The OCR GCSE Biology Paper 4 (November 2021) covers osmosis, plant diseases, genetic inheritance, and composting processes. Key topics include meiosis, menstrual cycle hormones, and natural selection. Practical investigations focus on sugar concentration in potato cells, temperature effects on compost decomposition, and selective breeding for disease resistance. Concepts such as antibiotic resistance, the role of bacteria in composting, and optimizing biological processes are emphasized. Ethical considerations, data analysis, and the application of scientific principles in environmental management, conservation, and public health are central themes.