Classifying Organisms - an Intro to Domains and Kingdoms. 1. Why biologists organize things into groups (classification).2. Levels of classification with examples.â¢ Domain â¢ Kingdomâ¢ Phylumâ¢ Classâ¢ Orderâ¢ Familyâ¢ Genusâ¢ Species3. The characteristics used to classify organisms into domains and kingdoms. by.