20 LIVING THINGS AND THE ENVIRONMENT 



hand for this work we say it is adapted to its function of grasping 

 objects. Each part of a plant or animal is usually suited for some 

 particular work. The root of a green plant, for example, is fitted to 

 take in water by having tiny absorbing structures growing from it. 

 The stems have pipes or tubes to convey liquids up and down and 

 are strong enough to support the leafy part of the plant. The 

 thin, flat leaves are arranged to receive a very large amount of 



sunlight and to act as 

 solar engines. Each part 

 of a plant does work, and 

 is fitted, by means of cer- 

 tain structures, to do that 

 work. The lungs of a 

 land animal are adapted 

 for taking oxygen from 

 the air, while the gills of 

 a fish can take their sup- 

 ply only from water; 

 that is, only from the air 

 that is dissolved in water. 

 It is because of such adap- 

 tations that living things 

 are able to do their work 

 within their particular 

 environment. 



Plants and Animals 

 and their Natural En- 

 vironment. — Those of us 

 who have tried to keep 

 potted plants in the 

 schoolroom know how difficult it is to keep them healthy. Dust, 

 foreign gases in the air, lack of moisture, and other causes make the 

 artificial environment in which they are placed unsuitable for them. 

 A goldfish placed in a small glass jar with no food and no green water 

 plants soon dies. The artificial environment lacks something that 

 the fish needs. Each plant and animal is limited to a certain en- 

 vironment because of certain individual needs which can be pro- 

 vided for only by that particular environment. 



A natural barrier across a stream. No trout would 

 be found above this fall. Why not? 



