Download Evolution Notes

I.
Background
A. Charles Darwin
1. Born on February 12, 1809, same as
Abraham Lincoln.
2. Sailed around the world on the HMS
Beagle.
3. Made observations that led to the
theory of evolution
4. Wrote Origin of Species.
B. Galapagos islands
1. ¾ the size of the Hawaiian Islands.
2. Each island has a different climate.
3. About 625 miles off west coast of
South America.
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II. Evolution – process by which modern
organisms have descended from ancient
organisms.
A. Natural selection:
1. Individuals that are better suited to
their environment survive and
reproduce most successfully.
2. Also called survival of the fittest.
3. Ex: Arctic hares
hair color
white (dom) vs. brown (rec)
• Which allele will show up the most?
• Which organism has a higher chance
of survival in the arctic?
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B. Natural selection vs. selective breeding
1. Natural selection allows nature to
decide which traits are past to the
offspring.
a)Predator-prey relationship determines
this. (fastest, strongest survive)
2. Selective breeding – allowing certain
individuals with desired
characteristics to produce the next
generation.
a)Ex: farmers want fattest hogs, cows
that produce the most milk, reddest
tomatoes, etc.
b)Traits benefit humans, not nature.
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C. Homologous structures – structures that
have different mature forms but develop
from the same embryonic tissues.
1. Figure 15-15, page 384.
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2. Darwin concluded that homologous
structures show common ancestry.
3. Functions may be different when mature
(fin vs. wing), but look similar at the
embryonic stage of development.
D. Divergent vs. Convergent Evolution
1. Divergent evolution – process of 2 or
more related species becoming more and
more different.
a)Diverge = separate
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b)Figure 16-13 Divergent Evolution
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2. Convergent evolution – unrelated
species become more and more similar in
appearance as they adapt in the same
kind of environment.
a)Converge = come together
b)Figure 17-23 Shark, penguin, dolphin
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III.Fossil record
A. Fossil – any preserved part or trace of
an organism that once lived.
1. Formed when organism is buried before
it decays.
2. Found in sedimentary rock (layers of
mud, silt, and sand on top of it).
B. Determining the age of a fossil
1. Age is determined by the location in
rock.
a) Fossils closest to the surface are
“newer” than those deeper.
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b)Figure 17-3 page 419
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2. Radioactive dating:
a)Half-life – time required for half of
the radioactive atoms in a sample to
decay.
b)Carbon-14:
1)Half-life is 5,730 years.
2)Used for younger fossils.
c)Uranium-238:
1)Half-life is 4.5 billion years.
2)Used for older fossils.
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