Lesson 2: Reproducibility in biology

LESSON PLAN: MIDDLE/HIGHSCHOOL
Authors: Dr. Thomas Gregor & Dr. Johanna T. Ohlmeyer
Lesson 1 in the Integrative Sciences: Biology and Physics series
[ezcol_1quarter]Main Idea:[/ezcol_1quarter] [ezcol_3quarter_end]Physical patterns such as the stripes on a zebra, or even icicles hanging from a street lamp during the winter months, are not made reproducibly. Biological processes seem to have solved this problem. Most patterns in biology are exquisitely precise and reproducible: we all have five fingers on each hand, two legs, etc.[/ezcol_3quarter_end]

[ezcol_1quarter]Objectives:[/ezcol_1quarter] [ezcol_3quarter_end] 1. To understand that there is an underlying commonality in how our bodies and those of other animals are built.
2. To find out how precise and reproducible the patterns on the wings of fruit flies are.
3. To be able to use the language of mathematics to quantify and express the precise replication of form in biology.[/ezcol_3quarter_end]

[ezcol_1quarter]Students’ Skills:[/ezcol_1quarter] [ezcol_3quarter_end]Observation, generalization, application, analysis, making use of knowledge and synthesis. These skills were drawn from the Bloom taxonomy of educational objectives and the constructivist list.[/ezcol_3quarter_end]

[ezcol_1quarter]Materials[/ezcol_1quarter] [ezcol_3quarter_end] 1.  For the lecture/discussion: visual organizer, table drawn on the board. Textbooks, material references: pictures of different animals, sketches of a generic body plan, and a fly wing with the AP and DV axes clearly depicted
2. For the activity: Handouts. Dissecting microscope. Histological slides containing mounted Drosophila melanogaster wings (8-10) belonging to different fruit flies. Wings can be easily dissected from flies in isopropanol and mounted in slides with a very small drop of mounting medium. Note that it is important to have as little as possible mounting medium so that the wing surfaces are snug between the slide and the cover slip. Any biology department at a local university should have a geneticist that will be happy to help with this setup.[/ezcol_3quarter_end]

[ezcol_1quarter]Lesson:[/ezcol_1quarter] [ezcol_3quarter_end]1. Part I: The class starts with the question for initial class exploration: Why do we look so alike? The students are allowed to ponder the answer for a few minutes alone or in pairs, then each student should write their answer on an index card “entry card,” and finally offer his or her ideas to the class for open discussion

 2. The teacher should lead the students’ discussion starting from the exploration of the similarities and differences among human beings, mammals, reptiles, etc. In order to construct the visual organizer, the teacher should have a table drawn on the board listing in one column the similarities, and in the other column the differences among organisms. The organizer is filled as the students’ input is received. For middle-school children, it may be a good idea to show the students pictures of the organisms under discussion. The aim of this initial part of the lesson is that by analyzing body shapes, the students understand that animals have many differences; but at the level of how our bodies are built, we share the same basic “body plan.”

 3. Part II Set the main idea into context: The lesson will examine patterning; specifically, how to develop the body plan repeatedly. The teacher should define and explain the meaning of a “body plan,” and show an unspecific diagram of an organism with the main body axes (anterior/posterior, dorsal/ventral, proximal/distal) clearly depicted. Using the diagram and other pictures depicting these axes, the class can explore the next question: Are all body plans the same? At the end of this section the class should agree that at certain levels we share the same characteristics as other animals (i.e. the same body plan). At this time, the idea that establishing patterns not only exist in the whole body but also during the development of eyes, limbs, etc. should be discussed and illustrated.

 4. Part IIIThe lesson activity: Students should work in groups of two or three and start by reading through the handout. The students’ task is to examine the slides under the dissecting microscope, looking for patterns on a fruit fly wing. Ask the students to notice the number, distance, and position of the veins, as well as the type of “hairs” in the surface and at the borders of the wing. Ask the students to draw a representative fly wing. The students should write two or three sentences about how different the wings are from each other. The idea is that each student should understand that if we look at many, many wings, to our visual examination the position, proportions, and distances between hairs or veins are reproducible.

