It is reasonable to assume that all types of animals on the Ark were young animals because they would weigh less, eat less, and sleep more. Many animals become dormant, lethargic or even hibernate during stormy weather. Also, after the Flood, they would live longer to produce more offspring. No one knows for sure how many animals were on the ark. Limiting it down to two of each kind does not mean there were two of each species or variety that we have today. There seem to be about 8,000 basic kinds of animal in the world.
Through the instructions that God gave or through the wisdom of Noah, he was given the ability to provide a watering mechanism to disperse water to the animals throughout the ark and possibly even a food distribution system. In Genesis 1:29-30, the Bible teaches that after creation all the animals were vegetarians. Even if since the Fall, some animals had started eating meat (since God chose the ones to be brought on the ark), it seems certain He would have chosen the young ones who would not have been involved with this yet. So there would not have been a problem with, for example, the lion trying to eat the lamb. Some have suggested that there was a moon pool, a hole in the center of the floor, which would provide a place for fishing and, if necessary, a way to dispense animal waste from the ark. 1
The minor problems that the Bible believers cannot always answer are nothing compared to the problems and questions that the evolutionists cannot answer. Although it is not exactly known how Noah took care of all the animals on the ark, it is safer to believe the Bible until it is proven wrong instead of doubt the Bible until it is proven right. For someone to reject the Bible and then accept the story that we all came from a rock is silly!