the "superior" ones. Perfectly helpless babies of any "race" will survive the 

 first year only under the suitable care of elders. That is, the survival rate 

 depends more upon the care and protection that babies receive than upon 

 individual variation in the capacity to carry on as organisms — ^after the early 

 difficulties are overcome. A poor home will destroy the promising and the 

 worthless in about the same proportions. 



The struggle of plants is against enemies, against competitors, against 

 changing physical and chemical conditions. All but a very few individuals 

 are likely to be destroyed in the course of a season, without regard to the 

 particular qualities which might be of advantage in the "struggle for existence". 



What Is Meant by the Struggle for Existence? 



One in a Thousand Some species can keep alive only if each adult 

 (or pair of adults) bears many thousands of new individuals — eggs or seeds. 

 The early stages are subject to frost and drought. And since they contain 

 concentrated food material, they are exposed also to hungry plants and ani- 

 mals of many kinds. A little later the young are still exposed to changing 

 conditions of moisture, temperature, light — and hungry hordes of other 

 enemies. 



From one spot to another on the surface, in the soil, in a pond or in the 

 ocean, the physical conditions vary. Here it is colder, and there warmer. 

 Here the concentration of carbon dioxide is high; there it is low. Here there 

 is an excess of one kind of salt, and a shortage of another; but there the con- 

 ditions are just the reverse. These variations mean that one organism can live 

 here, but not there; that this one can live here, but not another. 



Other features also vary. At some points the moisture varies tremen- 

 dously from season to season, perhaps even from day to day or hour to hour. 

 At another point the nights are very cold and the days very hot. At tide level 

 this spot is well covered with sea water for hours at a stretch, but later it is 

 almost dry and exposed to the glaring sunlight. A living plant or animal may 

 get a start at some point, but be constantly threatened not alone by "enemies", 

 but by the fluctuations in physical conditions. The urge of each organism to 

 get food and to meet the various threats and dangers results in a complex 

 process which has been called the "struggle for existence". 



Among human beings the "struggle for existence" is in part a struggle of 

 intelligence and understanding rather than one of swift movements or tough 

 skin or powerful muscles. For the bulk of the human race, infants seem to 

 survive in larger or in smaller proportions according to the kinds of families or 

 civilizations they are born into (see charts on opposite page and on page 547). 



This struggle includes many processes that are in themselves rather mild 

 or even passive — like the growing of a shell by the clam, or the growing of a 



544 



