Tree Thinking:
Reading and Interpreting Phylogenies
Review:
Constructing Phylogenetic Trees
You are now able to construct a phylogenetic
tree using character data
a. Trees are built with shared, derived
characters that indicate relatedness
b. Trees illustrate degrees of relatedness
c. Nodes represent past divergent events
Learning Objectives
You should be able to:
• Correctly interpret phylogenetic trees
• Identify the most recent common ancestor of
a given group
• Draw trees that show equivalent genealogies
Is the frog more closely related to the
fish or the human?
a.
b.
c.
d.
Fish
Human
Equally related to both
There is not enough information to decide
Is the frog more closely related to the
fish or the human?
a.
b.
c.
d.
Fish
Human
Equally related to both
There is not enough information to decide
Time
Is the frog more closely related to the
fish or the human?
Time
The frog is more closely related to the
human than the fish
These two trees show the
same evolutionary history!
Free Rotation at Nodes
Remember
Trees can be drawn in different ways
=
What really matters?
More recent common ancestor
Based on this tree, who is the horse’s closest relative?
4
3
2
a.
b.
c.
d.
e.
Lizard
1
Seal
Tie between the lion and cat
Tie between the seal, cat, and lion
Tie between the seal and the lizard
Known relationships among the Hominoids (apes):
1. Humans and chimps are each other’s closest relatives
2. The closest relative of the gorilla is a tie between
humans and chimps
3. The closest relative of the orang is a tie between
humans chimps and gorillas
In Groups:
Draw as many trees as you can that all illustrate the
SAME correct genealogical relationship
Which tree is a different genealogy
from the other three?
A
B
C
D
Learning Objectives
You should now be able to:
• Correctly interpret phylogenetic trees
• Identify the most recent common ancestor of
a given group
• Draw trees that show equivalent genealogies
Questions?
Kris Karsten karsten@callutheran.edu
Cath Kleier ckleier@regis.edu
Frank Messina frank.messina@usu.edu
Theresa Rogers terogers@callutheran.edu
Kristin Swihart swihart@colorado.edu
Becky Williams toxwilliams@gmail.com
Facilitated by: Stanley Lo stanleylo@northwestern.edu
Upcoming Topics
• Accurately determine relative timing of the
evolution of characters of interest by mapping
traits onto a tree
• Recognize that scientific names (taxonomy) do
not always match up with evolutionary
relationships (systematics)
• Applications of phylogenetics
Alignment
Learning Goal
Learning
Objective
Assessment
What will
students learn?
If they have
learned it, what
will students
know and be able
to do?
How will students
demonstrate they
know it or are
able to do it?
What will
students do to
learn it?
Students will
understand
phylogenetic trees
as representations
of evolutionary
history
Students will:
Formative:
Students will:
Correctly interpret
phylogenetic trees
Will take place
within each of the
learning activities
with feedback.
Answer clicker
questions on tree
interpretation
Identify the most
recent common
ancestor of a given Summative:
group
All of the learning
Draw trees that
objectives are
show equivalent
addressed by
genealogies
distinguishing
between different
genealogies
Learning
Activity
Justify answers to
a partner
Groups translate
written summary
of relationships
into alternative
trees