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Stickleback Evolution Unit

TEKS (Knowledge and Skills Statements):

6.12(E) Organisms and environments. The student knows all organisms are classified into domains and kingdoms. Organisms within these taxonomic groups share similar characteristics that allow them to interact with the living and nonliving parts of their ecosystem. The student will describe biotic and abiotic parts of an ecosystem in which organisms interact.

7.11(B) Organisms and environments. The student knows that populations and species demonstrate variation and inherit many of their unique traits through gradual processes over many generations. The student will explain variation within a population or species by comparing external features, behaviors, or physiology of organisms that enhance their survival such as migration, hibernation, or storage of food in a bulb.

7.12(A) Organisms and environments. The student knows that living systems at all levels of organization demonstrate the complementary nature of structure and function. The student will investigate and explain how internal structures of organisms have adaptations that allow specific functions such as gills in fish, hollow bones in birds, or xylem in plants.

8.11(B) Organisms and environments. The student knows that interdependence occurs among living systems and the environment and that human activities can affect these systems. The student will explore how short-and long-term environmental changes affect organisms and traits in subsequent populations.

*Process standards of formulating hypotheses, collecting, and recording data, constructing tables and graphs, and analyzing data to formulate reasonable explanations are used throughout this lab and incorporate the scientific investigation and reasoning skills TEKS across all grade levels.

Lesson Summaries:

Introduction to Stickleback Evolution: 90 minutes

Students will look at the anatomical differences between marine and freshwater stickleback fish through a virtual lab, experiment 1. For the experiment, students should be able to complete parts 1-3 on their own, as well as the initial quiz for the experiment. The teacher will help students with the chi-square test, but after explanation and data entry, students should attempt analysis questions on their own.

Stickleback Defense Lab: 45 minutes

Students will continue their exploration of stickleback fish, now looking at a different trait that can vary between marine and freshwater stickleback.

Stickleback Gill Rakers Lab: 45 minutes

Students will move into freshwater stickleback habitats and determine if there is a difference in the gill rakers between populations that live in lakes versus populations that live in a stream. Students will analyze these data to determine if there is a relation to food source.

Phenotypes and Habitat Choice: 75 minutes

Students will be tasked with analyzing one specific anatomical trait of the stickleback and share these results with the class. Students will then look at all of the traits analyzed to determine if there are any traits that can lead in a prediction of habitat choice, lake versus stream.

DAY 1 - Lesson Plan: Introduction to Stickleback Evolution

Objective

Students will be introduced to the science and techniques used to analyze the forms and structures of stickleback to study evolutionary processes.

Materials

Computer, accessing the following website: https://www.hhmi.org/biointeractive/stickleback-evolution-virtual-lab

Lab Sheet

Headphones (Optional)

Lesson Plan

Engage – Show the movie on the following website to introduce stickleback evolution. You can stop the video at 11:44

https://www.hhmi.org/biointeractive/making-fittest-evolving-switches-evolving-bodies

Pose the following question to students: In the video, it was stated that all around the world, the same sequence was deleted in the DNA, turning off the pelvis switch, and thus evolution can and will repeat given the same conditions. Do you think this is always the case? Explain.

Explore – Have students go to the virtual lab. Students will complete the introduction, overview and tutorial. Check for understanding after these three sections to make sure students understand what they are looking at when exploring the stickleback fish. “What is the purpose of the spines?” “Describe a complete, reduced, and absent pelvis.”

Explain – Students will apply their knowledge of the stickleback pelvis to experiment 1, answering questions 11-23. Students will identify the presence (or absence) of a pelvis and graph the results. Students will analyze the data collected.

Elaborate – Students will be introduced to the concept of a null hypothesis. Together, the class will create a null hypothesis for the pelvis of stickleback fish. The teacher will walk students through a chi-square analysis, answering questions 24-27 together.

Evaluate – Students will take the online quiz for the analysis portion and answer questions 28-30. Option: Have students send a PDF of their progress page, which contains data for quiz scores, to your email or submit through your LMS. To send a PDF, the student needs to type their name in the box and then click print. The student will change the destination to save as PDF. Students can also screen capture the progress page to share.

https://www.hhmi.org/biointeractive/making-fittest-evolving-switches-evolving-bodies

https://www.hhmi.org/biointeractive/stickleback-evolution-virtual-lab

Name: ________________________________________________________Date: __________________Period: _______

Virtual Stickleback Fish Evolution

Go to: https://www.hhmi.org/biointeractive/stickleback-evolution-virtual-lab. This lesson was modified from the original Advanced Student Lesson provided by the Howard Hughes Medical Institute.

