5 public questions tagged with this topic.
The detritus food chain begins with dead organic matter, which is broken down by decomposers before being passed on to consumers.
Ref: NCERT Class 12 Biology Chapter 12: Ecosystem Energy Flow - Food Chains Food Webs Trophic Levels
Decomposers are involved in food chains, especially in the detritus food chain, where they break down organic material.
Ref: NCERT Class 12 Biology Chapter 12: Ecosystem Energy Flow - Food Chains Food Webs Trophic Levels
Keystone species are not necessarily the most abundant, but they have a disproportionately large impact on ecosystem structure.
Ref: NCERT Class 12 Biology Chapter 11: Organisms and Populations Responses to Abiotic Factors - Regulate Conform Migrate Suspend
“Primary herbivore” for sea urchins' role in kelp forest ecosystems. 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—“Top predator”, “Primary producer”, “Secondary carnivore”—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. Linking the wording to measurable consequences for fitness, abundance, or flux gives the conclusion its scientific meaning and prevents a purely mnemonic interpretation.
Ref: Fundamentals of Ecology, Odum & Barrett, 5th Ed., Ch. 4
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
