3.8 Threats to biodiversity

• Describe what is meant by over exploitation.

  When a natural resource is harvested at a greater rate that it can be replaced.
• State which component of biodiversity is affected by over exploitation.

  The genetic diversity.
• Describe what is mean by the ’bottleneck effect’.

  Occurs when the size of a population is greatly reduced. This will reduce genetic diversity.
• The bottleneck effect causes a decrease in genetic diversity. Explain why this is a disadvantage.

  Smaller populations will not be able to respond to environmental change. They will be forced to inbreed and this can result in poor reproductive rates.
• The bottleneck effect leads to small populations inbreeding . why is this a disadvantage?

  This can result in an increase in the frequency of individuals who are homozygous for recessive alleles.
• What causes habitat fragmentation?

  The clearing of natural habitats.
• Describe the impact of habitat fragments degrading.

  Results in increased competition between species as fragments become smaller.
• State which component of biodiversity is most affected by habitat fragmentation.

  Species diversity.
• Describe how scientists can solve the issues associated with habitat fragmentation.

  Habitat corridors which link isolated habitats.
• State the benefits of building habitat corridors.

  Increases access to food

  Increases access to mate

  Allows recolonisation of small fragments after local extinction
• State the definition of an introduced species.

  A species that is moved to a new geographical location either accidentally or intentionally.
• State the definition of a naturalised species.

  When an introduced species becomes established within wild communities.
• State the definition of an invasive species.

  A naturalised species becomes invasive if it:

  -spreads rapidly

  -Eliminates native species
• Give two reasons why an invasive species might reduce species diversity.

  -Invasive species preying on the native species

  • outcompeting them for resources
  • hybridising with the native species
• State selection pressures invasive species are free from.

  The predators, parasites, pathogens, and competitors that limit their population in their native habitat.