Download environmental education lesson plan format

Mutations, Adaptations and Me
Created for SPICE by Aida Miró-Herrans and Sonya Adkins
May 2011
Through this unit, students will gain understanding about the process of
natural selection and how it has led to differences in human populations.
Using kinesthetic learning, they will discover the importance of DNA
mutations in the process of adaptation. They will also learn how adaptation
to the environment has led to different observable traits.
Materials List:
One roll of yarn
Stopwatch
Markers (marbles, M&M, beans, etc) of two different colors (20 per
color per student/pair)
Small containers (cups) to put markers in (4 per student/pair)
Box of transparency sheets
Roll of clear tape (1 per group of 2-3 students)
Provided Power Point slides
Color copies of provided sheets (laminated)
o Bear picture sheet
o Temperature map (11 X 17in)
o Skin color squares
Lesson 1: The Forces That Change Us
KEY QUESTIONS: How is DNA important to adapting to the environment?
How does natural selection lead to new adaptations? What other forces lead
to new or different traits? How is natural selection different to genetic
drift?
SCIENCE SUBJECT: Biology
GRADE LEVEL: 7th and 8th grade
SCIENCE CONCEPTS: natural selection, genetic drift, adaptation to
environment, evolution, DNA mutation
OVERALL TIME ESTIMATE: 2-3 50-minute classes
LEARNING STYLES: Outdoors learning, visual, kinesthetic
VOCABULARY:
DNA: Genetic material found in all living cells that has instructions for the
growth, maintenance and reproduction of the cell
Gene: A segment of DNA on a chromosome that gives information for a
specific function. It is the basic unit of heredity.
Mutation: Change to the DNA sequence
Phenotype: The observable physical characteristics of an organism
Population: All the organisms of the same species that live in the same area
Allele: One of two or more possible forms of a gene or DNA sequence
Adaptation: A trait that makes an organism better suited to its
environment
Natural selection: The process through which members of a species that
are better suited to their environment survive and reproduce at a higher
rate than other members of the species
Genetic drift: Change in the frequency of an allele (gene variant) in a
population because of random sampling
Speciation: Process for the formation of a new species
LESSON SUMMARY:
Activity 1 Natural selection from the beginning This lesson demonstrates
how selection acts on a trait from the first moment it appears in a
population. Students will simulate the process of natural selection acting on a
trait through three generations of the population.
Activity 2 Genetic drift: the randomness of change In this lesson
students learn that there are other forces that lead to differences in
organisms of the same species. They will observe the effect of random
sampling and how it changes the frequency of a trait in a population.
STUDENT LEARNING OBJECTIVES:
The students will:
Recognize that changes that lead to new species start with a mutation in
DNA
Understand how natural selection works to create organisms better suited
to their environment
Understand that there are other causes, additional to natural selection, that
lead to new species.
MATERIALS:
Activity 1
One roll of yarn
Stopwatch
Whistle (optional)
Activity 2
Markers (marbles, M&M, beans, etc) of two different colors (20 per
color per student/pair)
Small containers (cups) to put markers in (4 per student/pair)
BACKGROUND INFORMATION:
There are four processes that lead to evolutionary changes: mutation,
migration, natural selection, and genetic drift. A mutation is a change in the
DNA sequence. A mutation on a gene can lead the phenotype that the gene
specifies for to change. Each different form of the gene or DNA sequence
is called an allele. An organism that migrates to a new population with a
different allele as the organism changes the frequency of the alleles in the
population.
Natural selection is the process through which members of a species that
are better suited to their environment survive and reproduce at a higher
rate than other members of the species. A mutation on a gene can lead to a
trait that improves an organism’s ability to survive and/or reproduce. As
the genes are inherited by the offspring, the allele of the better suited
(and higher reproducing) organisms will increase in the population. Over
time, individuals with that trait will become the most common, while
individuals with other alleles will most likely go extinct. This is the beginning
of the process of speciation.
While some mutations occur on genes and affect phenotypes, other
mutations cause no observable changes and the organism survives and
reproduces like the rest. In these cases, the alleles can change in frequency
in the population because a random sample of the population is reproducing.
If an individual with the new allele happens to produce more offspring, the
allele will increase in frequency in the population. Genetic drift will
eventually lead one of the alleles to be the only allele in the population. In
the case of two alleles, this happens when either the new allele is lost from
the population because it is not inherited, or the new allele increases in the
population and the original allele is lost from the population.
Genetic drift can play an important role in speciation when a random subgroup of a population moves to a new area (could be in search of resources)
or when a physical barrier divides a population and there is no migration
between the groups. Only a sample of all the possible alleles leaves with the
sub-group. As random sampling affects each of the groups differently, each
sub-group could end up with a different allele as its main allele.
