In Systema Naturae, published in 1735, Carolus Linnaeus began classifying organisms into two kingdoms of living things: Animalia for animals and Plantae for plants. He based his classification on the nutrition of the organisms and the organisms' mobility. Since that time, the classification of organisms has changed to include three domains and six kingdoms. Why do scientists need to classify organisms? How can an advanced classification system help scientists today? How can classifying organisms help a scientist determine an organism's evolutionary history?