Transcript understanding evolutionary relationships, west coast 2013

Unit Title
Understanding evolutionary relationships
(for majors introductory biology)
Learning goals
1) Understand how phylogenetic trees are
constructed
2) Understand how to interpret phylogenetic trees
3) Understand how scientists use phylogenetic
trees to address a variety of questions
in biology
Learning Outcomes
HOC
Use data to
evaluate and
defend
phylogenetic
hypotheses
Describe relationships
and evolutionary
histories depicted in a
tree
Understand the vocabulary of
evolutionary trees
LOC
What students will already know
• Understand that shared
derived similarities are used
to select among trees
• Know basic vocabulary
associated with phylogenies
• Have built phylogenies
using morphological traits
as characters
• Know that sequences can
be used as characters
• Have seen convergent
evolution in a
morphological context
Understanding phylogenies
Convergent evolution
Tidbit Instructions
• Each person has
– 6 amino acid sequences
• Each sequence represents a species. All students are working with
the same 6 species and all are numbered the same way.
– 3 phylogenetic hypotheses
• these are only three of a large pool of possible phylogenies!
• To do individually:
– Arrange sequences based on similarity
– Select the phylogenetic hypothesis that best matches the data
• After 5 minutes each person will vote on their best supported
phylogenetic hypothesis
• Clicker Vote
Discuss!
• Discuss your answer in
your group; what
strategy did you use?
• Do you want to change
your answer? Two
minutes!
• Clicker Revote
• Second clicker results
4
1
Species Key
species 1 = Human
2 = Sperm Whale
3 = Dolphin
4 = Dog
5 = Fruit Bat
6 = Horseshoe Bat
• write the species names out on the tips of your bestsupported tree
Species Key
species 1 = Human
2 = Sperm Whale
3 = Dolphin
4 = Dog
5 = Fruit Bat
6 = Horseshoe Bat
• pair with someone from a group that chose another
phylogeny to identify possible reasons for differences
• first pair to explain the disparity wins a prize!
• Back in your group, take five minutes to
brainstorm about why data from these two
genes might support different hypotheses and
write list on the board
• What kind of evidence would help you
distinguish between your different ideas?
• Feel free to ask the instructors questions
Two genes determine different
phylogenetic relationships
• Hemoglobin
– Transports oxygen in Red
Blood cells
– Highly conserved
• Prestin
www.cell.com
– Inner ear motor protein
– Role in high frequency sound
detection
– Certain variants important in
acquisition of echolocation
news.rice.com
Take a minute to think about this clicker question…
What evolutionary process best explains this
dichotomy?
A. convergent evolution in prestin;
echolocation evolved twice
echolocation
echolocation
B. convergent evolution in globin;
echolocation evolved once
echolocation
Follow-ups
• Homework Assignment
– Isomorphic problem in a socially relevant system
• Summative assessments
Thank you!
Summative assessments (some examples)
-- essay question: given a few trees and some data (either genetic or
morphological), select the best hypothesis (tree), and defend your
choice (Learning Outcome 1,2)
-- essay/diagram question: given a phylogeny of a group of
organisms, what can you infer about the common ancestor of taxa X
and Y with respect to a particular character? (Learning Outcome 3)
--Alternatively, given a phylogeny make inferences about the
number of gains or losses of a trait (Learning Outcome 4)
-- short answer/matching: given a phylogenetic tree, answer some
questions identifying sister taxa, common ancestors, clades ,etc.
(Learning Outcome 3)
-- essay question: design a forensic study to determine the source of
an infective virus or bacterium, or the identity of a fish or other food
source, using phylogenetic tools (Learning Outcome 5)
Unit Learning outcomes
Students will be able to:
1) Use data to evaluate phylogenetic hypotheses
2) Explain why phylogenetic trees are hypotheses, not
observations
3) Describe evolutionary hypotheses depicted by a
phylogenetic tree.
4) Map evolution of a character on a tree and reconstruct
ancestral traits.
5) Apply evolutionary trees to address a contemporary
problem
Unit Learning outcomes
Students will be able to:
1) Use data to evaluate phylogenetic hypotheses
2) Explain why phylogenetic trees are hypotheses, not
observations
3) Describe evolutionary hypotheses depicted by a
phylogenetic tree.
4) Map evolution of a character on a tree and reconstruct
ancestral traits.
5) Apply evolutionary trees to address a contemporary
problem
Unit Learning outcomes
Students will be able to:
1) Use data to evaluate phylogenetic hypotheses
2) Explain why phylogenetic trees are hypotheses, not
observations
3) Describe evolutionary hypotheses depicted by a
phylogenetic tree
4) Map evolution of a character on a tree and reconstruct
ancestral traits
5) Apply evolutionary trees to address a contemporary
problem