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Biology 3466B Study Guide - Herbivore, Species Complex, Design Of Experiments


Department
Biology
Course Code
BIOL 3466B
Professor
Yolanda Morbey

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Adaptation Ch. 10 363-391
Adaptation a trait, or integrated suite of traits, that
increases the fitness of its possessor and is said to be
adaptive
Phenotypic differences between species are called
adaptations
Phenotypic differences between populations within
species are called local adaptions
Objectives
Distinguish these terms: adaptation, natural
selection, evolution
Design studies to test for adaptation
Explain reaction norms & phenotypic plasticity
Debate constraints on adaptation
Consider When Studying Adaptations
Differences among populations or species are not
always adaptive
Not every trait of an organism, or every use of a trait
by an organism is an adaptation
No every adaptation is perfect
Methods to Test for Adaptation
Comparative method
o Between species or between populations
o With or without phylogenetic correction
Selection experiments
Tests of adaptive hypotheses
Tests of Adaptive Hypotheses
A well designed experiment isolates and tests the effects that
a single, well-defined factor has on the phenomenon in
question
“In an ideal experiment, the control and experimental groups
are treated identically except for exactly one factor”
Eg. Zonosemata Flies
STEP 1: Evolutionary Analysis; state question precisely
What is the adaptive function of the wing markings and
wing-waving display in the Zonosemata fly?
STEP 2: Tests several alternate hypotheses
Experimental Design
Defining a test and effective control group is critical
All of the treatments must be handled exactly the
same
Can discriminate multiple hypotheses
Minimize cofounding effects
Randomization is a key technique for equalizing
other, miscellaneous effects among groups
Repetition on many individuals is essential
Observational Studies
Used when experiments are impractical or
inappropriate
Seeks to find circumstances in nature that resemble
an experiment
The Comparative Method
(among species; no phylogenetic correction)
“ The comparative method seeks to evaluate hypotheses by
testing for patterns across species, such as correlations
between traits and features of the environment”
Eg. Testes Size in Bats
Large testes size is an adaptation for living in a large
social group
The selection factor is the environment
The environment is used to infer as adaptation
Phylogenetic Dependence
When preparing a scatterplot for use as the basis of claims about
nature:
Want ALL data points to be independent of each
other
Each point therefore makes a separate statement
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Adaptation Ch. 10 363-391
A simple scatterplot may provide weak evidence
that 2 traits evolved in tandem (when
phylogenetically dependent)
(end up with only 2 data points)
Phylogenetic Independent Contrasts
Look at patterns of divergence as sister species evolve
independently away from their common
(represented by the same colored lines)
QUESTION: When species diverge from a common ancestor,
does the species that evolves larger group size also evolve
larger testes?
How to use Felsenstein’s Approach:
a. Phylogeny of the extant species being studied
b. Plot all sister species pairs on scatterplot with
lines connecting their points
c. Slide each pair (without stretching or tilting
connectors) until left point rests on the origin
d. Erase points on the origin and connector lines
Left with scatter plot of points
Each point = divergence of contrast between pairs of
sister species as they evolved
If contrast are correlated then can conclude that when a
species evolves a larger group size that its sister species, it
also evolves larger testes (hypoth. can be accepted)
Comparative Method (within species)
Compare phenotypes across environments to test
adaptive hypothesis
Box 10.2 Calculating Phylogenetically
Independent Contrasts
(not sure if we need this its from the text)
1. Calculate the contrast for pairing of sibling species
at the tip of the phylogeny
10/31/2011
2
Phylogenetic dependence
7
Phylogenetically independent contrasts
8
extant species: M-Q
ancestral species: R-U
same coloured lines (4): sister species that
diverged from a common ancestor
Phylogenetically independent contrasts
9
question: when species diverge from a common
ancestor, does the species that evolves larger
group sizes also evolve larger testes?
Phylogenetically independent contrasts
(b) plot pairs of sister species
10
(c) convert to contrasts
Phylogenetically independent contrasts
11
(d) plot divergence between
pairs of sister species
Phylogenetically independent contrasts
if contrasts are
correlated, then can
conclude that when a
species evolved a larger
group size than its
12
sister species, it also
evolved larger testes
10/31/2011
2
Phylogenetic dependence
7
Phylogenetically independent contrasts
8
extant species: M-Q
ancestral species: R-U
same coloured lines (4): sister species that
diverged from a common ancestor
Phylogenetically independent contrasts
9
question: when species diverge from a common
ancestor, does the species that evolves larger
group sizes also evolve larger testes?
Phylogenetically independent contrasts
(b) plot pairs of sister species
10
(c) convert to contrasts
Phylogenetically independent contrasts
11
(d) plot divergence between
pairs of sister species
Phylogenetically independent contrasts
if contrasts are
correlated, then can
conclude that when a
species evolved a larger
group size than its
12
sister species, it also
evolved larger testes
10/31/2011
2
Phylogenetic dependence
7
Phylogenetically independent contrasts
8
extant species: M-Q
ancestral species: R-U
same coloured lines (4): sister species that
diverged from a common ancestor
Phylogenetically independent contrasts
9
question: when species diverge from a common
ancestor, does the species that evolves larger
group sizes also evolve larger testes?
Phylogenetically independent contrasts
(b) plot pairs of sister species
10
(c) convert to contrasts
Phylogenetically independent contrasts
11
(d) plot divergence between
pairs of sister species
Phylogenetically independent contrasts
if contrasts are
correlated, then can
conclude that when a
species evolved a larger
group size than its
12
sister species, it also
evolved larger testes
10/31/2011
2
Phylogenetic dependence
7
Phylogenetically independent contrasts
8
extant species: M-Q
ancestral species: R-U
same coloured lines (4): sister species that
diverged from a common ancestor
Phylogenetically independent contrasts
9
question: when species diverge from a common
ancestor, does the species that evolves larger
group sizes also evolve larger testes?
Phylogenetically independent contrasts
(b) plot pairs of sister species
10
(c) convert to contrasts
Phylogenetically independent contrasts
11
(d) plot divergence between
pairs of sister species
Phylogenetically independent contrasts
if contrasts are
correlated, then can
conclude that when a
species evolved a larger
group size than its
12
sister species, it also
evolved larger testes
You're Reading a Preview

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