8 public questions tagged with this topic.
Higher biodiversity contributes to ecosystem stability by ensuring functional redundancy and resilience to disturbances.
Ref: NCERT Class 12 Biology Chapter 12: Ecosystem Ecosystem Services and Functions
“Decrease” for as species accumulate on an island, immigration rates generally. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. Island biogeography explains species richness as a dynamic balance between immigration and extinction. Immigration generally declines as an island fills with species, whereas extinction rises as more species divide finite area and maintain smaller populations. The remaining alternatives—“Increase”, “Remain constant”, “Fluctuate randomly”—refer to different states, processes, or scales and therefore do not express the same causal relationship. Larger islands usually support more habitats and larger populations, lowering extinction risk; less isolated islands receive colonists more readily and may experience rescue effects. These mechanisms also apply to habitat fragments that function as ecological islands. The cited framing is therefore most useful when treated as a conditional biological claim, with assumptions about scale and environmental context kept explicit.
Ref: Biogeography, Lomolino et al., 5th Ed., Ch. 1-4
“Top-down control” for control involving predators controlling prey. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. Species management must identify the demographic stage and ecological process that most strongly limits population growth. Prevention, early detection, removal, habitat manipulation, and biological control act at different points in an invasion or recovery trajectory. The remaining alternatives—“Bottom-up control”, “Wasp-waist control”, “Abiotic control”—refer to different states, processes, or scales and therefore do not express the same causal relationship. Effective control reduces propagule pressure or population growth without causing unacceptable non-target effects. Repeated monitoring is necessary because seed banks, dormant stages, recolonization, and density-dependent compensation can reverse short-term gains. Linking the wording to measurable consequences for fitness, abundance, or flux gives the conclusion its scientific meaning and prevents a purely mnemonic interpretation. Field observations could test this account by measuring the proposed driver and the demographic or ecosystem response while controlling plausible confounding factors.
Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 21
“Controlling population sizes of other species” for keystone species primarily influence ecosystems by. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. Rates depend on temperature, moisture, substrate quality, consumer physiology, and the elemental balance between organisms and their food. These controls explain why the same process can differ among terrestrial, freshwater, and marine systems without changing its definition. The remaining alternatives—“Increasing competition”, “Having high biomass”, “Occupying broad niches”—refer to different states, processes, or scales and therefore do not express the same causal relationship. Ecosystem processes are constrained by energy conservation and by the cycling of matter. Energy enters mainly through primary production, is lost as metabolic heat at every transfer, and therefore cannot be recycled in the way that carbon, nitrogen, phosphorus, or water can. This distinction matters because similar surface patterns can arise through different mechanisms, whereas ecological prediction depends on identifying the mechanism that actually changes rates.
Ref: NCERT Biology Class 12, Ch. 15 Biodiversity and Conservation
“Over a long period of time” for colonization rates balanced by extinction rates. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. Island biogeography explains species richness as a dynamic balance between immigration and extinction. Immigration generally declines as an island fills with species, whereas extinction rises as more species divide finite area and maintain smaller populations. The remaining alternatives—“Initially, then diverge”, “Only on large islands”, “Only on small islands”—refer to different states, processes, or scales and therefore do not express the same causal relationship. Larger islands usually support more habitats and larger populations, lowering extinction risk; less isolated islands receive colonists more readily and may experience rescue effects. These mechanisms also apply to habitat fragments that function as ecological islands. The cited framing is therefore most useful when treated as a conditional biological claim, with assumptions about scale and environmental context kept explicit.
Ref: The Theory of Island Biogeography, MacArthur & Wilson, Ch. 2-4
Net reproductive rate R0 measures generational replacement. An R0 of 1 means that, on average, each female produces exactly one daughter that survives through the relevant life-table schedule, replacing herself in the next generation. Under unchanging conditions, successive generations therefore maintain the same expected size. Values above 1 cause generational increase, and values below 1 cause decline. This replacement criterion is analogous to λ = 1 and r = 0, though R0, λ, and r refer to different temporal formulations and should not be substituted numerically without generation-time information. Population stabilization does not imply that births and deaths cease; it means gains and losses balance in expectation. Age structure can also cause transient changes even when R0 equals 1, because a population not initially at its stable age distribution may fluctuate before settling. Environmental and demographic stochasticity introduce further variation. Thus R0 = 1 identifies the deterministic threshold between increase and decrease, not a guarantee that every census will contain exactly the same number of organisms.
Ref: Ecology: Concepts and Applications, Molles, 9th Ed., Ch. 11
“Ocean” for which ecosystem supports longest food chains. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. Rates depend on temperature, moisture, substrate quality, consumer physiology, and the elemental balance between organisms and their food. These controls explain why the same process can differ among terrestrial, freshwater, and marine systems without changing its definition. The remaining alternatives—“Temperate forests”, “Tropical rainforests”, “Desert”—refer to different states, processes, or scales and therefore do not express the same causal relationship. Ecosystem processes are constrained by energy conservation and by the cycling of matter. Energy enters mainly through primary production, is lost as metabolic heat at every transfer, and therefore cannot be recycled in the way that carbon, nitrogen, phosphorus, or water can. The cited framing is therefore most useful when treated as a conditional biological claim, with assumptions about scale and environmental context kept explicit.
Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 17-19
Omnivores feed across more than one trophic level and can provide alternative energy pathways when one resource declines. Such flexible links may damp population fluctuations and reduce dependence on a single prey species, thereby improving stability under some conditions. More specialists and fewer links can make communities vulnerable to loss of particular resources, while strictly linear chains offer little redundancy. Nevertheless, omnivory can destabilise certain models, so the relationship is conditional rather than universal. Rates must be compared on the same area, biomass, leaf-area, and time basis because changing the denominator can reverse an apparent ecosystem ranking. Climate, nutrients, disturbance, species traits, and food-web structure interact, so broad ecological generalisations describe tendencies rather than universal rules. Energy is lost as metabolic heat at every trophic transfer, while elements such as nitrogen and phosphorus are recycled through organisms and the physical environment. Mechanistic interpretation connects individual physiology and species interactions to population change, community composition, and ecosystem-level fluxes.
Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 17-19
