Download Evolution

Evolution: Lamarck
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Evolution:
Change over
time
Lamarck
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Use / disuse
Theory of
inheritance of
ACQUIRED
traits
Evolution: Darwin
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Darwin’s Voyage on the HMS Beagle
Evolution: Darwin / Natural
Selection
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Darwin observed that
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organisms produce more offspring than the
environment can support
organisms VARY in many traits
these variations can be inherited
Some traits better fit for the environment than
other traits
Evolution: Darwin / Natural
Selection
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Darwin = individuals best suited for a particular
environment are more likely to survive AND
reproduce than those less well adapted
Darwin saw natural selection as basic
mechanism of evolution
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As a result, proportion of individuals with favorable
characteristics increases
POPULATIONS (not individuals) gradually change in
allele frequency in response to the environment
Evolution: Natural Selection
Evolution: Natural Selection vs
Artificial Selection
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Artificial Selection
- man creates pressure
Four Evidence of Evolution
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Biogeography
Fossils
Comparative Anatomy
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Homologous Structures
Comparative Embryology
Molecular Biology
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DNA / Proteins / Amino Acid sequences
Evidence for Evolution: Fossils
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Transitional
Fossils
Evidence for Evolution:
Comparative Anatomy
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Homologous
Structures:
Similar
structure
(what does
that suggest);
different
function (what
does that
suggest)
Evidence For Evolution:
Molecular Biology
Convergent vs Divergent
Evolution
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Analogous structure: similar function,
different structure
Ex. Wing of insect and bird
Convergent Evolution
Divergent Evolution  Homologous
Structures
Microevolution vs
Macroevolution
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Micro = small changes, still same species
Macro = speciation
Microevolution = change in allele
frequencies in a gene pool
Microevolution: Gene Pool
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Gene pool =
total numbers
of allele in a
population
Allele
frequency =
% of that
specific allele
in gene pool
Hardy Weinberg Equilibrium
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Hardy-Weinberg equilibrium: even if
alleles are shuffled in the next
generation (new genotypes appear)
allele frequency / proportions in the
gene pool stay the same from
generation to generation
Hardy-Weinberg Equilibrium
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Large population
Isolated population
No genetic mutations
Random Mating
No Natural Selection
Hardy-Weinberg Equilibrium
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ALLELE FREQUENCY
p = “A” freq
q = “a” freq
p+q=1
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GENOTYPE FREQUENCY
p2 = “AA” freq
2pq = “Aa” freq
q2 = “aa” freq
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p2 + 2pq + q2 = 1
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Hardy-Weinberg:
Genotype & Allele Frequencies
Hardy-Weinberg:
Genotype & Allele Frequencies
Hardy-Weinberg
Practice Problem
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In a certain population, the frequency of
homozygous curly haired (HH) is 64%.
What percentage of the population has
curly hair?
Given: p2 = .64 Find: p2 + 2pq
p = .8 q = .2 2(.8)(.2) = .32 or 32%
64% (HH) + 32% (Hh) = 96% curly
haired
5 Causes of Microevolution
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Population becomes SMALL due to
chance: GENETIC DRIFT
Population is NOT isolated: GENE FLOW
Mutations occur
Mating is NOT random
Natural selection exists: some traits are
better fit than others
Causes of Microevolution:
Genetic Drift: Gene pool changing
due to CHANCE
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BOTTLENECK EFFECT
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Pop shrinks due to
natural disaster
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FOUNDER EFFECT
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Colony leaves
Gene Flow &
Non Random Mating
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Gene Flow
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NONrandom Mating
Causes of Microevolution:
Natural Selection
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3 outcomes of Natural Selection:
Stabilizing, Directional, Disruptive/Diversifying
Macroevolution: Speciation
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Speciation – the creation of new species
Species:
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a population or group of populations whose
members can interbreed and produce fertile
offspring
Reproductive Barriers
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Reproductive barriers prevents different
species from mating with each other:
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Mating times / seasons different
Different habitat
Different mating behavior so little attraction
between species
Reproductive Barrier:
Geographic Barrier
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Allopatric Speciation: When a population is
cut off from its parent population, species
evolution may occur
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gene pool is changed by natural selection,
genetic drift, or mutation
Geographic Barrier:
Adaptive Radiation
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Adaptive radiation (ex of allopatric speciation)
on an island chain – from one main species
there are multiple different species evolving