As you complete each part of the virtual lab, answer the questions below in the space provided.

QUESTIONS

INTRODUCITON

1. Define “model organism.” _____________________________________________________________________

___________________________________________________________________________________________

2. How do spines protect ocean stickleback fish? _____________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

3. How did ancestral populations of ocean-dwelling fish come to live in freshwater lakes? ____________________

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

4. Watch the video about pelvic reduction in freshwater stickleback. The loss of stickleback pelvic spines is similar to the loss of which body parts in some other four-legged vertebrates? _________________________________

5. Watch the video with evolutionary biologist Dr. Michael Bell. Why is the threespine stickleback a model organism for studies in evolution? (List at least two reasons.) _________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

6. Watch the video with Dr. David Kingsley explaining hind-limb reduction. Name two other vertebrate animals whose evolutionary histories included the loss of hind limbs. _________________________________________

___________________________________________________________________________________________

OVERVIEW

7. Click on the interactive stickleback fish. Describe where its spines are located. ____________________________

___________________________________________________________________________________________

___________________________________________________________________________________________


8. Watch the video about the stickleback fish armor.

a. In addition to the spines, what is another component of the “armor” of a stickleback fish? ___________

_____________________________________________________________________________________

b. Explain how the stickleback armor protects the fish from some predators. _________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

TUTORIAL 1

9. Describe the following structures:

a. Complete pelvis: _______________________________________________________________________

b. Reduced pelvis: ________________________________________________________________________

c. Absent pelvis: _________________________________________________________________________

10. Start Tutorial 1. Continue to practice scoring fish until you have mastered the technique; then proceed to Experiment 1.

EXPERIMENT 1

11. Explain in your own words the overall objective of Experiment 1. ______________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

12. In a population, what happens to organisms that are better adapted to the environment in which they live? ___

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

13. In the virtual lab window, complete Part 1: Staining the Fish.

a. How were the fish you will be using in this virtual lab caught? ___________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

14. In the virtual lab window, proceed to Part 2: Scoring the Fish.

15. Before scoring the fish, watch the short video on Bear Paw and Frog Lakes. According to Dr. Bell, what is an important difference between Bear Paw Lake and Frog Lake? _________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

16. In the window on the right, click on the link to read more about random sampling. Why are random samples, rather than entire populations, used in most research studies? ________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

17. What is one advantage of studying larger-sized samples? ____________________________________________

___________________________________________________________________________________________

18. Complete Part 2 of the lab in the window on the left.

19. Examine the pelvic score data you just collected. Does the pelvic phenotype differ between Bear Paw Lake and Frog Lake fish? Explain. ________________________________________________________________________

___________________________________________________________________________________________

20. Complete the graph below.

21. Complete the Experiment 1 Quiz. Take time to read the explanation for each correct choice provided after each question.

22. Explain why the stickleback fish in Frog Lake are more similar to ocean and sea-run stickleback than they are to the stickleback fish in Bear Paw Lake. _____________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

23. After completing the quiz, click on Experiment 1 Analysis. We are going to do the first part of this section together.

24. For this analysis, what is your null hypothesis? _____________________________________________________

___________________________________________________________________________________________

25. Complete the following tables as you perform the chi-square calculations in the lab.

Bear Paw LakePhenotype Observed (o) Expected (e) (o-e) (o-e)2 (o-e)2/ePelvic Spines PresentPelvic Spines Absent

Total = Total = X2 =

Frog LakePhenotype Observed (o) Expected (e) (o-e) (o-e)2 (o-e)2/ePelvic Spines PresentPelvic Spines Absent


Morvoro LakePhenotype Observed (o) Expected (e) (o-e) (o-e)2 (o-e)2/ePelvic Spines PresentPelvic Spines Absent


26. For each chi-square calculation, how many degrees of freedom are there? _______________________________

How did you arrive at this number? ______________________________________________________________

27. What are the p values for the data from each lake? Do you “reject” or “fail to reject” the null hypothesis for the data from each lake?

