Title
Compare-Contrast-Connect: Mass Extinctions in Earth’s History
NGSS Crosscutting Concepts
NGSS Disciplinary Core Ideas
Table of Contents
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.
| 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
- When you compare the extinctions above, which was the most extensive? Which was the least?
- What, if anything, do the hypothesized causes of the extinctions listed in SF Table 7.2 have in common?
- It is hypothesized that only one mass extinction has been caused by a single species. Which extinction is this? Which species is implicated?
- Do you think climate change could have an impact on the species currently living on our planet? Explain the reasoning for your answer.
