Interconnections between species

• What is a population in ecological terms?

  A population is a group of organisms of the same species living in the same geographic region.
• What three specific features can populations be described by?

  Distribution, size, and density.
• What are keystone species?


  Species that have a greater effect on the ecosystem than expected given their population size.
• What are the types of relationships between species in an ecosystem?

  • Mutualism (+/+): Both organisms benefit.
  • Commensalism (+/0): One benefits, the other is unaffected.
  • Predation (+/–): One hunts and kills the other for food.
  • Parasitism (+/–): One obtains nutrients at the expense of a host.
  • Amensalism (0/–): One is harmed, the other is unaffected.
  • Competition (–/–): Both compete for the same resources.
• What are the five main levels of ecological organization?

  1. Cell: Individual cells of a larger organism.
  2. Organism: An individual living thing.
  3. Population: A group of the same species in a region.
  4. Community: Interacting populations of different species.
  5. Ecosystem: Multiple communities and their physical environment.
• What is population size?


  The total number of members within any given population.
• What is carrying capacity?


  The maximum number of individuals an environment can support sustainably.
• What components alter a population's size?


  Total births, deaths, immigration, and emigration.
• What are r-selection and K-selection reproductive strategies?

  • r-selection: Produces many offspring with little parental care; high mortality rate.
  • K-selection: Produces few offspring with high parental care; stable population growth.
• What does population distribution refer to?


  The geographical spread of a species across different areas.
• What are the three types of population distribution?

  Uniform, random, and clumped arrangements.
• What is population density?


  The number of individuals found in a given area.
• How do density-independent factors affect populations?


  They are properties of the environment that are unaffected by density changes.
• How do density-dependent factors affect populations?


  They change with the density of a species and become stronger as density increases.
• What are examples of density-independent and density-dependent factors?

  Density-independent factors:

  • Climate
  • Natural disturbances
  • Unlimited resources

  
  

  Density-dependent factors:

  • Disease
  • Predation
  • Competition
  • Resource availability
  • Waste accumulation
• What happens to population growth at low densities?


  Population growth can be exponential.
• What is the effect of increasing density on population growth?


  Population growth rate slows until it remains constant.
• What is mutualism?


  A relationship where both organisms benefit from interacting.
• What is an example of mutualism?


  Coral and photosynthetic algae living together.
• What is commensalism?


  A relationship where one organism benefits and the other is unaffected.
• What is predation?


  Interactions where one organism hunts and kills another for food.
• What is parasitism?


  A relationship where one organism obtains nutrients at the expense of another.
• What is amensalism?


  A relationship where one organism is harmed while the other is unaffected.
• What is competition?


  Interactions where two organisms compete for the same resources.
• What is interspecific competition?


  Competition between individuals of different species.
• What is intraspecific competition?


  Competition between individuals of the same species.
• What are keystone species?


  Species that play a disproportionate role in maintaining ecosystem structure.
• What happens when a keystone species is removed?


  It typically has a larger effect on the ecosystem than the removal of other species.
• What is an apex predator?


  A predator that has no natural predators and is at the top of its food chain.
• What is the role of apex predators in ecosystems?


  They control the numbers of their prey and other organisms in the ecosystem.
• What are ecosystem engineers?


  Organisms that create, significantly alter, or maintain the structure of an environment.