BIOL 121 Lecture Notes - Convergent Evolution

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6 Apr 2012

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Evolution 2: Evidence for the evolution March 5th, 2012
- The Theory of Evolution has not been “proven” but it has not yet been disputed, therefore it is
the best theory we have to date
- Evidence for Darwin’s theory, The Decent with modification
1. Species can change through time
Past organisms
a. Fossil records imprints of organisms in the rock stratum (each stratum represents a
geological time era), usually the “hard parts” of organisms are left behind (ex. Shells) or
sometimes tracks
*Through these tests the Earth has been determined to be ~4.6 billion years old
Billions of years ago = bya
Millions of years ago = mya
*It is estimated that life first emerged ~3.5bya
b. Extinctions species that were once here and are no longer here
Darwin explained that this occurs because these species were not ‘fit’ (their species was
out competed and they did not leave enough off springs) = Evolutionary Deadends
c. Transitional Forms extinct species that are similar to species that are observed today
Darwin explains that this is because species can change over time
Ex. How terrestrial animals water animals; Whales
Present day organisms
a. Vestigial Traits traits seen on the organism that serves no purpose
(Ex. Human “tail bones”)
b. Artificial Selection -
* Homoplasy: different ancestral origins
*Convergent evolution
* Analagous
1. Stuctural homology: the structure is inherited from a previous ancestor
2. Developmental homology: the structure of embryos
3. Genetic homology:
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