Evolution 3e TE v5

4 Battling Beaks

modeling
2 class sessions

ACTIVITY OVERVIEW

NGSS CONNECTIONS

Students use a model to simulate the role of genetic mutations in natural selection.
They discover that mutations provide the variation on which natural selection
acts. Some mutations cause traits that have the effect of enhancing an organism’s
survival in its current environment. Students explain that individuals possessing
these adaptive traits survive to have relatively more offspring. Thus, these traits
become proportionally more common in the next generation. This activity provides
an opportunity to assess student work related to Performance Expectation
MS-LS4-4.

NGSS CORRELATIONS

Performance Expectations

MS-LS4-4: Construct an explanation based on evidence that describes how
genetic variations of traits in a population increase some individuals’ probability of
surviving and reproducing in a specific environment.

Working towards MS-LS4-6: Use mathematical representations to support explana-
tions of how natural selection may lead to increases and decreases of specific traits
in populations over time.

Working towards MS-LS3-1: Develop and use a model to describe why structural
changes to genes (mutations) located on chromosomes may affect proteins and
may result in harmful, beneficial, or neutral effects to the structure and function of
the organism.

Disciplinary Core Ideas

MS-LS4.B Natural Selection: Natural selection leads to the predominance of
certain traits in a population, and the suppression of others.

MS-LS4.C Adaptation: Adaptation by natural selection acting over generations
is one important process by which species change over time in response to
changes in environmental conditions. Traits that support successful survival and

EVOLUTION  45

ACTIVITY 4  BATTLING BEAKS

reproduction in the new environment become more common; those that do not
become less common. Thus, the distribution of traits in a population changes.

MS-LS2.A Interdependent Relationships in Ecosystems: In any ecosystem, organisms
and populations with similar requirements for food, water, oxygen, or other
resources may compete with each other for limited resources, access to which
consequently constrains their growth and reproduction.

MS-LS3.BVariation of Traits: In addition to variations that arise from sexual
reproduction, genetic information can be altered because of mutations. Though
rare, mutations may result in changes to the structure and function of proteins.
Some changes are beneficial, others harmful, and some neutral to the organism.

MS-LS3.A Inheritance of Traits: Genes are located in the chromosomes of cells,
with each chromosome pair containing two variants of each of many distinct genes.
Each distinct gene chiefly controls the production of specific proteins, which in
turn affects the traits of the individual. Changes (mutations) to genes can result in
changes to proteins, which can affect the structures and functions of the organism
and thereby change traits.

Science and Engineering Practices

Constructing Explanations and Designing Solutions: Construct an explanation that
includes qualitative or quantitative relationships between variables that predict or
describe phenomena.

Using Mathematics and Computational Thinking: Use mathematical representations
to describe and/or support scientific conclusions and design solutions.

Developing and Using Models: Develop and use a model to predict and/or describe
phenomena.

Analyzing and Interpreting Data: Analyze and interpret data to determine
similarities and differences in findings.

Crosscutting Concepts

Cause and Effect: Phenomena may have more than one cause, and some cause and
effect relationships in systems can only be described using probability.

Patterns: Patterns can be used to identify cause and effect relationships.

Structure and Function: Complex and microscopic structures and systems can
be visualized, modeled, and used to describe how their function depends on the
relationships among its parts, therefore complex natural and designed structures/
systems can be analyzed to determine how they function.

46 EVOLUTION

BATTLING BEAKS ACTIVITY 4

Common Core State Standards—Mathematics
6.SP.B.5: Summarize numerical data sets in relation to their context.
6.RP.A.1: Understand the concept of a ratio, and use ratio language to describe a
ratio between two quantities.

Common Core State Standards—ELA/Literacy
RST.6-8.3: Follow precisely a multistep procedure when carrying out experiments,
taking measurements, or performing technical tasks.
W.6-8.2: Write informative/explanatory texts to examine a topic and convey ideas,
concepts, and information through the selection, organization, and analysis of
relevant content.

WHAT STUDENTS DO
Students simulate the effect of natural selection on an imaginary forkbird species.
Genetic mutations, represented by tosses of a number cube, introduce variation
into the population. Differential survival and reproduction of particular types of
forkbirds changes the composition of the population over time. At the close of
the activity, the class discusses the role of mutation and resulting variation in the
process of natural selection.

MATERIALS AND ADVANCE PREPARATION

■■ For the teacher

1 Visual Aid 4.1, “Forkbird Data Table”
1 Scoring Guide: constructing explanations (exp)
1 Science Skills Student Sheet 7, “Analyzing Models”
1 Scoring Guide: developing and using models (mod)

■■ For each group of four students

4 plastic forks with 1 tine
4 plastic forks with 2 tines
4 plastic forks with 4 tines
4 small plastic cups
1 number cube
1 Battling Beaks Arena
* 1 cup of “wild loops”

EVOLUTION  47

ACTIVITY 4  BATTLING BEAKS

■■ For each student

* 1 piece of graph paper
1 Literacy Student Sheet 4a, “Writing Frame—Constructing Explanations”

(optional)
1 Scoring Guide: constructing explanations (exp) (optional)

*not included in kit

Create the 1- and 2- tined forks by breaking off extra tines. To produce plastic
forks with two tines, break off the middle tine(s). Obtain any dry O-shaped cereal.

SAFETY NOTE
Do not let students eat the cereal because it will have been handled by several
students.

TEACHING SUMMARY

GET STARTED

1. Students become familiar with the forkbird model.
a. Have student read the introduction about the role of variation in natural
selection.
b. Introduce the forkbird model.
c. Ask students, “Do you think that all three forkbird types will be equally
successful at gathering the food?”

DO THE ACTIVITY

2. Student groups role-play a forkbird population over many generations.
a. Briefly introduce the rules of the simulation.
b. Instruct students to make a data table in their science notebooks.
c. Distribute the materials to each group of four students.
d. Instruct students how to share their group data with the entire class.
e. Instruct students to create line graphs using the class data.

BUILD UNDERSTANDING

3. Students analyze and interpret the results.
a. Instruct students to work with their partners to analyze and interpret their
graphs.
b. Direct students to answer Analysis items 1 and 2 in their science
notebooks.

48 EVOLUTION

BATTLING BEAKS ACTIVITY 4

c. Have students discuss Analysis item 2 about what would happen if the
type of food available to the forkbirds changed.

d. Discuss Analysis item 3 about mutations as a class.

4. (mod quick check) As a class, students consider the strengths and limitations
of the forkbird model in Analysis item 4.

a. Begin a discussion about why scientists use models.

b. Project the developing and using models (mod) Scoring Guide.

c. Project Science Skills Student Sheet 7, “Analyzing Models,” and complete
it as a whole class as the response to Analysis item 4.

5. (exp assessment) Students answer Analysis item 5, which is an opportunity to
assess them on Performance Expectation MS-LS4-4.5556

Project or provide students with a copy of the constructing explanations
(exp) Scoring Guide.

TEACHING STEPS

GET STARTED

1. Students become familiar with the forkbird model.

a. Have student read the introduction about the role of variation in natural
selection.575859

b. Introduce the forkbird model.

In this model, forks and cereal represent a population of wild birds
feeding. Introduce the variation within the forkbird population by holding
up examples of 1-tined, 2-tined, and 4-tined forks. Emphasize that the
different forks represent three different types of beaks that forkbirds have,
yet all forkbirds are members of the same species (as was the case for the
beige and green “worms” in the “Hiding in the Background” activity).

c. Ask students, “Do you think that all three forkbird types will be equally
successful at gathering the food?”

Encourage students to predict what they think will happen during the
activity and why. Explain to students that while this activity may be a lot
of fun, it is not a competition between individual students. The goal is to
perform a simulation that models the process of natural selection. Suggest
that students think about strengths and weaknesses of the simulation as
they conduct the activity.

55 SEASEX1
56 NEPEL44
57 NGLS4B1
58 NGLS4C1
59 NGLS2A2

EVOLUTION  49

ACTIVITY 4  BATTLING BEAKS

DO THE ACTIVITY

2. Student groups role-play a forkbird population over many generations.60

a. Briefly introduce the rules of the simulation.

Within each group of four, the two birds gathering the highest numbers of
loops survive to reproduce. The type of offspring each surviving forkbird
will have (i.e., whether it is a replica of the parent or a randomly occurring
mutant) is determined by the toss of a number cube, as outlined in the
Student Book. 6162

Note that there are no limitations about how the forkbirds can gather the
food using the forks. The amount of feeding time does not need to be
consistent from generation to generation, since two of the four birds at
every table survive. However, feeding times should be about 20 seconds
or less, since there is a limited amount of cereal, and counting large
numbers of “wild loops” should not become the focus. The activity can
be conducted in a more orderly fashion if you enforce the start and stop
times for the class as a whole. Alternatively, each group can monitor its
own feeding times and complete the activity more independently.

As in the toothpick/worm simulation in the “Hiding in the Background”
activity, the forkbirds reproduce asexually. While sexual reproduction
introduces layers of complexity to evolutionary change, it is no different in
principle.

b. Instruct students to make a data table in their science notebooks.

The table should have columns for all three kinds of forkbirds and should
have enough rows for the initial generation of forkbirds plus 10 additional
generations. A sample data table is shown in Teaching Step d.

c. Distribute the materials to each group of four students.