Lake p value Null hypothesisBear Paw Lake

Frog Lake

Morvoro Lake

28. Complete the Chi-square Analysis Quiz. Take time to read the explanation for each correct choice provided after each question.

29. Explain what it means to reject the null hypothesis. _________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

30. Explain what it means if the null hypothesis cannot be rejected. _______________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

The following worksheet is the modified virtual lab excluding chi-squared analysis.

Name: ________________________________________________________Date: __________________Period: _______

Virtual Stickleback Fish Evolution

Go to: https://www.hhmi.org/biointeractive/stickleback-evolution-virtual-lab. This lesson was modified from the original Advanced Student Lesson provided by the Howard Hughes Medical Institute.

As you complete each part of the virtual lab, answer the questions below in the space provided.

QUESTIONS

INTRODUCITON

1. Define “model organism.” _____________________________________________________________________

___________________________________________________________________________________________

2. How do spines protect ocean stickleback fish? _____________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

3. How did ancestral populations of ocean-dwelling fish come to live in freshwater lakes? ____________________

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

4. Watch the video about pelvic reduction in freshwater stickleback. The loss of stickleback pelvic spines is similar to the loss of which body parts in some other four-legged vertebrates? _________________________________

5. Watch the video with evolutionary biologist Dr. Michael Bell. Why is the threespine stickleback a model organism for studies in evolution? (List at least two reasons.) _________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

6. Watch the video with Dr. David Kingsley explaining hind-limb reduction. Name two other vertebrate animals whose evolutionary histories included the loss of hind limbs. _________________________________________

___________________________________________________________________________________________

OVERVIEW

7. Click on the interactive stickleback fish. Describe where its spines are located. ____________________________

___________________________________________________________________________________________

___________________________________________________________________________________________


8. Watch the video about the stickleback fish armor.

a. In addition to the spines, what is another component of the “armor” of a stickleback fish? ___________

_____________________________________________________________________________________

b. Explain how the stickleback armor protects the fish from some predators. _________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

TUTORIAL 1

9. Describe the following structures:

a. Complete pelvis: _______________________________________________________________________

b. Reduced pelvis: ________________________________________________________________________

c. Absent pelvis: _________________________________________________________________________

10. Start Tutorial 1. Continue to practice scoring fish until you have mastered the technique; then proceed to Experiment 1.

EXPERIMENT 1

11. Explain in your own words the overall objective of Experiment 1. ______________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

12. In a population, what happens to organisms that are better adapted to the environment in which they live? ___

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

13. In the virtual lab window, complete Part 1: Staining the Fish.

a. How were the fish you will be using in this virtual lab caught? ___________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

14. In the virtual lab window, proceed to Part 2: Scoring the Fish.

15. Before scoring the fish, watch the short video on Bear Paw and Frog Lakes. According to Dr. Bell, what is an important difference between Bear Paw Lake and Frog Lake? _________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

16. In the window on the right, click on the link to read more about random sampling. Why are random samples, rather than entire populations, used in most research studies? ________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

17. What is one advantage of studying larger-sized samples? ____________________________________________

___________________________________________________________________________________________

18. Complete Part 2 of the lab in the window on the left.

19. Examine the pelvic score data you just collected. Does the pelvic phenotype differ between Bear Paw Lake and Frog Lake fish? Explain. ________________________________________________________________________

___________________________________________________________________________________________

20. Complete the graph below.

21. Complete the Experiment 1 Quiz. Take time to read the explanation for each correct choice provided after each question.

22. Explain why the stickleback fish in Frog Lake are more similar to ocean and sea-run stickleback than they are to the stickleback fish in Bear Paw Lake. _____________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

23. After completing the quiz, click on Experiment 1 Analysis. We are going to do the first part of this section together.

24. For this analysis, what is your null hypothesis? _____________________________________________________

___________________________________________________________________________________________

25. Fill in the table below with the totals from the three lakes.

Null Expectation Bear Paw Lake Frog Lake Morvoro LakePelvic Spines PresentPelvic Spines Absent

26. Is the distribution of fish with and without pelvic spines different from your null expectation for Bear Paw Lake? Why?

