The Phylogenetic Tree illustrates the evolutionary relationships among the nine major animal phyla.  

The position of each phylum on the branches of the tree indicates the origin of each animal group in the history of life.  For example phylum Porifera (sponges) and phylum Cnidaria (jellyfish) are considered to be simple animals and phyla Echinodermata and Chordata are more complex animals.

Considering phyla Mollusca (starfishes), Annelida (earthworms), and Arthropoda (spiders, crabs, insects), they all are off shoots of the same major branch and they are closely related to each other than they are to Echinodermata and Chordata.