Chapter 24

• Carrying capacity

  maximum size of a population
• Label the phases in a population growth curve

  A) slow growth

  B) rapid growth

  C) stable state, no growth

  D) carrying capacity

  
• Explain phase 1 of a population growth curve

  • slow growth
  • small number of individuals present reproduce increasing the total population - birth rate higher than death rate so pop increases
• Explain phase 2 of a population growth curve

  • rapid growth
  • as number of breeding individuals increases, total population multiplies exponentially
  • no constraints act to limit the population explosion
• Explain phase 3 of a population growth curve

  • stable state
  • further growth is prevented by external constraints
  • birth rates & death rates are approximately equal
  • slight increases & decreases can be accounted for by fluctuations in limiting factors (e.g. presence of predators)
• Limiting factors

  determine the size to which a population can grow
• Examples of abiotic limiting factors

  • temperature
  • light
  • pH
  • availability of water or oxygen
  • humidity
• Examples of biotic limiting factors

  • predators
  • disease
  • competition
  • migration
• Immigration 


  • movement of individual organisms into a particular area
  • increases population size
• Emigration 


  • movement of individual organism away from a particular area
  • decreases population size
• Density independent factors 


  • affect a whole population regardless of its size
  • include earthquakes, fires, volcanic eruptions & storms
  • can dramatically change population size & in some cases can remove whole populations of a species from a region
• Interspecific competition


  • competition between different species for the same resource
  • results in reduction of resource available to both populations
  • less well adapted species is likely to be outcompeted - if conditions remain the same the less well adapted species will decline in number until it can no longer exist in habitat alongside the better adapted species
• Competitive exclusion principle 


  where 2 species are competing for limited resources, the one that uses the resources more effectively will ultimately eliminate the other
• Intraspecific competition 


  • members of the same species compete for the same resource
  • availability of resource determines population size - greater availability = larger population can be supported
• Effects of intraspecific competition

  fluctuations in number of organisms present in a population over time

  1. when resource is plentiful in a habitat, all organisms have enough of resource to survive & reproduce - increases population size
  2. as result of increased population, resources are now limited & there is not enough available for all organisms to survive - population decreases
  3. smaller population means less competition exists, so more organisms survive & reproduce - population increases

  
• Predator-prey relationships

  • stage 1: increase in prey population provides more food for predators, so more survive & reproduce - increase in predator population
  • stage 2: increased predator population eats more prey organisms - decreases prey population
  • stage 3: reduced prey population can no longer support large predator population, intraspecific competition for food increases - decrease in predator population
  • stage 4: reduced predator population results in less prey population being killed, more prey survive & reproduce - increase prey population