How does energy flow differ from nutrient cycling in ecosystems?

• A. Nutrients cycle repeatedly within the ecosystem, while energy flows through trophic levels and is dissipated as heat.
• B. Energy cycles; nutrients flow in one direction only.
• C. Energy and nutrients both cycle and are stored in biomass.
• D. Both energy and nutrients are stored indefinitely in organisms.

Answer: (C)

Energy in ecosystems moves in a one-way stream, starting from the sun and moving through producers to consumers and eventually to decomposers. With each transfer, most of the energy is transformed and released as heat, making it unavailable for the next step. Nutrients, by contrast, cycle repeatedly through organisms and the physical environment. They move between air, water, soil, and biomass, getting reused each time organisms take up, use, excrete, and decompose them. Biomass can store nutrients for a while, but energy is not recycled in the same way — it’s continually dissipated as heat and lost from the usable part of the system. So the key idea is that nutrients cycle within the ecosystem while energy flows through trophic levels and is dissipated as heat.