Fossils, Superposition, Geologic Time

This is produced when sediments fill in a cavity made when an object decayed

• mold
• cast
•  index fossil

Fossils of species that existed for short periods and were widespread

• uniformitarianism
• cyanobacteria
• index fossils

What is a cavity in rock made when an organism decayed

• mold
• cast
• fossil

 The oldest rocks are on the bottom and the rocks become progressively younger toward the top

• uniformitarianism
• natural selection
• principle of superposition
• index fossils

The principle that Earth’s processes occurring today are similar to those that did in the past.

• uniformitarianism
• natural selection
• principle of superposition
• cyanobacteria

What are among the earliest life-forms on Earth?

• cyanobacteria
• mold
• bears
• sponges

What are the remains, imprints, or traces of once-living organisms?

• index fossils
• fossil
• mold
• cast

Humans appeared in the ____ Era.

• Cenozoic
• Paleozoic
• Mesozoic
• Devonian

Geologic time is divided into units based on ____.

• geologic changes
• fossils and rocks
• types of life-forms living during certain periods
• all of these

Trilobites can be used to study the passage of geologic time because ____.

• they burrowed into sediments
• they lived in the oceans
• they lived throughout the Paleozoic Era
• their physical features changed through time