1. science
2. medicine
3. genetics

PRISM UHH GK-12
PRISM UHH GK-12
Hawaiian Origami Birds
Natural Selection
Concepts
In 1859, Charles Darwin
and Aflred Russel
Wallace proposed the
theory of evolution by
natural selection. Their
theory was later combined
with Mendelian
inheritance to explain the
connection of genes (units
of evolution) and natural
selection. This theory has
become the principle
explanation for species
diversity.
Standards addressed
7.5.4, 7.5.6
Duration
1 60 minute class periods
Source Material
w w w.indiana.edu/~ensiw
eb/lessons/origami.html
Vocabulary
Natural Selection
Phenotype
Genotype
Summary
After students have a strong understanding of Adaptations and Genetic
Variation, they will be introduced to Natural Selection. They will participate in
a natural selection simulation in which they will create and modify “paper
airplanes” over several generations to visualize how favorable heritable traits are
passed on. These paper airplanes represent wild birds of a population.
Objectives
• Students will simulate how genes are passed from one generation to the
next.
• Students will understand how traits that are favorable for survival
become more common over generations.
• Students will know that both genetic variation and environmental factors
causes of evolution and species diversity.
Materials
Paper
Ruler
Tape
Straws
Scissors
Coin
Six-sided die
Background
The Hawaiian Origami Bird (Aves hawaiiensis) lives on the rugged coastline of
Hawaii Island. It feeds on Opae'ula (Halocaridina rubra) which are found in
anchialine ponds around the island. Due to high development of the coastline on
the island, alchialine pools are decreasing and becoming less common. Only
birds that can successfully fly the long distances in search of Opae'ula will live
long enough to breed successfully. This simulation will allow students to breed
several generations of the Hawaiian Origami Bird to see how phenotypes and
genotypes are affected over time.
Biological evolution, which is the gradual change to a population of species over
many generations, is the process responsible for the diversity of species. Natural
selection is the process by which favorable traits that are passed on over
generations become more common in a population of reproducing organisms.
Natural selection is also responsible for how unfavorable traits (not conducive
for survival) become less common in the population. This process acts upon the
phenotype or the morphological characteristics of an organism. Organisms that
have favorable phenotypes that allow them to survive and reproduce in the wild
are more likely to survive than organisms that have unfavorable phenotypes.
If the phenotype is based on genetics, then the genotype associated with that
favorable phenotype will increase in frequency in the next generation and
generations to follow. Natural selection also acts upon populations, not
individuals alone. The changes to the phenotype and genotype must affect the
entire populations of organisms, not just select individuals of the population.
Teacher Prep for Activity
• Prior to this lesson, the teacher can cut the paper into different sized strips. Be sure to make many strips of
each size (they will vary from the original size of 3 cm x 20 cm). The width and circumference of the
strips will increase or decrease by 1-2 cm after each generation.
• Xerox Origami Data Sheets
• The procedure section can be Xeroxed and handed out or the diagrams can be written on the board.
Procedure
1). Split students into groups of two. Each student will prepare an ancestral bird: Cut two strips of paper, each 3
cm x 20 cm. Loop one strip of paper with a 1 cm overlap and tape. Repeat for the other strip. Tape each loop 3
cm from the edge of the straw.
2). Breed offspring. Each Origami Bird lays a clutch of three eggs.
Record the dimensions of each chick and hatch the birds using these instructions:
a. The first egg has no mutations. It is a clone of the parent, this measurement will be the same as the ancestral
bird. In the interest of time you may substitute the parent when testing this chick.
b. The other two chicks have mutations.
For each chick, flip your coin and throw your die then record the results on the table.
i.) The coin flip determines where the mutation occurs: the head end or tail end of the animal.
ii). The die throw determines how the mutations affect the wing:
After you have determined where the mutation occurs, cut new strips of paper and re-build another bird with the
new measurements. You can use the strips from the original bird if able.
iii). Lethal mutations:
A mutation which results in a wing falling off of the straw, or in which the circumference
of .the wing kujkjkjkjkjkjkjkj
is smaller than the circumference of the straw, etc. is lethal. Fortunately,
Aves hawaiiensis birds are known to “double clutch” when an egg is lost. If you should get a
lethal mutation, disregard it and breed another chick.
3). Test the birds:
Release the birds with a gentle, overhand pitch. It is important to release the birds as uniformly as possible.
