In Genesis, Noah brought one pair of each unclean animal into the Ark.
Genesis 7:2 distinguishes between clean and unclean animals. It instructs Noah to take seven pairs of every clean animal, but only one pair of every animal that was not clean. Genesis 7:8–9 then summarizes the animals entering the Ark “two by two,” reflecting the paired survival of the creatures.
This is often confused with the simpler statement that Noah took two of every kind. That summary captures the paired pattern, but the more detailed instruction makes a distinction: clean animals are counted in sevens, while unclean animals are counted as one male-and-female pair.
The classification of clean and unclean animals belongs to the ritual and dietary categories used in the biblical tradition. Genesis does not provide a modern zoological list of species or explain every classification. The question is specifically about the number of pairs of unclean animals, for which Genesis 7:2 gives one pair.