In the bible it says the ark contained to animals each after their own kind. Meaning 2 dogs for all the types of dogs, 2 frogs for all the kinds of frogs and so on and so forth. This significantly reduces the number of animals that would have been on the ark. Secondly there are several theories which say that the ark was built during a time when the world was still a super continent. Which means then when the ark landed it would be much easier for animals to spread out and eventually be separated as the plates moved apart. And as they separated each type of animal had to adapt to its changing environment which leads to the many different variations of each species of animal that we have today.
There are approximately 2,406,750 different species known to man right now, and there are 10,000 different species found each year. The arc was only 450 feet long, 75 feet wide, and 45 feet high(Genesis 6:15 in the Bible tells us the Ark's dimensions were at least 135 meters long (300 cubits), 22.5 meters wide (50 cubits), and 13.5 meters high (30 cubits)). 2,406,750 animals can/could not have fit on that size boat.
When thinking about the ark, you really need to ask yourself what they did with the animal waste. People think they would just throw it over the wall, but that is easier said than done. The amount of feces would be extraordinary. It would take a very long time to shovel out just one day's worth of it. This is only one of the reasons.
If it were a metaphor for some alien technology which kept hold of the DNA of all animals aboard some space craft or some program called "ARK", that would me more likely, but still not all that scientifically likely.
The fact is that the size of the ark, the number of animals, the science of those animals, the history of those animals, etc... Just don't add up. At all.