Biology Reference
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metabolite gradient produced
by the dark cells
substrate
gradient
A
substrate
threshold
nutrient substrate
metabolite gradient produced
by the dark cells
substrate
gradient
B
substrate
threshold
nutrient substrate
(adapted from Kupiec, 1986, 1997)
F
IGURE
17. Ontophylogenesis of a multicellular living organism. A:
The proto-
organism develops in a given environment.
B:
If the environment changes (in this
example, if the substrate concentration changes), the internal selective constraints
(the substrate and metabolite gradients) which depend on it likewise change. The
threshold necessary for growth of the dark cells moves. This results in modifica-
tion of the structure of the cell colony. One single mechanism explains its devel-
opment and its evolution.
