This article describes a teaching unit that used Lego Robotics to address state science standards for teaching basic principles of evolution in two middle school life science classes. All but two of 29 students in these classes were native Spanish speakers from Mexico. Both classes were taught using Sheltered Instruction Observation Protocol (SIOP). The evolutionary robots (Evobots) unit was comprised of twelve 60 minute classes. The students worked in cooperative groups to build and test Evobots that could either be the best at one thing (a specialist) or second best at everything (a generalist). After building the Evobots, the teams of students competed in four events: climbing, hauling, speed, and strength. Students then compared the different bots and proposed ideas explaining why each bot either won or lost the various competitions. Students used this information to write final papers summarizing the unit and their knowledge of concepts such as natural selection, adaptation, and niche specialization. Average knowledge gains were sizeable with the mean scores of the pretest and posttest of 26.9% and 42.3%.