Biodiversity

• Biodiversity


  The variety of living organisms
• Levels of biodiversity

  • Habitat diversity
  • Species diversity
  • Genetic diversity
• Habitat diversity


  The number of different habitats in an area
• Habitat diversity examples

  • Coastal area: beaches, sand dunes, mudflats, salt marshes
  • River valley: meadows, agricultural fields, streams, woodland
• Species diversity


  The number of different species (species richness) and the abundance of each species (species evenness) in an area
• Species diversity example


  • Woodland: many different species of plants, insects, birds and mammals
• Genetic diversity


  The variation of alleles (versions of a gene) within a species or a population of a species
• Genetic diversity examples


  • Human blood type determined by a gene with three different alleles
  • Variation in alleles within the dog species gives rise to different breeds
• Random sampling


  Ensuring each sample site has the same probability of being chosen
• Random sampling procedure

  1. Divide habitat into a grid

  2. Use random number generator to select coordinates

  3. Take samples from selected coordinates
• Non-random sampling


  Necessary when there is a lot of variety in the distribution of species and you want to ensure all different areas are sampled
• Types of non-random sampling

  • Systematic sampling
  • Opportunistic sampling
  • Stratified sampling
• Systematic sampling


  Samples taken at fixed intervals, often along a line
• Systematic sampling example


  • Quadrats placed along a transect line in a field
• Opportunistic sampling


  Samples chosen by the investigator, simple to carry out but data will be biased
• Stratified sampling


  Different areas in a habitat are identified and sampled separately in proportion to their part of the habitat
• Stratified sampling example

  • Heathland with patches of gorse - heath and gorse areas sampled separately
• Ethical considerations when collecting biodiversity data
• Steps for estimating biodiversity using samples

  1. Choose a site to sample

  2. Record number of different species or count number of each species

  3. Repeat sampling process

  4. Estimate total population from sample data
• Species richness


  The number of different species in an area
• Species evenness


  The abundance of each species in an area
• Species richness and evenness example


  • Habitat X has 2 species with 1 individual each, habitat Y has 2 species with 10 individuals each - habitat Y has higher species evenness
• Simpson's Index of Diversity


  A measure used to calculate the diversity of a habitat
• When sampling different habitats and comparing them, biologists use the same sampling technique. For example, if you're using a pitfall trap, you should make sure they're set up in the same way and left for the same length of time. If you're using a Malaise funnel, keep the light source the same distance from the top of the funnel and keep it for the same amount of time, e.g. 2 days.
• Practical investigations

  • Investigating the impact of mowing on the biodiversity of a school playing field by sampling a mowed and an unmowed field. Calculate the biodiversity for each field using Simpson's Index.
• Species richness


  The number of different species in an area. The higher the number of species, the greater the species richness.
• Species evenness


  A measure of the relative abundance of each species in an area. The more similar the population size of each species, the greater the species evenness.
• The greater the species richness and evenness in an area, the higher the biodiversity. The lower the species richness and evenness, the lower the biodiversity.
• Habitat X and Habitat Y

  • Both contain two different species and 30 individual organisms. In Habitat X, there are 28 organisms in species 1 and 2 organisms in species 2. In Habitat Y, there are 15 organisms of each species. Habitat Y has greater species evenness and therefore higher biodiversity.
• Simpson's Index of Diversity

  Accounts for both species richness and species evenness, rather than just treating all species equally regardless of their abundance.
• Biodiversity can be considered at the level of habitat diversity, species diversity or genetic diversity.
• Factors affecting biodiversity

  • Human population growth
  • Habitat loss
  • Over-exploitation
  • Urbanisation
  • Pollution
• Human population growth

  • Decreases biodiversity because of habitat loss, over-exploitation, urbanisation and pollution.
• Habitat loss


  • As the human population grows, more land is developed for housing and agriculture, destroying habitats and decreasing habitat diversity. This also decreases species diversity.
• Habitat loss

  • Deforestation in the Amazon to make way for grazing and agriculture decreases habitat diversity.
• Over-exploitation


  • Greater demand for resources like food, water and energy means resources are being used up faster than they can be replenished. This can destroy habitats or affect species directly, decreasing genetic and species diversity.
• Over-exploitation


  • Industrial fishing can deplete the populations of certain fish species and even cause extinctions, decreasing genetic and species diversity.
• Urbanisation

  • Sprawling cities and major road developments can isolate species, meaning populations are unable to interbreed and genetic diversity is decreased.
• Urbanisation


  • Populations of some animals, like snakes, living in areas isolated by roads show lower genetic diversity than populations in continuous habitat.
• Pollution


  • As the human population grows, we're producing more waste and pollution. High levels of pollutants can kill species or destroy habitats, decreasing biodiversity.