3.4.6 Biodiversity within a community

• The types of biodiversity include species diversity, genetic diversity and ecosystem diversity.
• Species richness is a measure of the number of different species in a community.
• Genetic diversity is the number of different alleles of each gene or the differences in base sequences in a population.
• Ecosystem diversity is the number of habitats within an ecosystem.
• An index of diversity describes the relationship between the number of species in a community and the number of individuals in each species.
• Natural ecosystem

  • Complex communities
  • High index of diversity
  • Very stable
• Agricultural ecosystem

  • Controlled by humans
  • Farmers select crops/animals to increase productivity - reduction in allele frequency
  • Environmentally harmful processes are used to increase yields
  • Remaining organisms have little resources so they cannot survive
  • Low index of diversity
• Selecting crops/animals with desired characteristics/high productivity

  • Farmer gets a high number of crop/animal with a particular characteristic (high yield)
  • More food
  • Higher profit
  • Reduces genetic diversity (allele frequency) as the crop/animal will be very similar genetically
  • Reduces species diversity as less plants = less food/habitats for insects/birds etc.
• Pesticides (insecticides, herbicides and fungicides are chemicals that destroy insects, plants and fungi)

  • Destroys organisms that could feed on crops which would reduce yield
  • Direct reduction in species diversity
  • Bioaccumulation – reducing species diversity
• Artificial fertilisers (NPK are sprayed on fields)

  • Boost plant growth – N and P needed to make DNA and proteins
  • Eutrophication - reducing species diversity
• Destroying hedgerows (shrubbed boundaries around fields) and replacing with fences

  • More space for growing crops
  • Less plant species
  • Less food and habitats for insects/birds
• Filling natural ponds/destroying wetlands

  • More space for growing crops
  • Decreases species diversity – lack of habitats for aquatic organisms and the species that rely on them
• Monocultures (only growing one crop species per field)


  • Increased yield for a particular crop
  • Decreases genetic diversity as all organisms are very similar to each other
  • Decreases species diversity to as less insects/animals etc.
• Practices recommended by conservation scientists

  • Preserving ponds/wetlands
  • Creating hedgerows – increases biodiversity and also more predators of pests so can use less pesticides
  • Organic farming – using natural fertilisers and NO pesticide use
  • Intercropping – growing different crops in the same area
• The need for global food provision increase has led to intensive farming.