Presence of gills in the tadpole of frog indicates that:

Explanation

Amphibians are on the border line between aquatic and true terrestrial animals. Fossil evidence from the Devonian period of earths history suggests that a large population of ish belonging to the group lobe-ins (dipnoi) came to live in shallow fresh water. Some of these crawled from one pool to another and therefore spent some time on land. This gave rise to the group that we recognize as amphibians which are the irst vertebrates to come on land. This suggests that frogs i.e amphibians a from gilled ancestors.