Natural selection and genetic drift can only operate if there is genetic
variation, which occurs from mutations. While the four mechanisms cause
changes over time, natural selection and genetic drift can lead to the
formation of new species. Over generations, as mutations arise and natural
selection and genetic drift cause only one allele to remain for each section
of DNA, groups of organisms that originally came from the same species,
become more and more different until they are considered different
species. So remember, evolution must always start with a mutation.
ADVANCED PREPARATION:
Activity 1
Cut yarn 1 ft long segments; one piece per student
Select area where students can run
Activity 2
Prepare a container with 7 markers of one color and 3 markers of the
other (for demo)
Prepare containers for each student pair with 7 markers of one color
and 3 markers of the other
Prepare “Extras” containers with 10 markers of each color
PROCEDURE with time estimates:
Activity 1 (Day 1)
Introduction (15min): Explain how DNA has the information for all the
functions in organisms. Specify that genes code for specific traits or
functions and that a change/mutation in the gene can lead to that trait being
different to the original. If the new allele/trait helps the organism survive
better in its environment, it can have more offspring. This is how natural
selection works. As those better suited organisms have more offspring than
the others, the frequency of that allele is going to increase in the
population.
Activity (20 min): Students will act out how natural selection occurs when a
mutation first arises and increases survival.
Round 1: No mutations
Two students will represent a population that has the same variant of a
trait. Each will have their hands tied together in the front with a piece of
yarn. The rest of the students will stand around in a defined area. Each
student will have a piece of yarn in their hands.
1. The two students (“parental generation”) will have 45seconds to tie as
many students’ hands as possible the same way their hands are tied.
a. Each student they manage to tie up represents an offspring
(“generation 1”).
2. Repeat a second round, but this time the students who got their hands
tied (“generation 1”) will tie the hands of the students that weren’t tied
before.
a. These students will represent “generation 2” offspring.
3. Keep count of how many offspring were produced in each generation.
The goal is to show that all the organisms have the same trait and are
generally equally successful at producing offspring.
4. Adjust time accordingly so that ~30% of the students are tied up in the
first generation.
Round 2: A beneficial mutation arises
Randomly select a student to have a mutation that creates a new allele of
the original trait. This new trait will be represented by the student having
his/her hands free with the yarn tied at the wrist of one hand. This student
and the original two from Round 1 will be the “parental generation”.
1. Now they have 45 seconds to tie the hands of as many students as
possible the same way their hands are tied (i.e. if both hands are tied,
they have to tie both hands; if one hand is tied, they tie one hand).
a. The students that get their hands tied represent the offspring from
that parental generation; these will represent “generation 1”.
2. After this round, the parental generation steps out of the game. The
second generation will now have 45s to repeat the hand tying process.
a. The students that get their hands tied represent “generation 2”.At
the end of the round there should be more “new variant” offspring.
Have the students fill the chart and tally how many offspring there were
for each generation. Then, have them graph the change in group size over
time (in generations) for the three groups (Natural Selection Data Sheet).
Discussion (15 min):
Discuss the amount of offspring produced in each generation in Round 2.
How many more offspring did the organism with the new allele have
compared to the original allele?
o How did the new variant arise?
 A random mutation
o What can we say about how natural selection works to cause
changes in organisms of a population?
 If a mutation causes a change that improves an organism’s
ability to survive, it will have more offspring. Over
generations that allele will become the most common in the
population.
o Does natural selection happen immediately or require time?
 Requires time
Discuss the difference between Round 1 and Round 2.
o What happened when a new beneficial allele appeared?
o How does the amount of offspring for the original allele vary
between Round 1 and Round 2?
 The individuals with the original allele had less offspring in
Round 2
Discuss how having to compete for resources against organisms that are
better adapted to the environment can lead to the reduction in offspring
of the less adapted organisms. Discuss the alternatives of
survival/extinction of the less adapted organisms.
Activity 2 (Day 2)
Introduction/Demo (10min):
Explain that sometimes a mutation on a gene does not cause an advantage
or disadvantage.
Show a container with 7 markers of one color and add 3 of another color.
The organisms with the new “color” allele continues to survive and
reproduce just as well as the organisms with the original “color” allele.
Because for this trait all the organisms are equal, there is a random
chance that organism with the new allele will reproduce or not. To show
this, pick 5 markers without looking, and place them in a new container.
We will assume that each individual has an offspring with the same allele
(i.e. for each marker in the new container, add a marker of the same
color) and the population grows again to ten (10) individuals.
Count how many of each colored marker you have. The new allele might
have reproduced or not.
Ask what is the frequency (how many) of the markers of each color in
the container. How do they compare to the frequency of the parental
population? Has the frequency of the two alleles changed? Is it still a
7:3 ratio?
