Investigating Changes In Trait Distribution

CHAPTER 1 – ENVIRONMENTAL CHANGE AND
TRAIT DISTRIBUTION

1.4.1:WARM-UP
Observing Populations at Two Generations
The histograms below show the distribution of fur-level traits in a population at two different
points in time. Review the two histograms and answer the questions below.
1. Do the two histograms show the same amount of
variation in the population at both generations?
2. Do the two histograms show the same distribution of
traits at both generations?
YES NO YES NO
The distribution of the traits changed over time.

1.4.1:WARM-UP
Observing Populations at Two Generations
The histograms below show the distribution of fur-level traits in a population at two different
points in time. Review the two histograms and answer the questions below.
1. Do the two histograms show
the same amount of variation
in the population at both
generations?
2. Do the two histograms show
the same distribution of traits at
both generations?
NO NO

1.4.1:WARM-UP
• At Generation 50, the distribution was
different since most of the ostrilopes
had a high amount of fur.
• There was also less variation since
there were only 4 fur traits.
• The population started with most
ostrilopes having low amount of fur.
• The population at this time had a high
variation – 7 different fur traits.
Why did the distribution changed from mostly individuals with traits for low
and medium levels of fur to mostly individuals with high levels of fur?

What makes the distribution of traits in a population
change?
Investigation
Question:
In the next activity, you will
use the Natural Selection
Sim to begin thinking about
what made the distribution
of fur traits in the Ostrilope
population change over
time.
1.4.2: SIM – UTILIZE SIM
OBSERVING FUR TRAITS AND TEMPERATURE IN THE SIM

Let’s examine some more
controls in the SIM
• Temperature Slider
- Observe the changing visuals.
- Only make ONE temperature
change to make conclusions.
MILDTEMP.

controls in the SIM
MILDTEMP.COLD TEMP.

controls in the SIM
MILDTEMP.COLD TEMP.HOT TEMP.

• Traits Histogram Window Run
- Run Sim by pressing NEXT
- Then hit “RUN” in the build
setup menu.
- Collect a few generations of data
- OpenTraits Histogram Window
(Bottom Left icon)
- Observe real-time histograms of
different features

• Speed Controls
- Use drop down to collect many
generations of data more quickly.

• Histograms in Analyze
- Use Analyze in Build Setup
menu.
- Move generation slider.
- Note the stripes show the
starting generation
histogram.

1.4.2: SIM – FUR AND TEMP A
Starting histogram – Fur and
Temperature A Mode
• Press Build, then Rebuild
• Click on Ostrilope
• Look at starting Ostrilope population
Note that it has the same distribution of fur
traits as in the Generation 1 Histogram
from the Warm-Up.
These ostrilopes have been living in a warm
environment, but that students are going to
change the environment to be colder.

Set the environment to cold (Level 1),
using the Temperature slider, and observe
what happens over 50 generations.
Zoom into the environment and select
different ostrilopes to observe individuals
with different traits.
After 50 generations have passed, students
should press ANALYZE to compare the
Generation 50 histogram with the
Generation 1 histogram.

Set the environment to cold (Level 1),
using the Temperature slider, and observe
what happens over 50 generations.
Zoom into the environment and select
different ostrilopes to observe individuals
with different traits.
After 50 generations have passed, students
should press ANALYZE to compare the
Generation 50 histogram with the
Generation 1 histogram.
Each bar tells us how many
individuals in the population have a
particular trait.

Launch the Sim and make sure you do the following:
1. Begin by setting the environment to cold (Level 1).
2. Observe individuals with different fur traits while the Sim is running.
3. Use theTraits Histogram Window while the Sim is running.
4. Press ANALYZE to compare histograms.
5. Upload a screenshot of the fur-trait histogram for Population A after 50 generations.
6. Answer the questions on their Amplify Science screens.
7. Time Permitting: Reset SIM and repeat your test to see if you get the same results.
Entire Screen Specific Area of the Screen

Discuss your responses to the questions with a partner.

1.4.2: SIM
Let’s review your work
The high fur-level trait became more common because
individuals with this trait could survive in the cold
environment.
"The population started with ostrilopes that had low,
medium, and high levels of fur. I saw that the ostrilopes with
the low level of fur shivered and died in the cold
environment, but the ones with the high level of fur
survived. "

1.4.2: SIM
Use your interpretation of the data to
hypothesize that the change shown in the
data was caused by the environmental
change – cold environment.
When a bar gets shorter, it means that
individuals died because they did not have
enough fur to survive in the cold
environment.

1.4.2: SIM
Traits for high fur became more common
and the traits for low fur became less
common.
• The ostrilopes with lower fur-level traits
shivered and died in the cold
environment.
• The ostrilopes with higher fur-level traits
survived in the cold environment. More
fur helped them survive, and they
became more common.

environment: everything (living and nonliving) that
surrounds an organism
Each of these environments includes many living things, such as plants and animals, and
nonliving things, such as rocks and water.
From left to right: Craters of the Moon National Monument, Idaho; Denali National Park,
Alaska; Guadalupe Mountains National Park,Texas; Channel Islands National Park, California.

adaptive trait: a trait that makes it more likely
that an individual will survive in a specific environment
non-adaptive trait: a trait that makes it less
likely that an individual will survive in a specific
environment

1.4.2: SIM
INTRODUCING ADAPTIVE AND NON-ADAPTIVE TRAITS
Higher fur-level traits
Lower fur-level traits
No, they shivered and died
What were the adaptive traits in this Sim mode?
In other words, which traits helped individual
ostrilopes survive best in the cold
environment?
What were the non-adaptive traits in this Sim
mode? In other words, which traits made it less
likely that an individual ostrilope would survive
in the cold environment?
Were individuals with the non-adaptive traits
able to change to an adaptive trait in the middle
of their lifetime?