Materials include forks, cups, and bins containing a single layer of cereal
when spread out evenly across the bottom.

Encourage groups to start recording data carefully by displaying
Visual Aid 4.1, “Forkbird Data Table,” and modeling how to enter the
initial numbers of the three types of forkbirds in the table. (See sample
completed data tables below.)

d. Instruct students how to share their group data with the entire class.

You may wish to create a spreadsheet or have students record their data
on the board or chart paper.You or a student should calculate the totals

60 NGSPDM1
61 NGLS3B2
62 NGLS3A1

50 EVOLUTION

BATTLING BEAKS ACTIVITY 4

once all groups have completed 10 generations. Make sure that students
record the class data in another table in their science notebooks because
they will need this to create their graphs.

SAMPLE GROUP FORKBIRD POPULATION DATA

Genration 1-Tined 2-Tined 4-Tined
forkbirds forkbirds forkbirds
Initial
1 0 4 0
2 0 4 0
3 1 2 1
4 1 1 2
5 0 1 3
6 0 0 4
7 0 0 4
8 0 0 4
9 1 1 2
10 0 1 3
0 0 4

SAMPLE CLASS FORKBIRD POPULATION DATA

Genration 1-Tined 2-Tined 4-Tined
forkbirds forkbirds forkbirds
Initial
1 0 32 0
2 3 22 7
3 5 14 13
4 4 6 22
5 3 7 22
6 3 5 24
7 2 3 27
8 1 2 29
9 2 4 26
10 0 3 29
1 2 29

e. Instruct students to create line graphs using the class data.63

By this point, most students should be able to make the graph without
much support, but encourage students to look at their previous graphs if
they need continued support.

63 NGSPAD1

EVOLUTION  51

Number of ForkbirdsACTIVITY 4  BATTLING BEAKS

A sample graph of the class data is shown below.

PROCEDURE STEP 11 SAMPLE STUDENT RESPONSE

30

25
Key

20 1-tined forkbirds

2-tined forkbirds
15

4-tined forkbirds

10

5

0
Initial 1 2 3 4 5 6 7 8 9 10

Generations

BUILD UNDERSTANDING
3. Students analyze and interpret the results.64656667

a. Instruct students to work with their partners to analyze and interpret their
graphs.68
Consider referring students to Appendix C, “Interpreting Graphs,” in
their Student Books. This appendix provides support for students to iden-
tify trends in line graphs, and it provides sentence starters for discussing
the meaning of the graphs.

b. Direct students to answer Analysis items 1 and 2 in their science
notebooks.6970
Circulate throughout the room as students answer these questions. If
necessary, prompt students with questions like, “Which type of forkbird
was initially the most common? What happened over the generations?
Which type of forkbird would you consider the most successful?”
Help students recognize that the initial forkbird population contained
only 2-tined forkbirds. Only as a result of mutations were 1- and 4-tined

64 NGSPAD1
65 NGSPCE2
66 NGSPUM1
67 NGCCPA1
68 MARP6A1
69 NGCCSF1
70 MASP6B5

52 EVOLUTION

BATTLING BEAKS ACTIVITY 4

forkbirds introduced. However, once variation appeared within the
population, 4-tined forkbirds outcompeted the 1- and 2-tined forkbirds
because they could scoop much more food.

c. Have students discuss Analysis item 2 about what would happen if the
type of food available to the forkbirds changed.71

Consider having students first discuss their answers in the groups and
then as a class. Students should be able to state that a change in the
environment—in this case, a change in the type of food available—would
result in forkbirds with a different type of beak being more successful.
Future generations would have more birds with this type of beak. Every
time the environment changes, the “best” beak shape is different.

d. Discuss Analysis item 3 about mutations as a class.

This item emphasizes that mutations can be positive, negative, or neutral,
and it often depends on the environment at the time.

4. (mod quick check) As a class, students consider the strengths and limitations
of the forkbird model in Analysis item 4.7273

a. Begin a discussion about why scientists use models.

Eventually arrive at an understanding, as defined in the glossary of
the Student Book, that a model is any representation of a system or its
components used to help one understand and communicate how the
system works. It is more than just a replica, such as a model car.

b. Project the developing and using models (mod) Scoring Guide.

Explain that students will not be assessed using this Scoring Guide in this
activity, but they will in the next activity.

Point out how it has the same levels as previous guides but different
descriptions for each level. Review the levels as needed. For more infor-
mation, see Teacher Resources III, “Assessment.”

c. Project Science Skills Student Sheet 7, “Analyzing Models,” and complete
it as a whole class as the response to Analysis item 4.

This sheet requires students to identify the parts of the model, which
part of the real world is represented by each part of the model, and how
each part of the model is similar to and different from its real-world
counterpart.

An example of a completed Student Skills Sheet 7 for the forkbird model
is shown on the next page.

71 NGCCCE2
72 SESSAM1
73 SEASMD1

EVOLUTION  53

ACTIVITY 4  BATTLING BEAKS
54 EVOLUTION
PART OF THE MODEL REPRESENTS WHICH PART THEY ARE ALIKE BECAUSE THEY ARE DIFFERENT BECAUSE
OF THE REAL WORLD
Fork They are both individual Forks aren’t alive, and we had to
Bird objects/birds that don’t change manipulate the forks to simulate
Number of tines from one generation/round to feeding.
Shape of the beak the next.
Beak shapes probably aren’t that dif-
They both represent different ferent within a population.
structures that have different
functions.

Cereal Food for forkbirds Cereal is edible, and there is a Wild populations wouldn’t eat
limited amount. manufactured foods, and birds would
look for food over a wider area.

Arena Forkbird habitat The arena-specific place had Forkbirds might be able to leave the
boundaries just like the habitat specified area.
of a forkbird.

The number that was rolled on Whether a mutation occurred Both are random. The probability of a mutation was very
high in the forkbird model; mutations
the number cube during reproduction are very rare in the real world.

Setting a fork aside after losing Forkbirds dying because they Both are eliminated from the In the real world, birds might be eaten
population or model. or start to decompose; they wouldn’t
a round didn’t get enough food continue to persist in the same form.

Picking up a new fork at the Forkbirds chicks being They are both new individual The number of offspring produced may
start of a new round produced objects/ birds. be variable and not always the same
number.

BATTLING BEAKS ACTIVITY 4

5. (exp assessment) Students answer Analysis item 5, which is an opportunity to
assess them on Performance Expectation MS-LS4-4.7475

Project or provide students with a copy of the constructing explanations
(exp) Scoring Guide.

Review the levels and criteria in the Scoring Guide for integrating the Disciplinary
Core Idea of Natural Selection and the Crosscutting Concept of Cause and Effect
with the Science and Engineering Practice of Constructing Explanations. Consider
having students read one another’s responses and provide constructive feedback to
each other before handing them in. Consider distributing Literacy Student Sheet
4a, “Writing Frame—Constructing Explanations” if students need structured
support with writing scientific explanations.767778

SAMPLE RESPONSES TO ANALYSIS

1. Look at your graph of the class results. 79

a. Describe what happened to the number of each type of forkbird over
many generations. 80

Initially, the only type of forkbird in the population was the 2-tined forkbird.
Within one generation, though, both 1- and 4-tined forkbirds appeared.
Over many generations, the 4-tined forkbirds survived and reproduced the
most. Although their numbers fluctuated somewhat, they grew from 0 to 29.
The 2-tined forkbird went from being the only type of forkbird to just barely
surviving.The 1-tined forkbird appeared in the population but was about as
successful as the 2-tined forkbird. Its numbers remained low.

b. Which type of forkbird was the most successful? Explain how the class
data support this conclusion. 8182

The 4-tined forkbird was the most successful. Once it appeared in the population,
it never disappeared. Instead, its numbers continued to increase.This is because it
was the best at gathering food since it could scoop more food than the other types
of forkbirds.

2. The forkbirds that you studied are a single species. Although they look slightly
different, they are part of a single interbreeding population. Imagine that a
change in the food supply occurred. 83

a. As a result of heavy rains, the major source of forkbird food is now soft
berries, like blueberries. After many, many generations, how many types of
forkbirds do you think will be in the population? Explain your reasoning. 84

74 SEASEX1 All three types of forkbirds should be able to gather soft berries, either by spearing
75 NGPEL44 or scooping. Assuming that each type of forkbird could gather enough food to
76 SELTWF1 survive, all three types could survive long term in the forkbird population.
77 ELRS683
78 ELWH682 EVOLUTION  55
79 NGCCPA1
80 MARP6A1
81 NGSPAD1
82 MASP6B5
83 NGLS2A2
84 NGCCSF1

ACTIVITY 4  BATTLING BEAKS

b. As a result of a drought, the major source of forkbird food is now
sunflower seeds. After many, many generations, how many types of
forkbirds do you think will be in the population? Explain your reasoning. 85

Sunflower seeds are likely to be much more difficult for the 1-tined and 2-tined
forkbirds to gather.The 4-tined forkbird, however, might be able to scoop the seeds
by supporting them between its tines. In this scenario, the 1-tined and 2-tined
forms might die out entirely, leaving only 4-tined forkbirds in the population
(except for occasional random mutations).

