AP Biology Chapter 53

1
AP Biology Chapter 53

• Population Ecology
• Concerned with measuring changes in population
  size and composition, ecological, and
  evolutionary causes of these fluctuations.

2
Population consists of individuals of a single
species that

• Simultaneously occupy the same general area
• Rely on the same resources
• Are influenced by similar environmental factors
• Have a high likelihood of interactions among
  themselves

3
Population characteristics

• Density of individuals per unit of area
• counts
• sample size
• estimate
• indirect indicators- of nests or burrows,
  droppings
• mark-recapture
• Dispersion pattern of spacing
• random unpredictable, patternless
• not very common
• clumped patchy aggregation (b)
• most common
• uniform even spacing (c)
• usually related to
  competion
• for resources, produces territories
  or spaces

4
Demography factors that affect growth decline
of populations

• Birthrate (natality, fecundity) of offspring
  produced
• Death rate (mortality)-greatest in first year and
  old age
• Immigration
• Emigration
• Age structure relative number of individuals of
  each age
• Survivorship curve plot of numbers still alive
  at each age

5
Survivorship Curves

• Type 1 curve-low death rate during early and
  middle ages drops steeply
• Type 2 drops sharply at left side of graph

6
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

7
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

8
Population limiting factors

• Density-dependent factors
• predation
• competition
• stress/crowding
• waste accumulation
• Density-independent factors
• weather/climate
• periodic disturbances