Fossils, preservation and an incomplete record
הוצג| English | משמעות |
|---|---|
| mineral replacement/ˈmɪnərəl rɪˈpleɪsmənt/ | החלפת מינרלים |
| trace fossil/treɪs ˈfɒsl/ | מאובן עקב |
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.
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?
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
A trace fossil preserves an organism's ACTIVITY - a footprint, burrow or dropping - rather than its body. A living animal is not a fossil, and a modern drawing is just a drawing.
Match each technical term to its precise meaning.
רמת קושי 2/5 · 140 מטבעות + בונוס קטן בהשלמה הראשונה היום
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.
In the lab: 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?
רמת קושי 2/5 · 140 מטבעות + בונוס קטן בהשלמה הראשונה היום
Stating the conditions and assumptions lets others repeat the work exactly, and recording the supporting evidence lets them check the conclusion. Hiding disagreeing results removes the evidence that could challenge a wrong conclusion, and one measurement can never establish a wider claim.
Work from known quantities
- 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.
Your turn: Two supplied fossils date to 150 and 110 million years before present. Find their age difference.
Two supplied fossils date to 150 and 110 million years before present. Find their age difference.
רמת קושי 2/5 · 140 מטבעות + בונוס קטן בהשלמה הראשונה היום
The result is 40 million years. Known: 150 and 110 million years before present. Age difference = 150 - 110 = 40 million years. Older fossils have the LARGER "before present" number.
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.
Not true: A missing fossil proves that no organism lived at that time. The fossil record is incomplete: fossilisation is rare and many fossils stay buried or destroyed. Absence of a fossil is evidence of nothing - it does not prove the organism was absent.
- Fossils are preserved remains or traces of organisms from the past, found in rocks.
- Many early organisms were soft-bodied and left few traces.
- Watch for: A fossil does not need to contain living tissue or a complete skeleton.
A missing fossil proves that no organism lived at that time.
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
The fossil record is incomplete: fossilisation is rare and many fossils stay buried or destroyed. Absence of a fossil is evidence of nothing - it does not prove the organism was absent.
Preservation in which minerals replace decaying organism material: write the technical term.
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
mineral replacement means Preservation in which minerals replace decaying organism material.