Bones are evidence of what pre-existing life

The right answer is animals (these are called fossils).

A fossil is the mineralized rest (such as bones, tooth) or the simple molding of an animal preserved in a sedimentary rock.

Fossils and processes of fossilization are studied mainly in paleontology, but also in those of geology, human prehistory and archeology.

they float because they are less dense than the water itself

something denser than water, like a rock, will sink to the bottom

videntify the dna change shown in the diagram and explain how that change can result in the increased genetic diversity often seen among siblings.identify the dna change shown in the diagram and explain how that change can result in the increased genetic diversity often seen among siblings.