TPO 39

The reading stipulates three reasons why a mass-extinction event had happened 200 million years ago. However, the lecturer casts a doubt on stipulated reasons, suggesting that three significant motives concerning why stipulated reasons do not hold true and are not plausible.

The first reason mentioned by the author of the reading suggests that a change in sea levels led to animals' vanishing and extinction. The point is challenged by the lecturer and she refutes it, arguing that although there was a fluctuation in the sea levels, it is not an appropriate explanation for the aquatic ecosystem's extinction. This is because they are capable of adapting to an environmental change. As a result, extinction should have happened in a short period of time that left no time for adaptation which is fallacious.

Another motive suggested in the reading is regarding the fact that the climate changed dramatically because of sulfur dioxide emitted in the atmosphere. As a result, the temperature plunged. This point is also rebutted by the professor, she claims that extinction had happened in a span time; however, so2 can not stay in that atmosphere for a long time because it will return to the land by rain. Therefore, there should have been a noticeable amount of so2 to caused a decrease in temperature.

The last reason mentioned points that an immense collision of asteroids with the earth contributed to the giant extinction. Calling this point into question, the professor states that there is no convincing evidence that proved the giant collision. Moreover, recent discoveries revealed there was a collision which goes back to 12 million years before the aforementioned extinction and this gap is not a great justification for this event