___________________________________________________________________________________________

___________________________________________________________________________________________

27. Is the distribution of fish with and without pelvic spines different from your null expectation for Frog Lake? Why?

___________________________________________________________________________________________

___________________________________________________________________________________________

28. Is the distribution of fish with and without pelvic spines different from your null expectation for Morvoro Lake? Why?

___________________________________________________________________________________________

___________________________________________________________________________________________

29. Explain what it means to reject the null hypothesis. _________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

30. Explain what it means if the null hypothesis cannot be rejected. _______________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

DAY 2 - Lesson Plan: Stickleback Defense Lab

Objective

The students will understand the concept of morphological variation between populations. Students will use deductive reasoning to speculate how and why this variance is more or less prevalent in a given environment.

Materials

Lab Sheet

Teacher PowerPoint

Fish Image Sets (10 pictures) – 1 per group OR Student PowerPoint with Computer

Calculator (optional)

Colored Fish ID Cards (for T-chart) – 1 set per group (You will need to cut and organize the cards ahead of time)

Chart Paper, Document Camera, or White Board

Lesson Plan

Engage – Using the teacher PowerPoint, present students with several images of higher trophic predators as well as an image of a stickleback. Ask students to imagine they are stickleback fish. What are the different challenges for stickleback living in the ocean versus freshwater environments?

Explore – Provide students with a set of images of three spine stickleback fish. The set will include fish from marine and freshwater locations in a random order. The students will be required to make initial observations based on the Day 1, digital lab, lesson. Further, the students will be asked to use his/her initial assumptions of each fish to consider it its origin is from a lake/stream or marine environment.

Explain – Returning to the PowerPoint, provide students with information regarding observational techniques by which to differentiate freshwater and marine populations, specifically looking at armor plates.

Elaborate – Students will return to their set of images and digitally quantify the armor plants on each of the images. The students will then be asked to reassess their assumption based on the armor plating of each individual. The students will also be asked to calculate an average number of plates for their selected marine and freshwater groups.

Evaluate – The teacher will post a freshwater and marine t-chart for the class to post on, as well as a blank graph. Each group will have a set of colored cards that are individually labeled with the fish ID. The students will sort the cards according to their findings into marine or freshwater. The group leader will attach the ID cards to the T-chart according to the predicted habitat choice. Students will be able to visually see how the entire class sorted the fish and analyze the results. The group leader will also graph their group’s averages. Students will be asked to identify trends in the data and possible explanations for these trends.

Fish_01 Fish_02

Fish_03 Fish_04

Fish_05 Fish_06

Fish_07 Fish_08

Fish_09 Fish_10

Fish Image Set (Not to scale)

Fish Image Key (Not to Scale)

Fish_01 (Boot Stream 75)

FRESHWATER


FRESHWATER

Fish_03 (Cluxewe Marine 14)

MARINE


MARINE


MARINE


MARINE


MARINE


FRESHWATER


MARINE


FRESHWATER

Fish ID Cards (Print Fish_01 on Red)

Fish_01 Fish_01Fish_01 Fish_01Fish_01 Fish_01Fish_01 Fish_01Fish_01 Fish_01Fish_01 Fish_01

Fish ID Cards (Print Fish_02 on Orange)


Fish ID Cards (Print Fish_03 on Yellow)


Fish ID Cards (Print Fish_04 on Light Green)


Fish ID Cards (Print Fish_05 on Dark Green)


Fish ID Cards (Print Fish_06 on Light Blue)


Fish ID Cards (Print Fish_07 on Dark Blue)


Fish ID Cards (Print Fish_08 on Purple)


Fish ID Cards (Print Fish_09 on Lavender)


Fish ID Cards (Print Fish_10 on Gray)

Name: _______________________________________________________Date: ___________________Period: _______

Stickleback Defense Lab

Introduction:

1. What are the different challenges for stickleback living in the ocean versus freshwater environments?

_____________________________________________________________________________________

_____________________________________________________________________________________

_____________________________________________________________________________________

Data Collection:

2. Sort the fish from your image set into two groups: marine or freshwater. Write the Fish ID numbers in the appropriate section in the table below.

