Try out these websites for revision practise, exttra research and an excellent UN website full of data and interactive population pyramids!
BBC Bitesize
http://www.bbc.co.uk/schools/gcsebitesize/geography/development/
Rich World, Poor World
http://www.channel4learning.net/sites/planet/takrch.html
Current problems and ways we can help
http://www.oxfam.org.uk/
Development indicator data…. (and lots of it!) http://hdr.undp.org/en/statistics/data/
