More common than you think ... but what exactly is an invertebrate? Life processes - Variation and classification - Invertebrates Learning Points Invertebrates are animals that have no backbone. Invertebrate groups are insects, arachnids and molluscs. A Twig Curriculum Film. Delivering key learning points. Get straight to the facts in just three minutes – directly linked to core learning, Twig's curriculum films will fit neatly into your lesson plans.