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11 Cards in this Set
- Front
- Back
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density dependent factors
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Biotic: Competition, resources, immunity
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density independent factors
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Abiotic: Weather, Fire, Storms, etc
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four phases of population cycle
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-increase
-peak -decline -low density |
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increase phase
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-densities rise rapidly
-survival high -sexual maturity reached quickly -breeding begins early in spring, often continues into winter -high dispersal |
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peak phase
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-increase ceases
-mortality low -sexual maturity reached late summer breeding is brief; no winter breeding -dispersal moderate |
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decline phase
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-Precipitous drops in numbers, or uneven declines lasting > 1 yr
-Summer breeding brief; no winter breeding -Dispersal low -Mortality high |
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low density phase
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-lasts 1-3 yr
-breeding season short -sexual maturity reached very late -mortality high |
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Christian Stress hypothesis
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-stress at high population density led to increased mortality and reduced reproduction
-Stress hormones are immunosuppressive and lead to increased disease |
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problems with Christian Stress hypothesis
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-Physiological responses are not consistently associated with high population levels
-Populations housed indoors at higher than wild densities did not show increased mortality -Increased parasite/disease not seen in wild |
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Chitty behavioral-genetic hypothesis
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Genetic propensity for behavior types
-Low density: high interaction behaviors (mate finding/tolerance) -High density: increased aggression, cometition for limited resources -Links evolutionary and ecological factors in a general theory |
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factors affecting populations
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-litter size
-predators -competition -dry season resources -social interaction |
