Biodiversity is the total diversity of living systems. In IB ESS Subtopic 3.1, it is examined at three interconnected levels: genetic diversity, species diversity, and ecosystem diversity. This is core content for both SL and HL.
| Level | Meaning and example |
|---|---|
| Genetic diversity | The variety of genes and alleles within a species or population. For example, different traditional rice varieties may possess different genes for drought tolerance or disease resistance. Greater genetic variation increases the likelihood that some individuals can survive environmental change. |
| Species diversity | The diversity of species within a community. It combines species richness, the number of species present, and species evenness, how equally individuals are distributed among those species. A forest with many species but dominated by one species may have lower diversity than a forest with similar richness but greater evenness. |
| Ecosystem diversity | The variety of ecosystems or habitats within an area, including their communities and environmental conditions. Madagascar, for example, contains rainforests, dry forests, wetlands and coastal ecosystems, each supporting different communities. |
These levels are connected. Low genetic diversity can make a population less resilient, increasing its risk of extinction and reducing species diversity. Species loss can then alter interactions such as pollination or predation, affecting the stability of the wider ecosystem.
A common misconception is that biodiversity means only “the number of species.” This describes species richness, not biodiversity as a whole. Biodiversity also includes genetic variation, species evenness and the variety of ecosystems.
Conservation priorities may emphasize different levels depending on environmental perspectives and social needs. Protecting a habitat can conserve many species simultaneously, while seed banks may protect genetic diversity important for future food security.
