Biology Reference
In-Depth Information
FIGURE 2.4
Trap-door functions in the Game of Life; knowing the arrangement of cells in the stable attractor in
which the system ends up does not indicate how it got there. The initial conditions may have been the straight line A,
the staggered line B or the 'knight'smove' C, which generates B, or a host of other possible starting conditions that have
not been illustrated. The final state is called an 'attractor' because several other states converge to it.
through the centimetre scale of snowflakes to the metre scale of sand dunes and up to, and
possibly beyond, the hundreds-of-light-years scale of galaxies. Morphogenesis of living
things is usually recognizably different from that of the physical world so it is worth taking
a moment to consider what the main differences are, in the hope that these differences will
highlight the key features that enable a living organism to use physical processes in a biolog-
ical way.
When asked what makes something 'biological' rather than purely physical, most biolo-
gists will instinctively, and correctly, focus on the Darwin/Wallace theory of evolution: if
the workings of a process are the result of, and can be modified by, natural selection, the
process is likely to be biological. Otherwise, it is not. That answer begs the question: what
makes a process open to modification by natural selection? Essential attributes of such
a process are flexibility and function.
