CBSE Class 10 Answered

i) Study of morphology and comparative anatomy of different animals helps us to a great extent in tracing evolutionary relationships. Homologous organs are organsof different organisms, which are dissimilar externally but similar in origin and in fundamental structural plan.  For. eg. The basic structure of the limbs in mammals, birds, reptiles and amphibians are similar, though they have been modified to perform different functions in various vertebrates.

The only explanation for such homologous organs is that these animals are the diverging descendants of the common ancestor from whom they evolved. Homologous characteristics help to identify an evolutionary relationship between apparently different species.

ii) Fossils are also hugely useful in tracing evolutionary relationships. The fossil records of geological time scale shows that fossils of only simple forms are found in lower or old strata while those of complex forms appear in upper or recent strata of the earth. This indicates that complex forms have gradually evolved from pre-existing simple ones. In addition, fossils also revela connecting links like Neuropteris and Archaeopteryx, which clearly indicate the evolution of one organism from the other.