Ask the students what they think would happen if 5 random individuals
from this “new” population have offspring. Would you get the same
ratio? This is what they will find out in this lab.
Activity (20min)
Explain that the students will be doing the same thing, but five times
instead of one, to show the change in frequency over five generations.
Hand container with the 7:3 markers and the “Extras” to each pair. The
students need to record how many of each color in the parental
population on the Genetic Drift Data Sheet.
Without looking (to make it random), they take five markers from the
container and place them into a new container.
Use the markers in the “Extras” container to add a marker of the same
color for each marker in the new container.
Record how many of each color in the Genetic Drift Data Sheet.
Repeat the process for five generations.
Graph the change in amount over time for each color from the parental
generation to generation five.
Discussion (20 min)
Have the students share with the class how the amounts of each color
changed from the parental population to the last generation.
Ask them whether the new allele:
o stayed at the same frequency,
o became as common as the original allele, or
o became the most common allele
Keep track of how many of the groups fall in each category.
What do the classroom results tell us about genetic drift?
Does it always have the same result? (No)
Why? (It is all up to random chance)
How is this different from natural selection? (For possible answers see
Assessment 1. ).
Discuss the graph.
How do the numbers change between the two colors? (When the
frequency of one color increases, the other decreases)
What would happen if we continued with more generations? (Eventually
one of the alleles will become the only allele in the population)
ASESSMENT
1. Have the students describe the similarities and differences between
natural selection and genetic drift.
Answers:
Similarities
1. Both processes start with a
random mutation in DNA
2. Both can lead to speciation
Differences
1. Natural selection is NOT a
random process
Genetic drift is a random process
2. In natural selection the new allele
helps the organisms that have it
survive better than others that
have a different allele
In gene drift all alleles are equally
beneficial
3. In natural selection the most
advantageous allele becomes more
common
In gene drift the new allele can
become the most common, stay at
the same frequency or disappear
from the population
2. Discuss scenarios of how each process could lead to a new species
arising.
3. Compare what the students understood about why organisms are
different and what they know now.
What I used to think…
What I know now…
EXTENSIONS
1. Look up: What happens in genetic drift when a new allele (a 3rd, 4th,
etc. new variant) arises? See simulation at
http://www.biology.arizona.edu/evolution/act/drift/drift.html
RESOURCES/REFERENCES
http://evolution.berkeley.edu/evosite/evo101/IIIDGeneticdrift.shtml
http://evolution.berkeley.edu/evosite/evo101/IIIENaturalSelection.shtml
http://evolution.berkeley.edu/evosite/evo101/IIIE6Nonrandom.shtml
Keeley, P. (2008). Science Formative Assessments: 75 Practical Strategies
for Linking Assessment, Instruction, and Learning. Corwin Press. Thousand
Oaks, California.
SUNSHINE STATE STANDARDS
SC.7.L.15.2-explore the scientific theory of evolution by recognizing and
explaining ways in which genetic variation and environmental factors
contribute to evolution by natural selection and diversity of organisms
SC.7.L.15.3- explore the scientific theory of evolution by relating how the
inability of a species to adapt to a changing environment may contribute to
the extinction of that species.
SC.7.L.16.1-Understand and explain that every organism requires a set of
instructions that specifies its traits, that this hereditary information
(DNA) contains genes located in the chromosomes of each cell, and that
heredity is the passage of these instructions from one generation to
another.
Name:_______________
Date:__________
Natural Selection Data Sheet
Instructions: Fill out the chart with the amount of organisms for each
category and plot the amounts for each allele.
Generation
Round 1
Original allele
Round 2
Original allele
New allele
Parental
Generation 1
Count
Generation 2
Parental
generation
Generation
1
Generation
2
Generation
Discussion:
1) How is the amount of organisms with the original allele different between
Round 1 and Round 2? In which round does the population size increase
more?
2) How is the amount of organisms with the original allele different between
Round 1 and Round 2
Name:_______________
Date:__________
Genetic Drift Data Sheet
Instructions: Fill out the chart with the amount of each colored marker and
plot the values on the graph.
Parental Generation 1 Generation 2 Generation 3 Generation 4 Generation
5
Color 1
Color 2
10
9
8
Count
7
6
5
4
3
2
1
Parental
generation
Generation
1
Generation
2
Generation
3
Generation
Generation
4
Generation
5
Lesson 2: How to “bear” the different climates on Earth
KEY QUESTION(S): How have animals adapted to live in different
climates? How does temperature play a role in evolutionary changes?
SCIENCE SUBJECT: Biology, Earth Science, Integrated Science
GRADE LEVEL: 6th-8th grade.
