498 Dynamics of the Ecosystem 



cultures was found to be 12-20 per cent in moderate light and 2-3 per 

 cent in the full light of summer, and higher plants are reported to 

 display eflBciencies of the same order (Wassink, Kok, and van 

 Oorschot, 1953). When the small amount of light reaching the algae 

 in a series of lakes was combined with their average photosynthetic 

 eflficiency, values for the rate of utilization of light incident on the 

 water surface in the manufacture of carbohydrate ranged from 0.043 

 to 0.38 per cent (Clarke, 1939). 



For the plant: 



absorbed light 



Absorption 



Assimilation 



Growth 



Increase 

 For the herbivore: 



Consumption 



Assimilation 



Growth 



Increase 

 For the carnivore: 



incident light 

 carbohydrates formed 



absorbed light 



plant growth 

 carbohydrates formed 

 net increase of plants 



plant growth 



plants consumed 



plant growth 

 plants assimilated 

 plants consumed 



herbivore growth 

 herbivore assimilation 

 net increase of herbivore 

 herbivore growth 



herbivores consumed 



Consumption = — _ — — — 



herbivore growth 



herbivores assimilated 



Assimilation 



Growth 



Increase 



herbivores consumed 



carnivore growth 

 carnivore assimilation 

 net increase of carnivore 

 carnivore growth 



For the animals of the ecosystem, sample values may be given for 

 herbivore and for carnivore production. It is said that 40 kg of grass 

 are required to make 1 kg of beef. This is a value involving 2 steps 

 in our analysis— the ratios of herbivore assimilation and of growth— and 