5. However, through the lenses of physics and mathematics, we can go further and find out how, precisely, these patterns are established and replicated. The question would be: Can we use mathematics to describe the reproducibility of the pattern observed in the fly wings, and is there a principle or rule in physics that governs or controls the setting of this reproducibility?

6. To address the quantitative aspect of the lesson, the students can look at the proportions of the wings (distance of AP axis to distance of the DV axis) in all 8-10 wings in the slide. The teacher should ask the students to calculate the average of their measurements and write the results from each group on the board. The students should copy the numbers on their handout and answer the questions: How close are the numbers? What do these results mean?

7. The FINAL unresolved question would be: Can we use mathematics to describe the reproducibility of the pattern observed in the fly wings, and is there a principle or rule in physics that governs or controls how patterning is established and reproduced? These are some of the research questions that Dr. Gregor is currently pursuing in his laboratory.

8. Exit card: Turn the index card over, label this side “exit card,” and write two things: The answer to the initial question again,and one question that you have.[/ezcol_3quarter_end]

[ezcol_1quarter]Class Closing:[/ezcol_1quarter] [ezcol_3quarter_end]
1. Collect entry/exit cards.
2. Homework: Think about the activity today and write a paragraph answering the questions: Does it surprise you how close the proportion numbers from each group are? What do you think these results mean?[/ezcol_3quarter_end]

[ezcol_1quarter]Assesment:[/ezcol_1quarter] [ezcol_3quarter_end]
1. Participation in class and discussions.
2. Grading: completeness and thoroughness filling the activity handout and index card.
3. Use a general rubric to evaluate students’ overall performance.[/ezcol_3quarter_end]

[ezcol_1quarter]Teacher’s Reflections[/ezcol_1quarter] [ezcol_3quarter_end]
1. Things that I did not cover.
2. Did I meet the lesson objectives?
3. Comments, conclusion,s and modifications
4. Pedagogical value of the lesson. Did my students learn the concepts and ideas explored in this class?[/ezcol_3quarter_end]

[ezcol_1quarter]Notes to the Teacher[/ezcol_1quarter] [ezcol_3quarter_end]
1. The teacher’s guidance is important to cement the idea of deep similarities and reproducibility across different animals.

2. Make sure the students understand that the activity on fruit fly wings explores reproducibility of form at different level than that of body plan.

3. Interaction of the teacher with the groups is crucial to make sure they know what to do and why. This lesson plan can be adjusted to meet middle or high school requirements.
[/ezcol_3quarter_end]

 

 

ACTIVITY: MIDDLE SCHOOL
Today we are learning about Reproducibility in biology.

cropped-owlet_logo.gifPhysical patterns such as the stripes on a zebra, or even icicles hanging from a street lamp during the winter months, are not made reproducibly. Biological processes seem to have solved this problem. Most patterns in biology are exquisitely precise and reproducible: we all have five fingers on each hand, two legs, etc.

 

YOUR ACTIVITY: In this exercise, you will analyze the patterns on the wing of fruit flies Drosophila melanogaster. Your teacher will place you in a group of two or three students, and each group will have access to a microscope.

1. Once you are in your group, you will receive one slide containing eight to ten wings that belong to different flies.
2. Take a few minutes to look at them and think: in what ways are they similar, and how are they different? Notice the number, distance, and position of the veins, and the type of “hairs” in the surface and at the borders of the wing
3. Draw a representative fly wing in the box below and answer the questions.

box1

 

 

 

 

 

 

How similar or different are the wings from each other?

 

 

 

 

Based on your visual examination, is the position and the distances between veins and among hairs reproducible from wing to wing?

 

 

 

 

 

4. Follow the diagram of the fly wing on the board and mark the axes on your drawing above. Fill the chart below. Measure the AP distance and the DV distance for each wing. Then find the proportion AP/DV for each wing, write it, and find the average. Communicate the results to your teacher, and have it recorded on the board along the results from your peers.

Untitled-1

 

 

 

 

 

Group Average AP/DV: _______________

Other Groups’ Average AP/DV: _________ , _________ , ___________ , __________

Class Average AP/DV: _______________

QUESTIONS:

1. Were the results from each group very similar or different?

 

 

2. What do these results mean? Is the way the fly wing pattern made a reproducible phenomenon?