Biology is the study of life. While biologists have made great strides in discovering things on Earth, there are many new things to learn. What is life? What properties are required to be considered "living"? These questions are essential to discoveries biologists make every day. With such a vast scope of information, biologists must organize and categorize these discoveries to show connections and patterns to known facts. In this unit, we introduce the major topics biologists study and the theories they use and apply to their work. Completing this unit should take you approximately 2 hours.