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