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a bone, tooth, shell, or other hard part of an organism that has been preserved the process that leads to preservation of any body part from an organism that lived in the past any trace of an organism that lived in the past any trace of an organism that has been converted into rock
It allows tissues to be preserved as casts or molds. It protects tissues from wind, rain, and other corrosive elements. It slows the process of decay by bacteria and fungi. All of the above.
Homologous genes have the same structure. Some DNA sequences, in some lineages, change at a steady rate over time. They can be calibrated. Natural selection is not important at the molecular level.
They include terrestrial, instead of just marine, species. They are easily accessible to researchers. They are the only fossil-bearing rocks from that period. Soft-bodied animals are preserved.
Speciation occurs rapidly. Species recover after a mass extinction. As a single lineage diversifies, descendant populations occupy many habitats and ecological roles. Natural selection is particularly intense.
They are always due to asteroid impacts. They are restricted to certain habitats or geographic areas. They affect just a few branches on the tree of life. They rapidly eliminate over half of all species.
