8.E.6A.4 Construct and analyze scientific arguments to support claims that different types of fossils provide evidence of (1) the diversity of life that has been present on Earth, (2) relationships between past and existing life forms, and (3) environmental changes that have occurred during Earth’s history.
FossilsLearning Objective:
Students will be able to summarize how scientists study Earth's past environment and diverse life forms by examining different types of fossils including molds, casts, petrified fossils, preserved and carbonized remains of plants and animals, and trace fossils. |
It is essential for you to know that a fossil is the preserved remains or traces of an organism that lived in the past, usually more that 10,000 years ago. Fossils give clues to the diversity of living things over the history of Earth, give clues to past climate and surface changes on Earth, and give clues to changes that have occurred with organisms over time.
There are different types of fossils based on how they were formed. The environmental conditions that favor fossil formation are also essential.
> Mold fossil – forms when sediments bury an organism and the sediments change into rock; the organism decays leaving a cavity in the shape of the organism.
> Cast fossil – forms when a mold is filled with sand or mud that hardens into the shape of the organism.
> Petrified fossil (permineralized fossil) – forms when minerals soak into the buried remains, replacing the remains, and changing them into rock.
> Preserved fossil – forms when entire organisms or parts of organisms are prevented from decaying by being trapped in rock, ice, tar, or amber.
> Carbonized fossil – forms when organisms or parts, like leaves, stems, flowers, fish, are pressed between layers of soft mud or clay that hardens squeezing almost all the decaying organism away leaving the carbon imprint in the rock.
> Trace fossil – forms when the mud or sand hardens to stone where a footprint, trail, or burrow of an organism was left behind.
Millions of fossils have been collected and studied. The fossil record gives important information about past life and environments on Earth. Certain fossilized organisms could only live in specific environments or under particular climate conditions. Extinction of life-forms as well as how and when new life-forms appeared is part of the fossil record.
There are different types of fossils based on how they were formed. The environmental conditions that favor fossil formation are also essential.
> Mold fossil – forms when sediments bury an organism and the sediments change into rock; the organism decays leaving a cavity in the shape of the organism.
> Cast fossil – forms when a mold is filled with sand or mud that hardens into the shape of the organism.
> Petrified fossil (permineralized fossil) – forms when minerals soak into the buried remains, replacing the remains, and changing them into rock.
> Preserved fossil – forms when entire organisms or parts of organisms are prevented from decaying by being trapped in rock, ice, tar, or amber.
> Carbonized fossil – forms when organisms or parts, like leaves, stems, flowers, fish, are pressed between layers of soft mud or clay that hardens squeezing almost all the decaying organism away leaving the carbon imprint in the rock.
> Trace fossil – forms when the mud or sand hardens to stone where a footprint, trail, or burrow of an organism was left behind.
Millions of fossils have been collected and studied. The fossil record gives important information about past life and environments on Earth. Certain fossilized organisms could only live in specific environments or under particular climate conditions. Extinction of life-forms as well as how and when new life-forms appeared is part of the fossil record.
Can you identify each type of fossil?
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