ENERGETICS AND ANIMAL PRODUCTIVITY
77
handle situations of imbalance because of the equilibrium assumption.
A very important point should be emphasized here, one that is most
apt to cause confusion when discussing the Lindeman model. A body is
made up of both matter and energy. The energetics approach is concerned only with energy, not the matter. The matter is recycled through
the biosphere, being used again and again through successive ages.
Energy is not recycled by the biosphere. Each time organisms transfer
potential energy from one trophic ievel to the next, a portion of the
energy is lost in the transfer, never to be regained by the system. Thus,
when we speak of standing crop, we are concerned not with the matter
this represents but with the amount of energy necessary to hold that
matter together.
The trophic dynamic approach to the problem, then, is concerned
primarily with food relationships (i.e. the food of the community), the
assignment of populations to food levels, and the total energy flow
through an area or community. A complete analysis of this kind results
in an energy balance sheet for the community and therefore should give
a number of internal checks on the consistency of the various estimates
of energies. If a model is to be a useful guide t o further research, it must
have particular characteristics which result in logical deductions and
predictions. Three important criteria for judging whether a model will
result in useful information are as follows: ( I ) the internal consistency
of the model; (2) the number of important testable hypotheses resulting
from the model; and (3) the relevance of the inodel to existing concepts
and hypotheses. How does the Lindeman model hold up under these
criteria? Slobodkin (1962) has indicated that Lindeman’s model is more
or less internally consistent and leads to testable hypotheses. This
model immediately raises three testable questions, which are: (1) What
is the maximum number of food links in an a,rea? (2) Is there a characteristic ratio between the calories contained in one trophic level and the
calories contained in the succeeding level? and (3) Are there any consistencies between the ratios of the productivity of a species and that of
its predators?
Criterion three mentioned above (the clarification and integration of
existing concepts and hypotheses) seems also to be met at this stage of
our knowledge by Lindeman’s model. It fits logically with the concept
of community. If the community is-real, then energy flow within community boundaries will be much greater than across community boundaries. Therefore, the tool for more certainly delimiting and defining
communities may be within the ecologist’s grasp. It is very likely that
the Lindeman model or some modification of it will give us a better
understanding of the community concept. Other ecological concepts
can be re-evaluated by use of the energetics a,pproach. For example, the
77
handle situations of imbalance because of the equilibrium assumption.
A very important point should be emphasized here, one that is most
apt to cause confusion when discussing the Lindeman model. A body is
made up of both matter and energy. The energetics approach is concerned only with energy, not the matter. The matter is recycled through
the biosphere, being used again and again through successive ages.
Energy is not recycled by the biosphere. Each time organisms transfer
potential energy from one trophic ievel to the next, a portion of the
energy is lost in the transfer, never to be regained by the system. Thus,
when we speak of standing crop, we are concerned not with the matter
this represents but with the amount of energy necessary to hold that
matter together.
The trophic dynamic approach to the problem, then, is concerned
primarily with food relationships (i.e. the food of the community), the
assignment of populations to food levels, and the total energy flow
through an area or community. A complete analysis of this kind results
in an energy balance sheet for the community and therefore should give
a number of internal checks on the consistency of the various estimates
of energies. If a model is to be a useful guide t o further research, it must
have particular characteristics which result in logical deductions and
predictions. Three important criteria for judging whether a model will
result in useful information are as follows: ( I ) the internal consistency
of the model; (2) the number of important testable hypotheses resulting
from the model; and (3) the relevance of the inodel to existing concepts
and hypotheses. How does the Lindeman model hold up under these
criteria? Slobodkin (1962) has indicated that Lindeman’s model is more
or less internally consistent and leads to testable hypotheses. This
model immediately raises three testable questions, which are: (1) What
is the maximum number of food links in an a,rea? (2) Is there a characteristic ratio between the calories contained in one trophic level and the
calories contained in the succeeding level? and (3) Are there any consistencies between the ratios of the productivity of a species and that of
its predators?
Criterion three mentioned above (the clarification and integration of
existing concepts and hypotheses) seems also to be met at this stage of
our knowledge by Lindeman’s model. It fits logically with the concept
of community. If the community is-real, then energy flow within community boundaries will be much greater than across community boundaries. Therefore, the tool for more certainly delimiting and defining
communities may be within the ecologist’s grasp. It is very likely that
the Lindeman model or some modification of it will give us a better
understanding of the community concept. Other ecological concepts
can be re-evaluated by use of the energetics a,pproach. For example, the