Only needed the prescribed number of each KIND, not every variation of species.
For example, from one pair of the dog kind we have all the varieties of breeds we see today.
Also, was no need to bring fully grown adult pairs of each kind, for example full size elephants.
Instead would be more advantageous to bring smaller juveniles on the ark that would be just coming of mating age when leaving the ark to take full advantage of breeding cycles post flood.