GEOLOGY

Detailed explanation-1: -A useful index fossil must be distinctive or easily recognizable, abundant, and have a wide geographic distribution and a short range through time.

Detailed explanation-2: -Because they were mobile animals, they tended to inhabit large, even global areas. They were also hard-shelled invertebrates, so they fossilized easily. These fossils are large enough to study without a microscope.

Detailed explanation-3: -Index fossils are fossils that are widespread but only existed for a short period of time. Index fossils help scientists to find the relative age of a rock layer and match it up with other rock layers. Living fossils are organisms that haven’t changed much in millions of years and are still alive today.

Detailed explanation-4: -Answer: Marine organisms are the best index fossil because most of the fossil-bearing rocks are recovered from the oceans.

Detailed explanation-5: -Index fossils are the remains of plants and animals that lived for a limited period. Best index fossils are common, widely distributed, and easy to identify. Some of the most common index fossils are ammonites, trilobites, and graptolites.