Evolution

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Evolution

• Change Over Time

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"Nothing in biology makes sense, except in light
of evolution." --Theodosius Dobzhansky
This is the most controversial scientific theory.
Yet, it is one of the strongest theories. The
amount of evidence supporting evolution is
greater than for almost any other theory.
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What is the Theory of Evolution?
(1) All life forms on earth developed from
earlier forms.
(2) All still living species continue to evolve
today.
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Two Types of Evolution
Microevolutionon a small scale, creating changes
in a population like we saw in Clipbirds Macroevol
utionon a big scale, forming totally new types
of organisms
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Mechanism of Evolution
How does it work? The easiest mechanism to
understand is Natural Selection.

• More organisms produced than can survive.
• Natural variation among individuals which is
  genetically controlled.
• Some individuals better adapted (fitter). They
  live longer and produce more babies.
• The population changes as more have that trait.

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Evidence for Evolution
Main areas of evidence include Anatomy Physiology
Embryology Molecular Biology (Genetics) Paleontol
ogy (Fossils)
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Anatomy
Homologous structureslook a lot the same even if
they have very different uses
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Physiology
How tissues and organs work in the body Vestigial
organsorgans or structures that are left over
in an imperfect form (they dont do any good any
more)
Erector pili and body hair
Wings on flightless birds
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Vestigial organs, cont.
Human tailbone (coccyx)
Eyes on blind fish living in caves
Wisdom teeth
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Vestigial organs, cont.
Human appendix 300,000 appendectomies in 2000 and
371 deaths from appendicitis
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Embryology
How an organism develops Organisms go through
some (not all) of the stages that their ancestors
went through
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Molecular Biology
Especially now that we have completed the genome
of many organisms, we can see just how close the
DNA is.
Genes from one animal can be put into another and
they work just fine. They are the same
gene. http//www.pbs.org/wgbh/evolution/library/03
/4/l_034_04.html
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Distribution of Related Species
100 species of marsupials in Australia but no
placental mammals (dog, cat, horse, bear)
New Zealand and Hawaii have unique plants and
animals.
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Fossil Record
Evidence of past life shows even more
variety. Some extinct forms show characteristics
that are in-between major groups. The more we
find, the more that gaps are filled in.