Biodiversity — Science definition

Defined in 5 courses:

Where it is taught

In use

Biodiversity is the variety of life in a place, and it is measured in at least three ways that can disagree.

Biodiversity, Variation & Ecosystem Resilience

All of that named, mapped diversity is what we mean by biodiversity, and biologists measure it at three levels: genetic diversity (variety within a species, which — as we saw with cheetahs and crops — buffers against disease and change), species diversity (the number and evenness of different species in a place, often summarized as species richness), and ecosystem diversity (the range of habitats, from coral reefs to rainforests).

Classification & Biodiversity

Human activities can change biodiversity, including genetic variation, species composition and ecosystem relationships.

Human Impact & Conservation

Questions using biodiversity

Problem 1

A longer survey finds more species than a shorter one. Must true biodiversity have increased?
Answer and explanation

No. Greater detection effort can reveal previously missed species. Standardize effort before interpreting it as a biological change.

Response criteria

  • Explain the relevant biological process accurately.
  • Use the supplied evidence and show calculation steps with units where needed.
  • Connect a labeled model or mechanism with the claim.
  • State an assumption, evidence limitation, or useful next observation.

Problem 2

Explain why a loss of biodiversity can matter to an ecosystem even when the total number of organisms stays the same.
Answer and explanation

Different species contribute different functions — fixing nitrogen, pollinating, decomposing, controlling other populations — so replacing many species with a larger number of individuals of a few leaves those functions unperformed. Diversity also provides alternatives: if several species perform a similar role, a disturbance that removes one may be absorbed by the others, whereas a community dominated by one species has no such margin. Total abundance therefore does not measure what diversity contributes.

Response criteria

  • State a biologically accurate conclusion.
  • Show the data, mechanism, or calculation that supports it.
  • Include units, conditions, or limits where relevant.

Problem 3

Two communities each contain 10 species. Explain why they may still differ in biodiversity.
Answer and explanation

Species richness counts how many species are present, but biodiversity also depends on evenness — how individuals are distributed among those species. A community with ten species in roughly equal numbers is more diverse than one where a single species holds 95 percent of the individuals and the other nine are rare, because the second is dominated by one species and its rare ones are vulnerable to loss. Richness alone therefore gives an incomplete comparison.

Response criteria

  • State a biologically accurate conclusion.
  • Show the data, mechanism, or calculation that supports it.
  • Include units, conditions, or limits where relevant.

Problem 4

Worldwide, what is the single leading cause of species extinction and biodiversity loss?
  1. Collecting animals for zoos
  2. Too many decomposers
  3. Volcanic eruptions
  4. Habitat loss and fragmentation
Answer and explanation

Habitat loss and fragmentation

Destroying and fragmenting habitat removes the places species need to live and is the biggest driver of biodiversity loss.

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