Question

what are homologous structures? give an example. is it necessary that homologous structures always have a common ancestor?

Answer 1

homologous structures are structurally similar but functionally different.
It leads to the divergent evolution.
Yes , homologous structures have a common ancestor. This is one of the reasons for saying it as divergent evolution

Answer 2

homologus organ

Organs which have same function but have different structure are called homologus organ.

for example :- frog,lizard,bird,human

Yes thay have common ancestor