This document discusses invertebrate and vertebrate animals. It describes the main characteristics of invertebrates as lacking a spinal column or internal skeleton, and having bodies covered by shells, exoskeletons, or soft skin. The main groups of invertebrates are listed as jellyfish, sponges, annelids, arthropods, echinoderms, and mollusks. Butterflies are highlighted as invertebrate insects belonging to the arthropod group. In contrast, the main characteristic of vertebrates is having a spinal column or internal skeleton. Dogs are given as an example vertebrate, describing them as placental mammals with four legs that are not aquatic animals