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#ecological factors

9 public questions tagged with this topic.

Biogeography

What affects the extinction rate according to MacArthur-Wilson theory?

“Size of island” for what affects the extinction rate according to macarthur-wilson theory. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. At equilibrium, species identities can continue to turn over even when richness is approximately stable. The model predicts a balance of rates, not an absence of colonization or extinction. The remaining alternatives—“Temperature”, “Predation rate”, “Evolution rate”—refer to different states, processes, or scales and therefore do not express the same causal relationship. 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. This distinction matters because similar surface patterns can arise through different mechanisms, whereas ecological prediction depends on identifying the mechanism that actually changes rates. 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

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Biogeography

Larger islands generally support more species due to:

“Lower extinction rates” for larger islands generally support more species due to. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. At equilibrium, species identities can continue to turn over even when richness is approximately stable. The model predicts a balance of rates, not an absence of colonization or extinction. The remaining alternatives—“Higher extinction rates”, “Lower habitat diversity”, “Fewer resources”—refer to different states, processes, or scales and therefore do not express the same causal relationship. 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. Linking the wording to measurable consequences for fitness, abundance, or flux gives the conclusion its scientific meaning and prevents a purely mnemonic interpretation.

Ref: Biogeography, Lomolino et al., 5th Ed., Ch. 1-4

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Island

Species richness significantly depends on:

“Island size and distance” for species richness significantly depends on. 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—“Island vegetation”, “Climate alone”, “Predation alone”—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

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Population Ecology

Which factor leads to reduced dispersion distance among patches?

“Increased connectivity among patches” for which factor leads to reduced dispersion distance among patches. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. Mechanistic support comes from showing how resource limitation, enemies, mate availability, or physiological stress changes demographic performance. A descriptive association alone does not establish regulation or causation. The remaining alternatives—“Increased resource availability”, “Higher isolation among patches”, “Smaller patch size”—refer to different states, processes, or scales and therefore do not express the same causal relationship. Population ecology links individual births, deaths, immigration, and emigration to changes in abundance. Per-capita rates determine the direction of change, while density dependence creates feedback when crowding alters survival or reproduction. This distinction matters because similar surface patterns can arise through different mechanisms, whereas ecological prediction depends on identifying the mechanism that actually changes rates. The cited framing is therefore most useful when treated as a conditional biological claim, with assumptions about scale and environmental context kept explicit.

Ref: Campbell Biology, Urry et al., 12th Ed., Unit 8 Ecology

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Extinction Topic

Which of the following is least associated with extinction risk?

“Generalist species” for which of the following is least associated with extinction risk. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. Extinction risk rises when abundance, geographic range, or genetic variation becomes small because demographic chance, environmental fluctuations, inbreeding, and rare catastrophes then have disproportionate effects. Correlated losses among subpopulations further weaken regional persistence. The remaining alternatives—“Narrow niche width”, “Top predator status”, “Habitat fragmentation”—refer to different states, processes, or scales and therefore do not express the same causal relationship. The mechanism should be evaluated across both local and global scales. Local disappearance can be reversed by recolonization, whereas global extinction is irreversible and requires the loss of every surviving population. The cited framing is therefore most useful when treated as a conditional biological claim, with assumptions about scale and environmental context kept explicit.

Ref: Conservation Biology, Primack & Sher, 6th Ed., Ch. 7

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Extinction Topic

Short lifespan species are more extinction-prone because:

“They cannot sustain population declines” for short lifespan species are more extinction-prone because. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. The mechanism should be evaluated across both local and global scales. Local disappearance can be reversed by recolonization, whereas global extinction is irreversible and requires the loss of every surviving population. The remaining alternatives—“They reproduce excessively”, “They overpopulate rapidly”, “They are r-strategists”—refer to different states, processes, or scales and therefore do not express the same causal relationship. Human-driven habitat conversion, exploitation, introduced enemies, pollution, and climate change often interact rather than acting independently. Traits such as slow reproduction or ecological specialization can magnify vulnerability. 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: Conservation Biology, Primack & Sher, 6th Ed., Ch. 7

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Predator Prey Model

Which of these contributes to predator’s carrying capacity besides victim abundance?

Alternative prey can raise a predator population’s effective carrying capacity because they provide energy when the principal victim is scarce. A generalist predator may switch its foraging effort, maintain survival and reproduction, and persist at densities that the focal prey alone could not support. In population models, predator growth depends on the summed contributions of consumable prey, so an additional positive term can keep net growth above mortality. Refuge space generally protects prey and may lower predator intake rather than support more predators. Mutualism and migration can influence abundance in particular systems, but neither is the direct additional food resource specified. Alternative prey can also produce apparent competition: one prey species supports more predators, increasing predation on another species even though the prey do not compete for resources. Whether alternative prey stabilize dynamics depends on predator switching, prey synchrony, and functional responses. The central carrying-capacity mechanism is energetic subsidy—more total accessible prey biomass permits a larger equilibrium predator population than the main prey population could sustain alone.

Ref: Ecology: Concepts and Applications, Molles, 9th Ed., Ch. 14

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PREDATOR

The predator carrying capacity is highest when:

Predator carrying capacity depends strongly on the rate at which prey resources can support predator maintenance, growth, and reproduction. When suitable prey are abundant, more energy enters the predator population, lowering starvation and allowing a greater equilibrium density. Scarce prey restrict recruitment and survival, while poor-quality prey may provide inadequate nutrients even if numerous. High competition among predators divides available food and ordinarily reduces the number each habitat can sustain. Abundance alone is not sufficient if prey are inaccessible or toxic, but under otherwise comparable conditions greater usable prey biomass raises the energetic ceiling for the predator population. The relevant evidence concerns process rather than wording alone. Linking the described pattern to energetic returns, fitness consequences, or receiver responses makes the inference biologically coherent and distinguishes it from the competing alternatives. Ecological categories are simplified models, yet they remain valuable when their assumptions are stated. The selected description captures the dominant net effect, while real systems may vary with density, habitat, life stage, and environmental conditions.

Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 10

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BIODIVERSITY & IDH

Which of the following does not influence species richness?

Community species richness is directly shaped by ecological variables such as area, productivity, habitat heterogeneity, disturbance, colonization, extinction, and biotic interactions. Larger areas tend to hold more individuals and habitat types. Productivity affects resource supply, although its relationship with richness can be positive, negative, or hump-shaped. Competition can reduce richness through exclusion or, under some conditions, promote niche differentiation. A DNA sequence is information at the molecular level and is not used as a direct ecological predictor of how many species occur in a sampled community. Genetic variation and evolutionary history ultimately influence traits, speciation, and adaptation, so DNA is not irrelevant to biodiversity in the broadest causal sense. However, merely specifying “DNA sequence” does not define an environmental or community process comparable to area, productivity, or competition. It may be used methodologically to identify cryptic species or estimate phylogenetic diversity, which can change measured richness if taxonomy improves, but that is a measurement issue rather than a direct determinant in this comparison. The intended distinction is between proximal ecological controls of community richness and underlying hereditary information within organisms.

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

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