Biodiversity & Resilience (HL IB Environmental Systems & Societies (ESS))

Understanding Biodiversity

Why is biodiversity important?

• 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 habitats, species and genes within a particular region

• It can be assessed at three different levels:

  • The number and range of different ecosystems and habitats

  • The number of species and their relative abundance

  • The genetic variation within each species

• Biodiversity is very important for the resilience of ecosystems

  • This is because biodiversity allows them to resist changes in the environment and avoid ecological tipping points

Habitat diversity

• This is the range of different habitats within a particular ecosystem or biome

• 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

  • The conditions are basically the same throughout the whole area

Species diversity

• An ecosystem such as a tropical rainforest that has a very high number of different species would be described as species-rich

  • Species richness is the number of species within an ecosystem

• Species diversity looks at the number of different species in an ecosystem, 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 are among each species, then the greater the 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

Genetic diversity

• Genetic diversity is the diversity of genes found within different individuals of a species

• Although individuals of the same species will have the same set of genes, these genes can take a variety of different forms

• This makes it possible for genetic diversity to occur between populations of the same species

• Genetic diversity within a single population also occurs

  • This diversity is important as it can help the population adapt to, and survive, changes in the environment

  • This could include changes in biotic factors such as new predators, pathogens and competition with other species

  • Or the changes could be abiotic factors like temperature, humidity and rainfall