SCIENCE CONCEPTS: adaptation to environments, natural selection,
evolution, DNA mutation
OVERALL TIME ESTIMATE: 2 days
LEARNING STYLES: Visual and kinesthetic
VOCABULARY:
Mutation: Change to the DNA sequence
Climate: the weather conditions in an area over long periods of time; can be
classified by temperature, humidity, and precipitation among other factors
Bergman’s rule: states that within a genus, in general, species that are
larger live in cold environments and species that are smaller live in warmer
environments
Gloger’s rule: states that within a species, individuals in environments of
high humidity (near the equator) have darker skin than those in less humid
environments
Adaptation: A trait that makes an organism better suited to its
environment
Natural selection: The process through which members of a species that
are better suited to their environment survive and reproduce at a higher
rate than other members of the species
LESSON SUMMARY: In this lab students will learn how temperatures vary
across the surface of the earth and how natural selection has led animals to
adapt to these temperatures.
STUDENT LEARNING OBJECTIVES:
Predict traits for animals at different temperature zones
Explain the role climate has in evolution
MATERIALS: Per group of 2-3 students
2 transparency sheets
Color copy of temperature map (11 X 17in) (laminated)
Color copy of bears
Bear information sheet
Role of clear tape
Provided Power Point slides
BACKGROUND INFORMATION:
Natural selection is the process through which members of a species that
are better suited to their environment survive and reproduce at a higher
rate than other members of the species. A mutation on a gene can lead to a
trait that improves an organism’s ability to survive and/or reproduce. As
the genes are inherited by the offspring, the allele of the better suited
(and higher reproducing) organisms will increase in the population. Over
time, individuals with that trait will become the most common.
As time passes and the organisms of a population become more and more
adapted to the environment, they become evermore different to other
populations that were of the same species, but adapted to a different
environment. If the populations remain isolated from each other (don't
mate with individuals from the other population), eventually the populations
become different enough to be considered different species.
One major factor affecting the differences in environment across the
planet is the temperature of Earth’s surface. Earth's temperature has such
an influence, that similar patterns can be observed among different species
as the distance from the equator increases. Bergman’s rule states that
within a genus, in general, species that are larger live in cold environments
and species that are smaller live in warmer environments. The increased
mass helps retain heat. Gloger’s rule states that within a species,
individuals in environments of high humidity (near the equator) have darker
skin than those in less humid environments. Darker skin pigmentation
protects from the sun's UV rays. As the distance from the equator
increases, the Earth receives less sunlight. Lighter skin pigmentation allows
skin to absorb UV rays from little sun exposure, so the body can make
vitamin D. Vitamin D deficiency can cause bone weakening diseases.
ADVANCE PREPARATION:
Make color copies of temperature map and bear pictures.
Make copies of “Bear Info” page for each group
Tape together two transparencies to make a sheet the same size as the
temperature map (so the students can stick the pictures to the
transparency sheet and the map can be reused for lesson 3)
Cut out bear pictures
Make copies of worksheet for each student
PROCEDURE AND DISCUSSION QUESTIONS WITH TIME
ESTIMATES:
Day 1
Introduction (10min):
Review that DNA contains the information for all the functions of the cells
in our body. A mutation in the DNA can sometimes lead to a new trait. If
the trait helps an organism survive better in its environment, it can have
more offspring. So adaptation to the environment is important to a species’
survival.
Explain that one major factor affecting the differences in environment
across the planet is the temperature of Earth’s surface. Discuss the colored
map (Slide #1 of Power Point). The colors represent the average year round
temperature of the Earth at 21,000years ago. The legend shows what
temperatures the colors represent. The red color represents the warmest
areas at about 30˚C and the purple represents the coldest at -20˚C. Clarify
that because it is the average yearly temperature, the cold and the hot
temperatures are actually more extreme. The coldest areas can be as low as
-65˚C (-85˚F) in the poles and as high as 55˚C (131˚F) in desert areas in
Africa. (That’s as hot as a 100 watt light bulb!!!).
While the map shows the temperature at 21,000 years ago, the organisms
we see today have been around and adapting for millions of years. The map
is to give us an idea of what the planet has looked like.
Ask based on the map whether the environment is the same throughout the
planet? (NO) Would you expect then, all organisms to have the same traits?
(NO, different organisms will have different traits that helped them adapt
to a specific environment)
Explain that the areas closer to the equator receive more sunlight. Darker
skin pigmentation protects from the sun's UV rays. As the distance from
the equator increases, the Earth receives less sunlight. Lighter skin
pigmentation allows skin to absorb UV rays from little sun exposure, so the
body can make vitamin D. Vitamin D deficiency can cause bone weakening
diseases. Ask the students what other traits might help an animal survive in
colder areas (far away from the equator)?. (Bigger size helps the body
generate more heat.)
Activity (20 min):
Hand out one temperature map with attached transparency sheet and
one set of bear figures.
