Populations in Ecosystems

• Define community?

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

  All the living (biotic) organisms found in one area, combined with non-living (abiotic) aspects of the environment.
• Describe biotic and abiotic factors?

  • Biotic - living features of an ecosystem (predators, disease)
  • Abiotic - non-living features of an ecosystem (light, temperature)
• Define habitat?

  Place where an organism lives in an ecosystem
• Define niche?

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

  The maximum size of population an ecosystem can support
• Name 4 abiotic factors that affect population growth?

  1. Temperature
  2. Light
  3. pH
  4. 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, lights, mates (intraspecific only).
• 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
• 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 & colonise the area
  • They change abiotic factors of the environment (decomposition adds nutrient to ground)
  • Over 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 shrub, 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 in question
• How might succession be managed in order to aid conversation?

  Sometimes succession need to be prevented in order to preserve an ecosystem at a certain point (e.g., stopping moorland from progressing into spruce forest). This is called plagioclimax