Every year I do the traditional "Bird Beak Lab." Students get to be like Darwin's finches and try to use assigned tools- tweezers, spoons, etc.- to grab food items (beans, rice, etc.) and see how the beak shapes determine the best food source for the finch. However, that's not STEM and not what we want students the learn. If the idea is help students gain an understanding of evolution, why not have students evolve?
In trying to incorporate engineering into my practice, I've had to be more creative and allow students to be creative, but they need a starting point and a practical purpose. In this "traditional" activity, there is no engineering occurring and no practical purpose to show evolution occurs. So lets flip it on its head.
Rather than each student start with a different "beak" give them the same beak with different food sources. Show them competition can lead to evolution because those organisms best able to adapt will survive. Maintain a threshold- to survive, your bird must get "x" food items. After a few rounds, allow students to "evolve". Given specific materials (paper, tape, cups, or other materials) and certain constraints (your genes only have information to make your "beak" longer, your genes only have information to make your beak rounder, etc.) have students design a beak that would help them survive better. Now obviously, one thing we emphasize is organisms adapt not based on what would be the easiest, but what helps them survive the most (the idea of why humans don't have wings to get around). Having constraints allows for students to understand that concept while still engineering what makes it better. This can occur through several rounds of building upon itself- always with a goal in mind to survive.
Throughout this process, students can learn what works, what doesn't work, and have creativity to try something that may or may not be successful. Evolution doesn't lead to all organisms surviving- some fail and go extinct. The point of changing this traditional lab is to show how evolution does lead to changes in organisms based on constraints and survival. Rather than giving students the end, they can get there on their own using STEM processes. Each time the process occurs, I, as a teacher, will see new ways to engineer the beaks, new ways students contribute to the learning of others, and new ways to solve problems.