Test each bird twice.
4). The most successful bird is the one that can fly the farthest.
Mark which chick was the most successful on the tally sheet provided.
5). The most successful bird is the sole parent of the next generation. Use the measurements from this bird to be the
parent of the next generation. The following generation will be continuing to breed, test, and record data for as many
generations as you can in the time allotted. Use the table to record the results of your coin flips and die throws, the
dimensions of all chicks, and the most successful bird in each generation.
Extensions and assessment
You can use the following questions for discussion of the topic. These can either be turned in for credit or can be
discussed during the next class period.
1. Did your experiment result in better flying birds?
2. Evolution is the result of two processes: variation and selection.
a. How did your experiment produce variation among the offspring?
b. How did your experiment select offspring to breed the next generation?
3. Compare your youngest bird with your neighbor’s youngest bird.
a. Compare and contrast the wings of of other birds with your own.
b. Explain why some aspects of the birds are similar.
c Explain why some aspects of the birds are different.
4. Predict the appearance of your youngest bird’s descendants if:
a. the selection conditions remain the same and the longest flying bird survives to produce the
most .offspring.
b. the selection conditions change the worst flying bird survives to produce the most
offspring.
c. the selection conditions change and the bird whose color blends with its environment
survives to .produce the most offspring.
5. Predict how the Aves hawaiiensis might adapt after the alchialine pools have disappeared from over development?
Name ___________________
Date _____________________
Origami Bird Data Sheet
Flip coin, throw die, record results. Plan the baby chicks, record their dimensions,
breed the chicks.
GENERATION 0:
No Mutation
3 x 20 3 x 20
_kk
Head k
COIN
_________x _________
Tail
Head
DIE
3 cm
COIN
x
Tail
Head
DIE
3 cm
Mark the winning bird. Only the most successful bird becomes a parent of the next
generation. The “no mutation” chick in the next generation is identical to the
winning bird in the immediately preceding generation. Continue to flip and throw,
plan chicks, breed them, and test them for more generations.
Tail
PRISM UHH GK-12
Exploring the Ohia Common Garden
Natural Selection
Concepts
Changes to the
environment may affect
how an organism may
survive in the wild.
Occasionally, organisms
have the ability to activate
different phenotypes in
response to its changing
surroundings. This lesson
uses an endemic Hawaiian
tree species, Ohia, to show
how this species changes
its phenotype in response
to different habitat
requirements.
Standards addressed
7.5.4, 7.5.6
Duration
1 full day for field trip
Vocabulary
Natural selection
Phenotype
Genotype
Glabrous
Pubescent
Phenotypic plasticity
Source Material
PRISM
Summary
After students have a strong understanding of Adaptations and Genetic Variation,
they will be introduced to Natural Selection. They will visit the Ohia Common
Garden in Volcano, Hawaii to see how Ohia (Metrosideros polymorpha) from
different elevations have morphological differences.
Objectives
• Students will simulate how genes are passed from one generation to the
next.
• Students will understand how traits that are favorable for survival become
more common over generations.
• Students will know that both genetic variation and environmental factors
causes of evolution and species diversity.
Materials
Background information about Ohia to lecture students before visiting garden
Permission to visit the garden
Dr. Elizabeth Stacy-can give presentation at garden about Ohia
Background
Biological evolution, which is the gradual change to a population of species over
many generations, is the process responsible for the diversity of species. Natural
selection is the process by which favorable traits that are passed on over
generations become more common in a population of reproducing organisms.
Natural selection is also responsible for how unfavorable traits (not conducive for
survival) become less common in the population. This process acts upon the
phenotype or the morphological characteristics of an organism. Organisms that
have favorable phenotypes that allow them to survive and reproduce in the wild
are more likely to survive than organisms that have unfavorable phenotypes.
If the phenotype is based on genetics, then the genotype associated with that
favorable phenotype will increase in frequency in the next generation and
generations to follow. Natural selection also acts upon populations, not
individuals alone. The changes to the phenotype and genotype must affect the
entire populations of organisms, not just select individuals of the population.
