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A4.2 Conservation of Biodiversity

A4.2.1 Biodiversity

There are three levels of biodiversity:

  • Ecosystem: the different ecosystems on Earth

  • Species: the different species in a community

  • Genetic: the different alleles in a population

Factors forming biodiversity of species:

  • Species richness: total number of different species in an area

  • Species evenness: relative abundance of each species in an area

A4.2.2 Current vs Past levels of Biodiversity

From Fossil evidence general trend: Biodiversity has generally increased since the origin of life (speciation > extinction)

A4.2.3 Causes of anthropogenic species extinction

Main cause of current biodiversity crisis:

  • Human population growth

  • Specific causes:

  • Hunting (and overexploitation)

  • Urbanisation

  • Habitat loss due to deforestation & agriculture

  • Pollution

  • Introduction of invasive species and disease

A4.2.4 Causes of Ecosystem Loss

Covered implicitly by:

  • Habitat loss (deforestation, agriculture, urbanisation)

  • Pollution

  • Invasive species

  • Overexploitation

A4.2.5 Evidence for a Biodiversity Crisis

Accepted evidence: Repeated biodiversity surveys from many habitats around the world.

A4.2.6 Causes of the Current Biodiversity Crisis

General cause: Human population growth

Specific causes includes: Hunting, Urbanisation, Habitat destruction, Pollution, Invasive species & Diseases.

A4.2.7 Need for Several Approaches to Conserve Biodiversity

In situ conservation: conservation of species in their natural habitat. Some examples include nature reserves, rewilding

Advantages:

  • Species have resources they’re adapted to

  • Large populations can be maintained

Ex situ conservation: Conservation of species in artificial environment. Some examples include captive breeding (e.g. zoos), seed banks, botanical gardens

Advantages:

  • Greater control of conditions

  • Increased reproduction rates

Disadvantages:

  • Doesn’t prevent habitat destruction & May lead to inbreeding

  • Reintroductions into wild less successful

A4.2.8 EDGE of Existence programme

EDGE stands for Evolutionarily Distinct and Globally Endangered. It is a global conservation initiative developed by the Zoological Society of London (ZSL). The EDGE of Existence programme prioritizes species for conservation based on two main criteria:

  • Evolutionarily distinct: few or no close relatives, irreplaceable

  • Globally endangered: species at risk of extinction

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