All flashcards
Flashcard 1: What does extinction mean when interpreting the fossil record of a species?
Answer: Permanent disappearance of a species; no later fossils exist. Species is gone forever from Earth, not just locally.
Flashcard 2: What is the simplest fossil-record definition of a species range?
Answer: The interval from FAD to LAD in rock layers. Species existed between its first and last fossil occurrences.
Flashcard 3: Which evidence best indicates a species went extinct in a stratigraphic sequence?
Answer: Fossils stop above a layer and never reappear in younger layers. True extinction means no return in any later time period.
Flashcard 4: What is a key limitation that can make extinction look earlier than it truly was?
Answer: Incomplete fossil record (preservation and sampling gaps). Not all organisms fossilize, creating false early extinctions.
Flashcard 5: Which term describes a species that lived for a short time but was widespread?
Answer: Index fossil. Short-lived species make excellent time markers for dating rocks.
Flashcard 6: Identify the best interpretation: Species A occurs in layers 1–4, never in 5–10.
Answer: Species A likely went extinct after layer 4 (its LAD is in layer 4). LAD in layer 4 means no fossils found above that point.
Flashcard 7: Which conclusion is supported: Species C is in layers 2–3, absent 4–5, present 6–8?
Answer: A gap in the record is likely; extinction is not supported. Reappearance after absence suggests preservation gap, not extinction.
Flashcard 8: Which evidence best indicates a species appeared (originated) in a rock sequence?
Answer: Fossils first appear in a layer and are absent in all older layers. Shows the species didn't exist before this time.
Flashcard 9: What does last appearance datum (LAD) mean in the fossil record?
Answer: Youngest known fossil occurrence of a species in rock layers. Marks the extinction or final local disappearance.
Flashcard 10: What does first appearance datum (FAD) mean in the fossil record?
Answer: Oldest known fossil occurrence of a species in rock layers. Marks when a species first evolved or migrated to an area.
Flashcard 11: What is the best fossil-record evidence that a new species evolved from an earlier one?
Answer: Transitional fossils showing intermediate traits in older-to-younger layers. Shows evolutionary connection between ancestor and descendant.
Flashcard 12: Which observation best indicates reworking (older fossils moved into younger rock) rather than true survival?
Answer: Worn older fossils mixed into younger sediments with mismatched ages. Erosion can redeposit old fossils into younger sediments.
Flashcard 13: Which term describes a temporary absence of fossils even though the species survived?
Answer: Fossil record gap (a hiatus in occurrences). Species survived but wasn't preserved or found in some layers.
Flashcard 14: What is the most direct fossil evidence for a mass extinction event?
Answer: Many unrelated species show LADs near the same boundary layer. Simultaneous extinctions indicate catastrophic environmental change.
Flashcard 15: Identify the best interpretation: Species B is absent in layers 1–6 and present in 7–10.
Answer: Species B likely appeared by layer 7 (its FAD is in layer 7). FAD in layer 7 marks the species' first occurrence.
Flashcard 16: Identify the species with the earliest appearance: A FAD layer 5, B FAD layer 2, C FAD layer 7.
Answer: Species B. Layer 2 is older than layers 5 and 7, so B appeared first.
Flashcard 17: Identify the species with the latest last appearance: A LAD 9, B LAD 4, C LAD 6.
Answer: Species A. Layer 9 is younger than layers 4 and 6, so A survived longest.
Flashcard 18: Which pattern best supports gradual evolution in the fossil record?
Answer: A sequence of small trait changes across many successive layers. Slow, continuous change shows evolution happening gradually.
Flashcard 19: Which pattern best supports punctuated equilibrium in the fossil record?
Answer: Long stability, then abrupt change and a new species appearing. Rapid speciation after long stasis defines this evolutionary model.
Flashcard 20: What does it suggest if many marine fossils disappear at the same layer worldwide?
Answer: A widespread extinction event, not a local habitat change. Global synchronous disappearance indicates mass extinction.
Flashcard 21: Identify the conclusion: Species Y is found in older layers, but never above layer 10.
Answer: Species Y went extinct at or after layer 10 (its LAD). Layer 10 represents the youngest occurrence before extinction.
Flashcard 22: Identify the most likely conclusion: Fossil species X is in layers 3–7 only.
Answer: Species X appeared by layer 3 and went extinct after layer 7. FAD at layer 3, LAD at layer 7 shows species' time range.
Flashcard 23: Which evidence indicates two separated rock outcrops are the same relative age?
Answer: They contain the same index fossil species. Index fossils correlate distant rock layers to the same time period.
Flashcard 24: Identify the pattern that supports gradual evolution in a fossil lineage over time.
Answer: Slow, continuous changes across successive layers. Fossils show incremental morphological changes through time.
Flashcard 25: Which option best explains why a species might be absent from a layer without being extinct?
Answer: It was not preserved or it lived elsewhere at that time. Fossilization is rare; absence doesn't always mean extinction.
Flashcard 26: Which type of fossil is most useful for correlating rock layers by age?
Answer: Index fossil. Their short time range precisely dates rock layers globally.
Flashcard 27: What is the law of superposition used for when reading fossil layers?
Answer: Lower layers are older; higher layers are younger. Sediments deposit sequentially, making bottom layers oldest.
Flashcard 28: Which evidence best indicates a species has appeared in the fossil record?
Answer: Fossils begin above a certain layer but are absent below it. Species didn't exist in older times, then evolved or migrated in.
Flashcard 29: What is extinction in the fossil record?
Answer: A species disappears and no younger fossils of it are found. No fossils of that species exist in rocks formed after that time.
Flashcard 30: Identify the likely cause: Fossils of species Z are missing in one layer but present above and below.
Answer: A preservation gap or unconformity, not definite extinction. Presence above and below rules out extinction at that time.