#succession stages

ECOLOGICAL SUCCESSION

Which of the following is the correct sequence of succession stages?

Nudation first creates a bare or newly available site, migration then brings propagules into that site, and ecesis follows when those immigrants establish and grow. Later processes include aggregation, competition, reaction, and stabilization, so the stated sequence correctly captures the opening phases. Organisms can drive succession autogenically by changing their own habitat, while floods, erosion, sedimentation, or climate can drive allogenic change. Biological agents such as grazers and pathogens may also redirect succession by altering competitive relationships. Distinguishing the driver

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

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ECOLOGICAL SUCCESSION

Which of the following is *not* a seral stage?

Ecesis is a process rather than a seral community: it is the successful germination, establishment, and growth of immigrants after their arrival. Pioneer, intermediate, and climax communities describe recognizable positions or assemblages in a successional sequence, whereas ecesis describes what colonists do. Classical succession terminology divides community development into site exposure, arrival, establishment, interaction, environmental reaction, and relative stabilization. Modern ecology treats these as useful descriptions rather than a rigid deterministic program. Local resource conditio

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

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SUCCESSION

Which is NOT a feature of early successional species?

Early-successional species are typically selected for rapid occupation of recently disturbed, well-lit habitats. They often produce many small, widely dispersed seeds, germinate quickly, grow rapidly, mature early, and complete relatively short life cycles. Shade intolerance is common because their high photosynthetic capacity performs best in open conditions, while dense later canopies suppress them. Slow growth therefore conflicts with the standard pioneer syndrome and is more characteristic of many late-successional species that conserve resources, tolerate shade, and invest in long-lived t

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

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SUCCESSION

During ecological succession, productivity:

Productivity changes differently depending on whether gross primary production, net primary production, or net ecosystem production is measured. During early succession, expanding leaf area and improving soil conditions raise gross production rapidly. Net production can peak in young or intermediate communities because photosynthesis is high while maintenance respiration is still relatively low. As biomass accumulates, respiration by plants, animals, and decomposers increases, and net ecosystem production declines toward approximate balance in a mature system. Gross production may stabilize ra

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

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SUCCESSION

Which of the following is true about secondary succession?

Secondary succession follows disturbance of a previously established community when soil and at least some biological legacies remain. Examples include recovery after fire, windthrow, logging, cultivation, or abandonment of pasture. Surviving roots, seed banks, spores, soil microbes, nutrients, and nearby source populations accelerate recolonization. Grasses and fast-growing shrubs may appear first, followed by trees and more shade-tolerant species, although pathways depend on disturbance severity, climate, and invasive species. Primary succession instead begins on surfaces lacking developed s

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

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SUCCESSION

During succession, the climax community is characterized by:

A mature or conventionally defined climax community has high standing biomass and relative stability because long-lived organisms and complex trophic interactions dominate after prolonged succession. Plants accumulate woody tissue and extensive roots, while soils store organic matter and nutrients. Gross primary production may remain substantial, but community respiration also becomes large because the accumulated biomass must be maintained. Net ecosystem production therefore approaches a lower value than in rapidly growing earlier stages. Stability here means persistence or recovery around a

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

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SUCCESSION

Which one of the following is a pioneer species in a xerarch succession?

Xerarch succession begins in an extremely dry habitat, and a bare-rock sequence, or lithosere, commonly starts with lichens. Lichens tolerate severe water shortage because they can dry almost completely, suspend metabolism, and reactivate when moisture returns. Their fungal hyphae attach to rock and absorb brief water pulses, while the algal or cyanobacterial partner photosynthesizes. Secreted acids and repeated expansion and contraction contribute to rock weathering. Trapped dust, mineral fragments, and dead lichen tissues gradually form a thin organic substrate. Crustose lichens may be follo

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

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SUCCESSION

Primary succession on bare rock would likely begin with which group?

Primary succession on bare rock begins where soil, organic matter, and an established biological community are absent. Lichens are effective pioneers because the partnership between a fungus and a photosynthetic alga or cyanobacterium can survive desiccation, temperature extremes, and low nutrient supply. The fungal component anchors to rock, retains water, and releases organic acids, while the photosynthetic partner supplies carbohydrates; cyanobacterial partners may also fix nitrogen. Physical and chemical weathering loosen mineral particles, and dead lichen material contributes organic matt

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

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