Biodiversity
Biodiversity describes the variety of life at genetic, species, and ecosystem levels. Understanding biodiversity helps explain community structure, ecological resilience, and why species richness and species evenness provide useful information about biological communities.
Follow the arrows to see how matter or diversity changes within an ecological system.
Biodiversity
What Is Biodiversity?
Biodiversity is the variety of life in a particular area or across Earth. It includes variation at multiple levels, including genetic diversity, species diversity, and ecosystem diversity.
High biodiversity does not simply mean that an area has many individual organisms. It describes the variety and distribution of life. Two ecosystems could contain the same number of individual organisms while differing greatly in biodiversity.
Biodiversity is broader than species count. It can include genetic variation within species, the variety of species, and the variety of ecosystems.
Genetic, Species, and Ecosystem Diversity
Genetic diversity is variation in genes or alleles within a species. It can give populations a greater range of traits and can increase the potential for some individuals to survive changing environmental conditions.
Species diversity refers to the variety of species in a community and includes both the number of species and their relative abundances. This is where concepts such as species richness and species evenness become especially important.
Ecosystem diversity refers to the variety of ecosystems and habitats within a region. A landscape containing forests, wetlands, streams, grasslands, and other habitat types has greater ecosystem diversity than a landscape dominated by one habitat.
Why Is Biodiversity Important?
Biodiversity can increase the range of ecological roles present in a community. Different organisms perform different functions, including capturing energy, cycling nutrients, decomposing organic matter, pollinating plants, controlling populations, and modifying habitats.
Greater biodiversity can also provide ecological resilience. If environmental conditions change, a diverse community may contain more organisms with traits or ecological roles that allow some populations to persist.
More ecological roles
Different species can contribute different functions to nutrient cycling, energy flow, predation, decomposition, and habitat structure.
More biological options
Genetic and species variation can increase the likelihood that some organisms can persist when conditions change.
What Happens When Biodiversity Declines?
Biodiversity can decline when species are lost, populations become genetically less variable, or habitats are simplified or destroyed. Major causes include habitat loss, habitat fragmentation, invasive species, pollution, overexploitation, and climate change.
A decline in biodiversity can reduce ecological interactions and alter ecosystem functions. However, the effects depend on which organisms are lost, how strongly they interact with others, and how the ecosystem responds.
How Do Ecologists Describe Biodiversity?
Ecologists use several measurements to describe communities. Species richness counts how many different species are present. Species evenness describes how evenly individuals are distributed among those species.
These measures are useful because a community with many species is not necessarily as balanced as another community with the same number of species. A community dominated by one species can have the same richness as a community in which individuals are distributed much more evenly.
Species Richness
How many species? Count the different species present.
Species Evenness
How balanced? Compare the relative abundances of the species present.
Common Misconceptions
If You See This on a Test, Think This
Quick Practice
1. What are three levels of biodiversity?
2. What does species richness measure?
3. What does species evenness measure?
4. Can two communities have the same richness but different evenness?
5. Why can biodiversity support ecosystem resilience?
Key Takeaways
- Biodiversity is the variety of life at genetic, species, and ecosystem levels.
- Genetic diversity is variation within a species.
- Species diversity includes species richness and species evenness.
- Ecosystem diversity describes the variety of ecosystems and habitats in a region.
- Species richness asks “how many species?”
- Species evenness asks “how evenly are individuals distributed?”
- A community can have high richness but low evenness if one species dominates.
- Biodiversity can contribute to ecosystem functions and resilience.
Need a worksheet for this topic?
Find classroom-ready Biology resources for oxygen cycling, biodiversity, species richness, species evenness, and ecology review.
Browse Teacher Resources →Let's make it click.
Get personalized Biology support from an experienced high school science teacher who can explain difficult concepts in a different way.
Learn About Tutoring →See Biology in action.
Explore interactive Biology simulations that help make ecological processes easier to visualize and investigate.
Explore Simulations →