E N E R G Y I N A N I M A L ECOLOGY
99
VII. CONCLUSIONS
It is clear from field data, evolutionary theory, direct calorimetry
data and a simple theoretical analysis that energy is of major significance in ecological systems.
It is possible t o show that the various theories that have been utilized
by workers in the field of ecological energetics are mutually intertranslatable.
The theoretical analysis is sufficiently rich at present t o permit
testing of empirical conclusions given any one of several kinds of raw
data. Even such practical questions as designating optimal procedures
for population exploitation and pest eradication are in principle
answerable within the existing theoretical framework.
The great lack a t the moment is sufficiently precise data. Until
recently, precise conversion coefficients for evaluating census data in
terms of energy have been missing. The error of mean estimates of
field situations attributable t o sampling variance in time and space
remains enormous.
The few laboratory analyses that have been made do not disagree
either with each other or with the results of field studies. Due to their
paucity as well as t o the high variance of field estimates the significance
of this lack of contradiction is not evident.
We can conclude that ecological efficiency is probably of the order
of magnitude of 5 t o 20%. A t present there is no evidence to indicate
either a taxonomic, ecological or geographic variation in ecological
efficiency. While evolution might tend towards a maximization of
ecological efficiency, there is apparently no theoretical reason why any
particular value should be preferred by all ecological systems. For any
particular species, the percentage of consumed energy transmitted t o
predators cannot exceed the percentage assimilated. The assimilation
percentage for most organisms a t most times is of the order of 20-40%
but this varies with the nature and abundance of the food supply.
At present, precise evaluation of efficiency in a few situations is
likely to be more significant than first order approximations in many.
ACKNOWLEDGEMENT
The research from my laboratory reported in this paper has been
supported by a grant from the National Science Foundation (G 9058).
REFERENCES
Armstrong, J. (1960). The dynamics of Dugesia t i g r i m populations and of DalphnM
pulex populations as modified by immigration. 104 pp. Ph.D. dissertation.
Department of Zoology, University of Michigan, Ann Arbor.
99
VII. CONCLUSIONS
It is clear from field data, evolutionary theory, direct calorimetry
data and a simple theoretical analysis that energy is of major significance in ecological systems.
It is possible t o show that the various theories that have been utilized
by workers in the field of ecological energetics are mutually intertranslatable.
The theoretical analysis is sufficiently rich at present t o permit
testing of empirical conclusions given any one of several kinds of raw
data. Even such practical questions as designating optimal procedures
for population exploitation and pest eradication are in principle
answerable within the existing theoretical framework.
The great lack a t the moment is sufficiently precise data. Until
recently, precise conversion coefficients for evaluating census data in
terms of energy have been missing. The error of mean estimates of
field situations attributable t o sampling variance in time and space
remains enormous.
The few laboratory analyses that have been made do not disagree
either with each other or with the results of field studies. Due to their
paucity as well as t o the high variance of field estimates the significance
of this lack of contradiction is not evident.
We can conclude that ecological efficiency is probably of the order
of magnitude of 5 t o 20%. A t present there is no evidence to indicate
either a taxonomic, ecological or geographic variation in ecological
efficiency. While evolution might tend towards a maximization of
ecological efficiency, there is apparently no theoretical reason why any
particular value should be preferred by all ecological systems. For any
particular species, the percentage of consumed energy transmitted t o
predators cannot exceed the percentage assimilated. The assimilation
percentage for most organisms a t most times is of the order of 20-40%
but this varies with the nature and abundance of the food supply.
At present, precise evaluation of efficiency in a few situations is
likely to be more significant than first order approximations in many.
ACKNOWLEDGEMENT
The research from my laboratory reported in this paper has been
supported by a grant from the National Science Foundation (G 9058).
REFERENCES
Armstrong, J. (1960). The dynamics of Dugesia t i g r i m populations and of DalphnM
pulex populations as modified by immigration. 104 pp. Ph.D. dissertation.
Department of Zoology, University of Michigan, Ann Arbor.