Answer:
Faunal Succession
Explanation:
The scientific principle that assumes that the different forms of animals throughout the Earths past occurred in a definite order is called the principle of faunal succession.
This principle determines that fossil organisms follow one another Â
in a definite, irreversible time sequence. Â
Fossil communities change through time as some species become extinct and new ones appear. Â
The principle was first recognized at the beginning of  the 19th century by William Smith.