Is it possible to draw a clear line between the kingdom of Animals and the rest of the kingdoms of organisms?

For most species of different kingdoms, this line exists. But there are such representatives who are characterized by some features of another kingdom. For example – green euglena. It has chloroplasts in its structure, as representatives of the plant kingdom. Also, she has a heterotrophic type of diet. Moreover, it belongs to the animal kingdom. The same goes for the sea slug. Some plants are able to feed on insects, and some move. Therefore, there are often no clear lines between the kingdoms of living nature.