#species impact

SPECIES

A species causing ecosystem changes despite being few in number is classified as a:

“Keystone species” for a species causing ecosystem changes despite being few in number is classified as a. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. 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 remaining alternatives—“Dominant species”, “Invasive species”, “Indicator species”—refer to different states, processes, or scales and therefore do not express the same causal relationship. The relevant inference should follow the pathway from resource supply to organismal uptake and then to ecosystem-level flux. Productivity, trophic transfer, decomposition, and nutrient regeneration are connected, but each measures a different part of that pathway. 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

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Species Control

Characteristic of invasive species:

“High reproductive rates” for characteristic of invasive species. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. 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. The remaining alternatives—“Low dispersal”, “Specialized diets”, “Narrow niches”—refer to different states, processes, or scales and therefore do not express the same causal relationship. Management outcomes depend on scale and context: suppressing abundance at one site does not guarantee regional eradication when dispersal reconnects treated and untreated populations. The cited framing is therefore most useful when treated as a conditional biological claim, with assumptions about scale and environmental context kept explicit. Linking the wording to measurable consequences for fitness, abundance, or flux gives the conclusion its scientific meaning and prevents a purely mnemonic interpretation.

Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 21

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Species Control

Incorrect statement about keystone species:

The keyed exception is “Influence proportional to abundance.” In the context of incorrect statement about keystone species, that statement differs from the governing ecological pattern and must be evaluated against the mechanism rather than accepted from wording alone. Management outcomes depend on scale and context: suppressing abundance at one site does not guarantee regional eradication when dispersal reconnects treated and untreated populations. The remaining alternatives—“Species other than consumers can be keystone”, “Removal reduces species richness”, “Removal causes trophic cascades”—refer to different states, processes, or scales and therefore do not express the same causal relationship. 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. Linking the wording to measurable consequences for fitness, abundance, or flux gives the conclusion its scientific meaning and prevents a purely mnemonic interpretation.

Ref: Ecology: From Individuals to Ecosystems, Begon et al., 5th Ed., Ch. 21

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Types of Species

Keystone species primarily influence ecosystems by:

“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

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Lotka Volterra Model

What represents the impact of one species on another in the equations?

“Competition coefficient” for what represents the impact of one species on another in the equations. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. Species interactions are classified by their net effects on the fitness of each participant, but those effects can change with density, resource supply, life stage, and environmental stress. Competition reduces access to shared limiting factors, whereas predation and parasitism transfer resources from victim to consumer. The remaining alternatives—“Carrying capacity”, “Growth rate”, “Reproductive value”—refer to different states, processes, or scales and therefore do not express the same causal relationship. Coexistence requires stabilizing differences that make each species limit itself more strongly than it limits its competitor, or an equalizing process that keeps fitness differences small. Without such mechanisms, persistent competitive asymmetry tends toward exclusion. Linking the wording to measurable consequences for fitness, abundance, or flux gives the conclusion its scientific meaning and prevents a purely mnemonic interpretation.

Ref: Ecology: Concepts and Applications, Molles, 9th Ed., Ch. 13-14

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