The earliest classification system was developed by Aristotle in the 4th century B. C. This system classified all living things as either plants or animals. The two-kingdom system remained in place until 1866, when the Protist kingdom was created. What new information MOST LIKELY led scientists to revise the existing classification system? Group of answer choices the hand lens showed scientists that plants were made up of cells the microscope enabled scientists to discover single-celled organisms the telescope enabled scientists to see objects they could not view before the microscope showed that cells of plants and animals have different structures