population size

• what is a limiting factor?

  An environmental factor that restricts the growth of a population in an ecosystem.
• what is meant by carrying capacity?

  maximum population size that can be maintained in a habitat
• what does a population growth curve look like?

  • lag (slow) phase
  • log (fast) phase
  • stable phase

  
• what happens in each phase of a population growth curve?

  • Lag- slow growth. small number of individuals initially present in the population reproduce and the growth of the population increases gradually
  • log - rapid growth. number of breeding individuals increases so the total population multiplies exponentially. No constraints to limit growth
  • stable phase- stable state. Further population growth prevented by external constraints. Population size fluctuates due to changes in limiting factors eg food supply. Birth and dearth rates equal approximately
• what factors are limiting factors divided into?

  • abiotic factors
  • biotic factors
• what three things generally have an affect on population size?

  • Migration
  • limiting factors
  • density independent factors
• what two types of migration are there?

  • Immigration- when the movement of organisms into a particular area increases population size
  • Emigration- the movement of organisms away from a particular area decreases population size
• what are density independent factors?

  • factors that have an affect on a population regardless of its size
  • factors that dramatically affect population sizes
  • eg earthquakes, volcanic eruptions or storms, which can sometimes cause the migration of an entire population from its habitat
• at what point in a population growth curve is death rate the highest?

  at the stable state