factors affecting populations

• Population – A group of animal or plants that can interbreed
• abiotic - the non-living aspects of an ecosystem e.g. light, temperature, water availability, oxygen availability and soil pH.
• Biotic - The living components of an ecosystem e.g. food availability, pathogens, predators and other species.
• Consumers - Organisms that feed on other organisms to obtain energy.
• Producers - Photosynthetic organisms at the start of the food chain that manufacture biomass for all living things
• Phase 1: slow growth

  • Small number of organisms limit reproduction
  • More births than deaths = increased population

  
• Phase 2: rapid growth

  • Exponential growth caused by increased number of breeding individuals and no limits to population increase.

  
• Phase 3: stable state 

  • External factors prevent further increase in population
  • Birth rates = death rates ( approximately)
  • Fluctuations caused by changes in limiting factors

  
• Immigration – The movement of an organisms to an area
• Emigration – The movement of organisms away from an area
• Density independent factors – Factors that impact a population size independent of the current size of the population
• Density dependent factors – Factors that affect a population based on its density or size