338 



Relations within the Species 



of crowding increases proportionally, the growth of the population can 

 be expressed as follows: 



dt 



= b 



K^) 



where b is the biotic potential, N is the size of the population at any 

 moment, and K is the ultimate maximal size possible for the popula- 

 tion in the given area. In words, the equation simply says that the 

 rate of increase of the population is equal to the potential increase 



80 



70 



60 



50 



1 40 



30 



20 



10 



fc 10 



6 |_ _ 



3 4 



Units of time 

 Fig. 9.11. Upper figure: graplis showing tlieoretical increase in total numbers 

 during (A) unimpeded and (B) self-limited population growth (logistic curve). 

 Lower figure: graph of numbers added to population in each time interval during 

 the logistic growth shown by ( B ) above ( values plotted at midpoint of each time 



interval ) . 



