Download Evolution Evidence

LAB:Variation in a Species
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What is the purpose of Part 1?
(Measuring Pumpkin seeds)
There is variation in size in Pumpkin plants.
Variation can be measured.
LAB:Variation in a Species
What is the purpose of Part 2?
(Calculate how long it takes pumpkin plants to take over
the Earth)
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There are reasons to explain why pumpkin
plants have not ever taken over the Earth
LAB:Variation in a Species
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What is the purpose of Part 3?
(Effect of predators on sweet cute Bonitos)
There are reasons to explain why the
population of bonitos on one island look
different from bonitos on another island
What is a species?
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A group of living things that
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Are similar
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Can breed together in nature
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To produce fertile offspring.
What is a population?
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A group of living things that
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Belong to the same species
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Live in the same area
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Can reproduce together
What is a gene pool?
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The total collection of genes in a population
at any one time.
Hardy & Weinberg
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What is allele frequency?
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1908: Hardy and Weinberg invented the
term “allele frequency” to describe the
percentage of dominant and recessive
alleles found in a populaton.
Hardy & Weinberg
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How is allele frequency measured?
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Example: a lizard population might have the
following allele frequency for the alleles F
and f:
FF = 0.64
(64%)
Ff = 0.32
(32%)
ff = 0.04
(4%)
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Hardy & Weinberg
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What is genetic equilibrium?
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1908: Hardy and Weinberg invented the
term “genetic equilibrium” to describe a
population in which the frequency of
alleles stays the same from one generation
to the next.
Hardy & Weinberg
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How was genetic equilibrium measured?
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Hardy-Weinberg equations:
p2 + 2pq +q2 = 1
p+q=1
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Hardy & Weinberg
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Hardy-Weinberg Equations
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Where p2 is the frequency of homozygous
dominant individuals
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Where 2pq is the frequency of heterozygous
individuals
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Where q2 is the frequency of homozygous
recessive individuals
Hardy & Weinberg
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What causes genetic equilibrium?
There must be…….
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A large population
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Members mating at random
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No mutation
No migration
No natural selection
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Hardy & Weinberg
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What can cause allele frequency to change?
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Migration (also called gene flow)
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Mutation
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Mate selection (non-random mating)
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Predators, disease, famine, drought, storms,
accidents.
Observing Variation
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(1) Variation exists in living populations.
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(2) Some variations are helpful and increase
life span.
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(3) Some variations are harmful and
decrease life span.
Observing Variation
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(4) A population may become physically
separated, so two groups form.
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(5) As mutations and meiosis occur, new
variations will appear.
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(6) Some offspring will survive better than
others.
Observing Variation
(7) Offspring that survive in one area may
not survive in another area.
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(8) Over time, more variations will
accumulate in the two populations.
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(9) The two populations will become
different because different variations occur
in the two groups.
Observing Variation
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(10) Individuals that die out do not get to
reproduce.
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(11) In some cases, the two groups become
so different from each other that they can no
longer interbreed.
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(12) Sometimes, a new species has formed.
What is this Process?
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Evolution of species
A set of natural processes that causes
change in a population of living things over
time.
Understanding Evolution
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Scientists study natural processes and look
for natural explanations.
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I will show you as much as I can about
evolution and why scientists say it is the
basis of all biology.
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Science cannot answer every question.
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What if you disagree with photosynthesis?
Evolution by Natural Selection
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Variation exists in every population.
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Sources of inherited variation: meiosis,
crossing over, mutation.
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Natural selection (predators, disease,
drought, cold, famine, flood, heat…..)
causes some individuals to survive while
others do not.
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Allele frequency change is called evolution.
Sometimes it causes speciation.
Jean Baptiste de Lamarck
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How did giraffes
get long necks?
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Evolution by
Inheritance of
Acquired
Characteristics
Jean Baptiste de Lamarck
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Animals face a need to change.
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Animals make themselves change
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Animals pass on the changes to offspring.
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“Inheritance of Acquired Characteristics”
Charles Darwin
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Age 25: set sail on 5 year voyage on HMS
Beagle as “Naturalist”.
Darwin observed
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Charles Darwin observed animals and
plants in the Caribbean, South America, the
Galapagos, Hawaii, Indonesia, Africa and
Europe.
