Chapter X 

 THE ORGANISM AND ITS ENVIRONMENT 



Types of Adaptations. Protoplasm can function as the physi- 

 cal basis of life only when it is so adjusted to its surroundings that 

 a more or less constant supply of energy and materials enter, and 

 only when no external conditions interfere with its energy-trans- 

 forming processes. Constant changes in the environment compel an 

 animal to expend energy in making corresponding adjustments. 

 Moreover, the obtaining of materials for nutrition, the safeguarding 

 of the organism from injury, and the assurance of perpetuation of 

 its kind by reproduction require energy expenditure. So all animals 

 are constantly engaged in a struggle with the environment; life is 

 perpetuated and maintained for a longer or shorter time in spite of 

 the adverse conditions they encounter, and at the expense, in some 

 animals at least, of tremendous losses. Fish and frogs, for instance, 

 spawn enormous numbers of eggs, of which only a very few ever 

 reach the adult stage. Starfishes shed countless numbers of eggs and 

 sperms into the water, from which chance meeting of sperm and 

 tgg results in the development of comparatively few adults. 



A character that fits the organism to cope with the environmental 

 difficulties it faces is termed an adaptation. According to their 

 origins, adaptations may be classed as species adaptations, that is to 

 say, adaptations which are a part of the inheritable features and 

 characters of the species and are possessed by all members of the 

 species; and individual adaptations, which are characters peculiar 

 to individual members. According to their nature, adaptations fall 



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