Populations and ecosystems

• What is succession?

  The gradual change in an community overtime.
• Difference and speeds of primary and secondary succession:

  Primary succession is when organisms colonise a lifeless habitat. This is slow.

  Secondary succession is when organisms re-colonise a devastated ecosystem. This is faster as soil is already created.
• Define interspecific competition:

  Individuals of different species compete for the same essential resource.
• Define intraspecific competition:

  Individuals of the same species compete for a resource- leads to a healthier population.
• 6 stages of succession:

  1. Bare ground
  2. Colonisers
  3. Pioneers
  4. Herbaceous plants
  5. Shrubs
  6. Stable climax community
• What is each stage known as during succession?

  A seral community.
• The 2 actions which form soil:

  erosion of rocks by weathering and death and decay of organic matter
• 5 features emerging from succession:

  1. Abiotic environment becomes less hostile and more habitable
  2. Greater number and variety of habitats / niches
  3. Greater biodiversity (until climax community)
  4. More complex food webs
  5. Increase in biomass
• What are abiotic factors?

  The ecological factors that make up the non-living environment of an organism. e.g. pH, rainfall
• Define community:

  Populations of different species living in the same habitat.
• Define ecosystem:

  A community and the non-living components of its environment.
• Explain the advantage of species occupying different niches:

  Less competition for food / resources
• Describe and explain how succession occurs: (6)

  • colonisation by colonisers and pioneers changes the abiotic environment e.g. becomes less hostile
  • enables other better adapted organisms to colonise and outcompete previous species
  • increases biodiversity
  • stability increases due to root network development and more complex food webs
  • the final stage is known as the climax community
• Reasons for stability in succession:

  1. root network development
  2. increase in soil quantity and quality
  3. more complex food webs
• What is the purpose of conservation?

  managing the environment to ensure that plants and animals are preserved
• 5 ways of preventing succession:

  1. grazing by animals
  2. ploughing of land
  3. mowing of lawns
  4. use of herbicide
  5. growing crops
• Reasons for conservation- ethical, economical and cultural:

  ethical- other species should be allowed to coexist

  economical- living organisms can provide millions of substances which could result in financial gain

  cultural- habitats and ecosystems enrich our lives
• 2 features of a climax community:

  1. abiotic environment more or less constant
  2. species remain for a long period of time
• Explain how succession results in a wide variety of fish living on coral reefs. Do not describe the process of succession (2)

  Increase in diversity of species and biodiversity provides more food sources and habitats / niches.
• Where can conflict arise during the conservation of succession? Give an example of how this is managed:

  There is conflict between human needs and conservation in order to maintain the sustainability of natural resources.

  e.g. forests are coppiced - provides timber for furniture and fuel, but the tree can still survive