4.2.1. Biodiversity

• What is a keystone species?

  • have a significant effect on ecosystem
  • many other species rely on them
• How do the following promote biodiversity?

  • construction of dams; flooded areas upstream, reduces flow rate downstream creating still/ slow moving water for aquatic species
  • felled trees; open up tree canopy allowing light to ground level
  • build lodges; creates sheltered habitat for insect species
• Explain how improvements in habitat diversity improves species and genetic diversity

  • more species live in the new habitats
  • species have a wider range of conditions to live/ adapt to
• Describe allopatric speciation

  • species become separated from original habitat and cause evolution because of different selection pressures and environmental conditions to the mainland
  • random mutations could also occur
  • advantageous characteristics to adapt to the new environment causes these individuals to survive and reproduce
  • beneficial alleles passed on
  • causing directional selection
• Conditions for speciation

  • mutation/ genetic diversity
  • natural/ directional selection
  • the environment/ selection pressure differs from mainland
  • time
  • reproductive isolation
• How do you use a belt transect to measure biodiversity?

  1. lay tape measure out
  2. place quadrat besides tape measure at constant intervals
  3. identify species in the quadrat
  4. count number of plants of each species
  5. repeat for positions of quadrat along tape
• How would you sample all stages of succession in a habitat?

  use a belt/ line transect and stratified sampling
• How would you minimise sampling bias?

  random selection of sites or set quadrats in intervals along the transect
• How do you sample insect biodiversity?

  pooter, sweeper nets, pitfall traps, light traps and tree beating