Biodiversity & Resilience (HL IB ESS OLD COURSE - IGNORE)

Revision Note

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

Photograph of a coral reef
A coral reef is an example of an ecosystem with high biodiversity due to high habitat diversity (Photo by Francesco Ungaro on Unsplash)

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

Photograph of pine forest
The lack of species diversity in the pine forests of Florida makes them vulnerable to collapse when pathogens enter the ecosystem (Photo by Worm Funeral on Unsplash)

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

Diagram showing the three components of biodiversity
Biodiversity is a broad concept encompassing the total diversity of living systems, which includes habitat diversity, species diversity and genetic diversity

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Alistair Marjot

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Alistair graduated from Oxford University with a degree in Biological Sciences. He has taught GCSE/IGCSE Biology, as well as Biology and Environmental Systems & Societies for the International Baccalaureate Diploma Programme. While teaching in Oxford, Alistair completed his MA Education as Head of Department for Environmental Systems & Societies. Alistair has continued to pursue his interests in ecology and environmental science, recently gaining an MSc in Wildlife Biology & Conservation with Edinburgh Napier University.

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