The Difference between Spontaneous and Base-analogue Induced Mutations of Phage T4.

gm.) per square meter. The nonassimilated material (feces) does not change trophic levels but is available to other primary consumers such as bacteria or detritus feeders. The annual energy flow of the snail population was estimated to be about 290 Calories/M2/year, but during the summer the average standing crop of 700 snails/M2 assimilated only about twice as much as the average population of 10-20 grasshoppers/M2 (Fig. 3). While it would appear that both populations utilize only a small percentage of the total net primary production of the ecosystem it should not be assumed that food is nonlimiting. The maximum portion of the net production which is actually available to the populations has not yet been determined, nor has the utilization of competing primary consumers been considered. The fact that growth rate per individual in snails declined with increasing density in the field suggests that the rate at which nourishment can be ingested and assimilated on a square meter of marsh is not unlimited. It is evident that populations which differ greatly in life history characteristics, age structure, and metabolic rate cannot be compared on the basis of numbers and biomass (i.e., "standing crop") alone. However, through the common denominator of energy flow valid comparisons can be made, and the true role of the populations in the community can be evaluated. Energy flow analysis is the logical first step in finding out how populations really function in nature.