3. In this activity, mutations were introduced. Consider the effects of the
mutations on your forkbirds. Classify each mutation as beneficial, neutral, or
harmful. Explain your reasoning using evidence from your investigation. 86

The mutation for 4 tines was advantageous because it allowed the forkbirds with that
mutation and beak shape to eat more food and produce more offspring.The mutation
for 1 tine was harmful because forkbirds with that beak structure couldn’t get as
much food. Having 2 tines seemed to be neutral because the forkbird could get enough
food to reproduce but not as much as the forkbirds with 4 tines. If the environment
changes, then what may have been beneficial could become harmful and vice versa.

4. (mod quick check) What are the strengths and weaknesses of the forkbird
model for explaining evolution by natural selection? 8788

See the completed Student Science Skills Sheet 7 in Teaching Step 4.

5. (exp assessment, MS-LS4-4) Using the forkbird model, explain the role of
mutations in changes in populations due to natural selection. 8990919293949596

85 NGCCCE2 SAMPLE LEVEL-4 RESPONSE
86 NGLS3B2
87 NGSPDM1 Mutations cause changes in the genes that may result in changes in how an organism
88 SEASMD1 looks. In our model, mutations caused a change to the structure of the forkbird’s beak.
89 NGSPCE2 Some beak types were better than others at allowing the bird to eat the food available
90 NGPEL44 in the environment.The 4-tined beak was the best at eating the wild oats.That beak
91 SEASEX1 type wasn’t present at the start of the model, but it appeared because of mutations.
92 NGLS4B1 Because individuals with this beak structure were able to get more food, they produced
93 NGLS4C1 more offspring.The next generation then had a higher percentage of 4-tined forkbirds
94 NGLS3B2 in it.This will continue as long as the environment remains the same. On the other
95 ELWH682 hand, 1-tined forkbirds did not do well at all, but they continued to appear sometimes
96 NGLS3A1 because of mutations. If the environment changes, and berries became the only food
available, then 1-tined birds might do better because they can stab the berries.The
56 EVOLUTION population might eventually become mostly 1-tined.Without mutations, a population
will not change.

BATTLING BEAKS ACTIVITY 4

REVISIT THE GUIDING QUESTION
What role does genetic variation play in the process of natural selection?
Mutations lead to genetic variation in a population or species. Without genetic
variation, there can be no change in the population of species over time. Even if an
individual acquires a variation in a trait in its lifetime, this kind of change cannot
be passed on to its offspring. Thus, this trait will not continue in the population.

ACTIVITY RESOURCES

KEY VOCABULARY
evolution
gene
mutation
BACKGROUND INFORMATION

MUTATIONS

Random mutations during DNA replication, occurring far more rarely than
shown in this simulation, continually introduce new variation into all populations.
Most new mutations are not selectively advantageous. If harmful, they tend to
be eliminated from the population quickly. If neither helpful nor harmful, they
may increase passively over the generations. Whether a mutation is advantageous
depends on the particular environment. For example, the allele for sickle cell
anemia also provides resistance to malaria, a disease that is common in tropical
climates. Since natural selection acts over many, many generations, even a slight
advantage conferred by a mutation may cause it to increase gradually in prevalence
within a breeding population.

EVOLUTION  57

VISUAL AID 4.1

FORKBIRD DATA TABLE

Generation 1-Tined forkbirds 2-Tined forkbirds 4-Tined forkbirds
Initial
1
2
3
4
5
6
7
8
9
10

©2017 The Regents of the University of California

5 Mutations: Good or Bad?

modeling
2 class sessions

ACTIVITY OVERVIEW

NGSS CONNECTIONS

Students follow the inheritance of a hemoglobin mutation through two generations.
Students identify patterns in their data and investigate the cause-and-effect
relationship between environmental conditions and the frequency of a trait in
a population. Based on their data collection and analysis, students construct
explanations for how changes to a gene influence an organism’s ability to survive
and reproduce. Specifically, students use the example of hemoglobin to explain
how structural changes to genes (i.e., mutations), lead to changes in protein
structure and function, and how this can lead to changes in the function of red
blood cells which, in turn, can affect survival of individuals with the mutation. This
activity provides an opportunity to assess student work related to Performance
Expectation MS-LS3-1.

NGSS CORRELATIONS

Performance Expectations

MS-LS3-1: Develop and use a model to describe why structural changes to
genes (mutations) located on chromosomes may affect proteins and may result
in harmful, beneficial, or neutral effects to the structure and function of the
organism.

Working towards MS-LS4-6: Use mathematical representations to support explana-
tions of how natural selection may lead to increases and decreases to specific traits
in populations over time.

Applying MS-LS4-4: Construct an explanation based on evidence that describes
how genetic variations of traits in a population increase some individuals’ proba-
bility of surviving and reproducing in a specific environment.

Disciplinary Core Ideas

MS-LS3.A Inheritance of Traits: Genes are located in the chromosomes of cells,
with each chromosome pair containing two variants of each of many distinct genes.
Each distinct gene chiefly controls the production of specific proteins, which in

EVOLUTION  59

ACTIVITY 5  MUTATIONS: GOOD OR BAD?

turn affects the traits of the individual. Changes (mutations) to genes can result in
changes to proteins, which can affect the structures and functions of the organism
and thereby change traits.

MS-LS3.BVariation of Traits: In addition to variations that arise from sexual repro-
duction, genetic information can be altered because of mutations. Though rare,
mutations may result in changes to the structure and function of proteins. Some
changes are beneficial, others harmful, and some neutral to the organism.

MS-LS4.C Adaptation: Adaptation by natural selection acting over generations is
one important process by which species change over time in response to changes
in environmental conditions. Traits that support successful survival and reproduc-
tion in the new environment become more common; those that do not become less
common. Thus, the distribution of traits in a population changes.

MS-LS4.B Natural Selection: Natural selection leads to the predominance of
certain traits in a population, and the suppression of others.

Science and Engineering Practices

Developing and Using Models: Develop and use a model to describe phenomena.

Using Mathematical and Computational Thinking: Use mathematical representations
to support scientific conclusions and design solutions.

Constructing Explanations and Designing Solutions: Construct an explanation that
includes qualitative or quantitative relationships between variables that describe
phenomena.

Crosscutting Concepts

Structure and Function: Complex and microscopic structures and systems can
be visualized, modeled, and used to describe how their function depends on the
shapes, composition, and relationships among its parts, therefore complex natural
structures/systems can be analyzed to determine how they function.

Cause and Effect: Phenomena may have more than one cause, and some cause and
effect relationships in systems can only be described using probability.

Patterns: Graphs, charts, and images can be used to identify patterns in data.

Common Core State Standards—Mathematics

6.RP.A.1: Understand the concept of a ratio and use ratio language to describe a
ratio relationship between two quantities.

6.SP.B.5: Summarize numerical data sets in relation to their context.

60 EVOLUTION

MUTATIONS: GOOD OR BAD? ACTIVITY 5

Common Core State Standards—ELA/Literacy

SL.8.1: Engage effectively in a range of collaborative discussions (one-on-one,
in groups, teacher-led) with diverse partners on grade 6 topics, texts, and issues,
building on others’ ideas and expressing their own clearly.

SL.8.4: Present claims and findings, emphasizing salient points in a focused
coherent manner with relevant evidence, sound valid reasoning, and well-chosen
details; use appropriate eye contact, adequate volume, and clear pronunciation.

WHAT STUDENTS DO

Students follow the inheritance of a hemoglobin mutation through two generations.
They investigate the effects of environmental conditions (incidence of malaria,
survival rates, and resource availability) on the increase or decrease of the trait.

MATERIALS AND ADVANCE PREPARATION

■■ For the teacher

32 First Generation profile cards for the class
32 First Generation Survivor profile cards for the class
1 Visual Aid 5.1, "Comparing Maps"
1 Scoring Guide: developing and using models (mod)

■■ For the class

34 hemoglobin plastic disks (16 HH normal plastic disks, 16 Hh sickle cell
carrier plastic disks, and 2 hh sickle cell anemic plastic disks)

■■ For each student

1 First Generation profile card
1 First Generation Survivor profile card
* transparent tape (optional)
* 1 pair of scissors (optional)
1 Student Sheet 5.1, “Hemoglobin Mutations and Natural Selection”
1 Student Sheet 5.2, “Hemoglobin and Red Blood Cells Storyboard”
1 Student Sheet 5.3a, “Storyboard Panels” (optional)
1 Student Sheet 5.3b, “Storyboard Key” (optional)
1 Scoring Guide: developing and using models (mod) (optional)

*not included in kit

This activity introduces the hemoglobin mutation that results in sickle cell disease.
Please be aware of any students in your class with sickle cell trait or anemia as they
may have increased concerns about their own survival.

EVOLUTION  61

ACTIVITY 5  MUTATIONS: GOOD OR BAD?

If you have class sizes below 26, in the second round, withhold pairs in which both
individuals are HH (F, H, L, and P as shown on the First Generation Survivor
profile cards) to ensure that at least some sickle cell anemic hh offspring are
produced. Separate the hemoglobin plastic disks into three piles: HH, Hh and hh.

TEACHING SUMMARY

GET STARTED

1. Students review what they know about mutations.
a. Ask students, “What is a mutation?”
b. Probe students to further elaborate.
c. Challenge students to describe the effects of mutations on an organism.
d. Ask students, “How do you think the same mutation could be harmful,
beneficial, and neutral?”