Marine Freshwater

3. What was your criteria for sorting the fish? Explain. _________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

4. After learning about ways to differentiate between marine and freshwater fish, what trait will you be using to resort your fish? ______________________________________________________________________________

5. Re-sort your fish, if needed. For each fish, count the number present of the identifying trait (answer to question 4). Complete the table below.

Marine FreshwaterFish ID # # of identifying trait Fish ID # # of identifying trait

6. Calculate the average for the # of identifying trait for marine and lake/stream.

a. Average # for Marine _____________________

b. Average # for Freshwater ____________________

7. Send your group leader to the T-chart and Graph. The group leader will place your numbered colored cards on the T-chart to match your table from question 5. The group leader will also place a point on the graph for the two averages calculated in question 6.

8. Once all groups have plotted their averages, create the class graph below. Don’t forget to label your axis.

9. Looking at the T-chart, were there any fish that had no discrepancy on habitat? Explain why you think that is.

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

10. Looking at the T-chart, were there any fish that the class could not agree on a habitat? Explain why you think that is.

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

11. Look at the graph. Do you notice a trend in the data based on armor? Explain.

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

12. Extension. Could you hypothesize an alternate reason for armor reduction?______________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

DAY 3 - Lesson Plan: Stickleback Gill Rakers Lab

Objective

Students will understand how stickleback gill raker morphology correlates with certain feeding patterns. Students will also understand the role natural selection plays in selecting certain traits for survival in a given environment.

Materials

Threespine stickleback for demonstration (if available)

Gill Raker Image Set – 1 per group OR Student PowerPoint with Computer

Lab sheet

Teacher PowerPoint

Lesson Plan

Engage – If available, show the students an actual stickleback specimen. Explain that stickleback have gill rakers that aid the fish in feeding. Show the students pictures of gill rakers and explain that they help trap food. Have them look at the images and then pose the question: What information can scientists obtain about the stickleback from studying these gill rakers? Have students discuss in groups of 3-4 and after 2 minutes, have them share out their answers in class.

Explore – Provide each group of students with a picture of stream fish gill rakers and a picture of lake fish gill rakers. Make sure each picture is labeled as stream or lake. Also, provide each student with a lab sheet. Tell students that scientists can use gill raker morphology to classify different populations of fish and learn more about which environment they live in. Tell students that they are going to look at a picture of a stream fish and a lake fish gill rakers. Have them write down their observations on each type of fish on their lab sheet and answer the questions on the lab sheet. After about 3-5 minutes, have students share out answers.

Explain – Explain the differences between the stream fish gill rakers and lake fish gill rakers. Discuss the different foods that stream fish and lake fish eat, for example, stream fish tend to eat invertebrates and lake fish tend to eat plankton. Talk about how their morphology helps them obtain food. Then, tell the students that they will be working in groups to count gill rakers and sort these fish as either lake fish or stream fish. They will use the data they have collected as well as the gill raker lengths in order to sort their fish. Go over the procedure for counting gill rakers and have students answer the discussion questions in part III when they are finished.

Elaborate – Show students two images of two lake fish that have very different number of gill rakers and different gill lengths. Have students compare and contrast the two images, write down their observations, and explain why those two might be different, despite living in similar environments.

Evaluate – After students have finished the gill raker lab, hold a class discussion about what students have learned so far about stickleback. Some questions to ask are: What do you think drives phenotypic (or physical) changes in stickleback? Thinking about our two lake fish you just saw, why does evolution not always occur in the same way? How does the evolution of these traits relate to natural selection?

Gill Raker Image Set (not to scale)

Fish_01 Fish_02

Fish_03 Fish_04

Fish_05 Fish_06

Fish_07 Fish_08

Gill Raker Image Key (not to scale)

Fish_01 (Kennedy lake13.01_11)LAKE

Fish_02 (Kennedy lake 13.01_12)LAKE

Fish_03 (Kennedy stream 13.01_02b)STREAM

Fish_04 (Kennedy stream 13.01_08a)STREAM

Fish_05 (Kennedy stream 13.01_04a)STREAM

Fish_06 (Kennedy stream 13.01_39b)STREAM

Fish_07 (Kennedy lake 13.01_19)LAKE

Fish_08 (Kennedy lake 13.01_22a)LAKE

Name: _______________________________________________________Date: ___________________Period: _______

Stickleback Gill Rakers Lab

Part I. Look at the gill rakers from the lake fish and stream fish. Write down your observations of each in the table below.

