52 



ECOLOGY 



Part II 



I diatoms ) > ( copepods | — ► (crustaceans] 



Fig. 4.1. In their own way of living Eskimos are finally dependent for food upon 

 diatoms and other algae, the microscopic plants that crowd the surface waters of 

 the arctic seas. The dependence is indirect but sure, just as farther south human 

 dependence for beef steak is upon plants. (After Transeau and Tiffany: Textbook 

 of Botany. New York, Harper & Bros., 1940.) 



Plant and Animal Relationships 



Building Materials and Protection. Plants furnish building materials for 

 all animals from insects to man. Wasps bite off wood fibers for their paper 

 nests, a host of insects lives within burrows in stems and tree trunks. The 

 habits of land birds would be changed beyond recognition if those birds did 

 not perch and nest in trees, or nest and feed in grass and mosses. There is 

 scarcely a mammal, short of ocean-going whales and their kin, that does not 

 at some time take to plants for shelter. Hundreds of field mice live among the 

 grasses of empty-looking fields; the wildcat climbs a tree for a meal of young 

 birds; in South America trees furnish the bandstands for the howling monkeys 

 and the hammocks for sleeping sloths. In the noon heat of the tropics the 

 silent forest is populous with hiding animals. 



With the main exceptions of beavers and man, mammals do not use wood 

 for building. Man is the great builder with plant fiber. From the time human 

 animals left their caves they began to make earthen and wooden houses and 

 long before that they must have used windbreaks of wood. The prehistoric 

 lake-dwellers lived in wooden houses raised on piles above the lakes, ideal for 

 safety as well as for fishing at home. 



Throughout history plants have supplied humanity with wood for boats 

 and wagons, and fibers for ropes and cloth. In recent years the elegant and 

 versatile rayons and plastics have been produced mainly from plant products. 

 The existence of all this outfit of civilization hinges upon a microscopic struc- 



