In Genesis, one pair of every unclean animal entered Noah’s Ark.
Genesis 7:2 distinguishes between clean and unclean animals. Noah is told to take seven pairs of each kind of clean animal, but one pair of each kind of animal that is not clean. Genesis 7:8–9 then summarizes the animals entering the Ark as coming two by two, male and female.
This is a frequent source of confusion because the passage contains two different instructions. The seven-pair figure applies to clean animals, while the one-pair figure applies to unclean animals. The text therefore cannot be accurately summarized as saying that every animal entered in seven pairs.
Genesis does not provide a modern zoological list of the categories. “Clean” and “unclean” are terms within the narrative’s ritual classification system. The passage also mentions birds separately, assigning seven pairs in the instruction given in Genesis 7:3.