Introduction / Context:
Memorizing the approximate start and end points of geologic eras helps you place major evolutionary and tectonic events. The Paleozoic saw the Cambrian explosion, colonization of land by plants and animals, and ended with the Permian mass extinction.
Given Data / Assumptions:
- The question uses conventional rounded figures from school texts.
- Exact values vary by modern recalibration, but exam keys use rounded ranges.
- We must choose the pair that best matches standard references.
Concept / Approach:
Traditional teaching places the Paleozoic from roughly 570 mya to about 225 mya (modern ICS values cite ~541 to ~252 mya, but many exam sets retain the older rounded numbers). Hence, among the provided pairs, “570, 225” aligns with the accepted school-level approximation for start and end.
Step-by-Step Solution:
Recognize Paleozoic boundaries (rounded): ~570 → ~225 mya.Scan options and select the matching pair.Confirm others do not coincide with conventional ranges.
Verification / Alternative check:
Cross-check with commonly used preparatory guides: they frequently list 570–225 mya for Paleozoic, preceding Mesozoic (~225–65 mya) in older schemes, confirming the test key expectation.
Why Other Options Are Wrong:
500, 100 / 470, 150 / 470, 225: These do not match the widely taught span of Paleozoic in standard exam materials.
Common Pitfalls:
Confusing updated ICS dates with legacy textbook ranges. Stick to the convention used in the options unless instructed otherwise.
Final Answer:
570, 225
Discussion & Comments