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Unformatted text preview: relative to K, then growth will be nearly
! What happens if N > K??!
(derivation of this is in Appendix at end of lecture slides)! Graphically:! r and K from the logistic growth eqn. are borrowed to
describe the ends of a continuum of life-history strategies! dN/dt = rN [1-(N/K)]!
Maximum growth rate is
reached at K/2! dN/dt = rN [1-(N/K)]! dN/dt!
nearly exponentially as
1-(N/K) is small (density
dependence weak)! area under this curve Growth rate decelerates to
zero as N=K and 1- (N/K)
approaches zero! high r, do well in exponential growth r-selected species (high intrinsic rate of population growth) ! traits that are successful when densities are far from K and popn growth is
driven by r : early reproduction, large number of offspring with little
parental care, etc.! N!
K-selected species (traits that are favored when population sizes
are near K): large investment in few offspring; continuous
reproduction, etc.! So how do we get to estimate things like r ?! Survivorship Curves! Demography: a study of the vital statistics (birth, death) of a population
and how they vary with age!
Life table: vital statistics of a cohort (group of individuals born about the
Survivorship (lx) =
proportion of individuals
surviving to age or stage x!
Reef coral (marine invertebrates) Type I: most individuals survive to old age (large mammals)!
Type II: constant probability of dying (some birds)!
Type III: most newly born individuals die, but survival of adults is high!
#(most commonly observed: marine invertebrates, insects, plants)! Can also use life table approach to look at the value of each age class!
Age-speciﬁc fecundity (mx) average number of offspring
produced by an individual of
age or stage x! Net Reproductive Rate (R0) = ave...
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- Spring '13