All flashcards
Flashcard 1: Identify the most likely cause if fossils in a layer are mixed from very different habitats and ages.
Answer: Reworking (older fossils eroded and redeposited). Erosion can mix fossils from different sources into one deposit.
Flashcard 2: What does a gradual change in a fossil trait across successive layers most strongly indicate?
Answer: Gradual evolution within a lineage. Progressive changes through layers show evolutionary transitions.
Flashcard 3: Identify the best conclusion if older layers show simple shells and younger layers show more complex shells.
Answer: Shell-bearing organisms changed over time toward greater complexity. Progressive fossil changes demonstrate evolutionary advancement.
Flashcard 4: Which statement best describes what the fossil record in rock layers shows about life on Earth?
Answer: Life has changed over time, with species appearing and going extinct. The fossil record documents evolution and extinction throughout Earth's history.
Flashcard 5: Which layer is youngest in an undisturbed sequence labeled (bottom to top) 1, 2, 3, 4?
Answer: Layer 4. The topmost layer in a sequence is the most recently deposited.
Flashcard 6: Identify the correct conclusion: Layer A is below Layer B in undisturbed strata. Which is older?
Answer: Layer A is older than Layer B. Applies the law of superposition: lower layers formed first.
Flashcard 7: What is the principle of faunal succession used for when comparing fossil layers?
Answer: To match the relative ages of layers using fossil assemblages. Similar fossil groups indicate similar time periods across locations.
Flashcard 8: What does it suggest if marine fossils are found in a layer above layers with land-plant fossils?
Answer: The environment changed to marine (sea level rose). Marine transgression occurred, flooding previously terrestrial areas.
Flashcard 9: What is an index fossil?
Answer: A widespread, short-lived species used to date layers. Must be geographically widespread but existed for a brief geological period.
Flashcard 10: What principle states that, in undisturbed rock layers, lower layers are older than higher layers?
Answer: Law of superposition. In undisturbed sequences, sediments accumulate over time with newest on top.
Flashcard 11: Which order is correct for undisturbed layers: oldest-to-youngest or youngest-to-oldest from bottom to top?
Answer: Oldest-to-youngest from bottom to top. Superposition principle places oldest rocks at the base of sequences.
Flashcard 12: What does it indicate when new fossil species first appear in higher rock layers above older species?
Answer: Evolutionary change over time (new species evolved). Shows descent with modification from ancestral forms below.
Flashcard 13: What is the main limitation of using fossil layers for relative age comparisons?
Answer: It does not provide an exact numerical age. Fossils show sequence but require radiometric dating for absolute ages.
Flashcard 14: What is relative dating?
Answer: Determining whether rocks are older or younger, not exact age. Establishes sequence of events without numerical dates.
Flashcard 15: Which pattern best supports punctuated equilibrium: gradual change or long stasis with sudden change?
Answer: Long stasis with sudden change. Theory proposes evolution occurs in rapid bursts between stable periods.
Flashcard 16: Which option is the best evidence that two separated rock columns formed at the same time: same rock type or same index fossil?
Answer: Same index fossil. Index fossils provide temporal correlation; rock types can persist through time.
Flashcard 17: What is an unconformity in a sequence of rock layers?
Answer: A gap in the rock record from erosion or nondeposition. Represents missing time when rocks were eroded or never deposited.
Flashcard 18: Identify the most likely explanation for a sudden disappearance of many species at one layer boundary.
Answer: A mass extinction event. Simultaneous disappearances indicate catastrophic environmental change.
Flashcard 19: What does it suggest if the same index fossil is found in two separate rock layers?
Answer: The layers are the same relative age. Index fossils indicate contemporaneous deposition across different locations.
Flashcard 20: Which type of fossil is most useful for correlating rock layers across long distances?
Answer: Index fossils. Their wide distribution and short existence make them ideal time markers.
Flashcard 21: What is the term for using fossil content to compare the relative ages of rock layers?
Answer: Biostratigraphy (relative dating with fossils). Uses fossil assemblages to determine relative ages of rock layers.
Flashcard 22: What is the term for matching rock layers of the same age using fossils and rock characteristics?
Answer: Correlation. Process of matching contemporaneous layers across different locations.
Flashcard 23: What does it suggest if land-animal fossils replace marine fossils upward through the layers?
Answer: The environment became more terrestrial (sea level fell). Marine regression exposed seafloor for terrestrial colonization.
Flashcard 24: What is stasis in the fossil record?
Answer: Little or no change in a species over long time spans. Species remain morphologically unchanged for extended geological periods.
Flashcard 25: Identify what a missing set of layers between older and younger rocks most likely represents.
Answer: An unconformity (missing time). Gap indicates erosion removed layers or deposition ceased temporarily.
Flashcard 26: Identify the best conclusion if fossils above a volcanic ash layer are very different from those below it.
Answer: A major event caused rapid biological turnover after the ash fall. Volcanic events can trigger extinctions and ecological reorganization.
Flashcard 27: What is the law of superposition as it applies to sedimentary rock layers and fossils?
Answer: Lower layers are older; higher layers are younger. In undisturbed sedimentary rocks, layers form sequentially from bottom to top.
Flashcard 28: Which inference is best if the same index fossil is found in two rock layers far apart?
Answer: The two layers are about the same relative age. Index fossils allow correlation of contemporaneous rock layers.
Flashcard 29: Which principle states that sedimentary layers are originally deposited in flat, horizontal sheets?
Answer: Original horizontality. Gravity causes sediments to settle in horizontal layers when deposited.
Flashcard 30: What does an unconformity in rock layers usually represent in the fossil record?
Answer: Missing time due to erosion or non-deposition. Gaps in the rock record where layers were removed or never formed.