Gill clefts and notochord appear in the embryonic development of all vertebrates from fishes to mammals. This supports the theory of

Wings of insects and birds are

Give differences between homologous structures and analogous structures.

In the past,the age of fossils was typically determined using the radiocarbon method and other techniques involving radioactive elements found in rocks. What are the more precise methods currently used that lead to the revision of evolutionary periods for various groups of organisms?

Select the appropriate option for the work done by $Ernst$ $Haeckel$.

Which one of the following organs has no evolutionary significance?