GENETICS AND EVOLUTION 655 
very small proportion of the seeds and spores of plants actually 
germinate and averagely few of the seedlings attain maturity. 
2. STRUGGLE FOR EXxIsTENCE.—Owing to the production of 
individuals far beyond the earth’s facilities to support them, 
there is a struggle for existence. An intense competition is con- 
Fic. 487.—Charles Darwin. (Gager.) 
stantly taking place in nature for food, water and light among 
individual plants and animals. The struggle is unequal because 
of the variability in structures, activities and close relations. 
3. ORGANISMS AND SPECIES DiFFER IN ResPECT TO THEIR 
Fitness FOR A GIVEN ENVIRONMENT.—Obviously, a water plant is 
unfitted to live in dry soil and a dry soil plant unfitted to live in 
the water. 
