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20 Cards in this Set
- Front
- Back
Population ecology
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the study of how and why population size changes over time and the effects that population change has on the population.
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r =
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per capita growth rate, b - d
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N =
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population size
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rN =
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rate of population growth
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Exponential Growth Equation:
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(dN/dt) = rN
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in the exponential growth equation, r is typically considered as a
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maximum r or rmax
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Logistic or Sigmoid growth involves three stages
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i. Initial exponential growth.
ii. Decelerating growth rates. iii. Fluctuations around some “average” population size, often called K or carrying capacity of the environment. |
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Logistic equation:
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(dN/dt) = rN((K-N)/K)
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in the logistic equation N = and K =
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i. N = current pop. size
ii. K = the highest value that N can take or the “carrying capacity” of the environment |
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in the logistic growth equation, r is typically considered as a
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relative or rrel
(How an individual can reproduce relative to the influence population size has on the individual) |
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The exponential model doesn’t take into account
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the limit that resources place on populations
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Carrying Capacity (K).
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the point at which the population size is in equilibrium with resources
ii. Or the number of individuals of a species that the environment can support. iii. Or the number of individuals that can survive in the environment. |
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Demography
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the study of factors that determine the size and structure of a population over time
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Demography involves
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the age classes, sex ratio, rates of immigration and emigration, survivorship, mortality, and fecundity of a population
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Life tables
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summarize the probabilities that an individual age class will survive and reproduce in any given year over the individual’s lifetime, based on survivor ship
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cohort
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All the individuals that are born at the same time, and are thus represented by an age class
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Type I survivorship curve:
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Typified by having a large percentage of survivors throughout much of the individual’s life time, which is followed by a rapid decline in individuals within the cohort. Examples include: humans, and some plants.
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Type II survivorship curve:
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Typified by a relatively constant decline in survivorship throughout the life of the species. Examples include: independent birds (although your book just says “birds”), and many perennial plants.
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Type III survivorship curve:
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Typified by having a low survivorship (high mortality) early in the life of the organism, followed by a fairly high survivorship throughout the remainder of the lifespan. Examples include: many annual plants, and most invertebrates, fish
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i. Fecundity
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the number of offspring an individual can have in its lifetime
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