Download notes for folder p. 73-75

I. 
Theory of Evolution
A. Overview
1. "Theory vs. Scientific Theory”
a. "Theory" in everyday language
is a guess
b. "Scientific Theory" is supported by a
large amount of evidence. It’s an
explanation of observations.
2. Definition of Evolution -- Change in the genes of
a population over time
a. The smallest unit that can change is a population.
b. An organism does not evolve, a population does.
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B. An early idea about how evolution occurred:
Lamarck: A French naturalist, published
his hypothesis in 1809.
1. Lamarck’s Theory was based on his observations.
a. He observed that blacksmiths had big muscles and
that family members stayed in the profession.
b. He believed organisms constantly strive to improve
themselves and become more advanced.
c. Their effort to improve causes the most
used body structures to develop while
the unused body structures
wasted away (Use Disuse theory)
d. The modification due to use or disuse is passed on to offspring
(Inheritance of Acquired Characteristics)
e. Another example he used is giraffes’
necks. They reached for food and
thereby developed longer necks.
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3. Weismann (1889): Proves Lamarck wrong through an
experiment.
a. cut off the tails of mice for 22 generations.
b. All offspring were born with tails.
c. He concluded that changes in the body during your
life are not passed down to offspring. (We know this
now through genetics, but also observations such as
people with pierced ears not passing on that trait.)
C. Charles Darwin
1. Voyage of the Beagle (1831-1836)
a. purpose of the voyage was to make maps of coast of
South America
b. Darwin’s purpose was to make geological studies to
locate minerals for mining. He was also the ships’
naturalist.
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c. Darwin observed plants and animals every time they
docked.
d. He noticed slight differences in them based on where they were.
e. He collected fossils and made notes about where he
found them.
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4. Visit to the Galapagos
Islands during his voyage
a. Local Finches (a type of
bird) had different types of
beaks based on what they ate
b. Tortoises had different
shells based on what island they
were on
c. Why were they different?
How did they get that way?
5. Darwin’s Theory was influenced by 3 people
a. Charles Lyell – wrote a book explaining that changes in
the Earth were slow and uniform
Darwin inferred that
slow Earth changes
could affect plants
and animals.
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b. Thomas Malthus – observed that the human population
was growing so fast that the supply of resources would
not be able to support the population
Darwin realized that in all populations (not just
human), there was always competition for food,
space, and mates. Those that “win” survive and
reproduce.
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c. Pigeon and Dog Breeders – select animals with the best
traits to get the desired pigeon or dog
Darwin thought this process would occur naturally,
just more slowly.
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6. Darwin’s Theory: Evolution has by natural selection.
5 points of his theory:
a. There is a variety within a population
b. Some traits are an advantage to have because they
improve the organism’s chance to survive and
reproduce. When an environment changes, the value
of the traits may change, with some traits becoming
more advantageous and some less so.
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c. More young are created in each generation than can
survive.
d. Those that survive and reproduce are those with the
traits that are an advantage to have
e. Over a long time, small changes accumulate and the
population changes.
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7. Darwin did not publish his theory for more than 20 years.
He published On the Origin of Species in 1859.
Evidence for Evolution:
1.  The fossil record shows modern organisms are related to
organisms that lived long ago. We can date fossils to put
them in order. This lets us see that organisms have evolved
(changed) step-by-step over a very long period of time.
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Evidence for Evolution:
2.  Organisms’ vestigial structures provide evidence that the organisms
evolved from ancestors that used the structures. Organisms with
homologous structures evolved from a common ancestor.
Evidence for Evolution:
3. DNA similarities across different species also show evidence for
descent from a common ancestor.
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Evidence for Evolution:
4. Similarities in vertebrate embryo development suggest all
vertebrates share a common ancestor.
Evidence for Evolution:
5.  Modern observations, such as changes in a species from selective
breeding (as in dogs) and the appearance of antibiotic-resistant
microbes, also support the theory of evolution.
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What can affect evolution? What can change a population?
1.  Natural selection -- “survival of the fittest”
2.  Migration -- immigration (organisms moving in) and emigration
(organisms moving out) can change a populations’ traits.
What can affect evolution? What can change a population?
3.  Selective/non-random mating -- Some traits (such as a more
colorful peacock fan) do not affect survival but make an
organism more or less likely to reproduce and pass on its genes.
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What can affect evolution? What can change a population?
4.  Genetic drift -- Random events that are independent of the
population’s traits and that happen to a small population can
drastically change the characteristics of that populations. An
example would be a hurricane wiping out most of the horses
with black manes in a small band of wild horses. The color
of the manes did not influence which horses died, but the
population after the hurricane had far fewer black manes.
5.  Adaptive radiation -- Descendents of a common ancestor fill
different niches (parts or roles) in the environment. Each niche
selects for different traits. Over many generations, the
descendents become more and more different from each other.
An example would be Darwin’s finches whose beaks were
different, depending on the type of food they ate.
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6. Speciation (formation of separate species from a common
ancestor) can also occur when populations are in similar
niches, but are separated by geography. The two groups cannot
interbreed, so they are likely to become different over time.
An example would be birds on either side of a mountain range.
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