Question

QUESTION 11 4 points Save Answer Explain the possible cause of the third mass extinction and possible cause for the fifth mass extinction in the life history. TT T Arial 3(12pt) + T - E - E P 25 Path:p Words:0

Answer 1

Earth has witnessed the presence of life for almost 4.6 billion years. However, owing to changes in climate, volcanic events, meteor showers, etc, life has witnessed a large chunk of populations from across the globe being wiped out. There have been five such major events. These were the Ordovician Mass Extinction, Devonian Mass Extinction, Permian Mass Extinction, Triassic-Jurassic Mass Extinction, and Cretaceous-Tertiary (or the K-T) Mass Extinction.

The third mass extinction was the Permian mass extinction event. This was the largest mass extinction event leading to the elimination of 90% of all plant and animal species. There have been several hypotheses for the cause of this event. Most of these hypotheses are still debatable. However, evidence suggests that there were temperature fluctuations during this period. Also, anoxia or lack of oxygen was high which could be the cause of death for many living organisms. There is also evidence for an increase in methanogenic species which could have led to increased global temperatures by leading to global warming. There are also debates on meteor strikes and volcanic eruptions, which are under debate.

The fifth mass extinction event was the Cretaceous-Tertiary or the K-T Mass Extinction event. This event led to wiping out 75% of all living species. Dinosaurs were one of the major groups of organisms that were completely wiped out during this event. The reason for this is believed to be a major asteroid or meteor impact. There have been evidences of this available in the forms of large craters that date back to this period.