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So there are the clear letters and units of information in the cell that can be determined

by sequencing RNA and DNA molecules. There are technical limitations, but with today’s

modern sequencing methods it is possible to sequence almost any amount of nucleic acids

and thus have any amount of this form of information available in a short time to answer a

question. For example, “transcriptomics”, i.e. the reading out of the RNA inventory of a

cell, enables us not only to find out globally which information is stored in all mRNA

molecules of a cell, but also to read out very precisely the inventory of switched-on genes

(“expressed genes”) that are active in this cell. In this way, a rapid inventory of the system

status of an immune cell or a cancer cell is obtained. In the future, this will be used more

and more intensively, for example to better design chemotherapy against cancer in patients,

or to know whether the immune defence is in good condition. So: No problem, a lot of

information about the living cell can be measured, at least with regard to DNA and RNA.

Nevertheless, there is a fundamental limitation for biological systems and even for all

sufficiently complex systems. Their behaviour is said to be “chaotic”, i.e. predictable only

over short periods. This is perhaps easiest to see if you think of the best-known chaotic

system: the weather. There, too, we can only predict what the weather will be like tomor­

row in, say, Würzburg, Erlangen or Amberg. Accordingly, this can only be described with

a certain probability, and over several days such a forecast is always relatively uncertain.

On the other hand, we know that the climate here in Lower Franconia, Middle Franconia

and the Upper Palatinate is a typical Central European one, we will neither expect a tropi­

cal storm nor deserts or glaciers here. This can be generalized: biological and more gener­

ally, so-called chaotic systems, can only be described exactly over relatively short periods

of time. Their long-term behaviour, however, is kept within fixed limits. In the case of

weather, this is called climate. More generally, such a confined system state is called an

“attractor” because it draws nearby system states into this stable ground state. A good

example from biology is our own health. Even there it is clear, sometimes I can be out of

breath or sweating, have a fast pulse etc., after a few minutes everything is back to normal.

On the other hand, if I catch germs, live unhealthy and that over longer periods, my system

state can also change radically, especially I can get sick. That is then a different attractor.

Because once you are sick, it takes some time and some effort to change from the sick

system state back to a healthy one. Many people, especially older people, nevertheless

remain chronically ill: the pathological condition is too strong, even with medicine the

person remains ill.

With this we already have the most important terms for the system description together

and can state: Biological systems can only be described exactly for a short time, but remain

attached to stable system states, so-called attractors, over longer periods of time. However,

if the system is disturbed or changed just enough, a new system state can then suddenly

exist, which then reinforces itself again. A so-called tipping point is reached. For example,

the forest has suddenly become a savannah or even a grass steppe or desert, to name a few

ecological examples at this point. It is therefore important to understand systems in terms

of their behaviour. Whenever they have feedbacks (positive, negative) and reinforcements,

small changes can build up – and this is exactly the reason why systems are then called

9  Complex Systems Behave Fundamentally in a Similar Way