Which term is used to describe the transfer of energy from one trophi…

The correct answer is Option (2) → Energy flow

Energy enters an ecosystem when green plants capture sunlight. It then passes from producers to herbivores and then to carnivores, one trophic level at a time. This movement is called energy flow. It goes in one direction only: at each step some energy is lost as heat, and it never comes back to the plants. That is why energy is not recycled, unlike nutrients, which go round again and again in nutrient cycling.

NCERT Extract:
Energy Flow – “Except for the deep sea hydro-thermal ecosystem, sun is the only source of energy for all ecosystems on Earth. Of the incident solar radiation less than 50 per cent of it is photosynthetically active radiation (PAR). We know that plants and photosynthetic bacteria (autotrophs), fix Sun’s radiant energy to make food from simple inorganic materials. Plants capture only 2-10 per cent of the PAR and this small amount of energy sustains the entire living world. So, it is very important to know how the solar energy captured by plants flows through different organisms of an ecosystem. All organisms are dependent for their food on producers, either directly or indirectly. So you find unidirectional flow of energy from the sun to producers and then to consumers.”

Figure 12.3 Energy flow through different trophic levels