Emergence 2009: Final Projects, IV


Biology 361 = Computer Science 361
Bryn Mawr College, Spring 2009


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Download/view: evolution10-1.nlogo


This model demonstrates how if an organism or population of organisms posses a trait that confers an advantage in a given environment their fitness in that environment will greater. This shows evolution of organisms that are best adapted to environment--environmental selection.

The SETUP button creates two different populations of animals: animals1 and animals2. These two populations differ only in the their life span.

The MAXAGEANIMALS1 and MAXAGEANIMALS2 allows you to chose the life span of animals1 and animals2 respectively.

The AVOIDPREDATORSAGE allows you to choose the age at which the two different populations learn to avoid predators. While you can only choose one variable for both populations, since they have different life spans they differ in the stage in their life during which they learn to avoid predators.

The PREDATOR-NUMBER button allows you to create a certain number of predators.

The PREDATION button introduces predators into the model which kill the organism when they land on the same patch as that organism.

The plot of Organisms Over Time shows the number of animals1 and animals2 in the population.

The monitors show the number of animals in the population that are above the AVOIDPREDATORSAGE age. This is also shown by the color of the animals. Darker animals are older than the learning-to-avoid-predator age and lighter animals are younger than the AVOIDPREDATORSAGE age.

Set the MAXAGEANIMALS1, MAXAGEANIMALS2, and PREDATOR-NUMBER sliders. Then press the SETUP and GO button to create the two different populations of animals. Next press the PREDATION button to introduce predators and observe what effect this has to the two different populations of organisms.
Notice that the selective pressure--predators, gives organisms that learn to avoid at a younger stage in their life an advantage. So as the model runs you should notice the number of older animals getting steadily larger. Also change the life spans, stage at which the different populations learn to avoid predators, and observe the effect this has on their relative fitness in the environment.
Try various life spans for the two different populations of organisms and see what effect setting the AVOIDPREDATORSAGE age very high or low has on the difference in number of organisms in each population when pressing the PREDATION button. Also how does the environment, number of predators, have an affect on the success of the two populations of organisms? Does a more dangerous environment enhance the fitness of one population of organisms to the other?
One way to extend this model is would be to keep the life spans of the two organisms the same but have the different organisms learn to avoid predators either early in their life or late in their life.
Thanks to Professor Grobstein and students in the Emergence class.


Models created using NetLogo.


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