Try the GCSE Bitesize website. The AQA syllabus is the most similar to Cambridge IGCSE.
Try the S-cool website for GCSE Biology notes and revision questions.
Doc Brown has a great website. Here is a link to the Biology, sections.
ClickBiology is a site with lots of good links for IGCSE Biology (videos, podcasts, games ets).
Check out Ruru Hoong's IGCSE Biology Revision notes
THERE ARE 21 UNITS IN IGCSE biology.
1. Characteristics and classification of living organisms
2. Organisation of the organism
3. Movement in and out of cells
4. Biological molecules
6. Plant nutrition
7. Human nutrition
8. Transport in plants
9. Transport in animals
10. Diseases and immunity
11. Gas exchange in humans
13. Excretion in humans
14. Coordination and response
18. Variation and selection
19. Organisms and their environment
20. Biotechnology and genetic engineering
21. Human influences on ecosystems