Genesis 7:15

“And they went in unto Noah into the ark, two and two of all flesh, wherein is the breath of life.”

KJV

Meaning

Pairs of living creatures come to Noah and enter the ark as the preservation plan is completed.

The phrase breath of life belongs to Genesis' theological description of living creatures and is not a technical scientific category.

The verse emphasizes life itself as what is being carried through the destructive waters.