To approach this question, it is important that you understand there is no one answer for the term biodiversity. There will be an exam board definition provided, so it would be best to start of with this. Biodiversity in essence means biological diversity. From here you can begin to breakdown the difference types of biodiversity, providing an explanation as well as examples, this will help you achieve the top end marks.
For example, there are 3 types of biodiversity according to the Edexcel specfication; species, genetic and ecosystem.