Biology Reference
In-Depth Information
of enzyme activity depend on differential gene expression (Jungermann
and Sasse, 1978; McGrane
et al
., 1992).
During evolution, organisms have not only undergone an
increase in the complexity of their structure, but also optimisation
of their regulation. Molecules such as hormones that act like signals
have arisen. Later in this chapter we will discuss in detail cell dif-
ferentiation and gene expression mechanisms which include the
action of these signals in the context of ontophylogenesis. Before
that, we must look in depth at two theoretical points which shed
light on the process of increasing the complexity of organisms and
show that ontophylogenesis is not only consistent with Bernard's
classic theory of the internal environment but in many respects is
a development of it.
6.1.2
The organism interiorises its environment
Ontophylogenesis is a phenomenon of hetero-organisation. In the
model of the heap of cells, the environment is propagated
via
the
nutrient gradients inside the organism forming cell microenviron-
ments. The structure of the organism arises owing to the environ-
ment being interiorised within it in this way, and is inseparable
from it.
This concept runs counter to the notion of an intrinsically
autonomous individual as conveyed by genetics and self-organisation,
theories which hold that the relationship of the organism to its
external environment is limited to the supply of nutrients that allow
it to form as individually determined within itself (by its genes or
the emergent properties). Natural selection indeed acts on the
organism, but in the adult stage, once it is already formed, and not
on its embryogenesis as is the case in ontophylogenesis. It would
thus be in the nature of embryogenesis to create an organism sep-
arated from the environment by a watertight barrier, ensuring its
existence thanks to its internal environment being constant. The
separation, in this finalist conception, of the living organism from
the environment is an essential characteristic of life. In actual fact,
this is a misinterpretation which distorts Bernard's theory of the
