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

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What is the main purpose of excretion in living organisms?

To exchange gases with the environment
To absorb nutrients from food
To remove waste products from the body
To reproduce offspring

The correct answer is: To remove waste products from the body

The main purpose of excretion in living organisms is to remove waste products from the body. This process is essential for maintaining homeostasis, which is the balance of conditions within the internal environment of an organism. As metabolic processes occur, various waste substances are produced, such as urea, carbon dioxide, and excess salts, which can be harmful if they accumulate. Excretion ensures that these waste products are eliminated, preventing toxicity and enabling the body to function effectively. Excretion plays a vital role in organisms by helping to regulate water and ion balance and preventing damage to cells from harmful substances. This functional aspect highlights the importance of excretory systems, such as the kidneys in mammals, which filter blood and produce urine to expel wastes. The other options reflect different biological processes. Exchanging gases with the environment is primarily a function of respiration. Absorbing nutrients from food relates to the digestive process, where ingested materials are broken down and utilized for energy and growth. Reproduction pertains to the processes involving the creation of new individuals, which, while crucial for species survival, is not related to the removal of waste.