BY4.5 Populations

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Population Size

  • organisms live in groups and communities
  • this is advantageous as they gain protection from predators and will breed and rear young more sucessfully

Population growth

Population: a group of organisms in a single species that can interbreed and occupy a particular area

4 stages of population growth:

  • lag phase
    • little or no population growth
    • adaption to environment occuring, preparation for growth, protein production, enzyme synthesis
  • log phase
    • exponential growth
    • population doubles in size every given unit of time
    • as the population grows, more individuals are available to breed
  • stationary phase
    • birth rate is equal to death rate
    • certain factors will limit population growth
    • population has reached its maximum size (carrying capacity) which describes the limit to the number of individuals an area can support
  • death phase
    • death rate is greater than birth rate
    • i.e when food sources have depleted

Factors that limit population growth:

Environmental resistance: all factors that may limit the growth of a population

this includes:

  • the availability of food
  • predation
  • parasitisim
  • disease
  • overcrowding
  • competition
  • accumulation of toxins

once the population is esatbished, its growth is determined by the birth rate (BR…


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