Phylum Arthropoda
Modern Arthropods includes the species of insects, shrimp, centipedes, spiders, and crayfish. However all species in the phylum Arthropoda have been traced back to an common ancestor. Since arthropods all descend from a common ancestor, they all seem to share five prominent characteristics. 1.) Bilateral left and right symmetry. Meaning that if you cut an arthropod vertically down its exoskeleton, the two sides would be identical. 2.) All arthropods have a segmented body. Meaning that arthropods have a series of repetitive segments. 3.) They have a hard exoskeleton. Arthropods don't have are invertebrates, therefore they have a hard exoskeleton to protect themselves from predators. It is basically an external shield. 4.) Arthropods have jointed legs. This means that they have bends like humans do with their knees. 5.) Arthropods have many pairs of limbs. Like the centipede, spider, or lobster, all these arthropods have way more then four legs. Now that we know a bit about arthropods, lets look closer into some individual species.