778 



ANIMALS AND THEIR ENVIRONMENT 



IF WE WERE TO SIT ON THE MIDDLE BEACH OF TODAY... 



AS THE YEARS GO BY, THE PREVAILING 

 WINDS WOULD PILE OP THE SAND, 

 WHICH WOULD BE CAPTURED BY 



GRASS... 



AS THE HUMUS INCREASED WE WOULD 

 FIND OURSELVES SUCCESSIVELY AMONG 



THE COTTONWOODS, THE PINES. 



THE OAKS... . 



AFTER A FEW THOUSAND YEARS WE 

 WOULD BE SURROUNDED BY A BEECH 

 AND MAPLE FOREST 



3AND-AT THE TIME WE 

 FIRST SAT ON THE 

 MIDDLE BEACH. 



SAND-WASHED UP BY THE 

 WAVES AND BLOWN BY THE 

 WIND, SINCE WE FIRST 

 SAT ON THE BEACH. 



M 



HUMUS-ADDED BY 

 PLANTS & ANIMALS. 



Figure 37.9. Diagram of the succession of communities with time along the shores 

 of Lake Michigan in northern Indiana. (Allee, et al.: Principles of Animal Ecology.) 



