BY4.5 Populations

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…