Michael Mosley is bitten by a leech Intermediate Mosquito Intermediate Barnacles feeding on bioluminescent dinoflagellate Beginner Mussels at Work Intermediate Eukaryopolis - Animal Cells: Crash Course #4 Intermediate Animal Behavior - CrashCourse Biology #25 Intermediate Speciation: Of Ligers & Men - Crash Course Biology Intermediate Chordates - CrashCourse Biology #24 Intermediate Complex Animals: Annelids & Arthropods Intermediate Simple Animals: Sponges, Jellies, & Octopuses Intermediate