Amoebe

You gotta love your basic amoebe, although amoebe is somewhat of a can of worms, similar to the term worms. Worm is a name for all animals that resemble the 'worm' archetype. They spread throughout many different phyla and are therefore often totally unrelated.

Similarly amoebe mostly indicates a type of locomotion and lifestyle.

There is the more official grouping or amoebozoans.

They can be up to half a centimeter across!!! (anyone remember 'the blob'?)

We don't have to go very far to look for them though. Amoebozoans our common in our gut with one species dominating; Entamoeba coli. It is the lion of our intestine. It roams our intestines looking for tasty 'wildebeests', or more accurately, Escherichia coli. It's pretty harmless though for us.

He has some family members who are not so nice. Entamoeba histolytica destroys the cell lining of the gut causing amoebic dysentery, known as Delhi belly to S.A.M. and Montezuma's Revenge to Varda.

Reference

The Ancestor's tale - a pilgrimage to the Dawn of Life, Richard Dawkins. Phoenix paperback 2005. p515.