Statement I: Species composition and stratification are the two main functional features of an ecosystem.
Statement II: In a terrestrial ecosystem, a much larger fraction of energy flows through the detritus food chain than through the grazing food chain.
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Only Statement II is correct.
An ecosystem has structural features (how it is built) and functional aspects (how it works). Species composition and stratification describe its structure. Energy, on the other hand, flows through two kinds of food chains, and their share differs between land and water.
Statement I: Species composition and stratification are the two main functional features of an ecosystem. — False. They are the two main structural features. The functional aspects are productivity, decomposition, energy flow and nutrient cycling.
Statement II: In a terrestrial ecosystem, a much larger fraction of energy flows through the detritus food chain than through the grazing food chain. — True. On land most energy passes through the detritus food chain, while in water the grazing food chain is the major conduit.
NCERT Extract:
Summary – “… Each ecosystem has characteristic physical structure resulting from interaction amongst abiotic and biotic components. Species composition and stratification are the two main structural features of an ecosystem. Based on source of nutrition every organism occupies a place in an ecosystem. Productivity, decomposition, energy flow, and nutrient cycling are the four important components of an ecosystem.”
Energy Flow – “In an aquatic ecosystem, GFC is the major conduit for energy flow. As against this, in a terrestrial ecosystem, a much larger fraction of energy flows through the detritus food chain than through the GFC.”