The oldest later is at the bottom, because as it starts building up to the top the oldest layer will indeed be at the bottom. When a person knows how long the fossil has lived, it's really probably that they can figure out the age of the fossil.
The Wooly Mammoth and Bison both have a tail in common. We think the tail was used for defending themselves or to signal a warning. We can conclude that the animal's history that they had an ancestor that had a tail in common. We think they're related because most of their bones look the same because they go down and then up. We think that they have an older ancestor because the Wooly Mammoth became extinct around 10,000 years ago.
Some similarities that the embryos have are eyes, hands, feet, and they're all crouched in the form of a ball. Some differences that the embryos have are different sizes, tail, and color. The two embryos that are most closely related are the human and the dog. The reason why is because they have around the same shape of body.