Control Systems in the Living World - Building the Most Complex Structure on Earth - page 4

An example of a simple, one-variable control system with a built-in controller
is a thermostat used for regulating a room's temperature. The control system con-
sists of a thermostat and a furnace. The thermostat is the controller of the system; it
receives information on the temperature of the room via a sensor (thermometer) and
compares it to the desired temperature, a selected set point. When the temperature is
lower than the set point, the thermostat switches on the circuit, which causes the fur-
nace to produce heat. When the temperature exceeds the set point, the circuit opens,
and the furnace switches off until the temperature falls below the set point again, and
the cycle repeats. But if regulation of a single variable, room temperature, cannot be
achieved without a control system, what should one think of incomparably complex
systems such as living cells or multicellular organisms, which have to both control
and regulate thousands of different variables, in differential patterns in tens or hun-
dreds of different cell types? The control system is a sine qua non of the existence of
all living organisms. The emergence and evolution of living systems are inseparable
from the evolution of the control system; the evolution of complex animal structures
and functions is associated by a parallel increase in the complexity of the control
systems.
If a control system with a controller is necessary for regulation of a single vari-
able such as the temperature of a room, it is absolutely necessary to regulate hun-
dreds and thousands of variables coordinated in time and the nanospaces of a cell.
In multicellular animals, the development and maintenance of normal structure are
a function of an integrated control system ( Figure 1.4 ). It is a hierarchical system of
controls on several levels of organization, in which higher levels of control impose
restrictions on lower levels to minimize the noise in the transmission of information
downward to the cell level, where gene expression is regulated and patterns of gene
expression are determined.
The continued evolution of control systems increased the independence of living
systems from their environment, and as a rule, the degree of complexity of a living
system parallels the degree of the complexity and sophistication of the control sys-
tem. More complex systems require more complex and sophisticated control systems.
Recognition of the presence of a control system that is capable of maintaining the
normal structure of the organism implies that it “knows” what the normal structure
is. But if it has information about its own structure, there is no reason to doubt that it
is capable of transmitting it to its offspring.
Biological Reproduction
However successful they are in maintaining their normal structure, living systems
have to succumb to the thermodynamic forces of disintegration and decomposi-
tion sooner or later; their life expectancy is temporally limited, varying from min-
utes in unicellulars to thousands of years in trees such as olives. Yet life on Earth
has been prospering and evolving for more than 3 billion years because living sys-
tems invented a special “trick” of circumventing the second law of thermodynam-
ics. In order to avoid their unavoidable demise, they live or subsist long enough to
reproduce themselves before dying. The progeny will also be engaged in the same