9 public questions tagged with this topic.
Primary producers, such as plants and phytoplankton, convert inorganic substances into organic material through photosynthesis.
Ref: NCERT Class 12 Biology Chapter 12: Ecosystem Ecosystem Services and Functions
Keystone species play a crucial role in ecosystem structure, and their removal can have cascading effects on the ecosystem.
Ref: NCERT Class 12 Biology Chapter 11: Organisms and Populations Population Attributes - Birth Death Sex Ratio Age Distribution
Predation helps regulate prey populations and maintain ecological balance, preventing overpopulation.
Ref: NCERT Class 12 Biology Chapter 11: Organisms and Populations Responses to Abiotic Factors - Regulate Conform Migrate Suspend
A keystone species plays a critical role in maintaining ecosystem balance, even if it is not the most abundant.
Ref: NCERT Class 12 Biology Chapter 11: Organisms and Populations Organism and Environment - Major Biomes Abiotic Factors
“Low biomass, significant ecosystem impact” for keystone species typically have. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. A sound explanation connects the stated pattern to a causal pathway and distinguishes it from alternatives that describe different levels of organization or different ecological processes. The remaining alternatives—“High abundance and biomass”, “Moderate biomass, low ecosystem impact”, “High biomass, no impact”—refer to different states, processes, or scales and therefore do not express the same causal relationship. Ecological interpretation requires separating the immediate process from its broader consequence. A mechanism operating through physiology or behavior can scale up to alter survival, reproduction, abundance, distribution, and community structure. 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: NCERT Biology Class 12, Ch. 15 Biodiversity and Conservation
“Trophic cascade” for top-down control exemplifies. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. 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. The remaining alternatives—“Nutrient cycling”, “Abiotic influence”, “Bottom-up model”—refer to different states, processes, or scales and therefore do not express the same causal relationship. 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. Field observations could test this account by measuring the proposed driver and the demographic or ecosystem response while controlling plausible confounding factors.
Ref: Fundamentals of Ecology, Odum & Barrett, 5th Ed., Ch. 4
“Increased prey populations” for removal of top predators leads to. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. 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. The remaining alternatives—“Decreased prey populations”, “Increased stability”, “No ecosystem impact”—refer to different states, processes, or scales and therefore do not express the same causal relationship. Evidence should connect encounter rates or resource use to survival, growth, or reproduction. The ecological label follows that causal effect rather than superficial proximity between organisms. 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: Fundamentals of Ecology, Odum & Barrett, 5th Ed., Ch. 4
“Removal causes cascading trophic effects” for correct statement about keystone species. 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—“Always large populations”, “Occupy highest trophic level”, “Impact proportional to biomass”—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. 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. 21
Maximum evenness occurs when every species contributes the same proportion of individuals to the community. Under that distribution, randomly sampled individuals are least likely to be concentrated in a single taxon, so uncertainty of species identity is high and dominance is low. If one species becomes disproportionately abundant, evenness and most diversity measures decline even though richness may remain unchanged. Low richness concerns the number of species, not equality among their abundances, while random spatial placement does not guarantee an even abundance distribution. Equal abundance therefore represents the upper limit of the evenness component of diversity. 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: NCERT Biology Class 12, Ch. 15 Biodiversity and Conservation
