C4.1.9,4.1.11 populations

• Competition


  When individuals of the same population exist in a specific niche, there tends to be competition among them especially if the growth rate is increasing. They may compete for food resources, water, shelter, light, root space, etc.
• Cooperation


  Individuals within a population may help each other rather than compete. This is more evident in social animals that live within a herd. They may cooperate to escape a predator, or cooperate to hunt a prey.
• Examples of Cooperation

  • Escaping a predator
  • Hunting a prey
• Herbivory


  Primary consumers feeding on producers. The producer may or may not be killed.
• Predation


  One consumer species (the predator) killing and eating another consumer species (the prey).
• Interspecific competition


  Two or more species using the same resource, with the amount taken by one species reducing the amount available to the other species.
• Mutualism


  Two species living in a close association, with both species benefiting from the association.
• Examples of Mutualism

  • Mycorrhizal fungi growing into the roots of plants in the Orchidaceae family and exchanging nutrients with the orchid
  • Photosynthesizing zooxanthellae living in the cells of hard corals and exchanging materials with the coral
  • Nitrogen-fixing Rhizobium bacteria living in root nodules of plants in the Fabaceae family and exchanging materials with the plant
• Parasitism


  One species (the parasite) living inside, or on the outer surface of, another species (the host) and obtaining food from them. The host is harmed and the parasite benefits.
• Example of Parasitism

  • Ticks living on the skin of deer and feeding by sucking blood from the deer
• Pathogenicity


  One species (the pathogen) lives inside another species (the host) and causing a disease in the host.