Species Richness (AQA A Level Biology): Revision Note

Species richness

• Species richness is the number of species within a community

• Species richness is the simplest way to measure species diversity

• A community with a greater number of species will have a greater species richness score

  • For example, a tropical rainforest has a very high number of different species, so it would be described as species-rich

• Species richness can be a misleading indicator of diversity, as it does not take into account the number of individuals of each species

  • For example, habitat A has 10 plant species (1 individual each), while habitat B has 7 species but over 20 individuals per species

  • Although habitat A is more species-rich, habitat B has greater abundance and evenness

  • This highlights the limitation of species richness — it doesn’t account for population size or distribution

• Conservationists often favour the use of an index of diversity as it takes into account species number and evenness