[ECOL 170C1] - Midterm Exam Guide - Comprehensive Notes for the exam (35 pages long!)

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U of A
ECOL 170C1
MIDTERM EXAM
STUDY GUIDE
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A
B
C
DIV. OF LIFE LECTURE 2
Learning phylogenies
Learning about phylogenies
A basic tree-
The phylogeny says 3 things:
1.) statement of relationships
Species B and C more closely related to each other than either is
to species A
2.) statement of ancestry
Species B and C shared a common ancestor not shared by
species a
Species A, B, and C once shared an ancestor not shared by any
other species
3.) history of speciation (or splitting in general)
Single ancestral species speciated to give rise to species a and
the ancestor of species B and c
Ancestor of species B and C speciated
Extant species:
Living species (B to C) that we see today
Ancestral species:
Extinct species that we infer from phylogeny (between back of A to top of
B)
Branch:
Where it comes off
Species, lineage
Some ancestral species, some extant species
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Node:
Where it touches the main line
Two branches split
Speciation
How many extant species (from above example):
3
How many ancestral species (from above example):
2
How many branches (from above example):
5
How many nodes (from above example):
2
You can rotate the branches but the tree would still be the same
Can also be seen as a graph showing evolutionary events over time
Distance between branches can show amount of time
For now, we will not use branch lengths to show time
Many ways to draw tree-
Should not matter if its right side up or down
Polytomies-
Polytomy:
Node where relationships are uncertain (>2 branches from one node)
Resolution:
Dichotomous tree (2 branches from one node) consistent w polytomy
These are the possible “answers” for the unresolved part of the ptree
Use polytomies to show parts of the phylogeny that were still not sure about
3 possible resolutions of polytomy (3 possible trees for relationships among
these 3 species)
Terminal units-
So far we have looked at trees w species as terminal units (A B C)
Terminal units can also be individual organisms or groups of species (ex.
Genera, families, phyla, etc.)
If the terminal unit represents a “higher taxon” (category above species, like
genus family) then terminal branch represents common ancestor of all species in
that group
At one point in time, each group consisted of only a single species
Trees and taxonomy-
When using higher taxa as terminal units, assume all species in group
descended from single common ancestor (what we call “monophyletic group”)
3 common term:
Monophyletic
All species descended from common ancestor
Paraphyletic
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