3.4.6

• Definitions

  Biodiversity = the variety of living organisms in an area

  It has 3 components:

  Species diversity – the number of different species and the number of individuals of each species within a community

  2. Genetic diversity

  3. Ecosystem diversity

  Habitat = places where an organism lives

  • Community = all the populations of different species in a habitat
• Biodiversity can relate to a range of habitats, from a small local habitat to the Earth; biodiversity can be considered at different levels

  Local biodiversity → the variety of species living in a small habitat e.g. pond / meadow

  • Global biodiversity → the variety of species living on Earth
• Quantifying species diversity

  Species richness

  The number of different species in a community

  Index of diversity

  • Describes the relationship between the number of species in a community and the number of individuals in each species
• The greater the species richness and species evenness, the higher the number

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  • Note: The lowest possible value of D is 1. The larger the value of D, the greater the diversity Index of diversity is a more useful measure of species diversity than species richness
• Index of diversity is a more useful measure of species diversity than species richness

  As well as measuring the number of species, it also measures the number of individuals in a species (different proportions of species)

  • So takes account for the fact that some species may be present in low/high numbers You could be given data from which to calculate an index of diversity and interpret the significance of the calculated value of the index
• Farming techniques reduce biodiversity

  Removal of woodland and hedgerows

  Monoculture e.g. replace natural meadows with one cereal crop

  Use of pesticides, herbicides and inorganic fertilisers

  • Crops better competitors for resources e.g. light / nutrients
• The balance between conservation and farming

  Humans need to make a balanced judgement between the demands for increased food production due to a rapidly growing human population, and the need to conserve the environment

  Some conservation techniques can be applied that increase biodiversity without unduly raising food costs or lowering yields, for example…

  • Use crop rotation of nitrogen fixing crops instead of fertilisers
• Maintain existing hedgerows and plant new hedges instead of using fences

  Reduce the use of pesticides

  • It is recognised that these practices will make food slightly more expensive to produce, so to encourage farmers there are a number of financial incentives e.g. from the Department for Environment, Food and Rural Affairs (DEFRA) and the European Union.