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27 Cards in this Set
- Front
- Back
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population
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a group of interbreeding or potentially interbreeding organisms of the same species in the same locale
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exponential growth
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- young individuals are added to the population continuously
- overlapping generations - in an unlimited environment dN/dt = (b – d)N which leads to dN/dt = rN r =instantaneous per capita rate of growth - EQUATION to PREDICT EXPONENTIAL GROWTH => N(t) = N(0)er^(t) - overlapping or continuous |
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geometric growth
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- young are added to the population seasonally or at discrete intervals
- in an unlimited environment - Equation (Model) for predicting growth: N(t) = N(0)[lambda]t where [lambda] = growth rate - discrete or seasonal |
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Biotic potential
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in an unlimited environment
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Unlimited Growth
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---species are introduced
---species receive protection ---exotics or invasives in a novel habitat |
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x
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age class or interval
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n(x)
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number of survivors at beginning of age interval x
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d(x)
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number of individuals dying between age interval x and interval x + 1
n(x)-n(x-1) |
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l(x)
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proportion of organisms surviving to beginning of age interval x
n(x)/n(0) |
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q(x)
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rate of mortality between age interval x and x + 1
d(x)/n(x) |
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L(x)
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average number alive in given age class
[n(x)+n(x+1)]/2 |
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T(x)
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intermediate step to get life expectancy, total years lived into future by age class
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e(x)
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life expectancy
T(x)/n(x) |
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Age-Specific Life Table Assumptions
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- Each age class was sampled in proportion to its actual numbers in population
- age-specific mortality and birthrates have been constant over time. |
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R values
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R0 = 1…….replacing self….population stable
R0 < 1…….not replacing self…..population declining R0 > 1…….more than replacing self…population growing |
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fecundity
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females produced by females
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lambda
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= N(t+1)/N(t)
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R(0)
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= l(x)*m(x)
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m(x)
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= F(x)/n(x)….where F(x) = total number of young or seeds and n(x) = number of parents
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stochasticity
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---Random variability
---should be incorporated in any population model ---based on statistical probability of random, unexpected events |
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sx
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= survivorship = 1 -qx
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Demographic Stochasticity
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random events that alter demographics
(birth, death, age distribution etc.) |
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Environmental Stochasticity
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…random variations in environment
(climate, storms, drought etc) |
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Allee Effect
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decline in either reproduction or survival when population density is low
--organisms with large territories or that are widely dispersed may have trouble finding mates --organisms dependent on pheromones or chemical cues may have trouble finding mates ---may be difficult for pollinators to find target species ---may be a breakdown in social structure…leading to greater predation or starvation |
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Some Causes of Susceptibility to Extinction
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Blue whale
---reproductive rate Carolina Parakeet ---behavior Everglades Kite --special diet |
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logistical growth
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has an upper limit, aka carrying capacity
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3 GENERAL TYPES OF SURVIVORSHIP CURVES
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Type I - mammals
Type II - birds, small mammals, lizards, turtles Type III - many invertebrates |
