CHAPTER ^ 



BIOLOGY OF THE SEA— How They Live 



In this chapter the ways of life of animals of the zones of the sea will be 

 examined under the broad headings of adaptation to habitat, distribution and 

 dispersal, food and food chains, symbiosis, adaptive coloration, animal behavior, 

 and ecology and evolution. Each of these is a huge and complex topic so we 

 can do little more than whet the reader's appetite with general principles here. 

 Furthermore, these few topics by no means exhaust the subject of "how they 

 live." Methods of locomotion, methods of defense, and breeding patterns are 

 three more aspects, for instance (Chapters 7 to 10). It is hoped that the diver will 

 be able to see each animal he encounters under water in the light of the prin- 

 ciples that are given so that he will be better able to appreciate the evolution 

 and adaptation of the system of animate nature and also so that he may be able 

 to increase the depth of his experience in the sea. Most of the principles that 

 are discussed, incidentally, are not peculiar to the sea, but apply to all life, 

 including mankind. 



ECOLOGY AND EVOLUTION 



The nature of the sea and its immutability compared to land— its relative 

 homogeneity and lack of sharp environmental contrasts— has been discussed. 

 In this chapter, we shall see how animals adapt to meet this environment. 



Several billion years ago, probably about 4.5 billion, the earth was formed 

 as an immensely hot conglomeration of condensed gases. Over the next few 

 billion years, this mass cooled to the .temperature of water in its liquid state; 

 below 212° Fahrenheit. By this time, the earth had become enclosed in a hard, 

 wrinkled crust several miles thick, and this crust had trapped water vapor within 

 it which began to be disgorged from volcanoes in great jets of steam. Huge 

 clouds were formed, and a deluge of rain began to fall, which did not let up 

 until the amount of water equivalent to about one-fifth of all the water in the sea 

 had filled the ocean basins. Cloud formation and rains continued with diminish- 

 ing intensity until, about a billion years ago, the waters in the seas had reached 

 approximately their present level. It was in the shallow, warm waters of this 

 sea that life arose by a chemical reaction involving combination of chemicals 



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