DO THE ACTIVITY

2. Students become familiar with hemoglobin and the phenomenon of sickled
red blood cells.
a. Have students read the information in the box about normal and mutated
hemoglobin.
b. Review the map showing the frequency of the hemoglobin mutation
across the world.97
c. Review the gene nomenclature, mode of inheritance, and traits.

3. Students are introduced to the model involving a fictional community.
a. Briefly introduce the scenario.
b. Distribute Student Sheet 5.1, “Hemoglobin Mutations and Natural
Selection,” and one First Generation profile card to each student, and
count the traits in the population.
c. Introduce malaria and how it affects the population.
d. Facilitate the class in determining how many individuals survive malaria.

4. Students model the survival of their community’s second generation in Part B.
a. Introduce the new scenario.
b. Distribute one First Generation Survivor profile card to each student,
and have students find their partners.

97 NGCCPA2

62 EVOLUTION

MUTATIONS: GOOD OR BAD? ACTIVITY 5

c. Have students discuss their new trait and determine the hemoglobin
genes of five offspring.

d. Facilitate the class in determining the initial and surviving offspring.

BUILD UNDERSTANDING

5. Students create bar graphs of their data.

Direct students to Procedure Step 12 in which pairs of students create two
separate or one combined bar graph—starting populations and surviving
populations of Generation 2.

6. Students analyze and interpret their data.

Students identify patterns in their community data on their Student Sheet to
answer Analysis item 1.

7. Students model the relationship between genes and an organism’s structure
and function in Analysis item 2.

a. Remind students of the idea of the crosscutting concept of structure and
function.

b. Relate structure and function to this activity.

c. (mod assessment) Have students individually develop models that show
the relationship between a mutation in a gene and the structure and
function of an organism.

8. Students discuss how their ideas about mutations have changed.

Revisit the question, “How do you think the same mutation could be harmful,
beneficial, and neutral?”

9. Students consider how the maps for the sickle cell mutation and malaria relate.

Direct students to Analysis item 5 which asks them to compare the two maps.

TEACHING STEPS

GET STARTED

1. Students review what they know about mutations.

a. Ask students, “What is a mutation?”98

Expect students to say that a mutation is a change or defect. Based on the
previous activity, students may connect mutation with beak-shape change.

98 NGLS3B2 If you have already completed the Reproduction unit, students should
be familiar with mutations and their effects on structure and function of
proteins and resulting traits.

EVOLUTION  63

ACTIVITY 5  MUTATIONS: GOOD OR BAD?

b. Probe students to further elaborate.

Ask students, “Where do mutations occur?” and “How do mutations
occur?”

Expect students to say mutations occur in DNA or genes. They could also
say that mutations occur in cells or in the body.

Explain to students that mutations arise randomly during reproduction
or could result from damage or exposure to things such as ultraviolet
radiation or microwaves.

c. Challenge students to describe the effects of mutations on an organism.

Begin by asking if mutations are always defects, or harmful. Use the
forkbird example to develop the idea that mutations can result in harmful,
beneficial, or neutral effects on the structure and function of an organism;
the effects of a mutation might depend on one of more factors in the
environment.99100

d. Ask students, “How do you think the same mutation could be harmful,
beneficial, and neutral?”

Encourage students to make predictions about how the same mutation
might be harmful, beneficial, and neutral. They may not have the correct
answer, but this sets them up for thinking about the hemoglobin mutation
in this activity.

DO THE ACTIVITY

2. Students become familiar with hemoglobin and the phenomenon of sickled
red blood cells.

a. Have students read the information in the box about normal and mutated
hemoglobin.

If you have already completed the Reproduction unit, this information
about gene inheritance should be a review. If you have not already done
the Reproduction unit, you may need to do a more thorough introduction
of genetics here. This is the introduction to the concept that all humans
have two copies of each gene, one inherited from each parent. 101

b. Review the map showing the frequency of the hemoglobin mutation
across the world.102

The hemoglobin mutation occurs throughout the world, but there are
regions of higher frequency. Help students interpret the map because they

99 NGCCSF1
100 NGCCCE2
101 NGLS3A1
102 NGCCPA2

64 EVOLUTION

MUTATIONS: GOOD OR BAD? ACTIVITY 5

will need to compare this map with a map later in the activity that shows
the frequency of malaria.

c. Review the gene nomenclature, mode of inheritance, and traits.

Students need to know that H represents the normal hemoglobin gene
and h represents the mutation. Each person has two copies of this gene,
one from the biological mother and one from the biological father. The
following table, also in the Student Book, summarizes the possible gene
combinations and resulting traits.

Genes Red blood cell trait
HH normal

Hh sickle cell carrier

hh sickle cell anemia

3. Students are introduced to the model involving a fictional community.103

a. Briefly introduce the scenario.

Students are representing a community in sub-Saharan Africa where there
are very limited health care resources (i.e., no access to hospitals and
medicine). In Part A, students will determine whether they survive or not
based on their hemoglobin genes.

b. Distribute Student Sheet 5.1, “Hemoglobin Mutations and Natural
Selection,” and one First Generation profile card to each student, and
count the traits in the population.

Each student will receive a First Generation profile card that displays
their hemoglobin genes, a description of their hemoglobin protein and red
blood cells, and a picture of their chromosomes.

In sickle cell anemic individuals (hh), all of their hemoglobin has a
mutation. This mutated hemoglobin forms long chains when not bound
to oxygen. The chains extend beyond the diameter of the red blood cells,
protruding into the membranes and deforming the cell structure.

Sickle cell carriers (Hh) will have half normal and half mutated
hemoglobin proteins. The mutated hemoglobin will still begin to form
chains within the cell, but these chains will be shorter because half of the
protein is normal. Because the chains of mutated hemoglobin are shorter,
they do not protrude into the cell membrane, leaving the red blood cells a
normal shape under most circumstances. A sickle cell carrier usually has
no or few symptoms of sickle cell anemia.

103 NGSPDM1

EVOLUTION  65

ACTIVITY 5  MUTATIONS: GOOD OR BAD?

Count the number of students with each trait. Students will use these
numbers as the beginning population on their Student Sheets.
c. Introduce malaria and how it affects the population.
Students read the information about malaria. Because this passage has
some challenging vocabulary, you might opt to read this passage aloud to
the class or have a student who is a strong reader read it aloud.
d. Facilitate the class in determining how many individuals survive malaria.
To easily count students, have them all stand up. Go through each trait,
and have students sit down if they do not survive.
• Normal individuals have a 50% chance of surviving malaria. Have HH

individuals count off by two—all the students who are ones sit down
due to death from malaria.
• Sickle cell carriers survive—Hh individuals stay standing.
• Sickle cell anemic individuals do not survive due to complications with
their sickle cell disease—hh individuals sit down.
• Students should record the number of individuals who survived in their
Student Sheets. Collect the First Generation profile cards to indicate
the wrap-up of Generation 1.
4. Students model the survival of their community’s second generation in Part B.
a. Introduce the new scenario.
The surviving individuals grow up and reproduce. In Part B, students
will determine the offspring that make up Generation 2. They will then
determine the survival of these offspring.
b. Distribute one First Generation Survivor profile card to each student,
and have students find their partners.
Each card is labeled with a letter and number (A1 through P1 and A2
through P2). Students should find their partner with the corresponding
letter on their profile cards: A1 finds A2, B1 finds B2, etc. All survivors are
either HH or Hh.

66 EVOLUTION

MUTATIONS: GOOD OR BAD? ACTIVITY 5

TABLE OF CARDS FOR FIRST GENERATION SURVIVORS

Card partner 1 Card partner 2
A1 (HH) A2 (Hh)

B1 (HH) B2 (Hh)

C1 (Hh) C2 (HH)

D1 (Hh) D2 (Hh)

E1 (Hh) E2 (HH)

F1 (HH) F2 (HH)

G1 (Hh) G2 (Hh)

H1 (HH) H2 (HH)

I1 (Hh) I2 (HH)

J1 (Hh) J2 (Hh)

K1 (HH) K2 (Hh)

L1 (HH) L2 (HH)

M1 (Hh) M2 (Hh)

N1 (HH) N2 (Hh)

O1 (Hh) O2 (HH)

P1 (HH) P2 (HH)

c. Have students discuss their new trait and determine the hemoglobin
genes of five offspring.104105

Provide students with their corresponding hemoglobin plastic disks that
match their survivor cards. Students with the sickle cell trait profile cards
will use the Hh plastic disk to determine which copy of their gene they
contribute to each offspring. Students with the normal profile cards will
contribute an H to all of their offspring. Although normal individuals
can only contribute a normal H gene to their offspring, an HH disk is
provided to reinforce the idea that they have two copies of the hemoglobin
gene, and their contribution of one copy of their gene is random.
Although no hh offspring are produced, two of these disks are provided.
Consider asking the class if any student needs one of these disks. When no
one does, consider asking why that is the case.

Have students work with their partners to complete the “Your Data” table
for Part B on the Student Sheet.

104 ELSL081
105 ELSL084

EVOLUTION  67

ACTIVITY 5  MUTATIONS: GOOD OR BAD?

d. Facilitate the class in determining the initial and surviving offspring.106107

Count the number of offspring with each trait. Students will use these
numbers to fill in the beginning population column on the “Class Data”
table for Part B on the Student Sheet.

