Aside from having no backbones or spinal columns, characteristics of invertebrates differ from group to group. Squids and spiders, for example, are going to differ greatly, even though they are in the same main animal group.The following article provides an overview of characteristics of invertebrates relating to their particular species and classifications. Please note that with over 30 phylum and 2 million different species of invertebrates, this article can only touch the very tip of the world of invertebrates.