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Transcript of Charles Darwin
On the origin of species
Naturalism: precursors for Darwin
18th century contributions to "Naturalism"
- Fixity and special creation became discredited
- Extinction of species
- Taxonomy (binomial nomenclature)
- Mass extinction events
- Old world
- Mechanism for evolution suggested:
- Diversity + Adaptation
- Possible common decent
- Vestigial Structures
Darwin sets sail
- Given task to expand knowledge of natural resources of the british empire
Darwin observed intensely varied geological and biological diversity along his journey
Many of his observation led him to theorize about the relation all organism have to one another
Animals of the Galapagos Islands
Each Galapagos Island had its own type of tortoise
Darwin perceived this to be a result of the differing environments the islands displayed
Ex: Island with lots of low foliage had short necked turtles
- populations have inheritable variations
- populations produce more offspring than an environment can support
- some traits allow individuals to better compete for resources (fitness)
- Thus the favored trait will increasingly be passed down to the following generations
- Humans choose specific desirable traits
- ex: Several variations of dogs can be traced to a common ancestor
Survival of the fittest?
fitness - an organisms ability to survive and reproduce in environment
.... as a result, traits that increase an organisms fitness are more likely to be passed on to subsequent generations
Mutations? good, bad or otherwise...
- permanent change in the sequence of bases in DNA
-spontaneous(no apparent reason)
- random chemical changes
- copying errors
- caused by mutagens (radiation and organic chemicals) called carcinogens(cancer causers)
- When specific traits that lead to increased ability to secure a mate.
- Because females generally produce few eggs, mate selection becomes a serious consideration
- Good gene hypothesis
- Runaway hypothesis
-Inheritance of specific traits determined by ecology alone
- Without direct sexual competition when
-e.g. sexual competition is strictly ecological
-there is little or no mate choice,
-females do not resist any male who wishes to mate,
-all traits will be equally propagated regardless of mating
-or the species is hermaphroditic or asexually reproducing (bacteria)