A complete, ready-to-teach lesson on gas exchange and the cardiovascular system. Includes learning objectives, a 15-min starter with links questions, content slides on alveolar structure, gas exchange, red blood cells/haemoglobin, and the cardiovascular link, plus a think-pair-share task, a scaffolded extended response (with chunked prompts and writing frame), depth/discussion questions, and an exit ticket. Everything you need for a full lesson, no additional planning required.