According to embryology, why do fish and birds have a common ancestor?

The process by which natural forces move weathered rock and soil brim one place to another is called

You arrive late to a biological seminar. however, just as you enter the room, you hear the speaker referring to the "five-prime end" and the "three-prime end" of a macromolecule. immediately, you know that they are talking about a: ]

What was the land like over 500 million years ago? what was under the sea?