A branching key asks one question at a time. Each answer chooses the next branch. It works only for the organisms and features it includes. Our four-card key is not safe for naming every unknown animal; missing observations require an uncertain answer. Safety: No collection, handling or species-safety decisions. Stop: Stop when the four cards and one uncertain card are checked. Do not collect animals to use the key.

Materials: Paper; Pencil 1. Copy the four observation cards: beetle—six jointed legs and three main body regions; spider—eight jointed legs and two main body regions; snail—no legs, soft body with a coiled shell; earthworm—no legs, long segmented body without a shell. These are simplified cards, not specimens. 2. Copy this complete key: Q1, jointed legs present? Yes → Q2; no → Q3. Q2, six legs? Yes → beetle card; no → spider card, but only if eight legs and two body regions match. Q3, coiled shell present? Yes → snail card; no → earthworm card, but only if the segmented-body feature matches. If a required feature is missing, stop at not enough evidence. 3. Run every card through the key. Write each route as question number, yes/no, next question and result. Check that the final card still matches all observations, rather than accepting the last label automatically. 4. Write your own yes/no question separating the supplied insect and spider: Does it have six legs? Explain why the fixed order avoids skipping the leg/no-leg decision. Add a card with legs not visible and record the honest stopping point. Done: Keep four complete routes, the separating question and the uncertain-card result. Proof: Keep the key and route log. Note questions read aloud or branch choices supplied by an adult. Stop: Stop when the four cards and one uncertain card are checked. Do not collect animals to use the key.