Anyone who has taught biology in the past 10 years has probably encountered the peppered moth virtual lab. It's a good one; it's based on a real situation and includes plenty of background information. The student plays the role of a bird picking moths off of trees. Two different environments are tested; a forest with light-colored trees and a forest with dark-colored trees, representing the effects of industrial melanism. Before I used this virtual lab, I did a paper-based version. Students would pick up paper hole punches on a background that matched and on a different colored background.
How is the natural selection simulation on Biology Simulations different than other options? I added a third environment. In this scenario, there are organisms of a single species with two different color phenotypes; brown and gray. One of the environments is primarily gray, one is brown, and one is green. The third environment produces a situation where one phenotype is not expected to be favored.
To run the simulation, select an environment (the desert is the default), and then click "Run Simulation". The student controls a canine-like predator with the cursor. They click on the prey to "eat" them. After 20 seconds the simulation ends, and data is displayed in the upper left corner. The starting and ending percentages for each color are presented. Each of the 50 individuals in the starting population is randomly assigned one of the colors. The starting population will be close to a 50/50% split between brown and gray. However, there will be variations from trial to trial.
The worksheet (Google Doc version) that goes with this lab involves multiple trials and calculation of an average. Students are then asked to analyze each situation to determine if natural selection is occurring, and how that will alter the prey species in the future. The worksheet also helps tie natural selection to real-world examples, including peppered moths and Grizzly/Polar bears.
The lab can be a discussion starter for how changes to ecosystems lead to change in species. This is appropriate to both long term natural changes (evolution of horses is a good example here), as well as human instigated change (urban areas, industrial melanism, current climate change). This simulation can also start a discussion about variations in different populations of a species living in different environments. This can then be extended to a discussion of speciation. While the trait examined in the simulation is color, students should keep in mind that any number of less visible traits are also affected by natural selection. Virtual labs are a good opportunity to give students a relatively simple framework of understanding that can then be applied to real-world data.