11
Modern systematists classify
Common ancestor
organisms in
phyogenetic tees to
reflect the evolutionary history of a group of
organisms. These trees reflect this phylogeny and
usually resemble the sample tree diagram.
Organisms are more closely related if they
have a more recent common ancestor. In the
example shown, the impala and oryx are more
closely related to one another than the impala
and the reindeer.
The steps involved in creating a tree are
similar to what was done in this activity. These
steps are: identification of the character traits,
identification of the different states of these
characters, and deciphering a pattern of evolution for the characters based on which ones are
the oldest versions.
1003
Activity 2
Variations:
Encourage students to compare and contrast phyletic trees of objects and phyletic trees of living
organisms. Refer to Activity l in discussions of living phyletic trees and the theory of common descent.
Use recent discoveries of deep-sea vent organisms or human evolution to spark discussions.
Adapted from:
Madder, Sylvia S., Biology, 4th Ed., Brown, 1993.
Thompson, Ron, Sherry Braun, Jay Young, and James Pulley, Biology Investigations, Heath Publishing,
1991.
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Activity 3
an alternative activity for Event 2
Teacher Sheet
Science as Inquiry
Life on Earth
How do organisms compare?
Overview:
The purpose of this activity is to compare similarities and differences among phyla of plants and
animals; relate structural adaptations to the evolution of these groups and develop phyletic trees among
the common groups of plants and animals representing life on Earth. It is assumed that students have had
previous experiences in creating phyletic trees (see Activity 2).
Materials:
Per lab group (3–4 students):
algae, live (chlorophytes, phaeophytes, rhodophytes)
plants, live or preserved, (mosses, ferns, gymnosperms, angiosperms)
animals, live or preserved (cnidarians, jellyfish, worms, mollusks, starfish, arthropods, echinoderms,
chordates)
probes, blunt
hand lens or stereo microscope
metric rulers
pencils
reference materials
Procedure:
This activity should be separated into 2 parts: plant diversity and animal diversity. Each lab station
should contain several representative genera from each of the divisions and phyla of plants and animals
listed above. A minimum of 3 representatives are need to support the objectives of the activity. A lab
station could contain the following:
Plant Diversity. Algaes—Fucus, Sargassium, Ulva, Polysiphonia. Mosses—Marchantia, Sphagnum,
Polytrichum, Mnium. Ferns—Polypodium, Pteridium, Asplenium, Polystichum. Lycopods—Lycopodium,
Psilotum, Equisetum, Selaginella. Gymnosperms—Ginkgo, Pinus, Juniperus, Tsuga. Angiosperms—
Magnolia, Lilium, Chrysanthemum.
Animal Diversity. Sponges—Grantia, Leucosolenia, Spongilla. Cnidarians—Hydra, Obelia, Aurelia,
Metridium. Worms—Taenia, Planaria, Ascaris, Lumbricus, Nereis. Mollusks—Mya, Helix, Ostrea,
Loligo. Arthropods—Limulus, Scolopendra, Spirobolus, Romalea, Argiope. Echinoderms—Asterias,
Cucumaria, Arbcia. Chordates—Entosphenus, Raja, Squalus, Amia, Necturus, Bufo, Anolis.
Materials for this activity can be purchased at any major biological supply house. You may substitute
any genera as long as major groups are represented.
Students use their phyletic tree-building skills to separate the common groups of plants and animals
and build a phyletic tree for each kingdom using representative organisms at each station. They base their
phyletic trees on comparative macroscopic observations. Ask them to provide evidence to support their
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Activity 3
schemes. Their evidence must include similarities and differences among the divisions and phyla of
living organisms. Structural adaptations related to the evolution of the groups can be introduced. Only
common names of the specimens should be used. (Possible extension: ask students to research taxonomic
names found in each group.)
It is important that students see the application of Activity 2, using these living or preserved specimens. To guide students through this exercise the teacher should become familiar with structural similarities and differences of these organisms, habitat and niche requirements of the representative genera at
each station, and range of distribution of these organisms. After students have constructed their phyletic
trees, ask them to defend their model to the class. As an extension, ask students to support the accuracy
of their phyletic tree using library reference materials.
Background:
The major groups are described and their characteristics that are important for classification purposes
are listed:
Plants.
