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

What is a key factor in the formation of crude oil?

1. Compression of dead plants and animals over millions of years

2. Rapid decomposition of living creatures

3. Extraction from oceanic surface water

4. Formation from volcanic activity

The correct answer is: Compression of dead plants and animals over millions of years

The formation of crude oil primarily involves the compression of dead plants and animals over millions of years. This process takes place in sedimentary environments where organic matter accumulates in layers. Over time, these layers get buried under additional sediment, and the heat and pressure from the overlying materials transform the organic matter into hydrocarbons, which is the main component of crude oil. The key part of this process is the prolonged period required for the transformation, which can be millions of years. The geological conditions necessary for this transformation, coupled with the right type of organic material, lead to the formation of crude oil that can later be extracted and refined for various uses. This understanding highlights the importance of geological processes in shaping the natural resources we rely on today. Other processes, such as rapid decomposition of living organisms, would not lead to the formation of crude oil since they typically break down organic matter quickly rather than allowing for the long-term accumulation and transformation required. The extraction from oceanic surface water and formation from volcanic activity do not play a role in the creation of crude oil, as these processes involve different mechanisms.