This document describes a science seminar about stickleback fish. It includes sections where students annotate passages about sticklebacks, are introduced to how the population has changed over generations from having more armor plates to fewer, and examine evidence cards about stickleback traits, environment, and lifespan. The goal is for students to analyze the evidence and determine which of two claims is best supported about what caused the changes in the stickleback population.

1. CHAPTER 4: SCIENCE SEMINAR

2. 4.1.1: WARM-UP
Annotate a passage from the article about stickleback fish, which
you read for homework. (5 min)

3. 4.1.2: INTRODUCING STICKLEBACKS
Introduce the new question about the stickleback fish and
explain the change the population has undergone. (10 min)

4. 4.1.2: INTRODUCING STICKLEBACKS
This map shows
where the
stickleback
population we are
studying was
found—in a lake in
Alaska.
This population of
sticklebacks has
lived in this lake for
approximately 13
generations.

5. 4.1.2: INTRODUCING STICKLEBACKS
Sticklebacks are tiny
fish, no longer than
your pinky.
As you can see, there
are spikes or stickles
on its back.
This is where the fish
gets its name.
Inside, these fish also
have bony plates of
armor.

6. 4.1.2: INTRODUCING STICKLEBACKS
Scientists can clearly see and count the
plates of armor of a stickleback fish by
using a special stain that colors the armor.
In this photo, you can see the armor plates
in red.
The individuals in the stickleback
population 13 generations ago had many
plates of armor; they were considered to
have high levels of armor. Over time, the
individuals have developed less armor.
As you can see, most of the individuals now
have only four plates of armor. They are
considered to have low levels of armor.
Scientists found that sticklebacks with low
levels of armor are faster swimmers than
sticklebacks with high levels of armor.

7. 4.1.2: INTRODUCING STICKLEBACKS
As you can see in this
histogram, most of the
sticklebacks in the
population were slow
swimmers 13
generations ago.
Now, most of the
sticklebacks are fast
swimmers.

8. 4.1.2: INTRODUCING STICKLEBACKS
What caused the stickleback population to have less
armor and become faster?
Scientists do not know why this drastic
change occurred. However, they do
know that when sticklebacks have less
armor they are able to swim faster. There
are a few reasons why swimming faster
could be helpful for sticklebacks.
When you looked at the sticklebacks in
your Warm-Up, did you have any
thoughts about what may have caused
the change?
What might we want to investigate in order to consider
what caused this change?

9. 4.1.2: INTRODUCING STICKLEBACKS
Biologists have narrowed down the possible factors in the environment
that led to the change in trait distribution, making your jobs easier. You
will be getting some evidence to help support the claims.

10. 4.1.3: EXAMINING EVIDENCE ABOUT
STICKLEBACKS
Students read and annotate evidence cards. Then
discuss them with their partners. (20 min)
Before you can determine
whether you think Claim 1
or 2 is correct, you will need
to analyze evidence about
the sticklebacks' previous
and current environments
This card shows the
average life span of
sticklebacks in the lake,
their current environment.

11. 4.1.3: EXAMINING EVIDENCE ABOUT
STICKLEBACKS
• How do they die?
• Are they killed by
predators?
• Do they die due to
starvation?
• Old age?
• …something else?

12. 4.1.3: EXAMINING EVIDENCE ABOUT
STICKLEBACKS
I see that fish with low-
armor levels are fast
and fish with high-
armor levels are slow.
Therefore, the table
shows that the more
armor a stickleback
has, the slower it
swims.

13. 4.1.3: EXAMINING EVIDENCE ABOUT
STICKLEBACKS
The table also shows that
fast swimmers live an
average of four years,
while slow swimmers live
an average of one year.
I wonder if that is because
the fast swimmers can
catch more food and eat
more, or if it is because
they can swim away from
predators without being
eaten.

14. 4.1.3: EXAMINING EVIDENCE ABOUT
STICKLEBACKS
Do fast sticklebacks live longer because they escape more predators or
because they catch more prey?
Sticklebacks reproduce once a year.
If fast swimmers live four years, then
these fast sticklebacks must
reproduce about four times during
their life span.
Slow swimmers, however, only live
for one year. Therefore, they most
likely reproduce only once during
their life span.

15. 4.1.3: EXAMINING EVIDENCE ABOUT
STICKLEBACKS
Do fast sticklebacks live longer because they escape more predators or
because they catch more prey?
Sticklebacks reproduce once a year.
If fast swimmers live four years, then
these fast sticklebacks must
reproduce about four times during
their life span.
Slow swimmers, however, only live
for one year. Therefore, they most
likely reproduce only once during
their life span.

16. 4.1.3: EXAMINING EVIDENCE ABOUT
STICKLEBACKS
Do fast sticklebacks live longer because they escape more predators or
because they catch more prey?
Sticklebacks reproduce once a year.
If fast swimmers live four years, then
these fast sticklebacks must
reproduce about four times during
their life span.
Slow swimmers, however, only live
for one year. Therefore, they most
likely reproduce only once during
their life span.

17. 4.1.3: EXAMINING EVIDENCE ABOUT
STICKLEBACKS

18. 4.1.4: DISCUSSING EVIDENCE AND
CLAIMS
Do fast sticklebacks live longer because they escape more predators or
because they catch more prey?
You will work with a partner to consider how the Stickleback Evidence Cards connect to the claims.
Then decide which claim is best supported by the evidence. The question you are trying to answer….
—The Chapter 4 Question—
You and your partner will
be discussing ideas, but
each student will sort their
own evidence cards under
the claim on the
appropriate page of the
Argument Organizer
student sheets.

19. 4.1.4: DISCUSSING EVIDENCE AND
CLAIMS

20. 4.1.4: DISCUSSING EVIDENCE AND
CLAIMS
You should place each Stickleback Evidence Card under the claim it
supports or goes against. If the evidence supports a claim, you should
write "supports Claim 1” or “supports Claim 2" on that card. If the
evidence refutes a claim, you should write "goes against Claim 1” or
“goes against Claim 2" on that card. If the evidence on one card
connects with another, you should write "connects with Evidence Card
A (or B, C, D, E, F)" on that card.

21. 4.1.4: DISCUSSING EVIDENCE AND
CLAIMS
Discuss each piece of evidence and then decide if it supports or
goes against either of the two claims. You do not have to agree
about the placement of the evidence cards. As you sort the cards
discuss their reasoning.

22. 4.1.4: DISCUSSING EVIDENCE AND
CLAIMS
Clip your Stickleback Evidence Cards
to your Argument Organizer student
sheets. Store them in your Science
folder. You will need these again in
Lessons 4.2 and 4.3.