Ohia lehua (Metrosideros polymorpha) is a Hawaiian endemic plant found in
almost all Hawaiian ecosystems. It is present on all Hawaiian islands, except
Niihau and Kahoolawe. Ohia is an extremely variable plant that ranges in
elevation from sea level to approximately 7000 feet. In order for Ohia to survive
and reproduce at such drastic environments, species at different elevations have
morphological differences. Ohia found at low elevations have larger, glabrous
(smooth with no hair) leaves while ohia at high elevations have smaller,
pubescent (with short fuzzy hair) leaves. One reason ohia at high elevations have
smaller, fuzzy leaves is because they are closer to the sun and the fuzzy hair might
protect the leaves from cold temperatures. Lower elevation Ohia are further from
the sun and need a larger surface area to collect more sunlight and they are without
fuzzy hair because they live at warmer temperatures. Ohia have a given
phenotype, but also have the ability to change its phenotype in response to
environmental changes. This phenomena is called phenotypic plasticity.
Teacher Prep for Activity
Weeks prior to the field trip, Dr. Elizabeth Stacy at the University of Hawaii, Hilo must be contacted for access
into the common garden. Dr. Stacy could possibly be available to meet with the students to discuss Ohia and
natural selection also. Her contact information is: Elizabeth Stacy, Assistant Professor Department of
Biology, University of Hawaii 200 West Kawili Street Hilo, Hawaii 96720, Email: [email protected]. Please
give yourself many weeks to months in advance to plan this field trip.
Procedure
After finalizing the plans to visit the Ohia common garden, give the students some background information on
Ohia before visiting the garden.
At the garden, Dr. Stacy will talk about Ohia and its morphological differences. After the lecture, students will be
split into groups and be asked to examine the different trees at the garden. They will be asked to collect a single
leaf from a tree from high elevation, mid elevation and low elevation. After they have collected their leaves, they
will be asked to explain why they think the leaves they collected belong to their respective habitats. After the field
trip is completed, have the students write a reflection about their trip to the garden. They could also be asked to
research another organism that displays phenotypic plasticity.
Assessment
Journal writing
Written report of another organism that displays phenotypic plasticity.
Extensions
If the class is unable to visit the common garden or a project extension is needed, a possible class simulation of
this exercise would be to grow tomato plants. Before growing the plants, ask the students if they think tomato
plants (with the same genotype) grown in sunlight would look different from tomato plants grown without
sunlight. Have them write down their predictions. Plant several plants in pots and place half the plants in direct
sunlight and place the other half in the classroom, away from any light. Water and feed both sets of plants the
same way. The plants grown in direct sunlight should grow upright, reaching for the sun while the plants grown
inside should grow low, creeping along searching for sunlight. This simulation shows that different environmental
factors can affect how an organism survives.
NATURAL SI
GOAL
Natural Selection introduces students to natural selection as the mechanism that produces change in the
genetic makeup of a population.
OBJECTIVES
SCIENCE CONTENT
Environmental factors put selective pressure on populations.
Natural seletion is the process by which the individuals best adapted to their environment tend to
survive and pass their traits to subsequent generations.
Members of a species are all the same kind of organisms and are different from all other kinds of
organisms.
CONDUCTING INVESTIGATIONS
Use a game simulation to experience change in a population, resulting from selective pressure.
Record and process information presented in a video about natural selection.
Use a multimedia simulation to explore the effects of natural selection on a population.
BUILDING EXPLANATIONS
Describe how selective pressure can affect the genetic makeup of a population.
Explain how the traits expressed by the members of a population can change naturally over time.
SCIENTIFIC AND HISTORICAL BACKGROUND
It m a y be said that natural selection is daily
and hourly scrutinizing throughout the world,
every variation, even the slightest; rejecting
that which is bad, preserving and adding u p all
that is good; silently and insensibly working,
whenever and wherever opportunity offers, at
the improver~entofeach organic being i n
relation to its organic and inorganic conditions
of lqe.
-Charles
Darwin
In 1831,22-year-old Charles Darwin
embarked on a 5-year voyage of discovery
as resident naturalist aboard the survey
ship Beagle. The impact of the incredibly
diverse and complex biota he encountered
in South America revolutionized his
perception of life on Earth. During the
voyage and the years following, Darwin
formulated a theory explaining the
uniqueness and origin of the organisms he
discovered. It was many years, however,
before he finally published his famous
book, O n the Origin of Species by Means of
Natural Selection, in 1859.
Darwin anguished over his manuscript.