As you show them all the bears (Slide #2), tell the students to think
about what traits would help bears best survive hot temperatures or
cold temperatures
o Bigger size helps keep the body warmer
o Darker skin pigmentation protects better from the sun’s UV
rays
o Lighter skin pigmentation allows sun to be absorbed to produce
vitamin D.
The students will use tape to stick the bears on the map where they
think each bear is best suited to survive the environment.
After the maps are finished, the groups will show and discuss with the
class where they thought each bear would survive best and why. If
some groups disagree with the location of a bear talk about why each
group thinks the location is best suited.
Show the students the map with all the bears (Slide #3) in the places
where they are actually found and have them relocate any bear they
placed incorrectly. (Save the maps for the next day)
Discussion (20 min):
Ask the students if they notice any similarities between the bears that live
in colder areas? (They tend to be larger and have a lighter colored coat ).
Warmer areas? (They tend to be smaller and have a darker colored coat ) Is
there a pattern as the temperature gets colder?
Day 2
Introduction (10 min)
Show the map with the bears in the correct locations and review from the
previous day what traits could allow the bears to survive better in warmer
climates and colder climates.
Activity (20 min):
Hand out the maps from the previous day and the “Bear Info” sheet
Have the students mark the equator on the map
They will measure the distance (in cm) from the equator line to each bear
picture
Fill in the worksheet with the distance and the mass
Discussion (20 min):
Discuss the results from the worksheet.
Discuss the role of adaptation to the environment in the formation of new
species. Propose to the students that all bear species came from one bear
species. Ask them how they think we could have gotten all the different
bear species. Explain that as populations of bears moved into new
environments and adapted to them, they became increasingly different from
the populations of bears in other environments. After many generations of
separation, the populations have become different enough to be identified
as different species. Therefore, adaptation and natural selection have led
to much of the species diversity we see on the planet.
Assessment:
Show the students the temperature map of the current average year round
temperature (Slide #4). They will be able to notice that the colder areas
have gotten smaller and moved more to the poles and the warm areas have
increased. If a mutation caused a mammal to start adapting to the current
climate environments, what will it look like in the future?
Have the students create a mammal and write a paragraph explaining where
the animal is from (what environment is it adapting to?) and describing what
traits it would have to help it survive that environment. Gloger’s rule and
Bergmann’s rule should still apply but shift according to the temperature
shift. They can also talk about their animals to the class and explain.
RESOURCES/REFERENCES:
All pictures used are licensed under GNU Free Documentation License,
Creative Commons Attribution-Share Alike 2.0 Generic, or
Creative Commons Attribution Share Alike 3.0.
Panda picture by J. Patrick Fischer at
http://upload.wikimedia.org/wikipedia/commons/0/0f/Grosser_Panda.JPG
Kermode bear picture by Jackmont at
http://en.wikipedia.org/wiki/File:Spiritbear.jpg
American black bear picture by Harvey Barrison at
http://en.wikipedia.org/wiki/File:Canadian_Rockies__the_bear_at_Lake_Louise.jpg
Polar bear picture by Alan Wilson at
http://en.wikipedia.org/wiki/File:Polar_Bear_-_Alaska.jpg
Grizzly bear picture at http://en.wikipedia.org/wiki/File:Grizzlybear55.jpg
Asian black bear picture by Guérin Nicolas at
http://en.wikipedia.org/wiki/File:Ursus_thibetanus_3_%28Wroclaw_zoo%2
9.JPG
Mexican grizzly bear at
http://en.wikipedia.org/wiki/File:Mexico_grizzlies.png
Syrian brown bear picture by Stahlkocher at
http://upload.wikimedia.org/wikipedia/commons/c/c2/Ursus_arctos_syriacu
s.jpg
Eurasian brown bear picture by Malene Thyssen at
http://en.wikipedia.org/wiki/File:Brown_bear_%28Ursus_arctos_arctos%29
_running.jpg
Kamchatka bear at http://en.wikipedia.org/wiki/File:Brown-bear-inspring.jpg
Sloth bear picture at
http://en.wikipedia.org/wiki/File:Sloth_Bear_Washington_DC.JPG
Sun bear picture by Tambako at
http://en.wikipedia.org/wiki/File:Sitting_sun_bear.jpg
Spectacled bear by Colin M.L. Burnett at
http://en.wikipedia.org/wiki/File:Spectacled_Bear_Tennoji_2.jpg
Brown bear picture by marschner at
http://en.wikipedia.org/wiki/File:Brown_bear.jpg
U.S. Fish & Wildlife Service, National Digital Library
http://en.wikipedia.org/wiki/File:Kodiak_Bear_at_Dog_Salmon_Creek,_USF
WS_11389.png
http://en.wikipedia.org/wiki/Giant_panda
http://en.wikipedia.org/wiki/Ursus_americanus_kermodei
http://en.wikipedia.org/wiki/Ursus_arctos_horribilis
http://en.wikipedia.org/wiki/Ursus_americanus_floridanus
http://en.wikipedia.org/wiki/Ursus_maritimus
http://en.wikipedia.org/wiki/Ursus_thibetanus
http://en.wikipedia.org/wiki/Mexican_grizzly_bear
http://en.wikipedia.org/wiki/Syrian_brown_bear
http://en.wikipedia.org/wiki/Eurasian_brown_bear
http://en.wikipedia.org/wiki/Kamchatka_Brown_Bear
http://en.wikipedia.org/wiki/Melursus_ursinus_ursinus
http://en.wikipedia.org/wiki/Helarctos_malayanus
http://en.wikipedia.org/wiki/Spectacled_Bear
http://en.wikipedia.org/wiki/Brown_Bear
http://en.wikipedia.org/wiki/Kodiak_Bear
http://en.wikipedia.org/wiki/Gloger%27s_rule
Meiri, S and Dayan, T. On the validity of Bergmann’s rule. Journal of
Biogeography. 30,331:351.
