Ecological Rules

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Ecological Rules
2013-12-17 15:08:16

Final Exam
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  1. Thorson's Rule
    • R vs K strategists decline a long a gradient of decreasing latitude or water temperature applied to only marine invertebrates. 
    • Hypothesized mechanisms: 2 principal modes of development for mollusks and gastropods.
    • 1) the larva may become planktonic and disperse with the water currents away from the natal range.
    • 2) Many undergo direct development to adults in the natal home range.
  2. Gloger's Rule
    • More pigmented forms in humid areas. Animals are darker close to the equator. 
    • Animals have less intense pigmentation in less humid areas (higher latitude) 
    • There is more bacteria in humid areas and darker coloration provides better resistance to microbial organisms.
    • Better UV protection.
    • Examples: Birds
  3. Allen's rule
    • forms living in warmer environments (low elevation/low latitude) have longer appendages.
    • Shorter appendages promote heat conservation in cold environments by reducing total surface area for heat loss
    • Long appendages= heat dissipation (ears/legs)
  4. Rapoport's rule
    Tendency for geographic range size to increase with latitude
  5. Bergmann's rule
    • Body size of endotherms is positively correlated to latitude
    • fewer small endotherms at higher latitudes
    • improved cold tolerance
    • less evaporative cooling in large endotherms
    • Ex: Bears
  6. Vermeij's hypothesis
    • Greater predator and prey offenses/defenses toward lower latitudes
    • Greater diversity in tropics due to predation pressure causing prey speciation, which in turn contributes to predator speciation.
  7. Why biodiversity is higher in some regions than others.
    • Reduced seasonality
    • Greater number of niches
    • Predation/Competition
    • Time for speciation to occur
    • etc.