The OCR GCSE Biology Paper 4 (November 2020) covers anaerobic respiration, natural selection, and genetic disorders. Key topics include yeast respiration, lactose intolerance, cardiovascular disease, and parasitic plants like mistletoe. Practical investigations explore enzyme reactions, phloem transport, and monoclonal antibodies for bacterial detection. Concepts such as osmoregulation, Huntington′s disease, and stem cell therapy for brain damage are examined alongside data interpretation and ethical considerations in genetic and medical advancements. The paper emphasizes experimental design, critical analysis, and the application of biology in conservation, public health, and biotechnology.