Chapter 53

• Population Ecology


  Explores how biotic and abiotic factors influence the abundance, dispersion, and age structure of populations
• Population Density Factors

  Biotic and abiotic factors affect population density, dispersion, and demographics
• Dispersion 


  The pattern of spacing among individuals within the boundaries of the population
• Mark-Recapture Method

  Capture, tag, and release sample of individuals in a population.(s) Capture second sample of individuals(n) and note how many are marked. (x) N=population size

  N= sn/x
• Emigration 


  The movement of individuals out of a population
• Patterns of Dispersion 


  Most common pattern is CLUMPED, this is when individuals aggregate in patches.
• Benefits of clumped

  • resource availability
  • Mating Behavior
  • Group defense against predators
• Uniform dispersion 


  Individuals are evenly distributed. Influenced by territoriality, the defense of other individuals.
• Random Dispersion 


  The position of individual is independent of other individuals
• Demography 


  Study of these vital statistics of a population and how they change over time
• cohort 


  group of individuals of the same age
• Survivorship curves 


  Graphic way of representing the data in a life table
• Survivorship Curves

  • Type 1: low death rates during early & middle life and an increase in death rates among older age groups
  • Type 2: A constant death rate over the organism's life span
  • Type 3: High death rates for the young and a lower death rate for survivors
• Reproductive Rates 


  Reproductive output for sexual organisms is measured as the average number of female offspring produced by the females in an age group
• population growth rate equation

  $N/t =$$B-D$

  N is the change in population size, t is the time interval, B is the number of births, and D is the number of deaths
• Exponential Population growth

  Population increase under idealized conditions
• Carrying Capacity 


  (K) is the maximum population size the environment can support
• Logistic model

  describes how a population grows more slowly as it nears its carrying capacity
• The logistic Model and real populations

  S-shaped curve. These organisms are grown in a constant environment lacking predators and competitors
• Organisms life history

  • The age at first reproduction (maturity)
  • How often the organism reproduces
  • How many offspring reproduced
• Semelparity

  Reproduce one and die
• Iteroparity

  repeated reproduction, produce offspring repeatedly
• Density-independent

  populations, birth rate, and death rate don't change with population density
• Density-dependent

  populations, birth rates fall, and death increase with rising population density
• Factors of density-dependence

  • Competition for resources
  • Disease
  • Predation
  • Territoriality
  • Toxic wastes