The kind of cells that the living organisms are made up of is a more basic characteristic for classifying organisms than the place where they live. On the basis of the kind of cells, all living organisms can be classified into eukaryotes and prokaryotes. Classifying organisms based on habitat (such as aquatic, terrestrial, aerial, etc) is misleading. This is because different kinds of organisms may live in the same habitat but they do not resemble each other. For example, corals, whales, octopuses, starfishes, fishes (sharks), etc., live in sea but differ with each other. Therefore, the kind of cells is considered to be a fundamental characteristic for the classification of organisms.