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Species and EcosystemsLarry Slobodkin once said that ecology without species is the ultimate abomination. I used this admirable phrase in several seminars, where I classified myself as an abominable ecologist, since I was working on size-structured models with no reference to species. There are many ecologists who feel, like Slobodkin, that ecosystems are simply collections of species, and the properties of the constituent species are what determines the nature of the ecosystem. I belong to a different school of thought, one that holds that the species that we see are the ones that fit into the ecosystem, and that it is the ecosystem that determines what species belong to it.
It is of course the functioning of the factory that determines these "emergent properties", and although the workers are the basic components of the labour force, we know that the managers simply hire enough workers to produce parts that satisfy the mathematical relationships necessary to turn out wagons. In other words, the emergent properties (the 1:1:2:4 ratios of components) come first, and the composition of the work force is constrained by the requirement to satisfy these relations. An ecosystem works very much the same way. For example, every ecosystem produces waste products, and there must be detritivores to consume this waste. Which species play this role may vary, just as factories in different locations hire their workers from different labour pools, but the job is essential and unless some species fills it, there will not be a persistent ecosystem. Similarly there must be primary producers, herbivores, carnivores, and so on. There are many different kinds of ecosystems possible, but there is a common structure that cannot be changed by individual species. The species that exist in any given ecosystem are like the workers in a plant - they are the ones that found a job. |
Developed and maintained by William Silvert. |
Consider a factory
that makes wagons. There may be several teams of specialised workers who make
wheels, axles, handles, and of course the body of the wagons. The dynamics of
this labour force can be quite complex. The workers who make red wagon bodies
are probably a lot more domineering than those who make just the handles, and
there can be all kinds of Freudian implications to the manufacture of wheels and
axles. To find out how much of each product is made involves studying the
personalities of these groups. And yet, there is an interesting pattern of
emergent properties that emerges from the study of the factory, which is that
the workers who make handles produce exactly as many handles as the body makers
produce bodies, while the axle makers produce twice as many axles, and the wheel
makers turn out an amazing four times as many wheels as handles or bodies! (The
Freudian interpretation of this lop-sided ratio between axles and wheels is one
of those things best left to the imagination of the reader.)