viii CONTENTS 



CHAPTER PAGE 



29. The Distribution of Animals 459 



Principles of distribution — Barriers to dispersal — Aids to dispersal — 

 Migration of animals — Reduction in range — Discontinuous range — Geo- 

 graphic realms — Animal distribution in the ocean — Review questions. 



30. Ecology and Wild Life Conservation 472 



Importance of conservation — Succession — Biomes — The web of life — 

 Balance of nature — Restoring wild life — Role of the predator — Farm 

 habitats — Review questions. 



31. The Bridge of Life 488 



The protoplasmic bridge — Early speculation on heredity— Meiosis— 

 Spermatogenesis — Oogenesis — Fertilization — Genes and ancestry — Re- 

 view questions. 



32. The Principles of Heredity 503 



The influence of heredity — Dominance and recessiveness — The mono- 

 hybrid cross— Genetic ratios— Intermediate genes— Independent segrega- 

 tion of genes — Linked genes and crossing over — Multiple genes and 

 quantitative characteristics — Sex determination — Sex-linked inheritance 

 — Review questions. 



33. The Development of the Individual 523 



Embryology— Early cleavage— Formation of the blastula and the 

 gastrula — Formation of the mesoderm and the coelom — Variations in 

 cleavage of the chordate zygote — Variations in the method of mesoderm 

 formation— Formation of the organ systems— Early embryogenesis of 

 the mammals— Experimental embryology— Review questions. 



34. The Changing World of Life 541 



Variation in the universe — Natural selection — Sexual selection— Artifi- 

 cial selection— Mutation and selection— Biological evolution— Evidences 

 of evolution — Review questions. 



Glossary 

 Index . . 



561 

 573 



