This activity reinforces concepts presented in the short film The Making of a Theory. Using a map of the Malay Archipelago and information about the animals found on different islands, students discover the Wallace Line: a sharp boundary that separates distinct Asian and Australian fauna.

The activity begins with reading a short passage about Alfred Wallace. Students are then given a map of the Malay Archipelago and a field notebook with animal observations. Students plot the animals on different islands and identify patterns in the distributions of animal species.They then write an explanation for why some islands have similar fauna while nearby islands have completely different fauna. Students revisit this explanation after watching the film and a short animation about how sea levels and continents have changed over time.