38 



Organic Evolution — Conservation 



Organic Evolution 



The basic resemblance of living things comes from their common origins 

 and countless kinships. Their extraordinary complexity and variety are due to 

 changes in them that have taken place during past ages and are continuing. 

 Living matter is known only as it appears in different species of organisms, A 

 species is a group of nearly related plants or animals that agree in certain 

 distinguishing characteristics. They interbreed freely and their characteristics 

 are inherited by their offspring. Species are inheritable patterns of life, re- 

 peated in generation after generation, though never exactly. They are patterns 

 and processes that require time to become established. No species of bird came 

 into being in a moment. Organic evolution is history. 



Origin of Life 



We do not know how life began. Neither do we yet know what keeps it 

 going. 



It is certain that the novelty of Uving matter is in the way it is put together, 

 its organization, not the materials. Not one of these is unique (Chap. 3), 

 The beginning of life might have been in the organization of a complex mole- 

 cule containing carbon, and perhaps capable of affecting other molecules. The 

 changes from the organization of such a molecule to that of the simplest 

 protozoan would be greater than those between a protozoan and man. 



Beginnings of Life 



We do not know when life began. Measurements of the radioactivity of 

 certain minerals have placed the age of rocks containing them at two billion 

 years (Fig. 38.1; Table 38.1), and there is evidence that these rocks are by 

 no means the youngest. A billion years and more may have passed before they 



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