These organisms could be floating
around in your birdbath or your
dog's water bowl.

Would you believe that you can find the organism in this image right outside your home?  Well, it's true. The organism in this image is a member of the phylum Rotifera. This phylum is made of animals commonly referred to as rotifers or wheel animals. You can find rotifers in puddles, rain gutters, and other places where there is standing water. In most cases you need a microscope to see them because most members of the Rotifera phylum are very small. Their size can range from 50 micrometers to slightly over 2 millimeters.

The millimeter is the smallest marking on this meter stick, and there are 1000 micrometers in a millimeter.

Despite being so small, rotifers are multi-cellular--the average rotifer has nearly a thousand cells! They are invertebrates like the placozoans, poriferans, and cnidarians. There are currently more than 2,000 known species that are considered members of this phylum.