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

Which of the following organisms respires?

1. Only animals

2. Only plants

3. All living things

4. Only bacteria

The correct answer is: All living things

All living organisms, including animals, plants, and bacteria, undergo respiration as a vital process for survival. Respiration is the biochemical process by which cells convert sugars and other substances into energy to power cellular activities. In animals, respiration primarily occurs through the intake of oxygen and the release of carbon dioxide as a byproduct. Plants also respire; they utilize the glucose produced during photosynthesis and exchange gases with the environment, taking in oxygen and ousting carbon dioxide, particularly during the night when photosynthesis is inactive. Bacteria, although they may vary in their respiratory pathways, also perform respiration, sometimes anaerobically, meaning they can generate energy without oxygen. Thus, categorizing respiration to only specific groups like animals, plants, or bacteria overlooks the essential fact that respiration is a fundamental life process present in all living organisms.