Key Stage 3 (KS3) Biology Practice Test 2025 - Free KS3 Biology Practice Questions and Study Guide

Anaerobic respiration is the correct answer because it is a form of respiration that occurs in the absence of oxygen. During anaerobic respiration, organisms can generate energy by converting glucose into ethanol and carbon dioxide, or in some cases, lactic acid, depending on the organisms involved. This process is essential for certain types of organisms, such as some bacteria and yeast, allowing them to survive and thrive in environments where oxygen is limited.

In contrast, aerobic respiration requires oxygen to produce energy and is the process used by most plants and animals. Cellular respiration generally refers to the overall process of converting glucose into usable energy, which includes both aerobic and anaerobic pathways. Photosynthesis, on the other hand, is the process by which plants convert light energy into chemical energy stored in glucose, not a type of respiration.