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ZingPath: Geologic Time

Analysis of Fossil Evidence

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Geologic Time

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Lesson Focus

Analysis of Fossil Evidence

Earth & Space Science

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This Activity Object engages learners in the organization and analysis of fossil evidence.

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Now You Know

After completing this tutorial, you will be able to complete the following:

  • Explain that fossils are evidence of past life.
  • Explain that the hard parts of organisms, such as teeth, jaws, vertebrae, and scales, most easily become fossilized.
  • Draw correct conclusions from fossil evidence.

Everything You'll Have Covered

The word fossil comes from the Latin fossilis, which means "dug up." Fossils are the remains, molds, or casts of a living organism from a former geologic age. The study of prehistoric animal and plant life, using fossil evidence, is called paleontology. Paleontologists use fossil evidence to help them understand what kinds of organisms existed and how life changed and evolved throughout Earth's history. They also create geologic maps, which are essential in the search for fossil fuels and minerals.

Fossil records are distributed through layers of rock, but most fossils are found in limestone, sandstone, and sedimentary rock. Remains of organisms are sometimes even found trapped in natural asphalt, amber, and ice. There are a variety of ways in which organisms were fossilized. Fossils of soft tissue organisms are rare because the soft tissue decays easily. The hard bony skeletons and shells of animals and woody materials of plants typically were preserved best.

Imagine that a prehistoric animal was quickly buried in the Earth by sinking into muddy soil, being covered by a sand storm or mud slide, or some similar event. Over time, layers of sediment covered the remains of the dead animal. Hard parts of the animal, like the teeth, bones, and scales, did not rot quickly when encased in the sediment. If these parts were spared the ravaging effects of scavengers and weathering, and if the temperature, pressure, acidity, chemical composition, and moisture level of the sediment were just right, something amazing happened. As the bones slowly decayed, water, infused with rock-like minerals, soaked into the bones. Minerals and chemicals that were originally in the bones were dissolved and replaced with other minerals. What remained was a fossil, a copy of the original bones. The fossil is heavier and more like rocks than bones. It is the same shape and size as the bones, but its chemical make-up is more similar to rock.

Tutorial Details

Approximate Time 20 Minutes
Pre-requisite Concepts classification of organisms, fossils
Course Earth & Space Science
Type of Tutorial Concept Development
Key Vocabulary direct evidence, Earth, evidence