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Unformatted text preview: relative to K, then growth will be nearly
exponential!
!
! 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 lifehistory strategies! dN/dt = rN [1(N/K)]!
Maximum growth rate is
reached at K/2! dN/dt = rN [1(N/K)]! dN/dt!
Growth accelerates
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 rselected 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!
Kselected 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
same time)!
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!
Agespeciﬁc 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

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