2.1 Introduction to Biodiversity

What is biodiversity?

Biodiversity is the variety of life across three levels: genetic diversity (variation within a species), species diversity (number and variety of species in an area), and ecosystem diversity (variety of habitats, communities, and ecological processes). High biodiversity generally makes ecosystems more resilient and stable.

Measuring species diversity

Species diversity combines species richness (the number of different species) and species evenness (how equally individuals are distributed among species). An ecosystem with many species but one dominant species has lower evenness and diversity than one where species are more equally abundant.

Why biodiversity matters

Biodiversity supports ecosystem services like nutrient cycling, pollination, and climate regulation. Greater genetic diversity increases a population's ability to adapt to disease and environmental change, while greater ecosystem diversity provides more niches and resources, buffering against disturbances like habitat loss or climate shifts.

Key terms

Biodiversity

The variety of life, measured at the genetic, species, and ecosystem levels.

Genetic diversity

Variation of genes and alleles within a species, increasing adaptability to change.

Species richness

The number of different species present in a given area.

Species evenness

How equally individuals are distributed among the species in an area.

Ecosystem diversity

The variety of habitats, communities, and ecological processes within a region.

Try an AP-style question

Which statement is correct?

1. A has greater richness
2. Same richness; A has greater evenness
3. Same evenness; B is more diverse
4. B has greater richness