728 General and Applied Biology 



Adaptations may be internal (structure and activities of internal organs, 

 tissues, etc.) or external (external phenomena), just as variations may 

 be internal or external. The adaptive modifications in living organisms 

 are apparently unlimited as we study the great variety of plants and 

 animals. For example, the specific types of wings, legs, mouth parts, 

 antennae, digestive tract, respiratory system, metamorphosis, etc., are 

 among the most conspicuous adaptations of the numerous kinds of in- 

 sects to fit them into various environments. Through adaptations, cer- 

 tain plants have become able to live in the arid regions of the desert 



UERON 



GULL 



Fig. 361. — Adaptations of the bills of birds, showing variations in structure 

 for different uses. The generalized bill of the Grebe is for eating seeds; spoonbill 

 and duck, for straining mud; the heron, for catching fish; whippoorwill, for 

 catching insects; hawk, for tearing flesh; petrel, for catching Crustacea; gull, for 

 devouring refuse. (From Atwood, A Concise Comparative Anatomy, The C. V. 

 Mosby Co.) 