He was diligent in his science, wanting
solid sources of evidence for his
sveculative ideas. But even when the
theory was clearly described and
supported to h s satisfaction, he feared the
societal response to his propositions. The
assumed affront to God, excused from the
role of creator of all nature, and the
reduced status of humanity, dismissed
from the pinnacle of creation, troubled
Darwin. But when he found out that
Alfred Wallace had reached essentially the
same conclusions about natural selection
and was preparing to publish his work,
I
Darwin brought his book to print. The
ideas disseminated quickly throughout the
scientific community, and in their wake a
new understanding of the progression of
life emerged.
NATURAL SELECTION
The idea is simple, really, and is
constructed on some fundamental
assumptions that have since been shown
to be sound.
Nature Produces Variation. During the
process of reproduction, random changes
occur in the genetic information directing
the manufacture of a new unit-an
offspring. Extreme changes are usually
lethal, and no offspring result. Those
genetic miscues are not perpetuated.
Modest changes translate into often subtle
and sometimes dramatic differences in
individuals. Individual offspring turn out
to be unique; one perhaps a little larger,
another more aggressive, and still others
darker in color, slower to respond, having
larger fins or wider teeth, on and on. The
result is variation in populations.
Life Is a Challenge. Many factors
converge to prevent organisms from
enjoying a peaceful, relaxed, successful
existence. The physical environment can
be harsh, and is often variable. Weather
and catastrophe put pressure on
organisms that can stress, weaken, and kill
them. At the same time, nature produces
many more organisms than can be
supported by the environment.
Organisms that are not adapted to
withstand environmental pressures are
doomed to fail.
Biotic factors put pressure on organisms.
Heterotrophc organisms eat other
organisms for energy and building blocks.
Organisms that fail to acquire food die.
On the other side of that equation,
organisms that are taken for food also die.
Microbes sometimes invade organisms,
causing disease. Life is always under
pressure.
Organisms in a Population Compete.
Every species has a niche in which it lives
and acquires the resources it needs for
survival. The problem is, all the other
members of an organism's species are
trying to make a living in that niche as
well. This creates competition among
members of a population for access to
limited resources. If resources are not
limited, members of the population could
coexist without complications. Those
individuals that succeed in getting
resources and that successfully reproduce
pass their genes to the next generation.
The measure of the success of an
individual organism is whether or not it
survives and reproduces. The traits that
prepared a successful organism to
complete its destiny are passed to the next
generation. Traits that resulted in
successful reproduction by their parents
are, in all likelihood, the traits that will
increase the offspring's chances of
reproducing. Successful individuals pass
the tools of success to their offspring.
As discussed earlier, however, the
perversity of the physical environment
and the pressures imposed by the biotic
community don't allow for the idea of a
perfect organism, ideally equipped to
survive. Survival has to happen in a
dynamic environment, so perfection is a
The measure of the success of a population
is its ability to withstand change in the
environment and to prevail. Nature's
hedge against complete disaster imposed
by disease, drought, or hoards of predators
is variation. When a new pressure is
imposed on a population, some
individuals may succumb. But some will
likely have adaptations that allow them to
survive and reproduce more offspring
than other individuals of that species. In
this way the population continues, but
changes.
Darwin did not have the benefit of
understanding the fundamentals of
genetics, although it was well accepted
that organisms passed the code for making
reasonably accurate reproductions of
themselves from generation to generation
through sexual processes. He was able to
observe firsthand the variation within a
population, particularly when he observed
the finches on the Galfipagos Islands. The
puzzle that Darwin pursued was how the
countless kinds of organisms came into
being. What forces created a new kind of
organism? What was the origin of species?
If a population existed in a constant,
supportive environment, natural processes
would produce variation in the
population, and the individuals would all
have reasonable chances of survival. The
success of a varied population would
perpetuate a varied population.
Pressure on the population might favor
some individuals over others because the
variations represent different adaptations,
and different adaptations affect the
potential for survival. So selective
pressure on a population will favor some
individuals, which will reproduce,
influencing the distribution of traits in the
individuals. The population changes in
response to selective pressure. (Notice,
individuals don't change in response to
selective pressure; they only survive or die.
Populations change depending on the
characteristics of the survivors.)
Over time a population may change
sufficiently for science to judge it to be a
different kind of organism than it was
before the selective pressure was brought
to bear on the original population. How
long does that take? And how different
does the "new" population have to be to
be deemed a new species?
