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Late Ordovician mass extinction: 445-444 Ma Global cooling and sea level drop, and/or global warming related to volcanism and anoxia [43] Cambrian:
An extinction event (also known as a mass extinction or biotic crisis) is a widespread and rapid decrease in the biodiversity on Earth.Such an event is identified by a sharp fall in the diversity and abundance of multicellular organisms.
The most famous of these mass extinction events — when an asteroid slammed into Earth 66 million years ago, dooming the dinosaurs and many other species — is also the most recent. But ...
The last such mass extinction led to the demise of the non-avian dinosaurs and coincided with a large meteorite impact; this is the Cretaceous–Paleogene extinction event (also known as the K–T or K–Pg extinction event), which occurred 66 million years ago. There is no definitive evidence of impacts leading to the three other major mass ...
The Cretaceous–Paleogene (K–Pg) extinction event, [a] also known as the K–T extinction, [b] was the mass extinction of three-quarters of the plant and animal species on Earth [2] [3] approximately 66 million years ago. The event caused the extinction of all non-avian dinosaurs.
Extinctions are a normal part of the evolutionary process, and the background extinction rate is a measurement of "how often" they naturally occur. Normal extinction rates are often used as a comparison to present day extinction rates, to illustrate the higher frequency of extinction today than in all periods of non-extinction events before it. [1]
Artist's rendering of the Chicxulub asteroid entering Earth's atmosphere 66 million years ago, triggering events that caused a mass extermination. Roger Harris/Science Photo library via Getty ...
Many scientists see macroevolution as a field of study rather than a distinct process that is similar to the process of microevolution. Thus, macroevolution is concerned with the history of life and macroevolutionary explanations encompasses ecology, paleontology, mass extinctions, plate tectonics, and unique events such as the Cambrian explosion.