First of all, experts in this area say there are no more than 18,000 species. How big was the ark? The dimensions given are 300 cubits long, 50 cubits wide, and 30 cubits high. To calculate this we must know the length of a cubit. The cubit was of varying lengths in the ancient world. But to be safe we will take the shortest cubit, which was 17.5 inches. In which case the ark would have been 438 feet long and 72.9 feet wide and 43.8 feet high.
It had three platforms or decks, 10 cubits high that were to be divided into rooms or stalls (“nests” in the Hebrew,) meaning each stall was to be the appropriate size for each animal to inhabit.
The holding capacity of the ark was about 1, 400, 000 cubit feet, which is equal to the holding capacity of 522 standard boxcars for livestock as used on modern American railroads. The average animal is about the size of a sheep. Large animals such as dinosaurs and elephants and other very large animals would have been young and much smaller. 240 sheep can be transported comfortably in one stock car; 125, 000 sheep could have been carried on the ark.
It was to be made waterproof by covering it with pitch inside and outside.
The window or opening was to be one cubit from the roof running all around the circumference of the ark for light and ventilation and for gathering rainwater for drinking and washing.
As the flood neared, God sent the animals to the ark: “Noah was six hundred years old when the flood waters came on the earth. And Noah and his sons and his wife and his son’s wives entered the ark to escape the waters of the flood. Pairs of clean and unclean animals, of birds and of all creatures that move along the ground, male and female, came to Noah and entered the ark, as God had commanded Noah”.
At the proper time God brought the animals to Noah and Noah placed them in the ark in their proper places. And as a built in protection against extreme weather and other severe climate changes God gave animals the ability to hibernate, thereby suspending all bodily functions, and pass winter in confined areas.