4.6 Biodiversity

• What is a community?

  A community is populations of different species that are living in the same habitat.
• What are the three components of community diversity?

  • (S)pecies Diversity.
  • (G)enetic Diversity.
  • (E)cosystem Diversity.
• What is species diversity?

  This is the number of species within a community.
• What is genetic diversity?

  This is the number of alleles of genes in a population.
• What is ecosystem diversity?

  This is the range of habitats within one area.
• Why is species diversity important?

  The higher the species diversity the more stable the ecosystem is and the less it is affected by change. A community with a high species diversity index will likely have at least one species able to tolerate the change.
• What is the impact of agriculture on biodiversity?

  1. Farmers may select a species for particular characteristics that make them more productive.
  2. Pesticides may be used to exclude species that compete with the farmed species.
  3. Monocultures are created which replace natural meadows with a single type of crop.

  All of these are severe to decreasing biodiversity, as the number of species and the genetic variety of their alleles is limited.
• The balance between conservation and farming.

  Conservation aims to increase biodiversity by protecting a particular habitat to encourage more species to grow and live here.

  Examples of this include; maintaining hedges instead of fences, maintaining ponds, crop rotation, using natural meadows for hay instead of grass for silage.
• The impact of plant diversity on animal diversity.

  A reduction in plant biodiversity from agriculture or deforestation causes a reduction in animal diversity because there is:

  • Less variety in habitats
  • Less variety of food sources (NOT less food)

  The opposite effects are obtained from conservation methods.
• What are the advantages and disadvantages of land clearance for agriculture?

  Advantages:

  • Increased productivity/yield of food crops.
  • Cheaper grazing for cattle and hence cheaper food.

  Disadvantages:

  • There's a loss of habitat so predator population may decrease and more pesticides may be needed.
  • There's a reduced habitat and so species diversity is also reduced.
  • More fertiliser will need to be used.
• What are the advantages and disadvantages of planting more hedges?

  Advantages:

  • An increase in species & biodiversity and so an increase in predators so less crop is damaged resulting in a higher yield and income.
  • There will be an increase in pollinators so crop yields will increase, resulting in more income.

  Disadvantages:

  • There's a reduced land area for crop growth and therefore less income.
  • It's more difficult to farm so less income.