Biotic and abiotic factors

• Biotic factors

  The living parts of an environment
• Abiotic factors

  The non-living parts of an environment
• Biotic factors

  • Availability of food
  • Arrival of a new predator
  • Competition between species
  • New pathogens
• Availability of food

  All animals eat other living organisms, whether animals or plants
• Availability of food falls

  Number of organisms in that community will also fall
• Arrival of a new predator

  Can cause the population of a prey species to fall, and affect existing predators
• Competition between species

  If a species is out-competed, its population can fall to the point where it becomes extinct
• New pathogens

  If an infectious disease emerges and spreads, it can wipe out a population of a species
• Abiotic factors

  • Light intensity
  • Temperature
  • Water
  • pH and mineral content of soil
  • Wind intensity and direction
  • Carbon dioxide
  • Oxygen
• Light intensity


  Can have a major effect on plants, as they need light to carry out photosynthesis
• Light intensity is too low

  Rate of photosynthesis falls, and plants will grow more slowly
• Temperature

  Can cause the distribution of species to change, as animals migrate and plant species disappear
• Water

  Both plants and animals need water to survive
• pH and mineral content of soil

  Many plants cannot grow in soil that is too acidic or too alkaline, and they need certain minerals like nitrate
• Wind intensity and direction

  Can affect plants, for example causing them to lose water
• Carbon dioxide

  Needed for plants to photosynthesize, and if levels fall, the rate of photosynthesis can decrease
• Oxygen

  Needed for aerobic respiration, and low levels of dissolved oxygen in water can be harmful to aquatic organisms