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  • Writer's pictureJolene Pappas

Sexual Selection

Updated: Apr 16, 2019

The sexual selection simulation examines intersexual selection and natural selection. In intersexual selection one sex (typically females) chooses mates based on a trait. This differs from intrasexual selection, where one sex (typically males) physically compete for access to mating opportunities.

Male color variation in sexual selection simulation
Females are more likely to select bright males for mating, but dull males are more likely to avoid predators

In this scenario, females are more likely to mate with the most brightly colored males. However, those males are also more likely to be eaten by predators. Students can control the amount of bright males in the starting population with the "Bright Males %" slider. Females always make up 50% of the population, so the graph only shows the males and the highest frequency any variation of male can reach is 0.5.

Data from a sexual selection simulation run
Data from a run with a Relative Predation Pressure of 0.

Students can also control the "Relative Predation Pressure." The higher the pressure, the more this species is being eaten. In an ecosystem, increased predation pressure could result from many scenarios. For example, this could be because there is a higher predator population, other prey is less available, or the predators prefer this species over other options. For the available worksheet, students test how predation pressure affects male coloration. They also do informal comparisons to figure out if the percentage of the population that starts bright affects results. While the provided worksheet is fairly guided, the simulation could be used in a more open inquiry fashion as well.

Data from an evolution simulation studying sexual and natural selection
Data from a simulation run with increased predation pressure

This simulation is loosely inspired by the PBS simulation, Sex and the Single Guppy. I used that activity for a number of years earlier in my career, but then I starting having problems getting it to run on my school's computers. Also, every year I used it I had to go through the hassle of getting around the district filters because the page was blocked due to the word "sex" (biology teacher problems...). Making my own simulation was my solution.

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