National Academies Summer Institutes for Undergraduate Education in Biology
Teachable Unit Framework
Title of Unit
Date and
Location of SI
Unit Developers &
Contact
Information
Context
Abstract
(< 200 words)
Rationale
Understanding Evolutionary Relationships
22-27 July 2013
University of Hawai'i, Manoa
David Marcey, marcey@callutheran.edu
Floyd Reed, floydr@hawaii.edu
Chad Barber, cbarber@callutheran.edu
Bob Thomson, thomsonr@hawaii.edu
Bruno Pernet, bruno.pernet@csulb.edu
Yvonne Chan, ylhchan@hawaii.edu
What kind of course is unit designed for? Introductory biology for majors
How long is unit? Two weeks
When will the unit be used in the course? Middle of the first semester
This teaching tidbit focuses on the use of molecular data (amino acid sequences) to
evaluate alternative evolutionary hypotheses. Students are provided with amino acid
sequences for 2 different proteins from 6 different species and asked to identify which
of 3 evolutionary trees best fit the data. The tidbit uses a think-pair-share to assist the
students in reaching consensus within their group, as well as reveal strong
disagreement among groups. We then pair disagreeing groups with one another and
ask them to identify the source of disagreement. Groups are then asked to develop
hypotheses about why their genes may disagree with one another. We guide the
students toward identifying how additional data and knowledge of gene functions may
affect their answer. The tidbit wraps up with the students identifying strong
evolutionary convergence associated with independent origins of echolocation in
mammals. This tidbit enabled the students to use data to decide among alternative
hypotheses and defend their position. It also pushed them to synthesize information,
strengthening their conceptual understanding of evolutionary relationships and how
scientists utilize data.
How did the idea for the unit arise?
We identified a number of important concepts and misconceptions in evolutionary
biology. Many of them were connected to "tree-thinking", so we decided to focus our
unit on that topic.
Why was this topic chosen?
Building, interpreting, and using trees are critical skills in biology.
What misconceptions or difficult topics are addressed?.
One misconception is that trees are observations, when in fact, they are hypotheses
with more or less support from data. We wanted to emphasize that for a given set of
terminal taxa, there are many alternative phylogenetic hypotheses, and that biologists
use data to select the best-supported of these. We also wanted to show that different
data sets might support different phylogenies, even for the same terminal taxa. Finally,
we wanted to connect our lesson to another important concept in evolution and treethinking, convergent evolution.
Teachable Unit Framework
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National Academies Summer Institutes for Undergraduate Education in Biology
Teachable Unit Framework
Learning Goals:
what students will
know, understand,
and be able to do;
includes content
knowledge,
attitudes, & skills
Learning
Outcomes:
Student behaviors
or performances
that will indicate
they have
successfully
accomplished the
goals
1. Understand how phylogenetic trees are constructed.
2. Understand how to interpret phylogenetic trees.
3. Understand how scientists use phylogenetic trees to address questions in biology.
1. Use data to evaluate phylogenetic hypotheses
2. Explain why phylogenetic trees are hypotheses, not observations.
3. Describe evolutionary hypotheses depicted by tree(s)
4. Map evolution of a character on a tree and reconstruct ancestral states.
5. Apply evolutionary trees to address a contemporary problem.
Incorporation of Scientific Teaching Themes
Active Learning
How students will engage actively
in learning the concepts
Assessment
How teachers will measure
learning; how students will selfevaluate learning
Activities outside of class:
Review of previous class meeting
notes on phylogenetics and
convergent evolution
Pre-assessments:
Quick quiz to make sure they
understand the basic concepts
from previous sessions.
Activities in class:
Quick quiz to make sure they
understand the basic concepts
from previous sessions. Possible
mini-lecture or additional group
work after the tidbit to make sure
that all the concepts are clear and
connected.
Post-tidbit assessments:
Formative assessments (clicker
questions) during the tidbit. After
the tidbit, a variety of summative
assessments aimed specifically at
targeted learning outcomes
(evaluating and interpreting trees,
selecting among competing
phylogenetic hypotheses, etc.)
Activities during tidbit:
Individual and group work with
real sequences and phylogenies;
numerous clicker assessments;
group analysis of a higher-order
question with instructors serving
as "askable experts".
Teachable Unit Framework
Diversity
How the unit is designed to
include participants with a variety
of experiences, abilities, and
characteristics
During the work, individual
students will answer questions
anonymously using clickers. This
should reduce barriers to
participation. Further, students
spend some time discussing in
pairs, enabling quieter students to
express their opinions in a less
threatening atmosphere.
Materials are designed with the
largest font size possible so as to
be easily viewed by all students.
Students will be meeting in several
different pairs during the activity,
ensuring a diverse set of
interactions and exchange of
ideas.
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National Academies Summer Institutes for Undergraduate Education in Biology
Teachable Unit Framework
Sample Presentation Plan (general schedule with approximate timing for unit)
Session 1
Time (min) Learning Outcome(s)
1 hr 30 min Understand the basics of
phylogenetic trees
30 min Review the principles of
convergent evolution
2 min
25 min
Teachable Unit Framework
Activity/assessment
Review class notes and
reading
Review class notes and
reading
Explanation, notes, suggestions,
tips
In previous classes a game of
telephone or exercise in analyzing
similarities or differences in texts
as a surrogate for molecular
sequences
Make connection for students
that convergent evolution can
occur with outward phenotypes
or at the molecular level
Remind them of
previously covered
material that will be
involved in activity
Learning outcomes 1
and 2 explicitly.
Outcomes 3 and 4 are
not directly addressed
but this activity will
introduce ideas in 3 and
4.
(Please see attached word
doc and powerpoint for
detailed steps)
-Have students group strip
amino acid sequences and
select a best possible tree
-Think/pair/share
-Reveal mystery taxa
-Think/pair/share
-Meet with student that
has alternate hypothesis
and come up with
explanation for
discrepancy and
hypothesize reason for
different trees despite the
same species
-Give gene information
-Clicker question about
convergent evolution
-Tell students they can write on
their strips or trees
-Make sure all students
understand all students are
working with the SAME taxa.
-Have students demonstrate to
each other why they grouped the
sequences as they did and chose
a particular hypothesis.
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National Academies Summer Institutes for Undergraduate Education in Biology
Teachable Unit Framework
15-20 min per
problem
Reinforce learning
outcomes 1 and 2, and
address learning
outcome 5.
5 min Learning outcomes 1-5
-Conclude main ideas
-- Assign a take-home
isomorphic problem
involving tree thinking
for a socially relevant
problem like viral coat
protein mutations
releated to infectious
human diseases.
-- Analyze several
sequences and draw a
novel phylogenetic tree
for sequences/species,
including using online
resources.
Connect what students
have just done explicitly to
the learning outcomes,
and connecting those to
the broader evolution
unit.
Add additional activities information as needed for the unit.
Resources for Teaching the Unit
Review paper about the biology of Prestin
Jones, G. 2010. Molecular evolution: gene convergence in echolocating mammals. Current Biology 20(2): 62-63
Instructor's .ppt file leading students through the exercise
Li et al. 2010. The hearing gene prestin unites echolocating bats and whales. Current Biology 20(2): 55-56
Word files containing blank phylogenies, as well as short sequences of alpha-hemoglobin and prestin for the
exercise.
Effectiveness of unit (if you have used it in your own teaching)
We have not yet used this in our own teaching.
Acknowledgements
Sarah Eddy, University of Washington. Thanks Sarah! Also all the other NASI groups that helped preview this
during development.
Teachable Unit Framework
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