It isn't easy to answer these questions. A
new species may emerge in an extremely
short time-a matter of days or weeks in
the case of bacteria. Or it may take
millions and millions of years for a
successful species like the white shark or
horseshoe crab to change enough to be
considered a new species.
Darwin observed the finches on the
GalApagos Islands. The 20 or so islands
are situated about 1000 km west of
Ecuador. The current islands range in age
from about 700,000 to 4 million years, but
scientists suggest that there may have been
other islands or sea mounts in the area as
long as 10 million years ago. The point is
that the GalApagos Islands are young, and
any terrestrial life had to make its way
there across the open sea or through the
air.
Some time ago a single finch species
arrived on the islands. Perhaps a small
flock was blown off course in a storm. The
birds apparently had no competitors for
resources, and they thrived. As time
passed, variation entered the population.
The most conspicuous variation was the
beak. Different subgroups within the
population were better adapted to exploit
different food sources. We can imagine
that the members of the population that
sought similar food sources would
associate, and other groups that shared
different traits would associate. Feeding
behavior isolated subgroups within the
larger population. Breeding among the
subgroup reinforced the trait that isolated
it in the first place, further separating the
subgroup.
Variation within the subgroup might have
produced other traits that also tended to
isolate the subgroup, perhaps coloration,
size, nesting habits, mating rituals, and so
forth. In time, isolation and change in
response to pressures from the
environment produced a new subspecies.
The exact time at which a splinter group is
awarded the status of species is a subject
for scientific debate. There are few
absolutes for defining a species, so the
moment at which it happens is nebulous.
Darwin concluded that speciation was a
natural outcome of ongoing life processes:
(genetic) variation in a population,
selective pressure in the environment, and
isolation of a segment of the population.
Darwin's momentous discovery is often
summarized as "survival of the fittest."
This creates a mental image of a ferocious
battle for survival, with the biggest,
strongest, most voracious individuals
always surviving to continue their kind.
This is not an accurate picture. Fittest
doesn't necessarily mean the individual in
the best condition or the one with the
biggest teeth and strongest bones. It
means the individual with the best
adaptations to survive the pressure being
imposed by the environment. Fittest
simply means the best equipped to
survive and reproduce.
Who or what determines fitness? The
selective pressure in the environment. The
pressure might come from the weather. A
return of the ice ages will select for those
individuals with adaptations for surviving
cold and select against those without
adaptations for cold. A new predator that
climbs trees will select for those treedwelling individuals that can flee or
defend against the predator, and select
against those that have no defensive
adaptations. A drought that reduces the
acorn crop may select for the smaller
members of a population that can survive
on less food and select against those that
require more food. The result of natural
selection is that the genetic makeup, and
therefore the suite of traits expressed by
the population, is constantly changing.
The change process in organisms is called
evolution. Organisms can be thought of
as work in progress; they are constantly
evolving from something into something
else.
If you follow the evolutionary process
back in time, perhaps 3.5 billion years or
so, logically you eventually arrive at the
first living organisms on Earth.
Remember, life is the Olympic flame that
burns in every organism. The flame is
handed from one organism to the next. If
it goes out, it cannot be rekindled. Life
has only one chance to carry the torch, and
every organism guards it tenaciously as
long as it can. So every organism alive
today has received the precious fire
through millions and millions of handoffs
without a fumble.
The processes of variation, natural
selection, and isolation have produced an
amazing array of organisms. There are
millions of species alive on Earth today,
and for each one there were at least a
hundred species that are now extinct. The
process of evolution has produced a
continuous parade of new species, each
adapted to the specific environments in
which it lived, and continues to do so
today.
ARTIFICIAL SELECTION
A discussion of artificial selection might
shed light on the selection process. We
humans have one adaptation (thanks to
natural selection) that makes us a
formidable organism to deal with-an
advanced brain. We can control our
environment to an unprecedented degree.
As a result we can manage food resources,
create shelter, manipulate energy, control
other organisms, and re-create the world
we live in.
One human enterprise is manipulating the
traits of organisms through artificial
selection. Think about the domestic dog.
Every breed From the skinny, shivering
Chihuahua to the robust, barrel-toting St.
Bernard, and all the retrievers, hounds,
terriers, poodles, spaniels, bulldogs, collies,
and Pomeranians in-between are the same
species. Where did all the diversity come
from? Variation, selection, and isolation.
