Because the worm has many rings around its bodies which makes it a an Annelid.
Annelid="Ringed" and refers to a series of rings or segments that make up the bodies of the members of this phylum.
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No. An example of unicellular organisms would be bacteria. Earthworms are multicellular and contain organs and organ systems. Unicellular organisms are typically invisible to the naked eye except when in large groups (such as yeast).
Multicellular. Pretty much all macroscopic organisms (organisms that can be seen and observed without a microscope) are multicellular. and turtle jizz
Because earthworms have more than one cell - there isn't much more to say than that. Either an organism is composed of one cell or it isn't. An earthworm isn't.
Oligochaeta.
No, it doesn't have six legs or more so it can't possibly be an insect.
No, an earthworm is not a chordate because it has a nerve cord that does not run down the back.
Setae on an earthworm (an annelid) point backwards to add traction as it moves, especially if it is moving up soil or something. Think of it as hooks, essentially a source of friction, for the generally smooth worm as it moves using peristaltic motion.
The annelids are segmented worms. Although some annelids have appendages and primitive sight organs (photo-reactive pigment spots), earthworms do not. Earthworms do, however, have the typical annelid neural ganglia, and the annelid circulatory system, including the aortic arches that function as the worm's heart. And, of course, earthworms are segmented.