NCERT Class 12 Environment & Ecology — Chapter 2: Ecosystem

The correct Answer is

Producer - captures radiant energy to make food

Explanation

Energy flow in an ecosystem describes the movement of energy through different trophic levels. Organisms are categorized based on their mode of nutrition and their position in the food chain, which dictates how energy is transferred.

Statement-wise Analysis

1. Statement

   Primary consumer - fixes Sun’s radiant energy

   : Primary consumer - fixes Sun’s radiant energy
   Incorrect. Primary consumers are herbivores that feed on producers. They obtain energy by consuming plant matter, not by fixing the Sun's radiant energy. The fixation of solar energy is performed by producers (autotrophs) through photosynthesis.
2. Statement

   Producer - captures radiant energy to make food

   : Producer - captures radiant energy to make food
   Correct. Producers, primarily green plants and some bacteria, are autotrophs. They capture solar radiant energy and convert it into chemical energy (food) through the process of photosynthesis. This forms the base of most food webs.
3. Statement

   Decomposer - increases energy availability at higher levels

   : Decomposer - increases energy availability at higher levels
   Incorrect. Decomposers (e.g., bacteria, fungi) break down dead organic matter. While they recycle nutrients back into the ecosystem, they do not increase energy availability at higher trophic levels. Instead, they release energy as heat during decomposition, making it unavailable for consumption by other trophic levels. Energy flow is unidirectional and decreases at successive trophic levels.
4. Statement

   Secondary consumer - initiates detritus chain

   : Secondary consumer - initiates detritus chain
   Incorrect. Secondary consumers are carnivores or omnivores that feed on primary consumers. The detritus food chain begins with dead organic matter (detritus), which is broken down by decomposers and detritivores. Secondary consumers are part of the grazing food chain, not the initiators of the detritus chain.

Key Takeaway

Producers are organisms that capture radiant energy from the sun to synthesize organic food, forming the foundation of energy flow in most ecosystems.