Which statement correctly identifies matter in ecosystems?

• A. It is continually recycled
• B. It is created and destroyed
• C. It flows in only one direction
• D. It is stored in rocks only

Answer: (A)

Matter in ecosystems is continually recycled through biogeochemical cycles. Elements move between living organisms and the physical environment, changing forms as they go. Plants take up inorganic nutrients and build organic matter; when organisms respire, decompose, or die, those nutrients are returned to inorganic forms that can be reused by others. This cycling keeps nutrients available for life while the total amount of matter remains constant, even though its form changes.

That’s why the statement about continual recycling fits best. Matter isn’t created or destroyed in natural processes; the law of conservation of mass applies, with energy being dissipated as heat instead. Matter also doesn’t flow in only one direction; it cycles through air, water, soil, organisms, and sediments. And it's not stored only in rocks—reservoirs include the atmosphere, oceans, soil, and living tissues, all connected in these cycles.