Genetic Algorithms: Choosing a Fitness Function

[ashmai]

Does anyone know of a good fitness function for evaluating an animal characteristic in genetic algorithms?
I'm doing a project. The prompt is: Select some features of an actual organism and design a genetic algorithm together with a reasonable fitness landscape to evolve the organism in time.
I'm using the Matlab genetic algorithms toolbox, but can't think of a good organism characteristic that has an interesting fitness function. I can do anything, like bird beak length, elephant ear radius, etc... I just need a good way to evaluate how the possible genotypes will survive - thus, I need a good fitness function! Maybe from literature?

 

[Pythagorean]

Is this homework?
it really depends on what's meant by "reasonable". What's the mathematics prerequisite? How biologically realistic should it be?

For instance:
You could model a 2D system of nonlinear differential equations between fox and rabbit populations and find an optimum point for either by adjusting some constant (the feeding rate of the foxes on rabbits or something).

The fitness function would then be the difference between say, the fox's population and the fox's maximum allowable population, and as the feeding rate is mutated, a most efficient feeding rate is found.

http://vlab.infotech.monash.edu.au/simulations/non-linear/fox-rabbit/