Uroboros
Uroboros, the Serpent biting its own tail
appears in New Kingdom
The image is taken from a 15th century
Greek alchemical text. (http://abacus.best.vwh.net/oro/oro3.gif ).
Here it symbolizes the eternity of life.
The CA is controlled by the following buttons:
Replant-No replant: Is a toggle switch which triggers
or stops zygote planting.
Shorter: Makes CA shorter
Longer: Makes CA longer
Obstacle a toggle switch which places an obstacle
at x=15.
Move obstacle+ moves it downward.
Move obstacle- moves it upward.
Kill CA
Upon loading the applet a zygote is planted, and differentiates into a mature CA.
Let it evolve until it matures into an Uroboros,
which hunts its own tail. Only the first CA state (state-0) is active,
all other states are memory states. State-0
is a stem state (cell) which lives forever. The rest are short
lived transitional
states (cells) or memory states which store the past events of
the stem state. Their maximal age is 58 time units where upon they
die.
As the Uroboros advances,
its stem cell enters the space vacated by the last dying memory state.
The CA maintains a steady state in which death rate
equals the birth rate. During each time step the stem cell generates
two daughter cells: One replaces the parent and becomes a stem cell.
The other becomes a transitional cell which starts advancing backward
toward its graveyard (the white space between head and tail). This
is known as asymmetrical
cell division.
Clicking on “kill CA” kills the stem cell whereupon
no new cells are formed. Death rate > (birth rate = 0) and the
Uroboros
. shortens.
If you click “replant” a new zygote is formed. After clicking
“kill CA” and “no replant” the Uroborus
vanishes. Uroborus fate depends on two buttons:
“kill CA” and “no replant” Uroborus vanishes.
“kill CA” and “ replant” A new zygote is planted.
Evolution
Click on “replant”, activate the “obstacle”
and let the stem cell interact with it. The Uroboros
will be perturbed and its structure changes. If it dies it will be replaced by
a new zygote regaining
its original structure. It
may however evolve into a new steady state structure (solution)
Asymmetrical cell division is a fundamental
property of life
The applet illustrates that life is maintained by
an asymmetrical division of a stem cell which generates a short lived
progeny. The human being originates from a zygote which divides asymmetrically.
One of its progeny matures into a short lived adult. The other is
called a gamete, which is destined to propagate life and accounts
for the fact that life is eternal.
Parthenogenesis
Generally two gametes, the ovum and sperm, have to
unite in order to form a zygote. However a zygote may be generated
also only by the female gamete. This process is called parthogenesis.
Three theories explain
how life started on earth:
2. It evolved from an-organic matter.
3. It reached earth from outer space (Panspermia)
Additional reading
Complexity
Streaming tissues