A dichotomous key is way to sort and identify living organisms through a sequence of questions. Dichotomous means “divided into two parts,” so each question will create two more groups based on their physical characteristics. My students identify 14 different arachnids by using a dichotomous key . They worked in groups to discuss questions over the anatomy of each arachnid. Each answer led them to another question over characteristics such as segmented abdomens, pedipalps, legs of equal length, tails, and cephalothorax. It was challenging and inspired many debates, but they were very successful!