546 BIOLOGY AND HUMAN LIFE 



Food-getting 

 Absorption 

 Finding suitable location and food 



Through outside agency Through fighting 



(wind, water, etc.) Members of own species 



Through migration Other species 



Through pursuit 

 Escape from enemies 



Predatory enemies ; parasitic enemies 

 Results of struggle 



Natural selection (elimination of the relatively less adapted) 

 Survival of the fittest 

 Accumulation of favorable variations 

 Gradual replacement of older types 

 Increasing adaptation of Hfe to special conditions 



3. Man's struggle 



Man's disadvantage as organism 



Thin skin Weak teeth and claws 



Sparse hair Slow movements 



Weak muscles Relatively dull senses 



Man's advantages 



Superior brain and intelligence 

 Enables him to utilize other organisms and inorganic re- 

 sources to supplement his body 

 Disposition to social life 



Leads to formation of large groups in which mutual aid 



is possible 

 Leads to division of labor and makes available for group 



great variety of talents 

 "In union there is strength" 



4. Systematic mastery of material needs 



Plant and animal cultivation versus fishing, hunting, root-digging, 



etc. 

 Use of tools in addition to weapons 

 Improvement of tools and development of machinery 

 Intensive cultivation 

 Better management 



Of soil ; of organisms 

 Improvement of types cultivated 



Through selection ; through breeding 



Through exploration for suitable types 



