Download mechanisms of speciation

+ 16-3 Process of Speciation
DONKEY
HORSE
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MULE
What
is
a
species?
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 Species: group
of
organisms that can
interbreed and
produce fertile
offspring
x
Horse and Eagle DNA
are too different to
create viable offspring
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Hippogriff
*not real
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Same species?

If organisms can produce fertile offspring = same species

If organisms cannot produce fertile offspring = different
species
Can a cat and dog
Can a lion and a
interbreed and
tiger interbreed
produce fertile
and produce fertile Slide
offspring?
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offspring?
+ What is a species?
X
HORSE
DONKEY
Are they the same
species?
What do you need to
know?
MULE
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Speciation
 Speciation: the formation of new species.
 Natural selection and sex selection, along with
random/chance events can change the relative
frequencies of alleles in a population and lead
to speciation.
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Categories of Speciation
Allopatric
Sympatric
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Copyright Pearson Prentice Hall
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Factors involved in speciation
 The gene pools of two populations must
become separated for them to become
“new” species
 As new species evolve, populations become
reproductively isolated from each other
 Reproductive isolation: when the members of
two populations cannot interbreed and
produce fertile offspring
 The basics of reproductive isolation video
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Isolating mechanisms
Reproductive
isolation can develop in
a variety of ways, including:
 behavioral isolation
 geographic isolation
 temporal isolation
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Behavioral Isolation
 When two populations are capable of
interbreeding but have differences in
courtship rituals or other reproductive
strategies that involve behavior.
 Albatross courtship ritual
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Behavioral Isolation

EXAMPLE: eastern and western meadowlarks are very similar birds
and their habitats overlap. However, these two species will not
mate, partly because they use different songs to attract mates.
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Geographic Isolation
 Geographic isolation occurs when two
populations are separated by geographic
barriers such as rivers or mountains.
 Allopatric speciation example
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Geographic isolation
Geographic barriers do not guarantee
the formation of new species.
If two formerly separated populations
can still interbreed and produce fertile
offspring, they remain a single species.
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Geographic Isolation
Potential geographic barriers may
separate certain types of organisms but
not others.
 Example: a large river will keep squirrels
and other small rodents apart, but it does
not necessarily isolate bird populations
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Temporal Isolation
 Temporal isolation occurs when two or more
species share the same habitats, but reproduce
at different times.
 Example: 3 similar species of orchid all live in
the same rainforest. They each release pollen
only on a single day. Because they release
pollen on different days, they cannot pollinate
each other.
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Group Activity
 Place the 14 example scenarios into one of
three catagories:
 1) Behavioral Isolation
 2) Geographic Isolation
 3) Temporal Isolation
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During times of drought
What does this graph tell
us?
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Individuals with
large beaks survive
better during times
of drought (when
food is scarce).
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The Grants provided evidence of the
process of evolution.
Beak size can be changed by
natural selection.
Natural Selection will favor ???
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Speciation in Darwin's Finches
Speciation in the Galápagos finches
occurred by:
founding of a new population
geographic isolation
changes in new population's gene pool
reproductive isolation
competition
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16-2 Evolution as Genetic Change
CH. 16 Quiz
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Copyright Pearson Prentice Hall
End Show
16-1
Which of the following statements is TRUE?
The relative frequency of an allele is not related
to whether the allele is dominant or
recessive.
Mutations always affect an organism's
phenotype.
Crossing over decreases the number of
different genotypes that appear in an
offspring.
Evolution does not affect the frequency of
genes in a gene pool.
16-1
Most inheritable differences are a result of
gene shuffling.
frequency of alleles.
mutations.
DNA replication.
16-1
The main sources of inherited variation are
gene shuffling and mutations.
gene pools and frequencies.
single-gene and polygenic traits.
genotypes and phenotypes.
16-1
A widow's peak in humans is an example of
a(an)
invariable trait.
single-gene trait.
polygenic trait.
mutation.
16-1
A graph of the length of the little finger on the
left hand versus the number of people having
fingers of a particular length is a bell-shaped
curve. This indicates that finger length is a
single-gene trait.
polygenic trait.
randomly inherited trait.
strongly selected trait.
16-2
16-2
Which of the following patterns of natural
selection on polygenic traits favors both
extremes of a bell curve?
a. stabilizing selection
b. disruptive selection
c. directional selection
d. genetic drift
16-2
Which of the following events could lead to
genetic drift?
a. A few new individuals move into a large,
diverse population.
b. A few individuals from a large, diverse
population leave and establish a new
population.
c. Two large populations come back together
after a few years of separation.
d. The mutation rate in a large population
increases due to pollution.
16-2
The situation in which allele frequencies remain
constant in a population is known as
a. genetic drift.
b. the founder effect.
c. genetic equilibrium.
d. natural selection.
16-2
Which of the following conditions is required to
maintain genetic equilibrium in a population?
a. movement in or out of the population
b. random mating
c. natural selection
d. small population
16-2
According to the Hardy-Weinberg principle, no
evolution will take place if
a. all five of the Hardy-Weinberg conditions are
met.
b. any one of the Hardy-Weinberg conditions is
met.
c. at least three of the Hardy-Weinberg
conditions are met.
d. none of the Hardy-Weinberg conditions are
met.
16-3
When two species do not reproduce because of
differences in mating rituals, the situation is
referred to as
a. temporal isolation.
b. geographic isolation.
c. behavioral isolation.
d. reproductive isolation.
16-3
The most important factor involved in the
evolution of the Kaibab and Abert squirrels of
the American Southwest appears to be
a. temporal isolation.
b. geographic isolation.
c. behavioral isolation.
d. different food sources.
16-3
One finding of the Grants' research on
generations of Galápagos finches was that
a. natural selection did not occur in the finches
b. natural selection can take place often and
very rapidly.
c. beak size had no effect on survival rate of
the finches.
d. natural selection was slow and permanent.
16-3
All of the following played a role in speciation of
Galápagos finches EXCEPT
a. no changes in the gene pool.
b. separation of populations.
c. reproductive isolation.
d. natural selection.
16-3
Beak size in the various groups of Galápagos
finches changed primarily in response to
a. climate.
b. mating preference.
c. food source.
d. availability of water.
END OF SECTION