Why has the diversity of life on Earth varied?
It has varied in response to imbalances between the origination of new species and the extinction of exisiting species.
Why can scientists estemation of how many species lived in the past be misleading?
Because the fossil record depends on how well fossils were preserved and how likely we are to find them from different time periods.
Why can the fossil record of genus-level diversity be used to interpret true trends in biodiversity through Earth’s history?
The fossil record of genus-level diversity has been largely corrected for these biases and can thus be interpreted in terms of true trends in biodiversity through Earth’s history.
When did the biodiversity of marine organisms dramatically increase?
During Cambrian through Devonian.
When did the largest known extinction happen and how much did it extinct?
The largest known extinction occurred 252 million years ago when approximately 75% of all genera became extinct.
What happened to the biodiversity after hte biggest known extinction?
Biodiversity recovered relatively rapidly after this event, and the general trend continues to the present. A significant disruption to this trend occurred 65 million years ago, at the end of the Cretaceous Period, but it too was followed by a period of rapid origination of new species (and genera).
Which mass extinction is best studied? And what was the cause of it?
The Cretaceous-Tertiary mass extinction is the best studied of all major mass extinctions.
Current scientific opinion favors the impact of a 10-km-diameter meteorite as the primary cause of this extinction.
What can be found in Chixulub Mexico?
A large crater dated as 65 million years old has been found in the subsurface at Chixulub, Mexico.
What happened at Chixulub Mexico? And what was the result of it?
The meteorite impact would have destroyed the ozone layer, blocked out sunlight for days to weeks, ignited wildfires worldwide, baked Devonian. organisms exposed to red hot reentering ejecta, bathed the land surface in acid rain, and caused substantial global warming from elevated atmospheric CO2.
What is the best explanation for the K-T event?
What are the causes of other mass extinctions?
Although asteroid or cometary impact seems to be the best explanation for the K-T event, the other mass extinctions seem to have been the result of Earth-bound causes: massive volcanism causing extreme global warming, or glaciation and sea-level fall.
