Biotics factors affecting organisms

• Biotic factors affecting the abundance & distribution of organisms
• Biotic factors are living elements of an ecosystem, such as plants and animals
• Availability of food:

  • All animals require food to live
  • The availability of food is a major factor in how many animals live in an ecosystem
  • Areas like rainforests with rich food supplies have more species of life than other areas like deserts and the Polar Regions where there is less food
• New predators:

  • The arrival of new predators in an ecosystem can have a devastating effect
  • In balanced ecosystems, predators and prey have evolved together
  • The arrival of a new predator can upset this balance
  • Example: introduction of the red fox to Australia causing concern over their effect on native birds and small mammals
• New pathogens:

  • When organisms inhabit new ecosystems, they often bring new pathogens
  • Example: Europeans colonising North America and introducing new pathogens like the influenza virus
  • Example: Ash dieback disease caused by a fungus killing many ash trees in the UK since 2012
  • Example: Myxomatosis, a disease affecting rabbits, purposefully released in the UK in the 1950s to reduce the rabbit population
• Out-competition:

  • Introduction of a new species into an ecosystem can result in it out-competing another native species
  • Example: grey squirrels brought over from North America out-competing the native red squirrel in the UK
  • Other examples include the Canada goose in Europe, the cane toad in Australia, Himalayan balsam in Cambodia, and harlequin ladybirds