He took massive notes (Cornell notes?)
He wrote three books about his experiences
Darwin’s Notebook
Common Ancestor
Evolution by Natural Selection
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Variation exists in a population. (Darwin
did not know how the variation was
passed…genetics was not yet understood)
Some organisms survive and pass on
genes…some do not.
Causes of this evolution: migration,
“heredity”, mate selection, predators,
disease, famine, drought,
Lamarck and Darwin: How would
they explain these observations?
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In 1960, a pesticide was sprayed at Tybee
Island, GA, killing 97% of all mosquitoes.
In 1979, the same pesticide killed less than
30% of all the mosquitoes.
Lamarck:
Wallace:
Evolution by Natural Selection
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Variation exists in a population. (Darwin and
Wallace did not know how the variation was
passed…genetics was not yet understood)
Some organisms survive and pass on genes…some
do not.
Causes of this evolution: migration, “heredity”,
mate selection, predators, disease, famine,
drought,
How can evolution occur?
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Migration
Mutation
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Meiosis and crossing over
Natural Selection (predators, disease,
famine, drought)
Non-random mating (sexual selection)
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Genetic drift (luck)
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How can allele frequency
change?
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Migration
Mutation
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Meiosis and crossing over
Natural Selection (predators, disease,
famine, drought)
Non-random mating (sexual selection)
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Genetic drift (luck)
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Evidence that evolution takes
place
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Biogeography
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Homologous or vestigial structures
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Homologous DNA and proteins
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Evolution observed right now
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Fossil evidence
Homologous skeletal structure
Vestigial whale pelvis bones
Vestigial anthers and pollen:
Dandelions are asexual
Bear evolution based on homologous DNA genes
Fossil evidence of horse evolution
Whale and
dolphin
evolution
based on
DNA
homology
Phylum Annelida segmented worm evolution
based on fossil and DNA homology
Living examples: Phylum Annelida
(segmented worms)
Evolution of flowering plants:
Phlox and its relatives
Phlox evolution based on fossil and DNA homology
Evolution of Turtles, with massive fossil evidence
Biogeography
Hawaiian Monk Seals
Embryo Homology
Plant embryo homology
Common Ancestor
Homologous Structures
Bees, ants and wasps have stingers which are
modified ovipositors…which explains why only
females can sting!
Evolution: Changes in allele
frequency over time
Evolution: Changes in allele
frequency over time
Evolution: Changes in allele
frequency over time
Evolution: Changes in allele
frequency over time
Whale evolution
Whale evolution
Hardy-Weinberg genetic equilibrium
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Allele frequency will not change as long as:
The population is large, so there is no
genetic drift
There is no migration (gene flow)
There is no mutation
There is random mating
There is no natural selection
The Founder Effect
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A few individuals are separated from the
original population.
All the descendants resemble the founders,
even if those traits are not best for the
environment.
EXAMPLE: island tortoises
Genetic Bottleneck
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A large population declines rapidly.
The survivors reproduce and the population
goes up in number, but the new population
resembles the survivors.
The genes of the new population are often
more uniform, with less variation
EXAMPLE: cheetahs
Natural Selection
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Stabilizing selection: natural selection
removes organisms at the extremes of a
population….like Goldilocks.
Natural Selection
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Directional selection: natural selection
removes organisms at one extreme and in
the middle, favoring one extreme.
Natural Selection
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Disruptive selection: natural selection
removes organisms with the average form
of a trait, favoring both extremes.
How to form new SPECIES?
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Reproductive isolation is required.
Prezygotic isolation (before fertilization)
Postzygotic isolation (after fertilization the
offspring is sterile)
Reproductive Isolation
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Allopatric speciation:
GEOGRAPHY (ocean, canyon, mountain)
Sympatric speciation
Organisms all live in same area, isolated by
song, timing, mutation
Adaptive Radiation
Songbirds from South America
Honeycreepers from
Hawaii
Convergent Evolution
Gradualism & Punctuated Equilibrium
Why was this little sticker so controversial?
Source: http://www.swarthmore.edu/NatSci/cpurrin1/textbookdisclaimers/CobbDisclaimer.jpg