Segmentation is visible on the outside of annelids, but it is also reflected internally with the serial repetition of body structures. Each segment has its own coelom, nerves, ganglia, blood vessels, muscles, and nephridia. Segments are separated from one another internally by partitions called septa. The environment in which an annelid is found depends upon the type of annelid. The earthworm will be used as the example of the Phylum Annelida in the following discussion.
Earthworms eat organic material contained within the soil.
This organic material consists of decayed or decaying plants and animals. Earthworms swallow soil and the organic material it contains while burrowing through the soil. The earthworm moves by using opposing muscles to push against the coelom which functions as a hydraulic skeleton. Each segment is somewhat independent but is coordinated with the segments surrounding it. When circular muscles of a segment are contracted, the segment is long and thin.