Classification is all around. Humans naturally classify things in their everyday life to establish a sense of order and make sense of their environment. Introduce students to animal classification by asking questions that elicit examples of this everyday classification such as organization within school subjects, home storage (drawers, closets, desks), meal planning, or packing for a trip. Point out that just as humans organize their lives with logical groupings, so scientists organize animals into groups with similar features.
The most common groupings are based on physical characteristics shared in common within a group of animals. For instance, at the kingdom level, you can ask whether an organism is a plant or an animal. Once it is established that it falls within the animal kingdom, determine phylum by asking if it has a spine to place it in the vertebrate or invertebrate group. Continue asking questions such as "Does it lay eggs?" "Does it bear live young?" "Is it warm-blooded or cold-blooded?" and "Does it have feathers, scales or hair?" to narrow down the class. Questions about color, skeletal structure, body markings and behavior help students zero in on the order, family, genus and species.
Diet and habitat provide further clues for determining an animal's proper scientific classification. Ask questions such as "Does it eat meat, only vegetation or both?" and "Where does this animal make its home? In a nest, in a burrow, a fallen log?" "Does it prefer wet or dry climates?"
Once students are familiar with the animal classification system, you can ask them to identify the correct categories for specific examples. Give each student an animal name or picture and ask him to work through the classification process to identify phylum, class, order, family, genus and species. You can vary the level of exact identification required depending on the age and skills of your students.
When the students are proficient at classifying animals according to Linnaeus's system, ask them to consider that while this system depends mainly on physical characteristics, other classification methods are possible. For example, you can classify animals by biome or by common behaviors, such as whether they stalk their prey or forage for food. Ask students to invent a new classification system and list the animals that would fall into each category.