A dichotomous key is a tool used by scientists to identify and classify organisms based on their physical characteristics. It consists of a series of questions that can be answered with a yes or no response, leading the user to a specific identification of the organism.
Three domains of life:
1. Bacteria: Domain consisting of unicellular prokaryotic organisms, many of which are capable of causing disease in humans.
2. Archaea: Domain consisting of unicellular prokaryotic organisms that are often found in extreme environments such as hot springs and deep-sea hydrothermal vents.
3. Eukarya: Domain consisting of organisms with eukaryotic cells, including plants, animals, fungi, and protists.