Help students determine how many of the offspring survive a high
incidence of malaria.

BUILD UNDERSTANDING

5. Students create bar graphs of their data.108109

Direct students to Procedure Step 12 in which pairs of students create two
separate (as shown below) or one combined bar graph—starting populations
and surviving populations of Generation 2.

Graphs should include data from their Student Sheets for all three red blood
cell traits. These graphs will appear in the next activity during the simulation,
when the graphs will show 30 generations of data. This step is to introduce
these graphs so students will be able to interpret them in the next activity.

By now, students should be proficient at creating graphs, but because this is
the first time in the unit they are creating a bar graph, refer them to Appendix
C, “Bar Graphing Checklist,” for support in creating this type of graph.

PROCEDURE STEP 12 SAMPLE STUDENT RESPONSE

60 60

50 normal HH 50 normal HH
sickle cell carrier Hh sickle cell carrier Hh
Number of individuals
Number of individuals
40 sickle cell anemic hh 40 sickle cell anemic hh

30 30
20
10 20
0 Generation 2 starting population
10

0 Generation 2 surviving population

6. SLatbuAdides nSEtPsUPaInAPaSlEyvzoelutaionn d3e interpret their data.110
Figure: Evo3e TE 5_1

SMtyuriaddePrnotRsegid9.5e/n11tify patterns in their community data on their Student Sheet to
answer Analysis item 1.

7. Students model the relationship between genes and an organism’s structure
and function in Analysis item 2.

a. Remind students of the idea of the crosscutting concept of structure and
function.

106 NGCCCE2
107 NGLS4C1
108 MARP6A1
109 MASP6B5
110 NGCCPA2

68 EVOLUTION

MUTATIONS: GOOD OR BAD? ACTIVITY 5

Stress that this concept applies at any level of structure and function,
from the whole organism (e.g., the bird beaks in “Battling Beaks”) to the
protein and cell, as in this activity.

b. Relate structure and function to this activity.111

The hemoglobin gene leads to the hemoglobin protein. This protein,
as with all proteins inside the cell, has a specific structure that dictates
its function in the cell. A mutation in the hemoglobin gene disrupts the
structure of the hemoglobin protein and, in turn, the structure of the red
blood cell. This altered structure clearly disrupts the function of hemo-
globin and the red blood cell in carrying oxygen throughout the body.

c. (mod assessment) Have students individually develop models that show
the relationship between a mutation in a gene and the structure and
function of an organism.112113

Students will use Student Sheet 5.2, “Hemoglobin and Red Blood Cells
Storyboard” and fill in the four boxes to develop a model for each of three
individuals.

You can differentiate the support provided for individual students by
distributing optional Student Sheet 5.3a, “Storyboard Panels,” or Student
Sheet 5.3b, “Storyboard Key.” Student Sheet 5.3a provides substantial
support by providing all of the possible images and/or text that could fill
the panels on Student Sheet 5.2. Students can cut and paste onto Student
Sheet 5.2 or draw the images by hand. Student Sheet 5.3b provides some
support, but not as much as 5.3a. It provides all of the labeled images as
a legend, but students have to fill in the storyboard panel with the correct
images and the correct number of each image.

Analysis item 3 in this activity can be assessed using the mod Scoring
Guide. For more information, see Teacher Resources III, “Assessment.”
This item corresponds to Performance Expectation MS-LS3-1. Review
the levels and criteria in the Scoring Guide for integrating the Disciplinary
Core Idea of Inheritance and Variation of Traits and the Crosscutting
Concept of Structure and Function with the Science and Engineering
Practice of Developing and Using Models.

8. Students discuss how their ideas about mutations have changed.

Revisit the question, “How do you think the same mutation could be harmful,

beneficial, and neutral?”

111 NGCCSF1
112 SEASMD1
113 NGPEL31

EVOLUTION  69

ACTIVITY 5  MUTATIONS: GOOD OR BAD?

Students will respond to this in Analysis item 4. Have students discuss how
their response to this question may have changed after doing the activity.
Encourage students to use evidence from their investigations to support
their ideas.

9. Students consider how the maps for the sickle cell mutation and malaria relate.

Direct students to Analysis item 5 which asks them to compare the two maps.

Use Visual Aid 5.1, "Comparing Maps," to help students notice that there is a
correlation between the shaded areas on the map.

SAMPLE RESPONSES TO ANALYSIS

1. Look at the numbers of individuals you recorded on Student Sheet 5.1 and
the bar graph(s) you created. Compare the number of individuals with each
trait in the beginning population to the surviving numbers. What patterns do
you notice? 114115116

Sickle cell carriers survive malaria, so the numbers of carrier individuals do not
change.There are twice as many normal individuals in the starting populations of both
generations compared with the carriers, but the numbers of survivors tend to be equal.

2. In your community, half of the normal and all of the sickle cell anemic individ-
uals died. Explain how normal and sickle cell anemic offspring were born in
the second generation. 117

Hint: Remember that you have two copies of each gene, one from each parent.

Sickle cell carriers have a normal and a mutated hemoglobin gene that they can pass
on to their offspring.The gene that is passed on is random. So if you have two carrier
parents (Hh x Hh), they can produce offspring that are normal (HH), sickle cell
carriers (Hh), or sickle cell anemic (hh).

3. (mod assessment, MS-LS3-1) Use Student Sheet 5.2, “Hemoglobin and Red
Blood Cells Storyboard,” to develop a model to explain the relationship between
a mutation in a gene and the structure and function of an organism. 118119120

Be sure to include the genes, the protein, the red blood cell, and the organism
in all three cases—a normal individual, a carrier, and a person with sickle cell
anemia.

Follow your teacher’s instructions for how to represent the genes, protein, red
blood cell, and organism.

Student responses may vary depending on whether you provide the sample
panels on Student Sheet 5.3a. A sample Level-4 response is shown at the end
114 NGCCPA2 of this activity.
115 MARP6A1
116 MASP6B5
117 NGLS3A1
118 SEASMD1
119 NGSPDM1
120 NGPEL31

70 EVOLUTION

MUTATIONS: GOOD OR BAD? ACTIVITY 5

4. Hemoglobin S is caused by a single mutation in the hemoglobin gene. Explain
how the environment affects whether this mutation is beneficial, harmful, or
neutral for a person. Use evidence from your investigation to support your
explanation. 121

Normal individuals die when they contract malaria and there is low-quality health
care. Having one mutated hemoglobin gene, like sickle cell carriers, allows you
to survive when there is malaria independent of health care. So this mutation is
beneficial in these people. But individuals with two mutated hemoglobin genes, like
sickle cell anemic people, die without good health care. So in this case, the same
mutation is harmful when there are two copies.

5. Compare the “Frequency of Hemoglobin S Mutation” and “Global
Transmission of Malaria” maps seen earlier in this activity. What is the
evidence for a cause-and-effect relationship between the frequency of malaria
and the frequency of the hemoglobin mutation? 122

The areas where people have the hemoglobin mutation are almost exactly the same
places where malaria is found.The evidence for a cause-and-effect relationship is the
evidence that sickle cell carriers are more likely to survive malaria.This explains why
sickle cell anemia and sickle cell carriers are more common in areas where malaria is
present than in areas without malaria.

REVISIT THE GUIDING QUESTION

How do mutations affect survival?

Mutations lead to changes in an organism’s structure and function. Sometimes
these changes result in traits that are more advantageous or better suited for a
situation or environmental condition. Individuals with these traits are more likely
to survive and reproduce, passing that mutation to their offspring. If the mutation
results in a less favorable trait, those individuals are less likely to reproduce so
that mutation is not propagated. If the mutation has a neutral effect, it is neither
selected for nor against.

ACTIVITY RESOURCES

KEY VOCABULARY

gene

mutation

natural selection

trait

121 NGSPCE2
122 NGCCCE2

EVOLUTION  71

ACTIVITY 5  MUTATIONS: GOOD OR BAD?

BACKGROUND INFORMATION

TYPES OF MUTATIONS

Mutations can be considered beneficial, harmful, or neutral based on the resulting
effect on the protein’s function. A beneficial mutation may improve the function
of the protein. A harmful mutation will disrupt the structure and function of the
protein. A neutral mutation may change the protein subunits but not result in a
significant overall structure or function change. Alternatively, a neutral mutation
may change the structure but not affect the function.

HEMOGLOBIN AND SICKLE CELL DISEASE

Hemoglobin is the oxygen-carrying protein inside red blood cells. Although
hemoglobin is referred to as a protein, it is actually composed of four subunits—
two copies of alpha-globin and two copies of beta-globin. Hemoglobin makes up
approximately 95% of red blood cells’ dry content (by weight).

There are many known mutations in human hemoglobin genes, although the
most widely studied and understood mutation is linked to sickle cell disease. This
mutation is a single DNA nucleotide change in the hemoglobin gene, resulting in a
valine instead of a glutamic acid at position six. This mutated form of hemoglobin
produces hemoglobin S. In times of high oxygen, this mutation does not have an
effect on hemoglobin or red blood cell structure and function. But in low-oxygen
conditions, when hemoglobin releases oxygen in tissues, a hydrophobic patch
is exposed on the protein. To mask its interaction with water, the hydrophobic
patches in mutated hemoglobin proteins aggregate and form chain-like structures.
This aggregation, in turn, alters the red blood cell structure, creating ragged edges
and spikes, which make the cells fragile and more susceptible to bursting while
traveling in capillaries. These irregular cells can also aggregate and block blood
flow. Because these cells tend to burst prematurely, it can result in a shortage of
red blood cells.

