"...Evolution does not occur on individuals, it acts on populations."
The toughest thing for people to understand when they are first learning about evolution is the idea that evolution does not occur on individuals. It acts on populations. This piece is a simplified visual version of this theory, where unequal death changes the way the population looks.
So how does the this piece work? In the code, each jellyfish born has a “phenotype value” (pv):
PV = 1
PV = 3
PV = 5
PV = 8
PV = 10
Within the code, the “birth” function analyzes the pv jellyfish “alive” (on screen) and considers those values as the gene pool. If there are 100% pv = 9. The child will likely be born a pv = 9 as well.
That being said we know in real life passing on genes isn’t perfect. You might look identical to your mom, where as your sister looks nothing like her. To consider this, the code also has a variation factor for each birth. There is a 66% chance the pv value passed on is identical, a 17% percent chance the pv value will increase by one, and a 17% percent chance the pv value will decrease by one. By adding this into the code it allows for the population to avoid fixation.
The “death” function within the code considers the type of selection acting upon the population. If the dial is set to “no selection”, the probability of each jellyfish dying is equal regardless of pv value. This allows us to witness genetic drift due to the small population size. Random chance will be responsible for the changes.
In the "Green Jellyfish Dominant" model, the probability of pv = 1 dying is significantly higher than p = 10. With this in mind it is important for me to clarify that it is still possible that p = 10 can die. Natural selection is not that perfect... black & white… binary. There is simply a higher chance of death occurring.