Lake Fish Gill Rakers Stream Fish Gill Rakers

1. In your own words, how are the stream fish gill rakers different from the lake fish gill rakers? In what ways are they the same?

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

2. Based off of your observations, what kind of food do you think the stream fish eat? What about the lake fish?

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

Part II. With your group, look at the 8 pictures. Count the number of gill rakers in each image. Make sure you count each and every gill raker. Using that data and the gill raker lengths provided, identify whether the fish is a lake fish or stream fish. You will be given a range for typical gill raker lengths and a range for the typical number of gill rakers for each type of fish. Use that information to help you sort the fish.

Lake StreamGill raker length: 1.06 to 1.62, average = 1.35 Gill raker length: 0.49 to 1.50, average = 0.88Number of gill rakers: 20 to 25, average = 22.3 Number of gill rakers: 18 to 24, average = 20.5

Data:

Fish number Gill raker length (mm)(avg. of 3 longest)

Bolnick Lab’s number of gill rakers

Your Number of gill rakers

Lake or Stream?

Fish_01 1.29 22

Fish_02 1.47 22

Fish_03 1.14 18

Fish_04 0.93 23

Fish_05 1.12 21

Fish_06 0.79 22

Fish_07 1.35 24

Fish_08 1.20 22

Part III. Reflect on the data you have collected answer the following questions.

3. Was sorting the fish into lake and stream easy for your group? Why or why not?

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

4. What additional data could you have obtained from the gill rakers in order to help sort the lake fish from the stream fish?

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

5. Explain how this lab relates to what you have learned about natural selection.

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

Part IV. Look at the two images of gill rakers obtained from fish living in different lakes on the screen. Compare and contrast these two gill rakers and answer the question below.

6. Using your knowledge of natural selection and evolution, what explanation could you give for why the gill rakers of these lake fish are so different?

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

Lake fish 1 Lake fish 2

The following worksheet is modified to remove the student counting of the gill rakers.

Name: _______________________________________________________Date: ___________________Period: _______

Stickleback Gill Rakers Lab

Part I. Look at the gill rakers from the lake fish and stream fish. Write down your observations of each in the table below.

Lake Fish Gill Rakers Stream Fish Gill Rakers

1. In your own words, how are the stream fish gill rakers different from the lake fish gill rakers? In what ways are they the same?

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

2. Based off of your observations, what kind of food do you think the stream fish eat? What about the lake fish?

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

Part II. With your group, look at the 8 pictures. Count the number of gill rakers in each image. Make sure you count each and every gill raker. Using that data and the gill raker lengths provided, identify whether the fish is a lake fish or stream fish. You will be given a range for typical gill raker lengths and a range for the typical number of gill rakers for each type of fish. Use that information to help you sort the fish.

Lake StreamGill raker length: 1.06 to 1.62, average = 1.35 Gill raker length: 0.49 to 1.50, average = 0.88Number of gill rakers: 20 to 25, average = 22.3 Number of gill rakers: 18 to 24, average = 20.5

Data:

Fish number Gill raker length (mm)(avg. of 3 longest)

Bolnick Lab’s number of gill rakers

Lake or Stream?

Fish_01 1.29 22

Fish_02 1.47 22

Fish_03 1.14 18

Fish_04 0.93 23

Fish_05 1.12 21

Fish_06 0.79 22

Fish_07 1.35 24

Fish_08 1.20 22

Part III. Reflect on the data you have collected answer the following questions.

3. Was sorting the fish into lake and stream easy for your group? Why or why not?

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

4. What additional data could you have obtained from the gill rakers in order to help sort the lake fish from the stream fish?

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

5. Explain how this lab relates to what you have learned about natural selection.

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

Part IV. Look at the two images of gill rakers obtained from fish living in different lakes on the screen. Compare and contrast these two gill rakers and answer the question below.

6. Using your knowledge of natural selection and evolution, what explanation could you give for why the gill rakers of these lake fish are so different?

___________________________________________________________________________________________

___________________________________________________________________________________________

___________________________________________________________________________________________

Lake fish 1 Lake fish 2

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