#ecosystem function

BIODIVERSITY

Which hypothesis explains function with increasing species richness in unpredictable ways?

The idiosyncratic hypothesis treats ecosystem performance as dependent on which species are present and how they interact, not as a smooth function of species number. Adding a species may increase productivity through complementarity, reduce it through competition, or produce little change if its role overlaps with existing organisms. Consequently, function can rise, fall, or fluctuate as richness changes, generating an unpredictable relationship. This contrasts with the redundancy model, in which several species share functional roles and initial losses have little effect; the rivet model, in

Ref: NCERT Biology Class 12, Ch. 15 Biodiversity and Conservation

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SPECIES HYPOTHESIS

A graph showing steep decline in function after initial loss indicates:

A steep functional decline after the first species loss is consistent with a keystone pattern when that initial removal eliminates a disproportionately influential species. The response reflects species identity rather than the number of species removed, distinguishing it from gradual rivet loss or buffered redundancy. Biodiversity–function hypotheses differ in how they assign ecological importance among species. Complementarity emphasizes distinct contributions, redundancy emphasizes overlap and compensation, rivet theory emphasizes cumulative weakening, keystone theory emphasizes particular

Ref: NCERT Biology Class 12, Ch. 15 Biodiversity and Conservation

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SPECIES HYPOTHESIS

Which hypothesis suggests unpredictable functional effects?

The idiosyncratic hypothesis treats functional consequences of diversity change as contingent on species identity and interactions. Because different combinations produce different outcomes, adding or removing species yields irregular and unpredictable changes rather than a common linear, threshold, or stepwise curve. Species richness counts taxa but does not show their abundance, traits, or interaction strengths. Dominant species may control bulk process rates, rare species may provide specialized functions or future insurance, and predators can restructure whole food webs through indirect ef

Ref: NCERT Biology Class 12, Ch. 15 Biodiversity and Conservation

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ECOLOGICAL SUCCESSION

Redundancy hypothesis implies function is maintained until:

The redundancy hypothesis groups species with overlapping ecological roles. Loss of one member may have little immediate effect because another can compensate, but function declines after losses remove enough members—or a uniquely important member—to cross the system's effective functional threshold. Biodiversity–function hypotheses differ in how they assign ecological importance among species. Complementarity emphasizes distinct contributions, redundancy emphasizes overlap and compensation, rivet theory emphasizes cumulative weakening, keystone theory emphasizes particular influential species

Ref: Ecology: Concepts and Applications, Molles, 9th Ed., Ch. 20

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Ecosystem Ecology & PRODUCTIVITY

Which is NOT a function of an ecosystem?

Ecosystem functions are processes that operate at the level of interacting organisms and their environment. They include primary production, transfer and dissipation of energy, decomposition, nutrient cycling, soil formation, and regulation arising from ecological interactions. DNA replication, in contrast, is a cellular molecular process by which an organism copies its genetic material before cell division or reproduction. It is essential to organisms and ultimately underlies population continuity, but it is not normally classified as an ecosystem-level function. Energy flow connects trophic

Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 17

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