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kamrunsreno
on FreezingBlue Flashcards.
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Vicariance Model
- a once continuous area split into two
- a barrier limits movement between areas
- (like the breakup of Pangaea)
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Dispersal Model
- movement of individuals away from an existing population, generally over long distances
- dispersal ability depends on the methods & pathways available
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Active Dispersal (vagility)
organism moves from one place to another under its own power
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Passive Dispersal (pagility)
organism carried by some other physical agent
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Corridor
- movement along continuous favorable habitat
- “easy” for many species
- (like the Berring Land Bridge)
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Filter (net)
- selectively blocks movement of some organisms
- organisms must be able to tolerate unfavorable habitat
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Sweepstakes
- a rare, chance dispersal from one place to another across a major barrier
- must survive journey to “new place”
- must be able to survive in “new place
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Generalities of Islands:
- dispersal =
- usually sweepstakes
- more plants than animals
- fewer species in higher trophic levels
- lots of endemism
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Hawaii
- 90% of species are endemic
- pre-human
- habitation
- no reptiles
- no amphibians
- only 1 mammal
- mostly birds & flying insects
- long-distance dispersal abilities
- 400 endemic fruit flies
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Dwarfism
- islands have limited space & resources
- more smaller animals can be supported
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Gigantism
- more resources
- less competition & predation
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General Evolutionary Trends:
- loss of dispersal ability
- long distance dispersal a liability
- loss of defensive mechanisms
- lack of predators
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