(a) A fossil bird called Archaeopteyx looks like a bird but it has many features which are found in reptiles. Archaeopteryx has featured wings like birds but teeth and tail like those of reptiles. Therefore Archaeopteryx is a connecting link between the reptiles and birds and hence suggests that the birds have evolved from the reptiles.
(b) Insects, octopus, planaria and vertebrates posses eyes but these animals can not be put togther on the basis of eyes because the structure of eyes in each of there organisms is different which suggests their separate evolutionary origins. Thus all these animals are put in different groups.
