II J 



THE INTERDEPENDENCE OF LIVING THINGS — 

 THE WEB OF LIFE 



Preview. Relations between members of the same species; care of 

 eggs by parents; care of young • Relations of mutual aid • Animal can- 

 nibalism • Relations of competition • Relation of members of different 

 species ■ Adaptations for food-getting in animals • Scavengers • Food- 

 getting in plants ; carnivorous plants • Symbiosis • Commensalism • Par- 

 asitism • The chemical relationship of plants and animals • Life habits of 

 bacteria • Relation of bacteria to free nitrogen • Rotation of crops • The 

 relations between insects and flowers • Suggested readings. 



PREVIEW 



Those who have been fortunate enough to be in California or Flor- 

 ida when the oranges are in bloom will never forget their odor ; nor 

 will they, when examining the grove, fail to notice the large number 

 of bees vi-siting the flowers. The bees are after nectar and pollen, 

 yet without these winged agents, the crop of oranges for the follow- 

 ing year would probably be small. This interrelationship between 

 insects and flowers was noticed by Charles Darwin, who pointed out 

 that the size of the clover crop in England depended upon the num- 

 ber of cats in a given region. His friend Huxley, who knew better 

 than Darwin how to popularize science, immediately went him one 

 better and added that the size of the clover crop depended upon the 

 number of old maids. When asked to explain, he gave this logical se- 

 quence of events. Old maids keep cats ; cats prey upon field mice ; 

 mice provide nesting places for bumblebees ; bumblebees pollinate 

 clover, upon which pollination the next year's crop depends. So he 

 had a perfectly logical chain of events. Throughout nature there is 

 this give and take between different organisms which we call the web of 

 life. When man interrupts or displaces a link in the chain of interre- 

 lationships, the web is broken and the whole fauna or flora of a region 

 may be changed, as in the case of the Englishman who took a bit of 

 water cress to Australia, planting some in a nearby stream to remind 

 him of home. This foreign plant, having no enemies and finding 

 conditions favorable for its growth, literally overran the waterways 

 until today the rivers of Australia are choked with water cress. Look- 



11 