Algae are aquatic organisms that produce their food through the process of photosynthesis. Although
all of them contain chlorophyll, there are other pigments that they can contain and usually they are
named for this other type of pigment (green algae, brown algae, blue-green algae). In classifying them ,
their color, structure and living habits become important. Structural features such as presence or absence
of flagella and unicellular or multi-cellular are examples of these distinguishing features. Living habits
refers to whether the algae is colonial or exists as a single individual. Suggested varieties to be used in
this activity are: Fucus, Sargassium, Ulva and Polysiphonia.
Fucus (or rockweed) is a brown, multi-cellular, marine algae and one of the larger varieties. They can be
stored for long periods in a refrigerator. Their name comes from their characteristic brown or brown-green
color which is due to the presence of a carotenoid pigment. Brown algae is harvested for human consumption
and used as fertilizer in some parts of the world. Algin which is a pectin-like material is derived from these
seaweeds. This substance is used in ice cream and cheeses to give them a smooth consistency.
Sargassium (or rockweed) is a brown algae They often have a slimy feel which protects them from
wave action. They will often break off and congregate in large masses in the ocean.
Ulva (or sea lettuce) are multi-cellular green algae and are referred to as seaweeds. Along with green
varieties there are also brown and red versions. It is edible and owes its common name to its lettuce-like
appearance. It consists of a blades of leaves with a root-like structure at its base called a holdfast. This
structure anchors Ulva in place.
Polysiphonia is a red, multi-cellular algae found in warmer marine waters. Its overall color varies
from reddish-brown to a purple. it is feathery and attaches to rocks, wharves or piers.
Mosses have stem-like structures that are arranged in leaf patterns. They are low-lying and prefer
moist environments. They are more familiar to us as a mat of green material which is really composed of
many plants growing tightly together. Suggested varieties to be used in this activity are: Marchanatia,
(liverworts), Sphagnam (peat moss), Polytrichum and Mnium.
Ferns are seedless plants that still flourish today. There are usually found in the tropical areas.
Suggested varieties to be used in this activity are: Polypodium, Pteridium, Asplenium and Polystichum.
Lycopods first developed during the Paleozoic period. Although during this time there were many
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Activity 3
varieties and sizes, only the smaller varieties have survived. Suggested varieties to be used in this activity
are: Lycopodium, Psilotum, Equisetum and Selaginella.
Gymnosperms are known for their production of cones, needle-like leaves and evergreen abilities.
Suggested varieties to be used in this activity are: Ginkgo, Pinus, Juniperus and Tsuga. Ginkgo (maidenhair tree) is one of the few remaining cycad species. These are palm-like trees that were very abundant
during the Mesozoic Era and probably were the main food source for vegetarian dinosaurs. The gingko is
primarily found in China.
Angiosperms are known for their flowering plant life cycle and were not prevalent until the Cenozoic Era. Suggested varieties to be used in this activity are: Magnolia, Lilium and Chrysanthemum.
Animals.
Sponges are sessile filter feeders, that is, they usually lived attached to something else and filter the
water through their body, leaving the food particles behind. Suggested varieties to be used in this activity
are: Grantia, Leucosolenia and Spongilla.
Cnidarian are tubed or bell-shaped animals that are radially symmetrical. They capture their prey
using stinging cells. Suggested varieties to be used in this activity are: Hydra, Obelia, Aurelia, and
Metridium.
Worms are composed of three groups—flatworms, roundworms, and annelids. Flatworms are
bilaterally symmetrical and have a ribbon-like appearance. Some are parasitic. Roundworms are also
bilaterally symmetrical and are not segmented. Suggested varieties to be used in this activity are: Taenia,
Planaria, Ascaris, Lumbricus and Nereis. Annelids are segmented worms.
Mollusks are soft-bodied, unsegmented animals. Their body usually has three parts—foot, mantle
and internal organs. Suggested varieties to be used in this activity are: Mya, Helix, Ostrea and Loligo.
Arthropods are segmented and have an external skeleton with jointed appendages. Suggested
varieties to be used in this activity are: Limulus, Scolopendra, Spirobolus, Romalea, and Argiope.
Echinoderms are radially symmetrical and have a spiny skin. Suggested varieties to be used in this
activity are: Asterias, Cucumaria, and Arbcia.
Chordates are segmented, have bilateral symmetry and a tube within a tube body plan. Suggested
varieties to be used in this activity are: Entosphenus, Raja, Squalus, Amia, Necturus, Bufo and Anolis.
When doing this activity, encourage students to use the same process that they used with the “hardware” phyletic trees. Also remind them that as they build their tree up, their structure should also reflect
the evolutionary changes that have occurred.
