The document discusses mass extinctions throughout history, noting that there have been five major die-offs, including one during the Jurassic period. Some scientists have proposed a cycle of mass extinctions occurring every 26 million years. Research indicates prior mass extinctions were caused by unbreathable atmospheres with high carbon dioxide levels that were hazardous to both land and sea life. The document raises the question of whether human activity could be triggering a sixth mass extinction event.

1. MASS EXTINCTION JoeleenMossett

3. What is Mass Extinction? There have been five major mass extinctions throughout the history of the world, most famous occurred during the Jurassic period. Diversity dynamics of Early Jurassic ostracods of the Cordillera Iberica (Spain) and the re-evaluation of the Pliensbachian-Toarcian mass extinction published on the cjes.nrc.ca on 22 October 2007

4. Mass Extinctions Throughout World History Some scientist have suggested that there has been a cycle if mass extinctions with a major die off every 26 million years.

5. Inhospitable Atmosphere Research has suggested that the levels of carbon dioxide in the air made the atmosphere hazardous, and unbreathable for both land and marine organisms.

7. Are We Causing Our Own Mass Extinctions? Could we be on the brink of a sixth mass extinction brought on by ourselves?