SUNSHINE STATE STANDARDS:
SC.7.L.15.1-Recognize that fossil evidence is consistent with the scientific
theory of evolution that living things evolved from earlier species.
SC.7.L.15.2-Explore the scientific theory of evolution by recognizing and
explaining ways in which genetic variation and environmental factors
contribute to evolution by natural selection and diversity of organisms.
SC.7.L.15.3-Explore the scientific theory of evolution by relating how the
inability of a species to adapt within a changing environment may contribute
to the extinction of that species.
Florida Black
Bear
Syrian Brown
Bear
Mexican Grizzly
Bear
Kermode Bear
Kodiak Bear
Spectacled
Bear
Eurasian Brown
Bear
Sloth Bear
Sun Bear
Kamchatka
Brown Bear
Polar Bear
Asian Black
Bear
Grizzly Bear
Panda Bear
Bear Information
Asian black bear
Panda
Male weight: 150 kg
Male weight: 150kg
Eurasian Brown Bear
Mexican grizzly bear
Male weight: 355kg
Male weight: 318 kg
Florida Black Bear
Polar Bear
Male weight: 140kg
Male weight: 680kg
Grizzly Bear
Sloth Bear
Male weight: 450kg
Male weight: 190 kg
Kamchatka Brown Bear
Spectacled Bear
Male weight: 650kg
Male weight: 200 kg
Kermode Bear
Sun Bear
Male weight: 225kg
Male weight: 70 kg
Kodiak Bear
Syrian Brown Bear
Male weight: 635kg
Male weight: 400kg
Ursus thibetanus
Ursus arctos arctos
Ursus americanus floridanus
Ursus arctos horribilis
Ursus arctos beringianus
Ursus americanus kermodei
Ursus arctos middendorffi
Ailuropoda melanoleuca
Ursus arctos nelsoni
Ursus maritimus
Ursus ursinus
Tremarctos ornatus
Ursus malayanus
Ursus arctos syriacus
Name:_______________
Bear Adaptation Worksheet
Measure the distance of each bear's habitat to the equator and fill out the chart. Then
graph your results and describe the pattern you observe.
Distance
from equator
(cm)
Species
Mass (kg)
Species
Asian black bear
Spectacled Bear
Eurasian Brown Bear
Panda Bear
Florida Black Bear
Polar Bear
Grizzly Bear
Sloth Bear
Kamchatka Brown
Bear
Mexican grizzly
bear
Kermode Bear
Sun Bear
Kodiak Bear
Syrian Brown Bear
Distance
from equator
(cm)
Mass (kg)
700
600
Mass (kg)
500
400
300
200
100
Distance to equator (cm)
1. How does mass change as the distance from the equator
increases?___________________________________________________
___________________________________________________________
2. How does this adaptation help the bears survive in their environment? _______
___________________________________________________________________________
Lesson 3: When Humans Took Over the Earth
KEY QUESTION(S): How have humans adapted to live in different
climates? How has natural selection led to different human phenotypes?
SCIENCE SUBJECT: Biology
GRADE LEVEL: 7th-9th grade.
SCIENCE CONCEPTS: Adaptation to environments, genetic inheritance
OVERALL TIME ESTIMATE: 1-50 min class
LEARNING STYLES: Visual and auditory
VOCABULARY:
Mutation: Change to the DNA sequence
Climate: the weather conditions in an area over long periods of time; can be
classified by temperature, humidity, and precipitation among other factors
Adaptation: A trait that makes an organism better suited to its
environment
Natural selection: The process through which members of a species that
are better suited to their environment survive and reproduce at a higher
rate than other members of the species
Phenotype: The observable physical characteristics of an organism
Migration: The physical movement of a group from one place to another
Gene: A segment of DNA on a chromosome that gives information for a
specific function. It is the basic unit of heredity.
