Biology is such a visual subject and there are huge benefits to be gained from watching a short informative video on the visual processes. In many circumstances a video or animation can help make a 2D picture or text come alive and support how you interpret the information. I would strongly reccomend watching videos or animations alongside your revision to help visulaise the processes involved. Here are some excellent documentary videos which I believe will support your learning. These videos have all been taken from youtube and none are my own with all rights belonging to the creators. In time I will post tutorials on all GCSE and A-Level topics, but for now enjoy these.