Mutations in the hemoglobin gene result in sickle cell disease, which is commonly
found in sub-Saharan Africa, Mediterranean countries, the Middle East, and India.
Individuals with one copy of the mutated hemoglobin gene are carriers and display
sickle cell trait. These carriers tend to only show symptoms if they are in oxygen-
deprived situations (e.g., at high altitude) or if severely dehydrated. Individuals
with two copies of the mutated gene develop sickle cell anemia. Since the mutation
is in the hemoglobin gene, it is inherited from one or both parents, and the
presence of sickle cell disease can be detected at birth. Identification can be done
through a simple blood test and is most often found during routine newborn
screening. Individuals with sickle cell disease will start to display symptoms during
the first year of life, typically around 5 months old. Symptoms vary from person to
person and can range from mild to severe.

72 EVOLUTION

MUTATIONS: GOOD OR BAD? ACTIVITY 5

Individuals who are heterozygous, and thus carriers for sickle cell, have red blood
cells that are shaped normally and function normally. In this way, the sickle cell
allele behaves as if it is recessive. However, when malaria is present, the allele no
longer behaves as if it is recessive. Thus, the sickle cell trait can’t be described in
simple dominant–recessive terms.

The only known cure for sickle cell disease is a bone marrow or stem cell
transplant. These transplants introduce healthy cells that can give rise to normal,
healthy red blood cells. Survival rates for those with sickle cell disease have steadily
increased over time due to advances in diagnoses and treatment.

MALARIA

Malaria is caused by the parasite Plasmodium falciparum and is transmitted by
Anopheles mosquitos infected with the parasite. Malaria is typically transmitted in
tropical and subtropical regions where there are warm temperatures and increased
humidity that promote the growth of the mosquitos. Warmer temperatures also
allow the parasite to complete its life cycle within the mosquito. The highest
transmission of malaria is found in sub-Saharan Africa and parts of Oceania. There
are also regions where Anopheles mosquitos thrive, such as western Europe and
the United States, but with increased economic development and public health
resources, malaria has been essentially eliminated.

Malaria symptoms range from uncomplicated to severe, but in general, malaria
is curable if detected and treated as soon as possible. The parasite infects and
uses red blood cells to reproduce in the host. Through this process, many waste
substances and toxins are released, which can accumulate in uninfected red blood
cells. Symptoms can appear 7–30 days after being bitten by an infected mosquito
and include flu-like symptoms (e.g., shivering, fever, headaches, vomiting, sweats,
tiredness). In regions where malaria is not prevalent, these symptoms tend to be
treated like the flu, which allows the progression of malaria to worsen. If untreated,
malaria can lead to organ failure, acute respiratory distress, severe anemia,
metabolic acidosis (excess acid in blood and tissues), hypoglycemia, and death.

Malaria can be diagnosed by finding the parasites in blood through microscopy.
Lab tests can also detect anemia, decrease in blood platelets, elevation of bilirubin,
and elevation of aminotransferases.

In the United States, malaria is treated with antimalarial drugs that can target the
parasite in the blood. However, there are areas of the world with parasites resistant
to many known drugs, so treatment can vary depending on where the infection
was acquired.

EVOLUTION  73

ACTIVITY 5  MUTATIONS: GOOD OR BAD?

Survival rates for those infected with malaria depend on the availability of
resources and access to health care. Malaria occurs mostly in poor regions of
the world, and in these regions, it is the leading cause of illness and death. Those
most vulnerable to the disease are youth under 5 years old and pregnant women.
In 2012, 3.2 billion people lived in areas at risk of malaria transmission, and
there were an estimated 207 million clinical cases and 627,000 deaths (with
approximately 91% of these deaths in sub-Saharan Africa). Interestingly, sickle
cell carriers can contract malaria but show mild symptoms and have an increased
survival rate compared with individuals with normal hemoglobin.
REFERENCES
Centers for Disease Control and Prevention. Where Malaria Occurs. (2017)
Retrieved from www.cdc.gov/malaria/about/distribution.html.
Piel, F. B., Patil, A. P., Howes, R. E., Nyangiri, O. A., Gething, P. W., Williams,
T. N., … Hay, S. I. (2010). Global distribution of the sickle cell gene and
geographical confirmation of the malaria hypothesis. Nature Communications, 1,
104. doi:10.1038/ncomms1104
Piel, F. B., Patil, A. P., Howes, R. E., Nyangiri, O. A., Gething, P. W., Dewi, M.,
… Hay, S. I. (2013). Global epidemiology of sickle haemoglobin in neonates: A
contemporary geostatistical model-based map and population estimates. Lancet,
381, 142. doi:10.1016/50140-6736(12)61229-X
Platt, O. S., Brambilla, D. J., Rosse, W. F., Milner, P. F., Castro, O., Steinberg,
M. H., & Klug, P. P. (1994). Mortality in sickle cell disease. Life expectancy and
risk factors for early death. New England Journal of Medicine, 330(23), 1639–44.
doi:10.1056/NEJM199406093302303

74 EVOLUTION

Name______________________________________________________________ Date____________

STUDENT SHEET 5.1

HEMOGLOBIN MUTATIONS AND NATURAL SELECTION

Part A: The Initial Population

Beginning population Malaria survivors

# of normal (HH)
individuals

# of sickle cell carrier
(Hh) individuals

# of sickle cell anemic
(hh) individuals

Part B: The Next Generation

Your Data

Offspring # Parent 1 gene Parent 2 gene Offspring Offspring red
contribution contribution hemoglobin genes blood cell trait

1

2

3

4

5

Class Data Beginning population Malaria survivors

©2017 The Regents of the University of California # of normal (HH)
offspring

# of sickle cell carrier
(Hh) offspring

# of sickle cell anemic
(hh) offspring

Name______________________________________________________________ Date____________

STUDENT SHEET 5.2

HEMOGLOBIN AND RED BLOOD CELLS STORYBOARD

©2017 The Regents of the University of California

LabAids SEPUP IAPS Evolution 3e
Figure: Evo3e TE 5_2 Student Sheet
MyriadPro Reg 9.5/11

©2017 The Regents of the University of California

sickle cell Name______________________________________________________________ Date____________
carrier
STUDENT SHEET 5.3a
sickle shaped red normal mutated all mutated hemoglobin
blood cells H gene h gene protein STORYBOARD PANELS

sickle cell
anemic

all normal hemoglobin protein normal normal normal red
H gene H gene blood cells

normal red
blood cell trait

normal red half normal hemoglobin mutated mutated
blood cells protein; half mutated h gene h gene

LabAids SEPUP IAPS Evolution 3e
Figure: Evo3e TE 5_3 Student Sheet

Name______________________________________________________________ Date____________

STUDENT SHEET 5.3b

STORYBOARD KEY

normal mutated
H gene h gene

normal mutated
hemoglobin hemoglobin
protein protein

normal red sickle shaped
blood cell red blood cell

©2017 The Regents of the University of California LabAids SEPUP IAPS Evolution 3e
Figure: Evo3e TE 5_4 Student Sheet
MyriadPro Reg 9.5/11

Name______S__a_m___p_l_e__s_t_u__d_e_n__t_r__e_s_p_o__n_s__e___________________________ Date____________

STUDENT SHEET 5.1

HEMOGLOBIN MUTATIONS AND NATURAL SELECTION

Part A: The Initial Population

# of normal (HH) Beginning population Malaria survivors
individuals 20 10
10
# of sickle cell carrier 10 0
(Hh) individuals

# of sickle cell anemic 2
(hh) individuals

Part B: The Next Generation

Your Data

Offspring # Parent 1 gene Parent 2 gene Offspring Offspring red
contribution contribution hemoglobin genes blood cell trait

1H H HH Normal

2H H HH Normal

3H h Hh Sickle cell carrier

4H H HH Normal

5H h Hh Sickle cell carrier

©2017 The Regents of the University of California Class Data Beginning population Malaria survivors
55 25
# of normal (HH) 20 20
offspring 5 0

# of sickle cell carrier
(Hh) offspring

# of sickle cell anemic
(hh) offspring

©2017 The Regents of the University of California

normal red Name______S__a_m___p_l_e__s_t_u__d_e_n__t_r__e_s_p_o__n_s__e___________________________ Date____________
blood cell trait
STUDENT SHEET 5.2
normal normal all normal hemoglobin protein normal red
H gene H gene blood cells HEMOGLOBIN AND RED BLOOD CELLS STORYBOARD

sickle cell
carrier

normal mutated half normal hemoglobin normal red
H gene h gene protein; half mutated blood cells

sickle cell
anemic

mutated mutated all mutated hemoglobin protein sickle shaped red
h gene h gene blood cells

LabAids SEPUP IAPS Evolution 3e
Figure: Evo3e TE 5_5
MyriadPro Reg 9.5/11

VISUAL AID 5.1

COMPARING MAPS

Hemoglobin S frequency
0.1–0.2% 0.03–0.09%

LabAids SEPUP IAPS Evolution 3e
Figure: Evo3e SB 5_3
MyriadPro Reg 9.5/11

©2017 The Regents of the University of California Malaria transmission Malaria transmission
occurs throughout occurs in some parts

LabAids SEPUP IAPS Evolution 3e
Figure: Evo3e SB 5_4
MyriadPro Reg 9.5/11



6 Mutations and Evolution

computer simulation
2 class sessions

ACTIVITY OVERVIEW

NGSS CONNECTIONS

Students continue investigating the inheritance and selection for the hemoglobin
mutation using a computer simulation. Students use mathematical representations
and analyze graphs to determine the distribution of the mutation in their
population over time. Students manipulate different parameters to investigate
multiple cause-and-effect relationships between environmental conditions and
natural selection in their population. This activity provides an opportunity to assess
student work related to Performance Expectation MS-LS4-6.

