2 RELATIONSHIPS OF THE LIVING WORLD Chap. 1 



On every hand animals depend upon plants directly and indirectly, for food, 

 for shelter, even for decoration. Long before mankind made bouquets, the 

 bowerbirds of Australia scattered blossoms on their courting grounds. Green 

 plants carry on the great business of making the food that is essential to 

 themselves and to animals. In spite of the schemes for providing the world 

 with synthetic food, a cow will keep her mouth to the grass for some time to 

 come. Plants also profit from the animals; many of them, including large 

 numbers of fruit trees, do not produce seeds without insect pollination. 



The two main ways to study animals are: with emphasis on their asso- 

 ciations in groups of other living organisms, and with emphasis on the indi- 

 vidual. 



As associated organisms animals are considered among others of their own 

 kind or of different kinds in environments of soil, water, or air, within a 

 complex web of influences. The environment of the butterfly on the flower 

 includes the sun, the rotating earth, and the atmosphere as well as the flower 

 (Fig. 1.1). Ecology is the study of plants and animals in their home environ- 

 ments. It is discussed near the beginning and again at the end of this book, 



Fig. 1.1. Escaping energy, the heat and light of the sun. Left, the sun in total 

 eclipse by the moon. The sun's corona of light streaming out great distances from 

 behind the darkened moon. Right, part of the profile of the sun showing its promi- 

 nences, great flames that extend hundreds of thousands of miles into space. All 

 processes of living are related, directly or indirectly, to the capture of the radiant 

 energy of the sun. (Courtesy, Mount Wilson and Palomar Observatories.) 



but the relations of living organisms to their surroundings pervade all of its 

 chapters. The animal body itself is a portable environment; the lungs and the 

 heart carry on unique activities in their own special surroundings. The evolu- 

 tion of animals is a history of relationships. 



Everybody has had experience with an animal in its home territory: clothes 

 moths in flannel, skunks along the byways, or robins on the lawn. Everyone 

 knows that plant lice suck up plant juices, that robins eat hugely of earth- 



