344 ELEMENTARY BIOLOGY 



you may see chickens peck at each other when they are feed- 

 ing ; they peck at anything that gets in their way. More 

 conspicuous are the competitions among the highest classes of 

 animals for their mates. Male seals and walruses will fight for 

 the possession of the females ; male stags and other mammals 

 will do the same. In such struggles the individuals are actually 

 exposed to injurious attacks, and the survival of the individual 

 depends upon his superior means of protecting himself. Some 

 birds also fight each other in this competitive way. 



We may conclude by recalling that every living thing is 

 exposed to a number of obstacles or direct dangers to well- 

 being ; that some of these arise from excess or shortage of 

 certain materials in the environment, and that others arise from 

 the various co-inhabitants of the world. To live, one must be 

 able to overcome these obstacles and to escape these dangers. 



