PAGE 



UNIT SIX • How Did Life Begin? 435 



22 • Opinions on the Beginnings of Life 437 



23 • History of Life on Earth 450 



24 • The Facts of Heredity 472 



25 • How Species Have Arisen 506 



UNIT SEVEN • Why Cannot Plants and Animals Live Forever? 525 



26 • The Limitations of Life 527 



27 • The Conflicts of Life 540 



28 • The Interdependence of Life 559 



29 • The Balance of Life 578 



UNIT EIGHT • What Are the Uses of Biology? 603 



30 • Biology and Health 605 



31 • Biology and Wealth 641 



32 • Biology and the Pursuit of Happiness 658 



IN CONCLUSION • Man the Creator (i]9 



APPENDIX A • Grouping of Plants and Animals 687 



APPENDIX B • Supplementary Readings 701 



INDEX 705 



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VIII 



