The backbone is made up of many small bones called

The backbone is not a single bone, but a column of drum-shaped bones called vertebrae (singular, vertebra). There are 33 vertebrae altogether, although some of these join together as the body grows. The vertebrae are separated by disks of rubbery material called cartilage. Cartilage is very important because it cushions the bones when you run or jump.  

they have identical fossils of organisms that have evolved over time.

both have animal fossils preserved in them due to weathering and erosion.

they contain different fossils because life on earth has changed through time.

the fossils in them were formed on the surface of earth due to exposure to sunlight.