NGSS CORRELATIONS

Performance Expectations

MS-LS4-6: Use mathematical representations to support explanations of
how natural selection may lead to increases and decreases to specific traits in
populations over time.

Applying MS-LS3-1: Develop and use a model to describe why structural changes
to genes (mutations) located on chromosomes may affect proteins and may result
in harmful, beneficial, or neutral effects to the structure and function of the
organism.

Applying MS-LS4-4: Construct an explanation based on evidence that describes
how genetic variations of traits in a population increase some individuals’
probability of surviving and reproducing in a specific environment.

Disciplinary Core Ideas

MS-LS4.C Adaptation: Adaptation by natural selection acting over generations
is one important process by which species change over time in response to
changes in environmental conditions. Traits that support successful survival and
reproduction in the new environment become more common; those that do not
become less common. Thus, the distribution of traits in a population changes.

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ACTIVITY 6  MUTATIONS AND EVOLUTION

MS-LS4.B Natural Selection: Natural selection leads to the predominance of
certain traits in a population, and the suppression of others.

MS-LS3.A Inheritance of Traits: Genes are located in the chromosomes of cells,
with each chromosome pair containing two variants of each of many distinct genes.
Each distinct gene chiefly controls the production of specific proteins, which in
turn affects the traits of the individual. Changes (mutations) to genes can result in
changes to proteins, which can affect the structures and functions of the organism
and thereby change traits.

MS-LS3.BVariation of Traits: In addition to variations that arise from sexual
reproduction, genetic information can be altered because of mutations. Though
rare, mutations may result in changes to the structure and function of proteins.
Some changes are beneficial, others harmful, and some neutral to the organism.

Science and Engineering Practices

Using Mathematical and Computational Thinking: Use mathematical representations
to support scientific conclusions and design solutions.

Constructing Explanations and Designing Solutions: Construct an explanation that
includes qualitative or quantitative relationships between variables that describe
phenomena.

Crosscutting Concepts

Cause and Effect: Phenomena may have more than one cause, and some cause and
effect relationships in systems can only be described using probability.

Patterns: Graphs, charts, and images can be used to identify patterns in data.

Structure and Function: Complex and microscopic structures and systems can
be visualized, modeled, and used to describe how their function depends on the
shapes, composition, and relationships among its parts, therefore complex natural
structures/systems can be analyzed to determine how they function.

Common Core State Standards—Mathematics

6.RP.A.1: Understand the concept of a ratio and use ratio language to describe a
ratio relationship between two quantities.

6.SP.B.5: Summarize numerical data sets in relation to their context.

Common Core State Standards—ELA/Literacy

SL.8.1: Engage effectively in a range of collaborative discussions (one-on-one,
in groups, teacher-led) with diverse partners on grade 6 topics, texts, and issues,
building on others’ ideas and expressing their own clearly.

84 EVOLUTION

MUTATIONS AND EVOLUTION ACTIVITY 6

SL.8.4: Present claims and findings, emphasizing salient points in a focused
coherent manner with relevant evidence, sound valid reasoning, and well-chosen
details; use appropriate eye contact, adequate volume, and clear pronunciation.

WHAT STUDENTS DO
Students use a computer simulation to extend their investigation around the
inheritance of the hemoglobin mutation. The simulation first extends their data
from the previous activity through 30 generations. Then students are able to adjust
the environmental conditions to see how access to resources and the prevalence of
malaria influence the distribution of the hemoglobin gene over time.

MATERIALS AND ADVANCE PREPARATION

■■ For the teacher

1 Scoring Guide: constructing explanations (exp)

■■ For each pair of students

* computer with Internet access
1 Student Sheet 6.1, “Changing Environments” (optional)
1 Scoring Guide: constructing explanations (exp) (optional)

*not included in kit

If necessary, arrange for access to computers with Internet connectivity. Become
familiar with the simulation. Adjust the parameters and run the simulation to see
what kind of results students are likely to obtain. For a link to the simulation, see
the teacher page of the SEPUP Third Edition Evolution website at www.sepuplhs.org/
middle/third-edition. This simulation is most effective if students work in pairs rather
than larger groups. If necessary, make arrangements for this in advance.

TEACHING SUMMARY

GET STARTED

1. Students review the results from the model of hemoglobin mutation inheri-
tance from the “Mutations: Good or Bad?” activity.
a. Remind students about the hemoglobin mutation that results in
hemoglobin S.
b. Discuss the results from the previous activity.

EVOLUTION  85

ACTIVITY 6  MUTATIONS AND EVOLUTION

2. Students are introduced to the simulation.

a. Explain that the simulation is designed to allow students to follow their
population over a longer period of time in a manageable way.

b. Review the different variables and how changing them alters the
environmental conditions or survival rates.

3. Students run the simulation to investigate the increase and/or decrease of the
sickle cell trait over time in Part A.

a. Circulate to ensure that students have set the parameters correctly.

b. Support your students in their analysis of the simulation results.

c. Discuss student responses to Analysis item 1.

4. Students use the simulation to investigate how changing the environmental
conditions affect the sickle cell trait in Part B.

a. Let students know that in Part B, students can begin addressing questions
they may have generated in Part A.

b. Ensure that students are adjusting the parameters correctly and keeping a
record of the settings they choose for each simulation.

BUILD UNDERSTANDING

5. Students analyze and interpret their data.
a. (exp assessment) Students use their data from their simulations to answer
Analysis item 2.
b. Discuss student responses to Analysis item 3.
c. Discuss student responses to Analysis item 4.

TEACHING STEPS

GET STARTED

1. Students review the results from the model of hemoglobin mutation inheri-
tance from the “Mutations: Good or Bad?” activity.123124

a. Remind students about the hemoglobin mutation that results in
hemoglobin S.

Ask students, “What happens if you inherit one copy of the hemoglobin
mutation?” Expect students to say that one copy of the mutation results in
sickle cell trait and you are a carrier.

123 NGLS3A1
124 NGLS3B2

86 EVOLUTION

MUTATIONS AND EVOLUTION ACTIVITY 6

Ask students, “What happens if you inherit two copies of the hemoglobin
mutation?” Expect students to say that the result is dysfunctional
hemoglobin protein that causes red blood cells to change structure and
results in sickle cell disease. 125126

b. Discuss the results from the previous activity.

Previously, the community had no health care and a high incidence of
malaria. In this situation, sickle cell anemic individuals did not survive to
reproductive age, about half of the normal individuals survived malaria,
and all of the sickle cell carriers survived malaria. 127128

DO THE ACTIVITY

2. Students are introduced to the simulation.129

a. Explain that the simulation is designed to allow students to follow their
population over a longer period of time in a manageable way.

b. Review the different variables and how changing them alters the
environmental conditions or survival rates.

• Percent chance of getting malaria: This is the percent chance (or
incidence rate) for each individual of getting malaria. The available
choices are 0, 25, 50, 75, or 100%. In your community in the previous
activity, the incidence was high, so set this to 100%.

• How good the health care is: This is the level of health care and
resources available. Three levels are available: no health care, ok health
care, or great health care.Your community has no health care.

The simulation defaults so the variables match the conditions in the
“Mutations: Good or Bad?” activity.

Note that initially there is only one set of variables that can be
manipulated. After students run an initial simulation, another set of
variables appears below the results. This allows students to run the second
simulation to compare how changing the environment compares with the
original run.

125 NGCCSF1 The simulation uses a computational algorithm that has a randomized
126 NGCCCE2 mating component. Both survival and genotype assignment are calculated
127 NGLS4C1 probabilistically. Thus, running the simulation multiple times with the
128 NGLS4B1 same variable settings will not give you the exact same results.
129 NGSPUM1

EVOLUTION  87

ACTIVITY 6  MUTATIONS AND EVOLUTION

3. Students run the simulation to investigate the increase and/or decrease of the
sickle cell trait over time in Part A.130131

a. Circulate to ensure that students have set the parameters correctly.

The simulation defaults to a 100% chance of malaria and no health care.

Let students know that the graphs are interactive, so if they click on any
of the labels in the key, that portion of the graph will be highlighted.
Hovering over a point on the graph reveals the precise value for that point.
The bar graph on the left can be expanded or collapsed, and students can
zoom in on the line graph on the right.

b. Support your students in their analysis of the simulation results.132133

By now, students should be proficient at creating and interpreting graphs.
Encourage them to look at their graphs from the previous activity if they
need a reminder about how to analyze these graphs.

