Advanced ecology

• Population


  All the members of the same species living in an area
• Factors that control the size of a population

  • Competition
  • Predation
  • Parasitism
  • Symbiosis
• Competition


  Organisms actively struggle for a resource that is in short supply
• Competition for resources


  • Plants compete for light, space, water and minerals
  • Animals compete for food, water, shelter, territory and mates
• Intra-specific competition


  Competition between members of the same species
• Intra-specific competition


  • between members of the same species
• Inter-specific competition


  Competition between members of different species
• Contest competition


  A physical competition between two organisms with only one winning the resource (winner takes all)
• Scramble competition


  Each organism tries to get as much of the resource as possible
• Scramble competition


  • Rabbits competing for grass
• Predation


  The catching, killing and eating of another organism
• Predator


  The animal that catches, kills and eats
• Prey


  The animal killed and eaten
• Predator-prey relationship


  • Used in the area of biological control of pests, involving the use of one organism to control the numbers of another
• Example of Predator-prey relationship

  • Ladybirds are used to control aphids
• Adaptations of predators


  • Hawks and other birds of prey have excellent sight so they can locate their prey
  • Ladybirds have strong mouth parts to enable them to chew aphids
• Adaptations of prey


  • Frogs are well camouflaged so that they are hard to see and attack
  • Ladybirds contain large amounts of formic acid which is unpalatable to predators
• Parasitism


  An intimate relationship between two organisms where one organism, the parasite, lives on another organism, the host. The parasite benefits and the host is harmed.
• Examples of Parasitism

  • Potato blight, Tapeworms, liverfluke in sheep
• Ectoparasites


  Live on the outside of the host
• Examples of Ectoparasites

  • Fleas on a dog
• Endoparasites


  Live inside the host
• Examples of Endoparasites

  • Liverfluke in sheep or cattle
• Symbiosis


  An intimate relationship between two organisms of different species where at least one of the species benefits
• Examples of Symbiosis

  • Nitrogen-fixing bacteria in the nodules of plants such as clover. The bacteria gain food, shelter, anaerobic conditions and the clover gets nitrates
• Population


  all the members of the same species living in an area
• Compétition


  Organisms actively struggle for a resource that is in short supply