Evolution Review Spring 2015 (Not all-inclusive, but a good overview)
Charles Darwin:
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Observed differences in organisms of the same species (natural variation)
Observed that some of these differences made some organisms in the population more
fit for their environment (fitness)
Inferred that fitness allowed organisms to survive, reproduce and then they would pass
on the alleles that are most fit (natural selection)
This is different than artificial selection where humans decide which organisms get to
reproduce and pass on specific alleles that humans decide are most fit or desirable
Made observations in the Galapagos Islands on tortoises and finches while sailing on the
HMS Beagle
Wrote all of his ideas in a book entitled, “On the Origin of Species by Means of Natural
Selection” which outlined HOW organisms evolved (natural selection)
Common descent – idea that all organisms had a common ancestor, but due to
mutations, different organisms were created over LOTS of time. So people/humans did
NOT evolve from monkeys!!! But humans and monkeys share a common ancestor –
which is why humans and monkeys have many similar features.
Other Scientists:
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Lyell and Hutton – geologists who thought:
o the earth was millions of years old (but it is really BILLIONS of years old)
o slow gradual changes in the landscape made huge changes over time
 ex. A river erodes dirt … over time it creates the Grand Canyon
Lamarck – created “rough draft” of Theory of Evolution, even though he was wrong
about most things!
Peter and Rosemary Grant – worked in the Galapagos and saw evolution over decades
(see last section of this handout)
Evidence for Evolution:
1. Biogeography – study of where organisms live now compared to their ancestors. This
helps with patterns of distribution and how organisms evolved.
2. The Fossil Record – provides a series of fossils that show slight changes over time
(depending on where the fossils are found you can tell how old they are) which support
evolution.
3. Age of the Earth – Billions of years old … this allowed enough time for the evolutionary
changes to occur
4. Homologous structures – structures shared by related species to show how they may
have evolved from a common ancestor (bone structure of human arm and frog – page
468)
5. Embryology – the study of embryos and how many different organisms share very
similar structures when they are embryos (human {page 999} and cat embryos {page
469} share many features - )
6. Common genetic code – the fact that ALL living organisms share the same 4 bases of
DNA (or RNA). This supports that all living organisms came from the same original
source.
7. Homologous molecules – small molecules that are shared by different species to
support that they evolved from a common ancestor (ex. Hemoglobin in human blood is
also found in other organisms, also gene for multiple legs is found in many organisms
{page 501})
Testing Natural Selection:
Peter and Rosemary Grant worked in the Galapagos Islands doing tests on finches. Over about
30 years they were able to see changes in the population of finches as a new species emerged.
They did this by collecting data to answer the following questions:
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Do birds have inherited natural variation?
Does this variation increase fitness?
There was a drought during the time of their experiment and this environmental factor created
a condition in which birds with stronger beaks were able to get food from a different source,
survive and reproduce … passing along the allele for a larger beak. They concluded:
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Environmental factors and competition drive natural selection.
(Drought) (birds with stronger beaks get food) (different population – more birds with
stronger beaks)