Biology Reference
In-Depth Information
(2) evolution
irreversible accumulation of historically mediated information.
Probably the most fundamental difference between
physical
and
biological
evolutions (in the sense defined in Table
14.8
) is that the former does not but the
latter absolutely depends on
self-replication
. Since the physical Universe can
evolve without self-replication while biological systems cannot develop nor evolve
without cellular self-replication, the following generalization may hold:
Self-replication is necessary for development but not for evolution.
¼
(14.21)
Several corollaries of Statement 14.20 can be formulated:
Physical systems can evolve but not develop; Biological systems can both develop and
evolve because they can self-replicate. (14.22)
Self-replication is the complementary union of development and evolution. (14.23)
Self-replication of individual organisms in synchronic time leads to development: Self-
replication of groups of organisms in diachronic time leads to evolution. (14.24)
There are two kinds of
emergence
in biology -
ontogeny
(development) and
phylogeny
(evolution). The difference between
ontogeny
and
phylogeny
is that
the former involves individual organisms developing within their life spans (or on
the “synchronic” timescale) while the latter involves groups of organisms that
evolve on the “diachronic” timescale (Sect.
4.5
), which is much slower than the
synchronic timescale. In other words,
What develops is individual organisms over a synchronic timescale; what evolves is groups
of organisms over a diachronic time scale.
(14.25)
Statement 14.24 is equivalent to Statement 14.23 and can be viewed as defining
the meanings of “synchronic” and “diachronic” times (or time scales) in terms of
the well-established difference between
development
and
evolution
in biology.
Statement 14.24 is in turn equivalent to the following statement:
Synchronic time is developmental, i.e., finite and cyclical; diachronic time is evolutionary,
i.e., infinite and unidirectional. (14.26)
It is possible to represent Statement 14.23 diagrammatically as shown in
Fig.
14.3
. The main points of Fig.
14.3
can be summarized as follows:
1. The
synchronic time
(or developmental time) and
diachronic time
(or evolution-
ary time) are orthogonal/complementary in the sense that focusing on (or
prescinding) one automatically excludes the other from view.
2. The
synchronic time
and
diachronic time
axes define a space (to be referred to as the
self-replicator space
or the
EvoDevo space
) in which every point represents a self-
replicator or the living cell, the material system capable of both
development
and
evolution,
and clusters of points represent taxons, clades, or species of organisms.
3. The time in EvoDevo space (to be referred to as the
biological time
, in contrast to
the physical or Newtonian time) is two-dimensional consisting of the
synchronic
and
diachronic
axes that are orthogonal. The biological time can be depicted
as a spiral motion consisting of a series of coupled cyclical (as indicated by the
curved red arrow) and translational (as indicated by the straight red arrow)
motions as represented by a series of gray disks.
