There are many possible groups you could create to organize the critter cards, just as there are many ways you could classify cars to go back to the example mentioned at the start of this activity. The cars could be organized as: cars made in the U.S., then cars made by Ford, all sports cars, all Mustangs, all convertible Mustangs. Of course, it helps if everyone involved in research isn't using a different system. Scientists who study living things agree to use the same overall classification system for living things.