Let's say you wanted to have a dog to
catch squid for you. Where would you get
such a dog? Because there is no such dog,
you would have to breed one. Squid live
in the water, so you need a dog that is
enthusiastic about water and swims well.
A retriever or a spaniel would be a good
breed to start with. So you get a bunch of
retrievers and spaniels and show them a
squid. Toss the squid in the water and see
whch dogs jump in to grab it. Of the
original subset of water-loving dogs, only
a few will pass the "goes for squid" test.
Breed the squidophiles and raise the pups.
Test them for squidophilia. Breed the most
promising of those.
Take the best squidders out in a boat and
see how good they are at spotting a squid
in the water. Breed those with the best
night vision. What's the best color (maybe
black) and hair length (shorter the better).
Identify those sharp-eyed squidophiles
that have the darkest, shortest fur. The
animals that have the traits that fit your
needs are the ones that you allow to
reproduce to get more offspring with their
traits.
After many generations of selective
breeding you produce a squid hound,
equal to the task you want it to perform.
And if you find you are not completely
satisfied with the dog's performance in the
future (maybe the breed shakes after
getting back into the boat after snaring a
squid), you can always continue to tinker
with the traits to make it "better" by
breeding members of the isolated
population that have the desirable trait, in
this case, stand and drip.
There is danger in this process. By
isolating a small population, you
significantly reduce the diversity in the
gene pool. If a genetic weakness, such as a
tendency to bite, kidney disease, joint
dysfunction, or shvering, shows up as a
trait in the breed, it may be difficult or
impossible to breed it out without losing
the traits you selected for in the first place.
A reduced gene pool caused by inbreeding
often introduces vulnerability and
weakness into the breed, due to lack of
variation.
Artificial selection has been used for years
to develop disease-resistant strains of
grains, higher-yielding corn, fastermaturing soybeans, square tomatoes,
seedless watermelons, and hundreds of
other agricultural plants. And, of course,
horses and livestock are selectively bred
for a variety of functions and products,
and the celebrated silk moth and the large
and exotic goldfish called koi have been
selectively bred for centuries to produce
the living products we see today.
Nahire does the same, but without
purpose, allowing some individuals with
the right stuff to produce more offspring
than others in the population. But in
nature, the selection is based on passing a
test, not possessing arbitrarily desirable
traits. And the "right stuff" is having the
traits that better prepare the offspring to
survive and reproduce, not measuring up
to a set of predetermined criteria.
You've heard the lament, "Just when I
learned the answers, they changed all the
questions." That's the way it goes out
there in the biosphere--every time an
organism "gets it right," the environment
changes the test, so the winner yesterday
may not have the right stuff to win today.
That's natural selection, and that's what
keeps life evolvkg on Earth.
WHY DO I HAVE TO LEARN THIS?
This investigation presents some sensitive
issues. The ideas of natural selection and
evolution of life on Earth can bring
scientific historical evidence and the very
essence of scientific inquiry into conflict
with deeply held beliefs concerning the
sacred origins of life. Both points of view
seek to answer the same questions, in a
and where did I
way: How did I get
come from?
Evolutionary biologists study the scientific
evidence provided by the inventory of
living organisms, and piece together the
fragments of life's prehstory, to synthesize
a credible story for the emergence and
progressive redesign of life on Earth.
According to the biologst, the 3.5-billionyear ongoing experiment has produced
Homo sapiens and the several millions of
other species living on Earth today. And
the biologist suggests that, just as it has
from the beginning, the description,
distribution, and diversity of life on Earth
today is a snapshot of a work in progress.
The evolutionary processes will continue
to reshape the image of life on Earth
indefinitely. We are here now simply as a
result of chance and natural selection, just
like every other living thng.
T h s course introduces students to the
scientific explanation for the origin of
species and, in the process, lays the
groundwork for answering the questions
of how I got here and where I came from.
It is not the intent of this course to
disparage the belief system of students.
Rather, we present the science ideas and
encourage students to engage them and
incorporate them into their growing
catalog of shared human knowledge.
For a full discussion of the issues
associated with the teaching of natural
selection, biological evolution, and the
origin of species, obtain this book or
browse it on-line: Teaching about Evolution
and the Nalure of Science. Details are in the
References chapter.