Unit 8.3

• Community


  An assemblage of populations interacting with one another within the same environment
• Species composition


  A listing of various species in the community
• Species diversity


  Includes both species richness and the abundance of different species
• Habitat


  The area where an organism lives and reproduces
• Ecological niche


  The role a species plays in its community, including its habitat and interactions with other organisms
• Fundamental niche


  All conditions under which the organism can survive, in the absence of biotic factors
• Realized niche


  The set of conditions under which a species does survive in nature, where biotic factors are present
• Competition between populations


  • Members of different species try to utilize a limited resource
  • Abundance of both species is negatively impacted
• Competitive Exclusion Principle


  No two species can indefinitely occupy the same niche at the same time
• Resource partitioning


  Decreases competition between species by leading to niche specialization and less niche overlap
• Character displacement


  Characteristics tend to become more divergent when populations belong to the same community than when they are isolated
• Predation


  One living organism, the predator, feeds on another, the prey
• Prey defenses


  • Heightened senses
  • Speed
  • Protective armor
  • Protective spines or thorns
  • Tails or appendages that break off
  • Poisonous chemicals
  • Camouflage
  • Warning coloration
  • Flocking behavior
• Batesian mimicry


  Mimic lacks defense of the organism it resembles
• Müllerian mimicry


  Mimic shares a protective defense with other species
• Parasitism


  Parasite derives nourishment from a host, and may use host as habitat and mode of transmission
• Commensalism


  A symbiotic relationship in which one species benefits and the other is neither benefited nor harmed