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~ Population Ecology

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Chapter 53 ~ Population Ecology Changes to population size Adding & removing individuals from a population birth death immigration emigration Population ... – PowerPoint PPT presentation

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Title: ~ Population Ecology


1
Chapter 53
  • Population Ecology

2
Changes to population size
  • Adding removing individuals from a population
  • birth
  • death
  • immigration
  • emigration

3
Population characteristics
  • Density of individuals per unit of area
    counts sample size estimate
    indirect indicators
    mark-recapture
  • Dispersion pattern of spacing random
    unpredictable, patternless spacing (a)
    clumped patchy aggregation (b)
    uniform even spacing (c)

4
Demography factors that affect growth decline
of populations
  • Birthrate (natality, fecundity) of offspring
    produced
  • Death rate (mortality)
  • Age structure relative number of individuals of
    each age
  • Survivorship curve plot of numbers still alive
    at each age

5
Population Growth Models
  • Exponential model (red)  idealized population in
    an unlimited environment (J-curve) r-selected
    species (rper capita growth rate)
  • Logistic model (blue) carrying capacity (K)
    maximum population size that a particular
    environment can support (S-curve) K-selected
    species

6
Carrying capacity
  • Can populations continue to grow exponentially?
  • of course NOT!
  • what sets limit?
  • resources, predators, parasites
  • Carrying Capacity (K)
  • maximum population size that environment can
    support with no degradation of habitat
  • not fixed varies with changes in resources

7
Model of growth
  • Decrease in rate of growth as reach carrying
    capacity

8
Population life history strategies
  • r-selected (opportunistic)
  • Short maturation lifespan
  • Many (small) offspring usually 1 (early)
    reproduction no parental care
  • High death rate
  • K-selected (equilibrial)
  • Long maturation lifespan
  • Few (large) offspring usually several (late)
    reproductions extensive parental care
  • Low death rate

9
Different life strategies
  • K-selection
  • r-selection

K-selection
mortality constant
r-selection
10
Population limiting factors
  • Density-dependent factors competition
    predation stress/crowding
    waste accumulation
  • Density-independent factors weather/climate per
    iodic disturbances

11
Age structure
  • Relative number of individuals of each age

What do the data imply about population growth in
these countries?
12
Human population
2005?6 billion
  • What factors have contributed to this exponential
    growth pattern?

1650?500 million
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