Biodiversity is a core ecological concept that describes biological variety at multiple levels. Understanding ecosystem diversity, in particular, helps explain why different places function differently and support different communities over time.

Core concepts: biodiversity and ecosystem diversity

Biodiversity is not just a species count; it also captures how organisms differ genetically, how many kinds of organisms exist, and how living systems are organised into distinct ecosystems. These levels are connected because changes at one level can influence the others.

Ecosystem diversity focuses on differences among ecosystems rather than differences among individuals or species within a single site.

What counts as “component parts” and “interactions”?

Component parts within an ecosystem

Ecosystem diversity includes variation in what an ecosystem is made of, such as:

• Abiotic components: temperature, precipitation, light, salinity, soil type, nutrient availability, pH, disturbance regime

• Biotic components: producers, consumers, decomposers; dominant vegetation; functional groups (for example, nitrogen-fixing plants)

• Structural features: vertical layering (canopy/understory), habitat complexity, microhabitats, physical refuges

Interactions within an ecosystem

Ecosystems also differ in how their parts interact, including:

The nitrogen cycle diagram traces how nitrogen moves between the atmosphere, soils/waters, and living organisms through microbially mediated steps. It emphasizes that ecosystem functioning depends on transformations (e.g., fixation, ammonification, nitrification, denitrification) that regulate nutrient availability and thus productivity. Source

Ecological pyramids summarize how ecosystem energy and biomass are distributed across trophic levels. The figure contrasts pyramids of numbers and biomass (which can be upright or inverted depending on the system) with energy pyramids (which are consistently upright), highlighting the typical loss of available energy at higher trophic levels. Source

• Energy capture and transfer: how primary producers convert energy and how efficiently energy moves through feeding relationships

• Matter cycling: decomposition rates, nutrient retention vs loss, and pathways of nutrient movement

• Species interactions: competition, predation, and symbioses that shape which organisms persist in that system

• Feedbacks: processes where organisms modify abiotic conditions (for example, vegetation altering soil moisture and temperature)

Because ecosystem diversity includes interactions, two ecosystems with similar species lists can still differ strongly if their abiotic conditions, structure, or rates of key processes differ.

Ecosystem diversity “within and among” ecosystems

Diversity within an ecosystem

Within a single ecosystem, there can be multiple habitat patches and microenvironments that support different organisms and processes. For AP Biology, this idea is useful because it highlights that:

• ecosystems are heterogeneous, not uniform

• local variation in abiotic factors can create different niches and interaction networks

Diversity among ecosystems

Ecosystem diversity also means the variety of ecosystem types across a region, such as forests, grasslands, wetlands, estuaries, coral reefs, and deserts.

A world biomes map visualizes ecosystem diversity at the regional-to-global scale by grouping areas with similar climate and dominant vegetation into biome types. Seeing biomes side-by-side reinforces why temperature and precipitation patterns are major drivers of differences among ecosystems. Source

Differences among ecosystems commonly reflect:

• long-term climate patterns (temperature and precipitation)

• geography and geology (elevation, parent rock, soil formation)

• water availability and chemistry (freshwater vs marine; salinity gradients)

How ecosystem diversity relates to other biodiversity levels

Species diversity vs ecosystem diversity

Species diversity describes biological variety within a community, while ecosystem diversity describes variety in ecosystem types and functioning across space. They often correlate, but they are not the same:

• a region can have high ecosystem diversity (many habitat types) even if some habitats have relatively low species diversity

• a single ecosystem can have high species diversity without increasing the number of ecosystem types in the region

Genetic diversity as a foundation

Genetic diversity supports population survival and adaptation, which helps maintain species in particular ecosystems. In turn, stable populations contribute to ecosystem processes (such as productivity and decomposition) that distinguish one ecosystem from another.

Why ecosystem diversity is central in ecology

Ecosystem diversity provides a framework for explaining why ecological patterns vary across landscapes:

• different ecosystems support different communities because abiotic conditions set constraints and opportunities

• differences in interactions (energy flow, cycling, and biotic relationships) shape ecosystem “function,” not just composition

• conserving biodiversity often requires protecting a range of ecosystems, not only particular species