Evolution II(1) - Is all evolution via natural selection Is...

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Is all evolution via natural selection?
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Is all evolution via natural selection? No. Evolution can occur via genetic drift as a result of neutral evolution. This is especially true in small populations that are evolutionary “bottlenecks.”
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Do we have five toes due to adaptation or genetic drift? http://ag.arizona.edu/ENTO/tree/eukaryote s/animals/chordata/ichthyostega/10_Ichthy ostega_foot.JPG Early tetrapod species had 5- 8 toes. Our ancestor had 5 toes. http://universe-review.ca/I10-72-Acanthostega.jpg
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Evolution refers to change over time. It may be adaptive or neutral (as occurs with genetic drift).
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Selectionism vs. neutralism Selectionists believed that natural selection is the major agent of evolution and that every trait is determined by selection. Neutralists believed that most evolution is neutral but that natural selection also plays a role. On the molecular level, most change is neutral. On the organismal level (which is the level on which natural selection acts ) more of the change is subject to natural selection.
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Adaptation Adaptation --a feature of an organism that increases its fitness (ability to survive and leave offspring) . An adaptation is the result of positive selection and it is a heritable trait. Different from the use of the word “adapt” to mean a physiological change. i.e.--When one goes up a mountain it takes us a few days to “adapt” or “acclimate” to the higher altitude.
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“Adaptation” (acclimatization) to low oxygen At high altitudes, acclimatization takes place: more red blood cells and capillaries are produced to carry more oxygen. The lungs increase in size to facilitate the osmosis of oxygen and carbon dioxide. There is also an increase in the vascular network of muscles which enhances the transfer of gases. http://anthro.palomar.edu/adapt/adapt_3.htm We “adapt” (acclimate) to low oxygen because we have evolved mechanisms (adaptations) to do that.
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Bar-headed geese fly over the Himalaya mountains Enhanced O 2 affinity of hemoglobin due to a single amino acid substitution in a hemoglobin molecule. This is an adaptation that has occurred as a result of natural selection.
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How can we identify possible adaptations? Complexity “Design”: A trait that appears to perform a specific function. Phylogenetic uniqueness: it is a unique trait different from that found in related species. Environmental uniqueness: it is a unique trait found in specific environments (convergence).
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How can we identify possible adaptations? Complexity “Design” http://www.jcu.edu.au/interest/stingers/ nematocyst%20unfired.jpg http://upload.wikimedia.org/wikipedia/commons/ b/b0/Nematocyst_discharge.png http://articles.mercola.c om/ImageServer/public/ 2008/February/2.26boxj ellyfish.jpg
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How can we identify possible adaptations?
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