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death by numbers

Kaitlin Cough, Elizabeth Harnett

1.) Ant Colonies: Social Organization

We saw that ants, while they do have a specific social organization, do not have a leader or director. Rather, they are all the same and all capable of doing each job in the colony. At any one time, there is generally a stable 50/25/25 ratio of ants doing each job, and when there are disturbances or changes in the environment the ant colony will try to maintain this ratio. This is due to the fact that ants emit hydrocarbons, each of which is slightly different for each of the different jobs. Every ant is capable of emitting each hydrocarbon and changing them at any time. Which one they emit, and which job they do, is dependent on them meeting 15 other ants within a set period of time--if they meet many who are doing the same job, they will switch jobs, and if they meet few doing their job, they will continue doing that job. Older colonies of ants adapt to disturbances, such as intruder ants, more quickly than younger ones and are able to stabilize the ratio faster simply because there are more of them, and therefore the 15 encounters happen sooner. They do not have a collective memory or history. Basically, we found that each ant is not different from the other, but by working together the colony has different traits (jobs). The different traits are made by the parts (ants) interacting with each other.

2.) Wolf Sheep Predation

The environment is stable when both the sheep and the wolves are dependent on a fluctuating energy source. The website mentioned that it was possible to create a stabilized environment without the sheep being dependent on the grass, however every time we tried to create a stabilized environment by either changing reproduction rate, energy rate or the number of initial sheep/wolves the sheep would usually grow exponentially whereas the wolves would become extinct. We could not figure out a way to create a stable environment when the sheep were not dependent on an energy source like the wolves. We concluded that to create a stable environment, both populations need to depend on a fluctuating food/energy source.

How much can we make sense of using computer models? What role does randomness play in them?

We think that randomness plays an important part in some of these systems. For example, in the Wolf Sheep Predation, though the beginning of the trial would fluctuate and look random in the end a pattern would be created. One population would increase whereas the other one would go extinct, or they would stabilize (with the grass). This reminded us of the Langton’s Ant that we looked at in class: though it started out looking random, eventually a pattern was created. Maybe on an individual level it is random, but as a group (on a larger scale) a pattern will be created, depending on the environment that the trial is taking place. Computer systems provided a good way for us to see the change of populations over time, and they account for a lot of different environmental variables.

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