Life Changes Over Time - Middle School Life Science
- What is a common limitation of the fossil record?
- It is incomplete because fossilization is rare. Most organisms decompose without fossilizing.
- Which conclusion is best supported if a fossil species stops appearing above a certain layer?
- That species became extinct by the time higher layers formed. Absence in newer layers indicates disappearance.
- What does it mean if the same species appears in many different rock layers?
- The species existed for a long time. Shows species survived through multiple time periods.
- What is relative dating in geology and paleontology?
- Determining which rocks or fossils are older or younger. Compares ages without specific time measurements.
- What is the fossil record?
- All known fossils and their positions in rock layers. Provides timeline of life's history through rock layers.
- Which dating method determines an actual age in years: relative dating or radiometric dating?
- Radiometric dating. Uses radioactive decay to calculate precise ages.
- Which evidence best supports common ancestry: similar fossils in the same layer, or transitional fossils connecting groups?
- Transitional fossils connecting groups. Shows evolutionary relationships between species.
- Which fossil type is a footprint or burrow: body fossil or trace fossil?
- Trace fossil. Shows evidence of behavior, not body parts.
- What is extinction, as shown by the fossil record?
- Permanent disappearance of a species from Earth. When last member dies, species is gone forever.
- What is a trace fossil?
- Evidence of activity, such as footprints, burrows, or coprolites. Shows behavior and movement, not body structure.
- Identify the correct relative-age conclusion: Fossil A is in a lower layer than Fossil B in undisturbed rock.
- Fossil A is older than Fossil B. Law of superposition: lower means earlier in time.
- What is a cast fossil?
- A solid copy formed when a mold fills with minerals. Creates 3D replica of original organism.
- What does the law of superposition state about undisturbed rock layers?
- Lower layers are older; higher layers are younger. Based on sediment deposition order over time.
- Identify the best fossil evidence for evolution: unchanged fossils or transitional fossils?
- Transitional fossils. Show intermediate forms between ancestral groups.
- What does the law of superposition state about undisturbed sedimentary rock layers?
- Lower layers are older than layers above them. Unless disturbed, sediments settle chronologically.
- What does a mass extinction refer to in the fossil record?
- A short interval when many species disappear worldwide. Global catastrophe eliminates numerous species rapidly.
- What is absolute dating?
- Determining an actual age in years, often using radiometric methods. Provides specific numerical ages for rocks and fossils.
- Which conclusion is supported if older layers contain simpler organisms than newer layers?
- Life has become more diverse and complex over time. Shows progression from simple to complex organisms.
- Identify the best fossil-based conclusion if many new species appear soon after a mass extinction layer.
- Biodiversity rebounded through rapid diversification of survivors. Surviving species evolved to fill empty ecological niches.
- What is a cast fossil?
- A solid copy formed when a mold fills with minerals or sediment. Creates a 3D replica of the original organism.
- What is the fossil record?
- All fossils and their positions in rock layers over time. Complete history of life preserved in Earth's rocks.
- What is a fossil in the context of evidence for past life on Earth?
- Preserved remains, impressions, or traces of ancient organisms. Physical evidence of organisms that lived long ago.
- What is permineralization in fossil formation?
- Minerals fill pores of remains, turning them to stone. Most common fossilization process for bones and wood.
- What is a mold fossil?
- A hollow impression of an organism left in rock. Forms when organism decays, leaving its shape in rock.
- What does a sequence of fossils showing gradual changes over layers most strongly indicate?
- Species change over time (evolution). Direct evidence of evolutionary change through time.
- What is a fossil in life science?
- Preserved remains or traces of past organisms. Physical evidence of ancient life preserved in rocks.
- Which fossil type is a preserved bone or shell: body fossil or trace fossil?
- Body fossil. Actual organism parts that became fossilized.
- What is relative dating in geology?
- Determining which rocks or fossils are older or younger. Uses position in rock layers, not actual years.
- What is a mold fossil?
- A hollow impression of an organism left in rock. Forms when organism decays, leaving its shape.
- Which type of rock most commonly contains fossils: igneous, sedimentary, or metamorphic?
- Sedimentary rock. Forms from layers of sediment that preserve organisms.
- Which dating method uses radioactive decay to estimate the age of rocks: relative or absolute dating?
- Absolute dating. Measures isotope decay rates to calculate precise ages.
- Identify the best use of index fossils when comparing two distant rock layers.
- To correlate layers and infer they are the same relative age. Same index fossils indicate simultaneous formation.
- What does it mean if a fossil species disappears above a certain rock layer?
- The species went extinct after that time. No fossils above means species no longer existed.
- Which layer is older in an undisturbed sequence: Layer A on top or Layer B below?
- Layer B below is older. Follows law of superposition in undisturbed rocks.
- What is an index fossil?
- A widespread fossil from a short time span used to date layers. Existed globally but only briefly, making it a time marker.
- Which statement best links fossils to evolution: fossils show organisms are identical over time, or they change over time?
- Fossils show organisms change over time. Different species in different layers prove evolution.