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This past week I have made several changes to my model. Initially my model consisted of two populations: one population that reproduces twice during its life span at a certain age and lives for a shorter time, and another population that reproduces once at a certain age and has a longer life span. I also had a population-capacity global variable to maintain the population size below a certain determined number.  One of the changes I made to the model was to make the two different populations of organisms reproduce at different rates but not have determined ages when they reproduce.  Another change was that in addition to having each population of organisms die at a certain age, I made their death rates a function of populations size, to model more realistically how population density is maintained constant over time. 

So currently the model consists of two populations that vary in terms of birth rates, death rates and life span. With the current values I have set for birth rate and death rate, population 1 on average has a density of 200 organisms and population 2 on average has a density of 100 organisms.  I intend to make sliders to allow the user to vary these variables to see how they affect population density.

I then introduced predators into the model which will kill an organism when they land on a patch that an organism is occupying. If the organisms are above a certain age they can learn to avoid predators. So for each population of organisms there is a certain range of ages when they can avoid predators: for population 1 the range is between ages 7 through 9, and for population 2 the range is between ages 7 and 49. I then made monitors to show how the predators are affecting the distribution of ages in the two populations. I hope to add a bar chart showing the number of animals at various ages over time.