Bergman’s rule: states that within a genus, in general, species that are
larger live in cold environments and species that are smaller live in warmer
environments
Gloger’s rule: states that within a species, individuals in environments of
high humidity (near the equator) have darker skin than those in less humid
environments
LESSON SUMMARY: In this lecture, students will learn how humans
colonized the planet and what traits we have developed to adapt to the
environment. They will discover how the environment has led to phenotypic
differences between human populations. The assessment will be done in the
same class as a groups exercise and discussion.
STUDENT LEARNING OBJECTIVES:
Explain why humans have different skin colors
Predict traits for humans at different temperature zones
MATERIALS: Per group of 2-3 students
2 transparency sheets
Color copy of temperature map (11 X 17in) (laminated)
Color copy of skin color squares
Role of clear tape
Provided Power Point slides
BACKGROUND INFORMATION:
Modern humans first appeared in Africa about 150,000 years ago. As we
went on to colonize the world, only a few left out of Africa about 60,000
years ago. When the population grew again, of those out of Africa, a few
moved to colonize Europe, a subgroup colonized Asia, and a subgroup
colonized Southeast Asia. From Southeast Asia, a subgroup went south into
Australia and another went north and colonized the Americas. See the Power
Point slide with the map of the world showing these movements (slide #5).
The circles in the map reflect the proportion of individuals moving compared
to the population in Africa.
As humans moved farther away from the equator, they had to adapt to
colder environments with less sunlight. One trait that allowed humans to
adapt to areas with less sunlight was a change in skin color pigmentation.
Humans in Africa started with dark skin pigmentation as it protects from
the sun's UV rays. Mutations in pigmentation genes caused lighter skin
pigmentation. Lighter skin pigmentation allows skin to absorb UV rays from
little sun exposure, so the body can make vitamin D. Vitamin D deficiency
can cause bone weakening diseases. Through natural selection, populations
farther away from the equator became lighter skin colored.
Earth's temperature has such an influence on organisms, that similar
patterns can be observed among different species as the distance from the
equator increases. In addition to Gloger’s rule, another adaptation that
many species have developed is an increase in body size (see Bergman’s
rule). The increased mass helps retain heat. See the temperature map with
bear pictures to see an example of both rules.
As time passes and the organisms of a population become more and more
adapted to the environment, they become more different to other
populations that were of the same species, but adapted to a different
environment. If the populations remain isolated from each other (don't
mate with individuals from the other population), eventually the populations
can become different enough to be considered different species. While
human populations have been isolated enough to have different phenotypes
in different areas of the earth, they have been around for a short time
compared to most other species. There hasn't been sufficient time so that
different populations accumulate enough changes to become different
species. Additionally, humans are very mobile, so migration has played a big
role in maintaining similarities between populations.
ADVANCE PREPARATION:
Make color copies of temperature map and bear pictures.
Tape together two transparencies to make a sheet the same size as the
temperature map (so the students can stick the pictures to the
transparency sheet and the map can be reused for lesson 3)
Cut out bear pictures
PROCEDURE AND DISCUSSION QUESTIONS WITH TIME
ESTIMATES:
Lecture (25min):
Differences in environments across the Earth (slide 1)
If you did Lesson Two, this material was covered. Quickly review the map
Review that DNA contains the information for all the functions of the cells
in our body. A mutation in the DNA can sometimes lead to a new trait. If
the trait helps an organism survive better in its environment, it can have
more offspring. So adaptation to the environment is important to a species’
survival.
Explain that one major factor affecting the differences in environment
across the planet is the temperature of Earth’s surface. Discuss the colored
map (Slide #1). The colors represent the average year round temperature of
the Earth at 21,000years ago. The legend shows what temperatures the
colors represent. The red color represents the warmest areas at about
30˚C and the purple represents the coldest at -20˚C. Clarify that because
it is the average yearly temperature, the cold and the hot temperatures are
actually more extreme. The coldest areas can be as low as -65˚C (-85˚F) in
the poles and as high as 55˚C (131˚F) in desert areas in Africa. (That’s as
hot as a 100 watt light bulb!!!).
While the map shows the temperature at 21,000 years ago, the organisms
we see today have been around and adapting for millions of years. The map
is to give us an idea of what the planet has looked like.
Ask based on the map whether the environment is the same throughout the
planet? (NO) Would you expect then, all organisms to have the same traits?
(NO, different organisms will have different traits that helped them adapt
to a specific environment).
