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Selection and community interaction. Selection: composite of the forces that limit the reproductive success of the genotype Fitness: comparative ability of a genotype to withstand selection Frequency dependent selection : selection against a gene depends on its frequency within the population. - PowerPoint PPT Presentation
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Selection and community interaction
Selection: composite of the forces that limit the reproductive success of the genotype
Fitness: comparative ability of a genotype to withstand selection
Frequency dependent selection: selection against a gene depends on its frequency within the population
Batesian mimicry: a palatable species mimics an unpalatable species and gains protection from predation
Batesian mimicry
Monarch butterfly(distasteful)
Viceroy butterfly(tasty)
Muellerian mimicry
Muellerian mimicry: 2+ unpalatable species share similar aposematic coloration
both species distasteful
Selection & industrial melanism
Peppered moth
http://web.nmsu.edu/~wboeckle/biston.html
Departure from highest fitness
it is quite as dangerous to be conspicuously above a certain standard of organic excellence as it is to be conspicuously below the standard
Bumpus 1899
Departure from highest fitness
Human birth weight
Selection modes - stabilizing
Selection modes - directional
Selection modes - disruptive
If some of these many species become modified and improved, others will have to be improved in a corresponding degree or they will be exterminated
Darwin 1859
Community interactions
Through the looking glassLewis Carroll"Now, here, you see, it takes all the running you can do, to keep in the same place."
Community interactions
Red Queen hypothesis - organisms have to evolve as fast as they can just to stay in the same place
Community interactions
predation commensalism mutualism
amensalism neutralism
competition
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0
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spec
ies
A
species B
Community interactions
Competition - two groups depend on same limited resource so each group leads to a demonstrable reduction in numbers of the other
Community interactions
Resource partitioning - species minimize harmful effects of direct competition by using different aspects of their common environment
Character displacement - measurable phenotypic differences accompany resource partitioning
Community interactions
Competitive exclusion - two groups cannot coexist in the same ecological niche
Owing to the high geometrical rate of increase of all organic beings, each area is already fully stocked with inhabitants; and it follows from this, that as the favored forms increase in number, so generally will the less favored decrease and become rare
Darwin, 1859
Community interactions
Coevolution: evolutionary changes in 1+ species in response to changes in other species in the same community
-can lead to an evolutionary ‘arms race’
Coevolution
Coevolution
Cospeciation: speciation process that occurs in 2 interacting species simultaneously
Coevolution