In $1938$,a coelacanth was found in

The presence of temporary gills in the embryos of snakes,birds,and humans indicates that:

'Ontogeny recapitulates phylogeny' is the brief definition of

In the embryos of all vertebrates,including humans,a row of vestigial gill slits appears behind the head,but they function only in fish and not in other adult vertebrates. This observation was challenged by which scientist?

Which one of the following is a pair of homologous organs?

Select the correct option for the structures $P$ and $Q$ shown below.