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

Which of the following is included in DOM?

1. Only plant matter

2. Fresh fruits and vegetables

3. Dead animals and leaves

4. Active microorganisms only

The correct answer is: Dead animals and leaves

Dead Organic Matter (DOM) refers to the remnants of once-living organisms that contribute to the nutrient cycle. The correct response highlights that DOM encompasses a variety of decomposing materials, including dead animals and plant materials such as leaves. The inclusion of dead animals indicates that all organic matter from various life forms decomposes and becomes part of the ecosystem's nutrient base, enriching the soil and providing materials for microbial activity and plant growth. Leaves, being a significant source of organic matter, break down and release nutrients that support the overall health of the ecosystem. While the other options may contain components relevant to organic matter, they do not fully represent the diversity included in DOM. For instance, focusing solely on plant matter, fresh fruits, and vegetables, or active microorganisms excludes the broader range of organic materials that contribute to the decomposition process and the nutrient cycle within ecosystems. Thus, the reference to both dead animals and leaves encapsulates the varied sources of organic material that define DOM.