👉 Invertebracy is a biological classification system used to organize animals into four groups based on their structure. It includes all living organisms that lack a backbone and are characterized by their absence of cartilage, which allows them to move freely without being supported by any bones or ligaments. These invertebrates include insects (insects, arachnids, crustaceans), mollusks (mollusk, squid, starfish, sea urchins, crabs, lobsters),