Variations:
Have students choose one phyla or division to research. Their research could include characteristics
of the taxonomic group, evolutionary origins, geographic distribution, adaptive specialization’s found in
the group, and economic value of the group.
Encourage students to think of other criteria that can be used to build phyletic trees. Introduce other
models scientists use to connect groups of plants and animals evolutionary such as cladograms. Have
students construct cladograms with representative organisms.
Adapted from: none
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Activity 4
Teacher Sheet
Science in Personal and Social Perspectives
Human Variation with Possible Adaptive Value
How might specific variations in traits affect survival?
Overview:
Assume that suddenly, for some unknown reason, selection for reproduction was based on a person’s
ability to digest starch. Those best adapted to this new environmental condition have better survival
chances, are healthier, and are able to continue the species. Sexual selection is based on healthier individuals. An enzyme present in human saliva, salivary amylase, begins starch digestion in the mouth. If
some humans have a greater amount of salivary amylase in their saliva, they would be healthier and
better suited to mate than humans having a smaller amount of salivary amylase. The purpose of this
investigation is to determine which students have a greater ability to digest starch and would be favored
by this new environmental condition.
Materials:
Per lab group:
glass-marking pencil
well plates, 2 (24 cell)
graduated cylinder, 25 mL
iodine solution, (5 g iodine, 10 g potassium iodide, 1 L water)
straw, drinking
starch solution (2 g cornstarch, 10 mL water)
medicine dropper or plastic micro-pipettes
glass stirring rod
tap water
test tube, 2 per student
Procedure:
Both starch and iodine solution can be bought commercially, but it is very easy to make. To prepare
iodine solution, add 5 g of iodine and 10 g of potassium iodide to 1 liter of water. The solution should be
pale yellow. Add more water if needed. Store this solution in brown bottles. It will permanently stain
clothing. To prepare starch solution, add 2 g of cornstarch to 10 mL of water and add this mixture to 1
liter of boiling water. Stir for two minutes and allow to cool.
This activity uses well plates or spot plates. These plates are usually plastic and are very expensive to
use. Since each student will need to conduct 10 trials, two 24 cell well plates are needed per lab group.
The plates do come in different size with a variety of wells and a variety of well capacities. Remember to
adjust your chemical amounts if you change the well volume capacity. For this procedure the 24 cell well
plates will be used.
Have students place the well plates on clean white sheets of paper. On the paper they can number the
cells from 1 to 10, representing the ten trials that are needed.
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Activity 4
White paper
1
2
3
4
7
8
9
10
1
2
3
4
7
8
9
10
5
6
5
6
Student 1
Student 2
24 cell well plate
This well plate can accommodate ten trials for two students, so you will need two of them for each
lab group of four students. Next have them add 10 drops of iodine solution to each of the numbered
wells. The volume capacity of these well plates is usually 2.8 mL.
In one of their test tubes have each student prepare a 6% saliva solution. First have them collect 1 mL
of their own saliva by salivating through a straw into a 25 mL graduated cylinder. Warn them to be
patient. This process does take a little time. After they have collected 1 mL of saliva, have them add 17
mL of tap water to their test tube and add the 1 mL of saliva to it. Mix gently with a stirring rod. Be sure
to warn them to rinse the cylinder thoroughly after each student has used it and to use individual straws
for the saliva collection process.
In their second test tube, have students mix 1 mL of their prepared saliva solution and 7 mL of the
starch solution. As soon as they have mix them, instruct them to start the timing process.
After three minutes has passed, students remove a small amount of the starch and saliva solution
from their test tube and place 1 drop in well #1. Be sure student return the remaining amount in the
dropper to the test tube. Students record color of the iodine solution after the starch and saliva solution
has been added. In the presence of starch, the iodine solution will be blue-black. If no starch is present,
the iodine solution will not change.
At 3-minute intervals, students continue to add 1 drop of the saliva-starch solution to the properly
numbered well (after 6 minutes, 1 drop should be added to well #2, after 9 minutes, well #3). After 30
minutes has passed, all 10 wells should have been used. After each drop is added, students should record
the color. Be sure to caution students to use their well plate series for the entire 30 minutes of 3 minute
intervals.
Students construct a data table for the entire class, recording the total students that found a color
change at a particular time interval. Each student will prepare a line graph that compares the number of
students reporting color changes at each time interval.
From the data obtained, separate students into two groups depending on their ability to digest saliva.
Those students who have the greatest ability to digest starch can reproduce but only with their own kind.
