Biology Reference
In-Depth Information
cover the distance in a time that varies in line with a statistical dis-
tribution (Fig. 2B). This is a case of an intrinsically random phe-
nomenon because the behaviour of the car is itself random. The
statistical variations are not the result of disturbances to a deter-
ministic mechanism. In addition, selection can be imposed on the
intrinsically probabilistic behaviour of the car. Only certain jour-
neys may be chosen, for example those made between two times
fixed in advance. That will restrict the distribution of the results
and it may even be that the remaining variability will be of the
same order of magnitude as that of a deterministic mechanism with
noise (Fig. 2B). Nevertheless, in this case the phenomenon remains
intrinsically probabilistic and the variability of the result is reduced
by the selection applied. This is a phenomenon that in concept is
analogous to natural selection, where the diversity of phenotypes
produced randomly by mutation is reduced by selection.
As everyone knows, the theory of natural selection is very
important in biology. It implies that if there were no selective con-
straints, all living forms would form but one continuum, in which no
form was distinguished from the others as a result of their contin-
uous variation (Fig. 4A). It is solely because of the action of envi-
ronmental selection that species can be separated one from the
other (Fig. 4B). Thus the order they represent is not intrinsic to
the organisms but is the result of their relationship to the environ-
ment. In addition, it is relative. If the selective constraint changes,
other species are selected (Fig. 4C). That explains why, although
all species have a common origin, they populate different ecosys-
tems. In contrast, in a deterministic mechanism with noise, such as
reaction-diffusion or self-organisation, the order only depends on
the specific relationships of the constituents which are intrinsic
to the organism. Order is therefore absolute and inherent in the
organisms. The random event is integrated into these theories
as noise, that is to say, as an accident that triggers the specific
reaction-diffusion or emergence phenomenon.
It is important to differentiate deterministic mechanisms with
noise clearly from intrinsically probabilistic mechanisms. It is true
that superficially they resemble each other in calling on random
