Transcript Evolutionary Theory (1)

Evolutionary Theory: Chapter
22
Evolution
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Evolution is change in a population over
time
The mechanism by which evolution
occurs is natural selection
The World Before Darwin
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Darwin published “On the Origin of
Species” in 1859, which challenged the
root of Western culture
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People thought the world was only a few
thousand years old and that the living things
on Earth were those that were created during
the 6-day creation period.
Many STILL DO & THAT IS FINE!!
Remember this is theory!
The World Before Darwin:
Jean Baptiste Lamarck
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Lamarck observed that there was change in
organisms over time and proposed a theory
with 3 parts:
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All organisms strive to survive.
This striving improves some body parts more than
others
The modifications that an organism acquires
during its lifetime are passed along to its
offspring.
Examples: blacksmith’s arms, giraffe’s necks
Charles Darwin: The Man
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Born in England in 1809;
dropped out of medical school
Went to divinity school
Sailed from Great Britain to
South America with the H.M.S.
Beagle in 1831
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Mission was to chart poorly
known parts of the South
American coastline
Darwin spent much of his time
looking at the flora and fauna of
South America, which differed
greatly from that of Europe
Galapagos Islands
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Darwin noticed that the
plants and animals on the
island archipelago
resembled those in South
America, but they were
slightly different
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Finches on different
islands had different
beaks, depending on the
available food supply
Giant tortoises
Darwin’s Theory of Evolution by Natural
Selection
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2.
3.
4.
There are heritable variations within
populations.
Some variations are favorable.
Each year, more offspring are produced than
can survive. Competition results!
Those that survive & reproduce are those who
possess the favorable traits. (“survival of the
fittest”)
5.
Over thousands of years, the favorable traits
become more common in the population and
the unfavorable traits disappear.
Evidence for Evolution
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There are many pieces of scientific
evidence that evolution has occurred
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The Fossil Record
Biogeography
Comparative Anatomy
Comparative Embryology
Molecular Biology
The Fossil Record
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A fossil is a preserved
remnant or impression
left by an organism
that lived in the past
Organisms are
compressed by
deposits (sand, silt,
etc.) and the “hard
parts” (teeth, bones,
etc.) may be preserved
as fossils
The Fossil Record
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The idea that all species were made/created at the same time is
NOT supported by the fossil record
With time comes increasing complexity of life
Georges Cuvier developed the field of paleontology (the study of
fossils)
Each stratum (layer) of rock is characterized by a unique group
of fossil species
The Fossil Record
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Relative Dating of Fossils:
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Fossils can be dated in relation to what is
found around them
Wallpaper analogy
Absolute Dating of Fossils:
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Since radioactive isotopes have fixed rates of
decay, they can be used to date a specimen
in years
Carbon-14 is used for relatively young fossils
(half life of 5600 years)
Biogeography
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Biogeography is the
geographical
distribution of species
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For example, species
found on islands are
found only there, but
are closely related to
species of the nearest
mainland or island
Comparative Anatomy
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Similar body structures are
evidence that two organisms
have a common ancestor
Homology
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Homologous structures:
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Similarity in characteristics
resulting from having a
common ancestor: Divergent
Evolution.
Anatomical signs of evolution
Vestigial structures:
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“leftover” structures that have
little to no use to an organism,
like the human appendix
Comparative Embryology
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Closely related organisms go through
similar stages in their embryonic
development
“Ontogeny recapitulates phylogeny”
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The development of an individual organism
(ontogeny) is a replay of the evolutionary
history of the species (phylogeny)
All Chordates share the following
characteristics:
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1. Rod shaped notochord for
support
2. Dorsal, hollow nerve cord
3. Pharyngeal gill slits at some point
in development.
4. Post-anal tail at some point in
development.
Molecular Biology
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There is much similarity among all living
things in our DNA sequences
There is a common genetic code for all
living things (ie. UUU codes for
phenylalanine in humans AND bacteria)
Even relatively unrelated organisms (like
bacteria and humans) have some amino
acid sequences/proteins in common