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Activity 4
Those who are least able to digest starch cannot reproduce at all, are deemed as unsuccessful and are
isolated (perhaps doomed to extinction)!
Background:
Genetic variations in class populations provide students with excellent examples of how populations
with specific variations can show adaptive value. Students can become aware of “fit” characters when
dealing with a simple concept of like the ability to digest starch. Adding the concept of reproductive
isolation gives added support to fitness concepts and can lead students to an understanding of how
reproductive isolation can happen and new species form.
Variations:
Students can examine other examples of variations in human populations and develop their own
scenario for reproductive isolation.
Adapted from:
Miller and Levine, Biology, Laboratory Manual, Prentice Hall, 1991.
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Assessment 1
Science as Inquiry
Homologies
Item:
Even though the limbs of a frog and a chicken are very different in outward appearance and function,
their internal structure is remarkably similar. How can you explain this observation?
Answer:
Homologous structures are evolutionary adaptations to specific environments from groups which
have risen from common ancestors. The adaptations have enabled organisms to survive successfully in
different environments.
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Assessment 2
Science as Inquiry
Phyletic Trees
Item:
A phyletic tree is a tool used to show specific relationships among groups of organisms. These
relationships deal primarily with:
A. geographic location of the group.
B. ecology of the group.
C. size of the group.
D. evolution of the group.
Justification:
Discuss how phyletic trees are built. What criteria are used to determine the branches of the tree?
Answer:
D. Systematists use phyletic trees as a tool to group organism according to their evolutionary relationships. Organisms with similar traits are grouped together and placed on different branches of the tree.
The organisms with the most ancestral traits are grouped at the base of the tree, while organisms with
more recently evolved traits are placed higher up on the tree.
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Assessment 3
Science as Inquiry
Adaptations, I
Item:
Explain why it is advantageous for a species to show variation among individuals.
Answer:
Variation within a species is advantageous because it enables the populations of the species to adapt
to changes in their environments.
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Assessment 4
Science as Inquiry
Adaptations, II
Item:
What role does isolation play in forming new species?
Answer:
Isolation keeps groups with different variations from interbreeding, which causes the differences
between the groups to build up.
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Unit Materials/References
Consumables
Item
angiosperms
annelids
arthropods
chicken wings
chordates
cnidarians
echinoderms
ferns
frogs
gloves, disposable
gymnosperms
iodine
jellyfish
lycopods
mollusks
mosses
roundworms
starch solution
starfish
straws, drinking
water
well plates (24 cell)
Quantity (per lab group)
3 types
3 types
3 types
1
3 types
3 types
3 types
3 types
1
1 pr
3 types
20 mL
3 types
3 types
3 types
3 types
3 types
20 mL
3 types
1
50 mL
2
Activity
3*
3*
3*
1
3*
3*
3*
3*
1
1
3*
2
3*
3*
3*
3*
3*
2
3*
4
2
4
Nonconsumables
Item
beakers, 150-mL
box, small (or plastic bag)
chart: human skeleton
drawing paper
forceps
graduated cylinders, 25-mL
hardware pieces
medicine droppers
metric ruler
pan, dissecting
pencils, marking
probes
Quantity (per lab group)
2
1
1
4
1
1
1 box
1
1
1
1
1
(continued)
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Activity
4
2
1
1, 2
1
4
2
2
1, 2, 3*
1
2
1
1003
Unit Materials/References
rods, stirring
scalpel
scissors
stereo microscope
test tubes
1
1
1
1
10
1
2
1
3*
2
*indicates alternative or additional activity
Key to activities:
1. Uncommon Relatives
2. The Nuts and Bolts of Phyletic Tree Making
3. Life on Earth
4. Human Variation with Possible Adaptive Value
Activity Sources
Biological Science Curriculum Study, Biological Science, An Ecological Approach, Kendall/Hunt
Publishing Co., 1987.
Madder, Sylvia S., Biology, 4th Ed., Brown, 1993.
Miller, Kenneth R., and Joseph Levine, Biology, Prentice Hall, 1991.Campbell, Neil A., Biology, Benjamin/Cummings Publishing Co., 1990.
Miller and Levine, Biology, Laboratory Manual, Prenctice Hall, 1991.
Thompson, Ron, Sherry Braun, Jay Young, and James Pulley, Biology Investigations, Heath Publishing,
1991.
Volpe, E. Peter, Understanding Evolution, 2nd Ed., Dubuque, Iowa: Wm. C. Brown Co. Publishers,
1970, p. 131.
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