Biologists use comparisons of form and function to classify life-forms into a hierarchy of groups.
Organisms group in the Eukarya domain are Plantae, Fungi, Animalia. The three kingdoms are distinguished by their modes of nutrition. Plants produce their own sugars and other food molecules by photosynthesis; fungi absorb dissolved nutrients; and animals obtain food by eating other organisms.
There is unity in diversity. Similarities between organisms are evident at all levels of hierarchy.
