The Evolution of a Graph: displaying and interpreting data

NAS/HHMI Summer Institute 2011

Presented by the ‘Model Organisms’:Stephanie Gardner and Laurie Iten, Purdue UniversityElizabeth Derryberry, David Heins, and Donata Henry, Tulane University

Facilitators: Robin Wright and Jeffrey Gardner

Context• 100-level biology majors’ class

that covers evolutionary biology

• Before this teaching unit, students introduced to:

- Different data types- Collecting data

Instruments & techniques

Methods & limitations

- Basic descriptive & inferential statistics• Teaching unit takes two 50 min.

lecture or lab periods.

Our teaching unit = snapshot

Of larger coverage of gathering, displaying & interpreting data

Teachable Unit: “The Evolution of a Graph”

Learning Goals

Students will understand:

• the importance of quantitative approaches to interpret data.• that evolution is the change in frequency of phenotypes (alleles) over

time (across generations).

Learning Outcomes

Students will be able to:

• make a prediction in a real scientific context.• choose the appropriate test to analyze a set of evolutionary data.• create an appropriate graph of their data.• interpret the result and scope of the inferential statistic in the context of

the hypothesis that there has been evolutionary change.

Threespine stickleback

“Low Morph”

“Complete Morph”

Mini-lecture: Threespine stickleback

Bell et al 2004 Evolution

• More armor • Advantageous where there

are no hiding places.

• Less armor • Advantageous where there

are places to hide.

Q: Which of the following relationships between stickleback plate phenotype and habitat would you expect to find?

A. Complete in ocean & complete in lakeB. Low in ocean & complete in lakeC. Complete in ocean & low in lakeD. Low in ocean & low in lake

OCEAN HABITAT LAKE HABITAT

Group Activity

Using your knowledge of the biology of these fishes (see your handout), take 10 minutes and write a prediction about how the frequency of occurrence of the two phenotypes might change over time.

Work in pairs.

Year n Complete Morph

Low Morph

1991 100 0.76 0.160

2001 3304 0.112 0.752

Group Activity

In pairs,

Take the data from your field sampling efforts (see table below) and produce a graph (remember to include appropriate components). You have 5 minutes (10-15 minutes for students).

Table: Frequency of occurrence of two stickleback morphs in Loberg Lake, Alaska. n = sample size

From: Bell et al 2004 Evolution

Group assessment

Exchange your graph with another pair

Annotate (i.e. make changes to) the other group’s graph, with two thoughts in mind:

1. Is this type of graph the most effective format for conveying the information?

2. Are all the appropriate components included?

You have 3 minutes (10 for students) minutes for this exercise.

Give the graph back to the original group.

Class discussion

Let’s come up with some ideas about what makes a graph effective and what the appropriate components of a graph are.

These ideas will be used to guide in the creation and evaluation of future graphs.

Clicker question 1

Which of these graphs most effectively conveys the data from our stickleback study?

A

B

C

Clicker question 2

A

B

C

Which of these graphs includes the most complete set of appropriate components?

Synthesize your work from today!

Take your prediction and your corrected graph and write two sentences to explain:

(1) whether or not your data supported your prediction

(2) how representing these data in a graphical format aided in your understanding of the evolution of morphology in stickleback.

Bring your written statement to the next class!

Homework

Teachable Unit: “The Evolution of a Graph”

Learning Goals

Students will understand:

• the importance of quantitative approaches to interpret data.• that evolution is the change in frequency of phenotypes (alleles) over

time (across generations).

Learning Outcomes

Students will be able to:

• make a prediction in a real scientific context.• choose the appropriate test to analyze a set of evolutionary data.• create an appropriate graph of their data.• interpret the result and scope of the inferential statistic in the context of

the hypothesis that there has been evolutionary change.

Teachable Unit: “The Evolution of a Graph”

Learning Goals

Students will understand:

• the importance of quantitative approaches to interpret data.• that evolution is the change in frequency of phenotypes (alleles) over

time (across generations).

Learning Outcomes

Students will be able to:

• make a prediction in a real scientific context.• choose the appropriate test to analyze a set of evolutionary data.• create an appropriate graph of their data.• interpret the result and scope of the inferential statistic in the context of

the hypothesis that there has been evolutionary change.

Additional fun stuff

http://learn.genetics.utah.edu/content/variation/stickleback/

Threespine stickleback as a supermodel

in evolutionary biology

Adaptive radiation

Insert image of Darwin’s finches