Fossils, preservation and an incomplete record
| English | Français |
|---|---|
| mineral replacement/ˈmɪnərəl rɪˈpleɪsmənt/ | mineral replacement |
| trace fossil/treɪs ˈfɒsl/ | trace fossil |
What would explain this observation?
- A footprint can be a fossil even when no body remains. Fossil evidence includes traces as well as preserved parts.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- Fossils are preserved remains or traces of organisms from the past, found in rocks. Parts may persist when conditions needed for decay are absent. Minerals can replace parts as they decay. Footprints, burrows and rootlet traces can also be preserved. Each route preserves different information about the organism.
- mineral replacement 矿物替代: Preservation in which minerals replace decaying organism material; trace fossil 遗迹化石: A preserved sign of activity such as a footprint or burrow.
Which is a trace fossil?
Many early organisms were soft-bodied and left few traces. Geological processes have destroyed much of the evidence. The record is therefore incomplete, limiting certainty about exactly how life began. Fossils nevertheless reveal how much or little organisms have changed and support reconstructions of evolutionary relationships.
Match each technical term to its precise meaning.
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- Many early organisms were soft-bodied and left few traces. Geological processes have destroyed much of the evidence. The record is therefore incomplete, limiting certainty about exactly how life began. Fossils nevertheless reveal how much or little organisms have changed and support reconstructions of evolutionary relationships.
- Interpret supplied fossil charts using their age axis and legend. Distinguish millions of years before present from a forward calendar timeline. In a tree, use branch points to identify shared ancestry; the left-to-right order of tips does not make one living species the ancestor of another.
Which two habits make the investigation or model in this case more defensible?
Interpret supplied fossil charts using their age axis and legend. Distinguish millions of years before present from a forward calendar timeline. In a tree, use branch points to identify shared ancestry; the left-to-right order of tips does not make one living species the ancestor of another.
Work from known quantities
- State the known values and their units. Choose the relation because its assumptions fit this case, then rearrange before substitution.
- Known: fossil A is dated to 120 million years before present and fossil B to 85 million years before present. A is older by 35 million years. A missing fossil in one layer does not prove the species never existed then: preservation, exposure and sampling can differ.
Two supplied fossils date to 150 and 110 million years before present. Find their age difference. Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
Two supplied fossils date to 150 and 110 million years before present. Find their age difference.
The result is 40 million years. Known: fossil A is dated to 120 million years before present and fossil B to 85 million years before present. A is older by 35 million years. A missing fossil in one layer does not prove the species never existed then: preservation, exposure and sampling can differ.
Check the conclusion and its limits
- A fossil does not need to contain living tissue or a complete skeleton. Older dates before present have larger numerical values. An evolutionary tree is a model of relationships based on evidence, not a ladder ranking organisms as better or worse.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
A missing fossil proves that no organism lived at that time. This claim is false: A fossil does not need to contain living tissue or a complete skeleton. Older dates before present have larger numerical values. An evolutionary tree is a model of relationships based on evidence, not a ladder ranking organisms as better or worse.
Fossils, preservation and an incomplete record: Many early organisms were soft-bodied and left few traces. Geological processes have destroyed much of the evidence. The record is therefore incomplete, limiting certainty about exactly how life began. Fossils nevertheless reveal how much or little organisms have changed and support reconstructions of evolutionary relationships.
A missing fossil proves that no organism lived at that time.
A fossil does not need to contain living tissue or a complete skeleton. Older dates before present have larger numerical values. An evolutionary tree is a model of relationships based on evidence, not a ladder ranking organisms as better or worse.
Preservation in which minerals replace decaying organism material: write the technical term.
mineral replacement means Preservation in which minerals replace decaying organism material.