South Carolina READY 4th Grade Science Practice Test 2026 - Free 4th Grade Science Practice Questions and Study Guide

An invertebrate is an animal that does not have a backbone or vertebral column. Spiders belong to a group of animals known as arthropods, which are characterized by having an exoskeleton, segmented bodies, and jointed limbs. Unlike dogs, fish, and eagles, which all have internal skeletons made of bone and are classified as vertebrates, spiders lack this characteristic of having a backbone. This key distinction is what makes spiders, as invertebrates, an excellent example for this question. Additionally, invertebrates encompass a wide variety of other animal groups, such as insects, mollusks, and crustaceans, further highlighting the diversity within this classification.