Answer: ecosystem.
- A ecosystem
- B single organism
- C one population
- D single species
Correct answer: A. ecosystem
Explanation: An ecosystem includes living organisms and their physical environment.
Energy pyramid showing a simple food chain (producer to herbivore to carnivore) with energy decreasing roughly tenfold at each trophic level.
Concept context
Ecosystems, food chains, energy flow, nutrient cycles, biodiversity, and conservation.