Here's why:
* Multicellular: Animals are made up of multiple cells that work together to form tissues, organs, and organ systems.
* Eukaryotic: Animal cells have a true nucleus and other membrane-bound organelles.
* Complex: Animals exhibit a high degree of complexity in their structure, physiology, and behavior.
Other kingdoms, like plants, fungi, and protists, include organisms that are not multicellular or are unicellular.
