AQA A Level Biology复习笔记4.6.1 Biodiversity Within a Community

• Biodiversity can be thought of as a study of all the variation that exists within and between all forms of life
• Biodiversity looks at the range and variety of genes, species and habitats within a particular region
• It can be assessed on different scales
  • The number and range of different ecosystems and habitats on the entire planet
  • The number of species and their relative abundance within a small, local habitat (like a pond)

   

• Biodiversity is very important for the resilience of ecosystems, in that it allows them to resist changes in the environment

Ecosystem or habitat diversity

• This is the range of different ecosystems or habitats within a particular area or region
• If there is a large number of different habitats within an area, then that area has high biodiversity
  • A good example of this is a coral reef. They are very complex with lots of microhabitats and niches to be exploited

   

• If there is only one or two different habitats then an area has low biodiversity
  • Large sandy deserts typically have very low biodiversity as the conditions are basically the same throughout the whole area

   

Species diversity

• The mix of different species that exist within a particular area or region can be measured to indicate levels of biodiversity
• It can be measured in different ways: species richness and species diversity
• Species richness is the number of species within a community
  • An ecosystem such as a tropical rain forest that has a very high number of different species would be described as species-rich

   

• Species diversity looks at the number of different species in a community, and also the evenness of abundance across the different species present
  • The greater the number of species in an ecosystem, and the more evenly distributed the number of organisms is among each species, then the greater the species diversity
  • For example, an ecosystem can have a large number of different species but for some species, there may only be 3 or 4 individuals. As a result, this ecosystem does not necessarily have high species diversity

   

• Ecosystems with high species diversity are usually more stable than those with lower species diversity as they are more resilient to environmental changes
  • For example in the Pine forests of Florida, the ecosystem is dominated by one or two tree species. If a pathogen comes along that targets one of the two dominant species of trees, then the whole population could be wiped out and the ecosystem it is a part of could collapse

   

Maintaining biodiversity

• There are many different reasons why maintaining biodiversity is beneficial
• Biodiversity impacts all organisms (including humans) on a global scale

Reasons for maintaining biodiversity table