Populations in ecosystems

• Define community

  All the different species that live in one area and interact with each other
• Define ecosystem

  ~All the living organisms found in one area, combined with non-living aspects of their environment

  ~Can vary from very large to very small
• Describe biotic and abiotic factors


  Biotic = living features of an ecosystem

  Abiotic = non-living features of an ecosystem
• Define habitat


  The place where an organism lives within an ecosystem
• Define niche

  The role of species within its habitat, consisiting of both its biotic interactions and abiotic interactions
• What is meant by carrying capacity

  The maximum size of population an ecosystem can support
• Name four abiotic factors that affect population growth

  ~Temperature

  ~Light

  ~pH

  ~Water/humidity
• What is meant by intraspecific and interspecific competition

  Intraspecific = competition between organisms of the same species

  Interspecific = competition between organisms of different species
• What resources might organisms compete for

  ~Food

  ~Water

  ~Shelter

  ~Minerals

  ~Light

  ~Mates
• Describe the pattern of a typical predator-prey relationship in terms of population change

  ~Prey is eaten by predator, resulting in predator population increasing and prey population decreasing

  ~Fewer prey means increased competition for food, so predator population decreases

  ~Fewer predators means more prey survives, and the cycle begins again
• How are quadrats used for estimating population size

  ~Can be placed on grid coordinates, or at intervals along a belt transect

  ~Results reported as either percentage cover or frequency

  ~For slow-moving or non-motile organisms
• How is mark-release-recapture used for estimating population size

  ~A sample of a species is captured, marked, then released back into the same area they were caught

  ~After a certain period of time another sample is captured, and the number of marked organisms are counted

  ~For motile organisms
• What is the equation for mark-release-recapture


  Estimated population size = total number of individuals in the first sample x total number of individuals in the second sample / number of marked individuals recaptured
• What assumptions does the mark-release-recapture method make

  ~Marked individuals distribute evenly

  ~No migration in or out of the population

  ~Few births or deaths

  ~Method of marking does not affect survival

  ~Mark does not come off
• Why are ecosystems described as being dynamic

  ~Populations constantly rise and fall

  ~Any small change can have a large effect

  ~Biotic and abiotic factors may alter the conditions of the ecosystem
• What is meant by primary succession

  Where an area previously devoid of life is colonised by a community of organisms
• Summarise the process of primary succession

  ~Pioneer species can survive harsh conditions and colonise the area

  ~They change abiotic factors of their environment

  ~Overt time, this allows more complex organisms to survive
• What is the climax community and how is it reached

  ~The final stage of succession, where the ecosystem is balanced and stable

  ~It is reached when the soil is rich enough to support large trees or shrubs, and the environment is no longer changing
• How might a species alter the environment that develops during succession

  ~A species may improve the environment to make it more suitable for other species

  ~Alternatively, a species may worsen the environment by making it less suitable for other species
• Define conservation

  ~The protection and management of species and habitats, in order to maintain biodiversity

  ~Methods need to be adapted to the ecosystem
• How might succession be managed in order to aid conservation

  ~Sometimes succession needs to be prevented in order to preserve an ecosystem at a certain point

  ~This is called plagioclimax