Chapter 13
Artificial Worms
Any intelligent fool can make things bigger, more complex,
and more violent. It takes a touch of genius – and a lot
of courage – to move in the opposite direction.
(Albert Einstein)
13.1 Artificial Worm Model
Natural selection works in the presence of chance or randomness. As random
mutations take place, the form or function of organisms changes. With changes in
the “appearance” of individual organisms may come an enhanced ability to survive
and to pass on the respective traits to subsequent generations. However, because
mutations continue to take place, and because the environment within which natural
selection occurs is not constant, it is not automatic that the fitness of offspring
increases from one generation to the next.
The following model—briefly mentioned in Cohen and Stewart [1]—illustrates
the workings of natural selection and randomness for a population of six worms of
different length. Each individual worm can, in principle, mate with any one of the
others. The decision of who mates with whom is randomly made. Of the three
randomly chosen pairs of mating worms, only the longer one of the two will survive
to bear exactly two offspring. The offspring, in turn, are either shorter or longer
(randomly decided) than their parent. Their actual length is determined by a coin
toss. If the coin shows head, one of the offspring will be exactly 1 unit longer than
the parent, and the other one will be exactly 2 units longer than the parent. In the
case that the coin shows tail, the two offspring are, respectively, 1 and 2 units
shorter than the parent. The moment the offspring are generated, the parent dies.
A save-disabled version of STELLA and the computer models of this book are available at
www.iseesystems.com/modelingdynamicbiologicalsystems.
B. Hannon and M. Ruth, Modeling Dynamic Biological Systems,
Modeling Dynamic Systems, DOI 10.1007/978-3-319-05615-9_13,
© Springer International Publishing Switzerland 2014
105
Artificial Worms
Any intelligent fool can make things bigger, more complex,
and more violent. It takes a touch of genius – and a lot
of courage – to move in the opposite direction.
(Albert Einstein)
13.1 Artificial Worm Model
Natural selection works in the presence of chance or randomness. As random
mutations take place, the form or function of organisms changes. With changes in
the “appearance” of individual organisms may come an enhanced ability to survive
and to pass on the respective traits to subsequent generations. However, because
mutations continue to take place, and because the environment within which natural
selection occurs is not constant, it is not automatic that the fitness of offspring
increases from one generation to the next.
The following model—briefly mentioned in Cohen and Stewart [1]—illustrates
the workings of natural selection and randomness for a population of six worms of
different length. Each individual worm can, in principle, mate with any one of the
others. The decision of who mates with whom is randomly made. Of the three
randomly chosen pairs of mating worms, only the longer one of the two will survive
to bear exactly two offspring. The offspring, in turn, are either shorter or longer
(randomly decided) than their parent. Their actual length is determined by a coin
toss. If the coin shows head, one of the offspring will be exactly 1 unit longer than
the parent, and the other one will be exactly 2 units longer than the parent. In the
case that the coin shows tail, the two offspring are, respectively, 1 and 2 units
shorter than the parent. The moment the offspring are generated, the parent dies.
A save-disabled version of STELLA and the computer models of this book are available at
www.iseesystems.com/modelingdynamicbiologicalsystems.
B. Hannon and M. Ruth, Modeling Dynamic Biological Systems,
Modeling Dynamic Systems, DOI 10.1007/978-3-319-05615-9_13,
© Springer International Publishing Switzerland 2014
105