Biology A-level is examined by year. Year 1 is examined in paper 1 and year 2 is examined in paper 2. Paper 3 consists of content from both years 1 and 2. When revising content for the papers it is imperative you revise the practical content, including methods and expected results. Although paper 3 is meant to be the 'practical' paper there is nothing to stop them examining practical content in papers 1 and 2 also. Statistical tests are also important to revise thoroughly as they hypothetically should only be examined in paper 2 and 3, however from personal experience I found they can also be examined in paper 1, hence these should be revised closely as they are easy marks. There is very little factual recall so it is important to have a good understanding of the content so that you can explain it well and clearly.