One characteristic used to place organisms into kingdoms is

One characteristic could be the structure of their nucleus. They could be classified as prokaryotes, which would include bacteria and most single-celled organisms. Or, they could be classified as eukaryotes, which would include most multi-celled organisms. Another characteristic would be there ability to make food. Like plants, they can make their own food through photosynthesis, but consumers, like you and I, would have to get our food from these plants, fungi, or other animals.