Transcript Testing Darwin`s postulates

Toby Bradshaw
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BIOL 354
Foundations in Evolution
and Systematics
http://courses.washington.edu/biol354
For those trying to get into this
course …
Course staff: Andrew Eckert,
Fernanda Oyarzun, DouShuan Yang
Textbook (reserve copies in
Odegaard)
Course website
• Syllabus
• Lecture topics/readings
• Discussion section
topics/readings/assignments
• Lecture overheads
• Course policies (grading, plagiarism,
etc.)
Goals for the course
• Learn to think evolutionarily,
integrating evolutionary principles
with your knowledge from other
disciplines to address real-world
problems in areas such as
medicine, ecology, physiology,
and conservation;
• Explore in depth some key
concepts in evolutionary biology,
moving from observed patterns
of phenotypic variation to
evolutionary hypotheses,
experimental design, and data
analysis;
Goals for the course
• Understand the historical,
theoretical, and experimental
bases for contemporary
paradigms in evolutionary
biology;
• Learn to read, understand, and
apply knowledge obtained from
the primary scientific literature;
• Communicate your knowledge of
evolutionary biology through oral
discussions and written papers;
and,
• Prepare for advanced
coursework or research in
evolutionary biology if you so
desire.
What was Darwin trying to explain?
• Why are there so many kinds
(=species) of living things?
• How do new species arise?
• How do populations of organisms
evolve over time?
• What produces the observed
biogeographical patterns of extant and
extinct life forms?
• How are species related to one
another?
• How do organisms adapt to their
environment?
Before Darwin, how
were these things
explained?
Darwin’s postulates make
evolutionary biology an
experimental science
“Unlike that of
physics, the
fundamental
paradigm of
evolutionary biology
has not changed in
over a century, and it
is sometimes
depressing to think
that we may be
forever sweeping up
behind the Darwinian
elephant.”
– Jerry Coyne
Darwin’s postulates
• Among individuals of a species,
there is variation in phenotypic
traits.
• At least some of this variation is
heritable.
• Individuals vary in their ability to
survive and reproduce (=fitness).
• Variation in some phenotypic traits
(=adaptive traits) is correlated with
variation in fitness.
 The species will evolve by
natural selection to become
increasingly well adapted to its
environment over time, as better
adapted individuals reproduce at
disproportionately high rates.
How might we test
whether phenotypic
variation is heritable
(i.e., does it have a
genetic basis)?
Color and pattern in milk
snakes
Habitat preference in
Mimulus (monkeyflower)
Height in humans
Intelligence in humans
Experimental tests
for heritability
Parents transmit discrete
traits (e.g., seed coat color
in Mendel’s peas) to
offspring
Trait variation is still
observed even in “common
gardens”
Phenotypic correlation
between parents and
offspring
Close relatives (including
clones or identical twins)
share more traits than less
related individuals
Heritability
VP = phenotypic variance
VG = total genetic variance
VA = additive genetic variance
VD = dominance genetic variance
VE = environmental variance
VP = VA + VD + VE
VG = VA + VD
H2 = VG / VP
h2 = VA / VP
When clones are planted in common
gardens, are we estimating H2 or h2?
With parent-offspring regression, are
we estimating H2 or h2?