Acknowledgements This project is done with great help of the following materials in reference: Books Basic Principles in Biology for HKCEE (Book 1), Fifth Edition By Y. K. To Hung Fung Book Co., LTD. Biology 1 ¡V A Modern Approach, Third Edition By W. K. Chan, S. F. Chu, S. W. Kong Aristo Educational Press Ltd. CD-ROMs Encarta 99 Encyclopedia Microsoft Corporation BodyWorks 6.0 The Learning Company