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Evolution
There is no 'Great Plan" out there to
conform with the evolutionary theory,
just organisms struggling to pass their
genes on to the next generation. That's
it."
History of Evolution
Important Players
James Hutton
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Published studies in 1785
Geologist
Theory of Uniformity- the earth was
created by the same forces that are in
existence today (plate tectonics)
Before Hutton, world was thought to be 6000
years old and formed by catastrophic events,
not geological ones
His research supported that the Earth to be
millions of years old
Thomas Malthus
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Worked with human population
studies
Observed that plants and animals
reproduce at a greater rate than
their ability for survival, creating
competition within a species
Important to Wallace and Darwin’s
theory
Jean-Baptiste Lamarck
1809- 1st to develop a scientific theory of
evolution known as Theory of inheritance of
acquired characteristics:
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Organisms developed new organs or modified old
ones to meet environmental challenges
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Working toward perfection- more complex, more
perfect
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Selective use or disuse would alter the size or
shape of organs or structures passed to offspring
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Examples Larmarck Observed
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Long Neck giraffes - short neck
giraffes that strained to reach higher
branches would grow longer necks
Fiddler crabs large claw (male) developed one larger front claw
because it used to claw often to attract
mates and ward off predators
Lamarck’s Theory
Proven to be False
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Change DNA by usage of the structures
(BOGUS! Mendel was not yet born so little
was known about genetics). Think of body
building and passing that on to your
offspring
No extinction of species, just changed into
other organisms
Lower order organisms were spontaneously
created to fill the void (nothing was due to
chance).
Alfred Wallace
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1850’s
Naturalist
Developed a theory similar to Darwin’s
His essay to Darwin motivated Darwin
to publish the book, On the Origin of
Species.
Charles Darwin
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1830’s
Known as the “Father of Evolution”
Naturalist on the HMS Beagle (shipping
vessel) collecting specimens of flora and
fauna and created detailed written
observations
Inspired by the biological diversity of the
Galapagos Islands
Voyage of the Beagle
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5 year voyage began in 1831
Only 5 weeks spent on the Galapagos
Islands
Found endemic species
Saw variations of organisms on the
different islands (thought that this could
be modification due to environment)
Evolution Terms
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Evolution – descent with modification /
changes over time
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Adaptation – inherited characteristic that may
increase organisms chance of survival
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Speciation – formation of new species
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Species – group of similar organisms that can
breed in nature and reproduce fertile
offspring.
Evolution Terms
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Homologous Structures – similar structures
found in different organisms that serve
different functions
Analogous Structures – structures that are
different in form but have the same
function.
Evidence of Evolution
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Biochemistry – DNA and amino acids
Embryological Development
Fossil Record
Morphology – form and structure of
organisms without consideration of function
Vestigial Organs - structure that no
longer serves a useful function in an
organism (ex. Human appendix)
Fossils
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Age of fossils can be determined by:
1. analyzing its position in the sedimentary layers
2. Radioactive dating
Archaeopteryx – earliest bird
(had reptilian and bird –like
characteristics
Vestigial Organ
4 Mechanisms for Change
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Natural Selection
Mutation
Migration
Genetic Drift
Why are brown beetles
more prevalent in a
population?
Each of the 4 mechanisms will change the
gene pool frequency
Natural Selection
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Process in which organisms with
favorable traits (traits well suited for
their environment) are more likely to
survive and reproduce
Survival of the Fittest or the “Sexiest”
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Imagine that green beetles are easier for
birds to spot (and hence, eat). Brown beetles
are a little more likely to survive to produce
offspring. They pass their genes for brown
coloration on to their offspring. So in the next
generation, brown beetles are more common
than in the previous generation.
Mutation
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change in DNA sequence that causes a
variation in the offspring
A mutation could cause parents with
genes for bright green coloration to have
offspring with a gene for brown
coloration. This would make the genes
for brown beetles more frequent in the
population.
Migration
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Some individuals from a population of
brown beetles might have joined a
population of green beetles. That would
make the genes for brown beetles more
frequent in the green beetle population.
Genetic Drift
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“Pure chance”
Imagine that in one generation, two brown
beetles happened to have four offspring
survive to reproduce.
Several green beetles were killed when
someone stepped on them and had no
offspring.
Patterns of Evolution
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Founder Effect
Speciation
Punctuated equilibrium
Adaptive/Divergent Radiation
Convergent evolution
Coevolution
Founder Effect
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Organisms become separated or
isolated and the gene frequency
changes
Founding organisms arrived on different
islands of the Galapagos and due to the
different availability of food slowly
changed the gene pool of the
population.
Speciation
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Reproductive isolation causes new
species to form
Types of Isolation:
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Behavioral
Geographic
Temporal
Punctuated Equilibrium
Pattern of evolution in which long stable
periods are interrupted by brief periods
of more rapid change
Hardy-Weinburg Theory
 No movement in or out of the
population
 No mutations
 No natural selection forces
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Evolution Terms
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Adaptive/Divergent
Radiation – process
that causes a single
species to evolve into
new forms and
eventually new species
Homologous Structures
Evolution Terms
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Convergent Radiation
process by which
unrelated organisms
come to resemble one
another because of
similar environment
Analogous structures
Cactus and spurge are another example
of convergent evolution.
Coevolution
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Two species that evolve in harmony
with one another because of the close
interaction they have with each other