Transcript File

Warm-up 2/9/2015
Who is Charles Darwin and
why is he important?
Evolution

scholars in the west believed that living
things or “species” had remained the same
since the time of creation. They viewed all
species
as
perfectly
created
and
unchanging.
A. Questions from Naturalist Studies * why did the bones of mammals such as
whales, humans, and bats differ in size
shape and function but yet the number ,
location and connections between bones
were so much alike?
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WHALE
HUMAN
BAT
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* Why do these organisms form in similar
ways in the embryo?
Human
Pig
Chicken
Fish

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* Why did some organisms have body parts with
no apparent function? (Vestigial Organs)
ex. some snakes have bones corresponding to a
pelvic girdle, a set to which hind limbs attach.
What were bones doing there if snakes had been
created perfect?
ex. humans have bony parts exactly like the
bones in a tail. What were parts of a tail doing in
a perfectly designed human body?
Snake
Human
Why are some structures similar in function
but differ in structure? (Analagous
Structures)
Lyell and Hutton
Hutton- Geological Change
Lyell- Principles of Geology

Different layers
held different types
of fossils. The
fossils of the
simplest organisms
are found deep in
the fossil record
while more
complex organisms
are found in more
recent fossil layers.

*If all species were created at the
same time and place, how could they
now be dispersed throughout the
world?

Mountain barriers or oceans would have
stopped them. Perhaps species originated
in more than one place.

* “Evolution” was already being discussed
in 1831, when Darwin was just a college
graduate of 22. His degree was in theology.
*Darwin’s true interests were in natural
history and so he took a job as the ship’s
naturalist on the H.M.S. Beagle and
recorded all of the natural flora and fauna
encountered on the ship’s voyage . The
ship was destined to map the S. American
coastline.
After careful study, Darwin came to suspect
that geographic isolation is related to
evolution and species diversity.

His Observations:

1) the Galapagos
Islands are near
Ecuador

2) Every island or
cluster has it’s
distinct species of
finch

3. All finch species
closely resemble a
finch living on the
coast of S. America
(and nowhere else)

4. Each species had a
distinct beak suited to
obtaining the type of
food available on it’s
island

His Hypothesis:
Perhaps all of the
species descended
from the mainland
finch, then changed
slightly after
becoming isolated
on different
islands.
Influences
Lamarck’s Evolution Hypothesis
1. Tendency towards perfection
2. Use and disuse
3. Inheritance of acquired traits

*Darwin
wondered
how
such
changes in organisms could occur

*Thomas Malthus, a clergy man and
economist provided the clue:

Malthus’ View:
Any human
population tends to
outgrow its
resources, and its
members must
compete for what
is available.
V. Darwin Develops the Theory of Natural
Selection as a Mechanism of Evolution

*Darwin hypothesized that the same
principle might apply in nature - beak size
or shape could lead to differences in the
ability to get resources.

*If there were “competition” for resources
in a population then individuals with
favorable traits might have an advantage
in survival and reproduction.

*Favored
individuals would
pass their traits on
to their offspring ,
their offspring
would do the
same, and so on.
Eventually
descendants of
favored individuals
would make up
most of the
population.
VI. Presenting the Information
 *Darwin did not announce his
theory right away, he wanted to
sift through the evidence and
look for flaws in his reasoning.

*In 1858 he received a paper for
another
naturalist,
Alfred
Wallace who had reached the
exact same conclusion.

*The next year, Darwin published his
theory in book form (On the Origin of
Species, 1859)
Principles of Natural
Selection:

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There are variation in organisms, and
some of this variation is genetic (can
be passed on)
More offspring are produced than
survive
These organisms compete for limited
resources
Individuals more suited for the
environment have more success
living and producing offspring
Change in species is seen over time
Descent with modification

Each living
species has
descended
with changes,
from other
species over
time.
Types of Selection

There are 4 major types of natural
selection, and 1 type caused by humans
(artificial selection)

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Stabilizing Selection
Directional Selection
Disruptive Selection
Sexual Selection
[Artificial Selection]
Types of Selection
Disruptive selection