1.4.3: MODELING TOOL
MODELING CHANGES TO THE DISTRIBUTION OF TRAITS
Show how and why Population A changed after
the environment changed from warm to cold.
GOAL
Fur vs.Temp A
You will be learning how to model
your ideas about changes in the
distribution of traits in populations
using the natural selection
simulation model.
Remember: Scientists create models to
communicate ideas about how things
work to other people.

Types of Models:
• Physical models, like a globe or a model
of a cell.
• Computer programs, like a computer
model that predicts weather or
the Natural Selection Simulation.
• Visual representations, like a food web or
a diagram of the water cycle.
You will be using a special tool called a
Modeling Tool to make visual models that
show your thinking about why populations
change over time.

Histograms:
There are two
histograms that
represent the
same population
at two different
points in time.

Timeline:
There is a timeline
at the bottom of
the image that
shows what points
in time these
histograms
represent.

Environment
labels:
There are labels
below each
histogram that
describe aspects
of the
environment and
whether the
environment is
changing.

Trait labels:
There is a legend
that shows
symbols and what
those symbols
mean.

Examine the Starting Population Histogram
The environment is changing from warm to cold, just like
in the previous Sim activity.
Which Ostrilopes would be more likely to survive and
which would be less likely to survive in the cold
environment?
More likely to
survive

These histograms are the same as the histograms you saw in the Warm-Up.
In the Sim and the Warm-Up, we observed that the distribution of traits changed over
time.
This example modeled the change we saw in the Sim.

We learned that traits for higher fur levels are adaptive traits
in a cold environment because they help ostrilopes survive in
cold environments.
Lower fur-level traits make it difficult to survive in a cold
environment.
This means traits for lower fur levels are non-adaptive traits
in cold environments.
You will continue to investigate what causes the
distribution of traits in a population to change as
you create another model.

You will receive one
copy of the Modeling
Tool:
Fur andTemperature,
Population B

POPULATION A POPULATION B
Share what similarities and differences
you notice between Population B and
Population A and their environments.

POPULATION A POPULATION B
• Like Population A, most
of the ostrilopes in
Population B have low
fur-level traits.
• There is much less
variation in fur-level traits
in Population B compared
to Population A.
• Both populations
experience an
environment that gets
colder suddenly.

In our next activity, we
will test our predictions
using the SIM.
Let’s discuss making
predictions.
We do not yet know how
the distribution of traits in
Population B will change as
a result of the environment
becoming cold.

We will make a visual
model to predict how
Population B will change in
a cold environment.
You will be able to check
your predictions in the Sim
in a few minutes.

Turn to a partner and
discuss the following.
Do you think Population B
will respond differently than
Population A did to an
environment that changes
from warm to cold?

Complete your models
individually.
You do not have to make
perfect predictions, but you
should show your best
guess at what might happen
to this population by
shading in the bars for the
Population After 50
Generations Histogram.

Note: The predictions are
what you think will actually
happen in the subsequent
Simulation activity.

Models should only show fur
traits that were already present
in the population (Fur-Trait
Levels 1 or 2 only).
Two possible proficient models
are:
1. The population will die out,
and thus Histogram 2 would
be left blank.
2. The trait distribution will shift
so that ostrilopes with higher
fur levels became more
common (shown below).
Possible Prediction about Histogram 2

1.4.4 TESTING PREDICTIONS IN THE SIM
Open Fur and Temperature B
mode in the Natural
Selection Simulation.
Press the Ostrilope icon and
point out the Fur-Trait Histogram
for the ostrilope population.
Note that it has the same
distribution of fur traits as the
Generation 1 Histogram from the
Modeling Tool activity.

Setting UpThe Sim activity.
• Set the temperature of the
environment to cold (Level 1)
and observe what happens over
50 generations.
• While running the Sim, you
should zoom into the
environment and observe several
individuals with different traits.
• When complete, press ANALYZE
to compare the Generation 50
Histogram with the Generation 1
Histogram.

Entire Screen
Specific Area
of the Screen

Discuss with a partner whether
your predictions are correct.
Did population B change the
way you had predicted?
Individuals cannot change traits mid-
life, so the population died out.

Did Population B change in the
way you predicted? Why or why
not?
Population B died out because it did
not have high levels of fur that were
required for a cold environment.

POPULATION A:
Individuals with high fur levels were
able to survive in the cold environment.
The individuals with low fur levels
shivered and died.
Since more individuals with high fur
levels survived, the high fur-level trait
became more common in Population A
over time, and the low fur-level trait
became less common.
The high fur-level trait was an adaptive
trait.

POPULATION B:
In the second Sim, the distribution of
traits in Population B could not shift like
Population A did - toward more
individuals with high fur level.
This is because new traits cannot
appear in a population just because
they would be helpful for survival.
Since Population B did not start out
with variation that included individuals
with the adaptive trait of a high fur
level, none of the individuals could
survive.

1.4.5 HOMEWORK
READ AND ANNOTATE THREE ARTICLES ABOUT DIFFERENT
ORGANISMS IN OREGON STATE PARK.
In order to help Dr. Alex Young and to apply your understanding of variation, traits, and
changes in trait distribution, you will be reading articles about different organisms living
in Oregon State Park.

Investigating Changes In Trait Distribution

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