Insects, octopus, planaria and vertebrates possess eyes. Can we group these animals together on the basis of eyes that they possess ? Justify your answer giving reason.
While making groups, we need to decide the characteristics that are responsible for the more fundamental differences among organisms. The characteristics that account for the broadest divisions among living organisms should be independent of any other characteristics in their effects on the forms and structural functions of organisms like cellularity, mode of nutrition and nature of cell.
Insects, octopus and planaria are invertebrates; they cannot be grouped together with vertebrates, as they lack an internal skeleton with a backbone. Also, all of them belong to different phyla on the basis of different characteristics they possess. Just on the basis of one characteristic, i.e., presence of eyes, these organisms cannot be grouped together.