Speciation and
Variation
Chapter 16
Learning Goals
1.
2.
3.
4.
Compare microevolution to
macroevolution
Describe the 2 different types of
speciation
Analyze the effects of genetic drift on a
gene pool.
Examine how founder effect and the
bottle neck effect are similar/different.
What is a species anyway?
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A species is a group that only mates with each
other.
When two organisms can not interbreed, they
are different species.
Ex. Homosapiens (human), diceros
bicornis(rhino), and drosophila malagastar (fruit
fly).
Can new species be created????
yes!!
Types of Speciation
1. Prezygotic: prevents
zygote forming . Sperm
and egg never meet up!
Ex. .reproductive isolation:
the species is isolated
and mating does not
occur.
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a.geographic
b. temporal
c. behavioral
Donkey
horse
2. Postzygotic: after
mating occurs, sperm and
egg do meet but zygote is
no good, “not viable”.
Ex. Hybrid sterility :
species interbreed, but
offspring are sterile .
mule
What is a zygote anyway?
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A zygote is formed when a sperm and egg
meet during fertilization and a diploid
single cell is formed.
1N egg
1N sperm
2N Zygote
1. Temporal isolation: when
organisms can’t successfully mate
due to different mating ritual, mating
times, or mating location.
Frog A: mate in
early April
Frog B: mate in
late April, early May.
Is this
reproductive
isolation?
explain
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Geographic Isolation: two populations are
separated by a geographical barrier, like
river, mountain or ocean.
Can the Grand
Canyon cause
geographic
isolation?
Explain.
Darwin observed finches on
different islands, and
concluded that adaptive
radiation occurred causing
finches to develop different
beaks.
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Behavioral Isolation : rituals or behaviors cause species to no longer
interact.
Ex. The Eastern meadowlark bird and the Western meadowlark are in
the same area but using different songs to attract mate.
Genetic Drift …genes move away!
Occurs when a small group from a larger
population leaves, the gene/allele
frequencies may change.
 Genetic drift is NOT natural selection.
 It is simply RANDOM CHANCE.
 Explain diagram.
Bottle Neck effect: an example of
genetic drift
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Bottle Neck: when small group are
left over due to a natural disaster.
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Example, a large group of
pecanaries (wild pig) are affected by
drought. The surviving member
don’t carry that same gene pool as
before.
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Explain the diagram…
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Gene pool before
gene pool after
Founder effect: another type of
genetic drift
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Genetic drift when a small group migrate away from the
original population. The new population will be different
than the original.
Ex. A small group of 12
Germans move to another
country…3 of them are
related and have
polydactylism.
After 250 years the gene
frequency increases from
25 to 75%.
What this because
having an extra finger
made them “better
suited” for their new
environment?
Microevolution = visible change
from one generation to next
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small changes in the
genes/chromosomes of a
population
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Ex.1 House sparrow is
larger in the Northern
U.S, associated with
colder temps .
Ex. 2 Peppered Moth of
London went from 90%
light colored to 90% dark
when the forest became
polluted.
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Marcoevolution = mutation + genetic drift +
gene flow + natural selection + 3.8 billion years
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major changes affecting many
species at once.
Indicate a change in the time
period.
Ex. 1. KT event end the
Cretateous period, causing
Dinosaurs, along with 65 % of
species to disappear.
Ex. 2 End of Permian period
caused by volcanic eruptions
killing 95% of life on earth.
Survivors fill in gaps and
flourish!!
Geologic Time Scale
Identify the KT event and the
end of the Permian time.
Put a star and label.
In what period do we have the
origin of birds?
In what era and period do
We currently live?