~ 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