AQA website - past papers
If you really want some past paper practice clicking here is your best bet. Then select the details as shown below:
Cognito - AQA Combined Science (Trilogy) Foundation Tier
Cognito - AQA Combined Science (Trilogy) Higher Tier
Physics and Maths tutor - AQA biology by topic: NB these are for Separate Biology. You will need to check the Trilogy specification so you only practise relevant questions - ask your teacher if you are unsure.