The simulation produces two different graphs, similar to the graphs
generated by students in the “Mutations: Good or Bad?” activity.

• Graph 1: This bar graph shows how many offspring survived to
reproduce in each generation. This graph should be similar to what the
students produced in the previous activity.

• Graph 2: This line graph shows the percentage of each trait in the
population for each generation over time.

Also encourage students to record questions they have in their science
notebooks.

c. Discuss student responses to Analysis item 1.

Percentages of each type of individual are given on the second graph.
Students can write ratios based on the total number of individuals given
in the first graph. To see these values, students need to mouse over the
bars or lines on the graphs.

Similar to the previous activity, students should see an increase in the
numbers of sickle cell carriers in the population. The numbers of normal
individuals decrease over time.

4. Students use the simulation to investigate how changing the environmental
conditions affect the sickle cell trait in Part B.134

a. Let students know that in Part B, students can begin addressing questions
they may have generated in Part A.

These questions should include whether the increase in sickle cell carriers
occurs in all conditions. Students should also investigate the two causes

130 ELSL081
131 ELSL084
132 NGCCPA2
133 NGCCCE2

81384  EVOLUNGTCICOCEN2

MUTATIONS AND EVOLUTION ACTIVITY 6

that affect the trait frequency—the chance of getting malaria and the level
of health care.

b. Ensure that students are adjusting the parameters correctly and keeping a
record of the settings they choose for each simulation.

Since students will be testing multiple parameters, suggest that they draw
the graphs in their science notebooks or print them.

Use optional Student Sheet 6.1, “Changing Environments,” if your
students need more structured guidance about which variables to change
and how to change them.

Students should find that increasing health care or decreasing the
incidence of malaria no longer selects for the sickle cell trait. Without the
high incidence of malaria, there is no selection for the trait.

BUILD UNDERSTANDING

5. Students analyze and interpret their data.135136137

a. (exp assessment) Students use their data from their simulations to answer
Analysis item 2. 138139140

Analysis item 2 asks students to generalize about how the environment
affects the frequency of the sickle cell trait. Students should identify
the chance of getting malaria and the availability of health care as two
environmental conditions.

This item can be assessed using the exp Scoring Guide. For more
information, see Teacher Resources III, “Assessment.” This item
corresponds to Performance Expectation MS-LS4-6.

Review the levels and criteria in the Scoring Guide for integrating the
Disciplinary Core Idea of Adaption and the Crosscutting Concept of Cause
and Effect with the Science and Engineering Practices of Constructing
Explanations Using Mathematics and Computational Thinking.

b. Discuss student responses to Analysis item 3.

You may wish to share that malaria used to exist in the United States and
was relatively common in the Southeast. An eradication program began in
1947, and by 1951, malaria was considered to be eradicated.

c. Discuss student responses to Analysis item 4.

135 NGSPUM1 This item gives students an opportunity to consider what would happen
136 MARP6A1 when changing both environmental variables to reduce selection favoring
137 MASP6B5 the sickle cell mutation.
138 NGSPCE2
139 SEASEX1 EVOLUTION  89
140 NGPEL46

ACTIVITY 6  MUTATIONS AND EVOLUTION

SAMPLE RESPONSES TO ANALYSIS

1. Use the data you collected or observations you made about the environment
to the complete the following: 141142

a. Use a mathematical representation, like a ratio or percent, to explain
what happened to the frequency of the sickle cell trait over time when the
chance of getting malaria was high and there was no health care. 143144

Student responses may vary. One sample response is shown here:

The frequency of the sickle cell trait increased over time. In the beginning,
11% of the population were sickle cell carriers. By generation 30, 35% of the
population were carriers. Sickle cell anemic individuals also increased from
less than 1% to 5% in my population, but the normal individuals with no
hemoglobin mutation decreased from 88% to only 60% of the population.

b. Is there a cause-and-effect relationship? If so, describe that relationship. If
not, explain why not. 145

Student responses may vary. One sample response is shown here:

With no health care, the sickle cell anemic people do not survive because they
do not get treated quickly enough. People with normal hemoglobin get malaria,
but without health care, they are not treated and do not survive. Only the sickle
cell carriers survive, so this part of the population grows up and reproduces.The
ability to survive is determined by the hemoglobin gene an individual has, the
quality of health care, and the chances of getting malaria.

2. (exp assessment, MS-LS4-6) Explain how environmental changes affect the sickle
cell trait over time in your population? Use evidence, including mathematical
representations, from your investigation to support your explanation. 146147148149

SAMPLE LEVEL-4 RESPONSE

There are two ways that changes in the environment affected how common the sickle
cell trait is—changing the frequency of malaria or changing the quality of the health
care. If there was no malaria and no health care, the hemoglobin mutation almost
disappeared from our population, going from 10% to 1.8% of our population.There
was no selection for the mutation in this case because the sickle cell trait is only an
advantage when malaria is common. But when malaria became common (75% or
100% chance) with no health care, there was an increase in the sickle cell mutation
in our population because the sickle cell trait increased the chances of survival and
reproduction in the presence of malaria when health care is poor.

141 MARP6A1
142 MASP6B5
143 NGSPUM1
144 NGCCPA2
145 NGCCCE2
146 NGPEL46
147 NGSPCE2
148 NGCCSF1
149 SEASEX1

90 EVOLUTION

MUTATIONS AND EVOLUTION ACTIVITY 6

Increasing health care meant that people who contracted malaria could be
treated and survive.With great health care, the percent of sickle cell carriers
did not increase over time. Instead I saw that the percentage of carriers dropped
to 4.9% from 11%.This occurred because there was no positive selection
(advantage) for the trait.
3. Explain why the frequency of sickle cell trait is so much higher in sub-Saharan
Africa than in most other parts of the world.
Student responses may vary. One sample response is shown here:
Based on the map from the last activity, there is a high incidence of malaria in
sub-Saharan Africa. Individuals that have one copy of the hemoglobin mutation (or
sickle cell trait) are able to survive malaria. Since having one copy of the mutated
gene seems to protect people from malaria, it is being selected for in this region of high
malaria.This selection was seen when we did the simulation.
4. What do you think would happen to the sickle cell trait in an environment
with no malaria and increased resources? Explain your prediction.
Student responses may vary. One sample response is shown here:
I predicted that the trait frequency would not change or would go down. If carriers
survive because they survive malaria, in a place without malaria there is no selection
for the trait. Everyone should live because there is no disease and good health care.

REVISIT THE GUIDING QUESTION
Why does sickle cell trait frequency vary across the world?
Evolution occurs when there is a change in trait frequency. One way a trait
frequency changes is through natural selection. In this activity, the hemoglobin
mutation was selected for by the presence of malaria. Environmental factors, such
as the access to and quality of health care, also present another form of selection.
Since the presence of malaria and quality of health care vary across the world,
selection for or against the sickle cell trait will also vary.
This is a good time to revisit the second driving question for this sequence of
learning. Revisit and add to or revise students' ideas as needed.

EVOLUTION  91

ACTIVITY 6  MUTATIONS AND EVOLUTION

ACTIVITY RESOURCES

KEY VOCABULARY
evolution
mutation
REFERENCES
Piel, F. B., Patil, A. P., Howes, R. E., Nyangiri, O. A., Gething, P. W., Williams,
T. N., … & Hay, S. I. (2010). Global distribution of the sickle cell gene and
geographical confirmation of the malaria hypothesis. Nature Communications, 1,
104. doi:10.1038/ncomms1104
Platt, O. S., Brambilla, D. J., Rosse, W. F., Milner, P. F., Castro, O., Steinberg,
M. H., & Klug, P. P. (1994). Mortality in sickle cell disease. Life expectancy and
risk factors for early death. New England Journal of Medicine, 330(23), 1639-44.
doi:10.1056/NEJM199406093302303

92 EVOLUTION

©2017 The Regents of the University of California Name______________________________________________________________ Date____________

STUDENT SHEET 6.1

CHANGING ENVIRONMENTS

In Part B of the “Mutations and Evolution” activity, you will investigate what happens to the
sickle cell trait when the environment changes. In particular, you will look for the effect
caused by decreasing the chances of getting malaria or by increasing the availability and
quality of health care.

1. Your community starts a pest control program to decrease the number of mosquitos
in the area.

The program is successful and results in a decrease in the chances of getting malaria.
Predict what will happen to the sickle cell trait when the incidence of malaria goes
down, even without health care. Explain your prediction.

2. Test your prediction by adjusting the chance of getting malaria using the second set
of adjustable variables and rerunning the simulation.

• Keep the health care variable the same: no health care.

• Repeat the simulation for each possible incidence of malaria.

• Be sure to record the results for each variable in your science notebook.

• Write down any other questions that you might have and would like to test.

3. Alternatively, your community decided to focus on building health clinics. Now there
is an increase in the availability and quality of health care. What would happen to
the sickle cell trait in a population with increased health care and a high chance of
getting malaria? Explain your prediction.

4. Test your prediction by adjusting the variables and rerunning the simulation.

• Set the chance of getting malaria variable to 100%, and leave it at that level as you
change the health care variable.

• Repeat the simulation for each possible level of health care.

• Be sure to record the results for each variable in your science notebook.

• Write down any other questions that you might have and would like to test.