Download "Nothing in Biology makes sense except in the light of evolution

"Nothing in Biology makes
sense except in the light of
evolution."
~Theodosius Dobzhansky
Evolution
 A scientific
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theory
Subject to verification
Explains observed phenomena based on
observable scientific facts
Continuously being tested as new evidence is
found
Evolution is change over time
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First theory of evolution proposed
by Jean Baptiste de Lamarck
(1744-1829)
He hypothesized that similar species descended
from a common ancester
All living species were descended from similar
extinct species evident in the fossil record
To support his hypothesis, he used acquired
traits
Acquired trait-one that is not determined by
genes-it arises during an organism's lifetime as
a result of its experiences or behaviors
He was the first to propose that species change
over time
Jean Baptiste de Lamarck and
acquired traits
THEN 50 years later…
 Charles
Darwin and Alfred Wallace
independently proposed the hypothesis
that species were modified by natural
selection
Darwin

Was 22 years old
when he took a job as
a naturalist aboard
the H.M.S. Beagle
 The Beagle traveled
to South America and
the South Pacific on a
five year voyage
Darwin’s Voyage
During that time,

Darwin collected
specimens and kept
records of his
observations
 He look at 13 similar
but different species
of finches on the
Galapagos Islands
On the islands,
 All
the finches seemed to share a common
ancester
 All had bill differences
In 1858, Darwin Published his book
The Origin of Species
Darwin’s Theories:
 Descent
with Modification: the newer
forms in the fossil record are actually the
modified descendants of older species
 all living things probably descended from
one (or a few) common ancestors
 similar organisms arise in the same
geographic locations
Cont.
 Modification
by Natural Selection: how
evolution occurs
 natural selection-process by which
organisms with favorable variations
reproduce at higher rates than those
without variations
Fitness
 The
ability to reproduce successfully
 The environment “selects” traits that will
increase in a population
Adaptation

The ability of an
organism to change
in order to help the
organism survive in
a given environment
 Unfavorable traits
gradually disappear
because the
organisms die out
Factors that Affect Natural
Selection
Overproduction- producing more
offspring than can possibly survive
2. Competition – food and resources
are limited. (only the strongest
survive)
3. Variations – slight differences among
offspring
1.
Organisms change over time
through mutations and sexual
reproduction