OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What type of system is characteristic of a natural ecosystem?

1. Open loop system that generates waste

2. Constantly evolving without any input or output

3. Works in a closed loop system with no waste

4. A linear system that relies on external resources

The correct answer is: Works in a closed loop system with no waste

In a natural ecosystem, a closed loop system is characteristic as it operates with minimal waste. This means that in a closed-loop system, the materials and energy are continually recycled through various biotic (living organisms) and abiotic (non-living components) processes. For example, nutrients from decomposed organisms are absorbed by plants, which are then consumed by herbivores, and subsequently by carnivores, creating a cycle that allows for sustainability within the ecosystem. This recycling of materials helps maintain the balance of the ecosystem without the need for external resources, distinguishing it from linear systems that would exhaust resources and generate waste. Additionally, the concept of no waste in a closed loop emphasizes the efficiency and interconnectedness of biological interactions, where every component has a crucial role in the flow of energy and matter. By transforming waste from one organism into a resource for another, natural ecosystems maintain their health and resilience.