This is a good question. There are different ways you can use the past papers from doing the papers by exam topic to doing full practice exams. We think it is best to cover the course and then use the past papers as a way of seeing how much you do and don’t know, identifying gaps in knowledge and monitoring progress.
We do not link to the new GCSE Biology past papers until the exam boards have released these. This is because many schools use the exam papers as mock tests and so we refrain from presenting these on our site until they are widely available.