The textbook is intended to provide clear, highly readable and easily understood information to the average student. It contains sufficient detail to satisfy the requirements of the New Edexcel Syllabus Specifications without the sometimes unnecessary detail which can cloud out underlying issues. Advanced level Biology Specifications (previously called syllabuses) have been revised since 2008. The first complete examination for this specification was held in May 2010. Every attempt has been made to ensure the relevance of the content to the syllabus specification. The book is intended to be a useful resource for students preparing for the Unit Four Biology paper for London Edexcel Examination. The book lists the syllabus specifications and the relevant notes are incorporated below each specification. This ensures that every syllabus specification has been covered. Students would be advised to study the content for each specification and then attempt the past paper Questions for each specification. This will help to reinforce the concepts and content.