21. 



NATURAL HISTORY 



Epiphytes in a semitropical forest. Note the aerial roots for securiiif? moisture 



from the air. 



tion against low temperatures and moisture. Oiled skin and feathers 

 of birds are examples. Bones are hollow and large air spaces are 

 found between muscles. In insects a special aerating system exists, 

 since in these heavier-than-air machines a very rapid oxidation of 

 fuel material must take place if the organism is to be efficient in 

 the medium. 



Life on the Land 



Adaptations in plants for life on the land are seen in the widely 

 branching root systems, the woody stiffened stems, the leaves placed 

 in positions where light may reach them, and in the various adaptive 

 movements which enable green plants to get a share of the much 

 needed light. In tropical rain forests, this relation to light is seen in 

 a vertical zoning where sun plants form long twining stems, making 

 their way up the tall trimks of trees to an upper zone where light is 

 available, while in the lower areas are found shade-loving plants which 

 prefer less sunlight. In animals, where movement is much more 

 evident, there are special adaptations in the form of legs, which 

 support the body off the ground and allow of various types of loco- 

 motion such as climbing, crawling, walking, running, and leaping. 



