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Compare-Contrast-Connect: Mass Extinctions in Earth’s History

NGSS Crosscutting Concepts:

NGSS Disciplinary Core Ideas:

Extinction occurs when an entire species dies off. Of all the species that have ever lived on planet Earth, over 99.9 percent of them are now extinct. Most people are familiar with the extinction at the end of the Cretaceous period (end of the Mesozoic era) that ended the reign of the dinosaurs. How does this mass extinction stack up to others in Earth’s history? SF Table 7.2 describes mass extinction events on Earth.

 

Most of the mass extinctions listed in SF Table 7.2 are due to factors related to climate change. Even asteroid or meteor impacts have major implications for world climate because they throw massive amounts of dust into the atmosphere, limiting the penetration of the sun’s warming rays.

 

SF Table 7.2. Table of mass extinction events by date and their possible causes
Date Event Name Level of Extinction Possible Cause
0.01 mya Quaternary 55% of large mammal genera End of ice age, hunting by early humans
66 mya Cretaceous-Paleogene 17% of families, including dinosaurs; 50% of genera; end of Age of Reptiles Asteroid impact, volcanic eruption
205 mya Triassic-Jurassic 23% of families; 48% of genera Breakup of Pangaea, extensive volcanic eruptions
252 mya Permian-Triassic 70% of all land species; 80-96% of marine species; end of Paleozoic era Formation of Pangea leading to depletion of shallow seas, volcanic eruptions, glaciation
345 mya Late Devonian 19% of families, 50% of genera Glaciation, meteor impact
450 mya Ordovician-Silurian 25% of families, 57% of genera Glaciation, causing changes in sea level

 

Question Set: 
  1. When you compare the extinctions above, which was the most extensive? Which was the least?
     
  2. What, if anything, do the hypothesized causes of the extinctions listed in SF Table 7.2 have in common?
     
  3. It is hypothesized that only one mass extinction has been caused by a single species. Which extinction is this? Which species is implicated?
     
  4. Do you think climate change could have an impact on the species currently living on our planet? Explain the reasoning for your answer.

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Exploring Our Fluid Earth, a product of the Curriculum Research & Development Group (CRDG), College of Education. University of Hawaii, 2011. This document may be freely reproduced and distributed for non-profit educational purposes.