What is a single-celled animal?

A single-celled animal is an animal cell that lives on its own, without other cells.  It can move around.  It can get its own food.  It gets rid of waste.  It divides to make more cells.  It can tell something about what is happening around it.  the single cells of a multicellular animal (one made up of many cells such as a tiger, an insect or a person) could not do this.  They need to live surrounded by lots of other cells.