This is just one example of a PhET Simulation from the University of Colorado at Boulder. These simulations are excellent demonstrations of scientific principles. All the simulations can be accessed by students from the home or they can be used at school.
In this particular simulation for Natural Selection, students can adjust the limiting factors for a population, or they can control the number of predators and watch what happens to their bunnies. They can also watch how adaptations affect the population and determine which adaptations are advantageous for different environments.