The role of adaptation to the environment in the formation of different
phenotypes
Explain that the areas closer to the equator receive more sunlight. Darker
skin pigmentation protects from the sun's UV rays. As the distance from
the equator increases, the Earth receives less sunlight. Lighter skin
pigmentation allows skin to absorb UV rays from little sun exposure, so the
body can make vitamin D. Vitamin D deficiency can cause bone weakening
diseases. Use Slide #3 (bears on temperature map) as an example to
explain. We can see that the bears' fur gets lighter as distance increases
from the equator. In bears, the body size also increases with distance from
the equator as the bigger size helps the body generate more heat.
Propose to the students that all bear species came from one bear species.
Ask them how they think we could have gotten all the different bear
species. Explain that as populations of bears moved into new environments
and adapted to them, they became increasingly different from the
populations of bears in other environments. After many generations of
separation, the populations have become different enough to be identified
as different species. Therefore, adaptation and natural selection have led
to much of the species diversity we see on the planet.
Human adaptation to the environment and phenotypic differences between
populations
Use Slide #5 to explain the process of human world colonization. State that
modern human first appeared in Africa about 150,000 years ago. As we
went on to colonize the world, only a few left out of Africa about 60,000
years ago. When the population grew again, of those out of Africa, a few
moved to colonize Europe, a subgroup colonized Asia, and a subgroup
colonized Southeast Asia. From Southeast Asia, a subgroup went south into
Australia and another went north and colonized the Americas.
Use slide #6 to show the temperature of the area where humans first
arose. Ask the students what color of skin would best be suited in that
environment. (Dark skin pigmentation). What do they think would happen as
humans moved farther from the equator? (Lighter skin color would be
better suited.)
Assessment (10min):
1. Hand out one temperature map with attached transparency sheet and
one set of skin color squares.
a. Clarify that there are many more skin tones, but we will use
seven to keep things simple.
2. The students will use tape to stick the skin color squares on the map
where they think each is best suited to the environment.
Discussion (15min):
After the maps are finished, the groups will show and discuss with the
class where they thought each skin color would be best suited and why.
Show the students the map with the distribution of skin colors (slide
#7).
Explain that as they see from the map, Africans, Indians and South East
Asians have dark skin color.
Ask students why they think these groups have darker skin.
o
They are closer to the equator and darker skin protects from UV
rays better
While in America there is also darker skin color near the equator, it is
not as dark as the other dark skinned groups. This is because all Native
Americans came from a group in South East Asia which already had
lighter skin (more bronzed colored).
Discuss the role of adaptations and natural selection in human phenotypic
differences.
o Why do different human populations have different skin colors?
 Possible answers:
 Skin color is an adaptation to different amounts of sunlight
exposure
 Populations closer to the equator have darker skin to
protect from UV rays and populations farther away from the
equator have lighter skin to be able to make vitamin D with
little sunlight
o How did this adaptation arise?
 It started as a mutation
o Why did it become common in the population?
 It helped the people survive better to their environment,
allowing them to have more offspring
o What role does the environment play in the formation of different
phenotypes?
 As populations move into new environments and adapt to
them, they became increasingly different from the
populations in other environments
ADDITIONAL ASSESSMENT
Have the students fill out the table below explaining what they used
to think about different human skin colors and what they know now.
What I used to think…
What I know now…
EXTENSIONS:
1. Have the students look up other traits that might have been selected
for based on distance to the equator.
a. Eg. Hair variation: Curly vs straight
(http://en.wikipedia.org/wiki/Hair)
RESOURCES/REFERENCES:
Jobling, M.A., Hurles, M.E., Tyler-Smith, C. (2004) Human Evolutionary
Genetics Origin, Peoples & Disease. Garland Science. New York.
Keeley, P. (2008). Science Formative Assessments: 75 Practical Strategies
for Linking Assessment, Instruction, and Learning. Corwin Press. Thousand
Oaks, California.
http://en.wikipedia.org/wiki/Early_human_migrations
Skin color distribution map by Emmanuelle Bournay, UNEP/GRID-Arendal at
http://maps.grida.no/go/graphic/skin-colour-map-indigenous-people
World map from
http://www.arcgis.com/home/webmap/viewer.html?services=c4ec722a1cd34
cf0a23 904aadf8923a0
Temperature maps from State University of New York at Albany: Model
NCAR CCM1 (R15 L12) 1992. http://www.ncdc.noaa.gov/cgibin/paleo/ccm1pwist.pl
SUNSHINE STATE STANDARDS
SC.7.L.15.2-explore the scientific theory of evolution by recognizing and
explaining ways in which genetic variation and environmental factors
contribute to evolution by natural selection and diversity of organisms
SC.7.L.16.1-Understand and explain that every organism requires a set of
instructions that specifies its traits, that this hereditary information
(DNA) contains genes located in the chromosomes of each cell, and that
heredity is the passage of these instructions from one generation to
another.