Transcript Evolution & How it Works

WELCOME BACK!!!
In Activity: Scent Lab
1. Pick up Scent Lab by
door & Read the
Directions
(we’ll work as a class in 5 min.)
Scent Lab
Pretend you are a wolf and
must find your pack using
your sense of smell.
Why is the adaptation of smell
important to the survival and
evolution of Wolf packs?
TEKS 7C
Analyze and evaluate how natural
selection produces change in
populations, not individuals
Population Genetics Lab
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Clear your desk & Read the introduction
Use the materials to model populations in
various scenarios:
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Population, Natural Selection, Mutation,
Reproductive Isolation, Gene Flow, Genetic
Drift, Barrier Isolation
Answer all questions on the handout
Return the materials to your teacher
Class Debrief
Concept Map Notes:
1.
2.
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5.
Speciation
Mutations
Gene Shuffling
Gene Flow (migrations)
Genetic Drift (bottle neck effect & founder effect)
Emergence of Evolutionary Thought
Galapagos Islands
Charles Darwin
1809 - 1882
Voyage of the H.M.S. Beagle
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Darwin was 22
joined the crew of the
H. M. S. Beagle as
naturalist
left England in 1831
arrived in the
Galapagos Islands in
1835
collected specimens &
recorded observations
Darwin’s Galapagos Observations:
1835
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Darwin’s hypothesis:
Perhaps all the species
descended from the
mainland finch, then
changed slightly after
becoming isolated on
different islands.
Concept Map Notes:
1.
2.
3.
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5.
Speciation
Mutations
Gene Shuffling
Gene Flow (migrations)
Genetic Drift (bottle neck effect & founder effect)
Evolution: How It Works
Mechanisms of Evolution:
 natural selection
 Mutation
 Non-random mating
 Population Genetics:
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Genetic drift
Migration (gene flow)
Mechanisms of Evolution:
Natural Selection
V = Variation: All life forms vary genetically within a
population.
I = Inheritance: Genetic traits are inherited from
parents and passed on to offspring.
S = Selection: Organisms with traits that are
favorable for survival get to live and pass on
their genes to the next generation.
T = Time: Evolution can happen in a few
generations, but major change, such as
speciation, often takes long periods of time.
http://evolution.berkeley.edu
Mechanisms of Evolution:
Natural Selection
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Natural Selection is determined
by the environment.
Mechanisms of Evolution:
Nonrandom Mating
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A preference by one
sexual partner for a
particular phenotype
The result of nonrandom
mating is that some
individuals have more
opportunity to mate than
others and thus produce
more offspring
Mechanisms of Evolution:
Causes of Mutations
1. DNA fails to copy
accurately
2. Environmental
influences can cause
mutations.
Mechanisms of Evolution:
Population Genetics
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Important terms:
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Gene Pool consists of all genes including
all the different alleles in population
Relative Frequency of an allele is the
number of times that the allele occurs in a
gene pool.
Single Gene Traits are controlled by a
single gene that has two alleles
Mechanisms of Evolution:
Genetic Drift
p.400
Genetic drift is a change
in a population’s allele
frequencies due to
chance. The smaller the
population, the larger
the effect.
 Bottleneck Effect
 Founder Effect
Genetic Drift (2007) by Michael Dumas
Genetic Drift: Bottleneck Effect
Disease, starvation, or some other disaster
can nearly wipe out large populations. Even
though the population recovers, the relative
abundance of alleles has been randomly
altered.
Genetic Drift: Bottleneck Effect
Gene pool
Genetic Drift: Founder Effect
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p.400
A few individuals leave
a population and
establish a new one.
By chance the allele
frequencies for many
traits may not be the
same as in the original
population.
Mechanisms of Evolution:
Migration (gene flow)
Movement of genes from one population to
another. If genes are carried to a population
where those genes previously did not exist,
gene flow can be a very important source of
genetic variation.
Evolution vs. Genetic
Equilibrium
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Hardy-Weinberg Principle: allele frequencies in
a population remain constant unless one or
more factors cause those frequencies to
change. (p.402)
Genetic Equilibrium: allele frequencies remain
constant (no change = no evolution).
Development of New Species:
Speciation
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Speciation is the
development of one or
more species from an
existing species.
How does speciation
occur? (p.404)
Speciation: How Does it Work?
(p.404)
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Sometimes barriers arise between parts of a
population and create local breeding units.
Then, two or more gene pools exist when
there was only one.
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Geographic isolation: populations can be
separated by geographic barriers
Reproductive isolation: any aspect of
structure or behavior that prevents
breeding (breeding seasons, behavior, etc)
Evidence of Evolution
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fossil record
homologous structures
vestigial organs
developmental embryology
biogeography – different species are
found in similar geographic regions
6. molecular (DNA) evidence – comparisons
can be made between organisms
Evolution Simplified
genetic variation in individuals
+
selection
+
time
evolution
“OUT” Exit Ticket
1.
Explain 3 examples of how
population genetics can affect
the evolution of a population.
A Final Thought
(read this quote & respond with your thoughts on paper)
Evolution is not merely an idea, a theory or a
concept, but it is the name of a process in nature,
the occurrence of which can be documented by
mountains of evidence that nobody has been able
to refute. It is now actually misleading to refer to
evolution as a theory, considering the massive
evidence that has been discovered over the last 140
years documenting its existence. Evolution is no
longer a theory, it is a fact.”
Ernst Mayr
Professor Emeritus
Harvard University