First life on earth in dinosaurs period is as a person
Answers
Answer:
This timeline of the evolutionary history of life represents the current scientific theory outlining the major events during the development of life on planet Earth. In biology, evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organization, from kingdoms to species, and individual organisms and molecules, such as DNA and proteins. The similarities between all present day organisms indicate the presence of a common ancestor from which all known species, living and extinct, have diverged through the process of evolution. More than 99 percent of all species, amounting to over five billion species,[1] that ever lived on Earth are estimated to be extinct.[2][3] Estimates on the number of Earth's current species range from 10 million to 14 million,[4] of which about 1.2 million have been documented and over 86 percent have not yet been described.[5] However, a May 2016 scientific report estimates that 1 trillion species are currently on Earth, with only one-thousandth of one percent described.[6]
While the dates given in this article are estimates based on scientific evidence, there has been controversy between more traditional views of increased biodiversity through a cone of diversity with the passing of time and the view that the basic pattern on Earth has been one of annihilation and diversification and that in certain past times, such as the Cambrian explosion, there was great diversity
Species go extinct constantly as environments change, as organisms compete for environmental niches, and as genetic mutation leads to the rise of new species from older ones. Occasionally biodiversity on Earth takes a hit in the form of a mass extinction in which the extinction rate is much higher than usual.[9] A large extinction-event often represents an accumulation of smaller extinction- events that take place in a relatively brief period of time.[10]
The first known mass extinction in earth's history was the Great Oxygenation Event 2.4 billion years ago. That event led to the loss of most of the planet's obligate anaerobes. Researchers have identified five major extinction events in earth's history since:[11]
End of the Ordovician: 440 million years ago, 86% of all species lost, including graptolites
Late Devonian: 375 million years ago, 75% of species lost, including most trilobites
End of the Permian, "The Great Dying": 251 million years ago, 96% of species lost, including tabulate corals, and most extant trees and synapsids
End of the Triassic: 200 million years ago, 80% of species lost, including all of the conodonts
End of the Cretaceous: 66 million years ago, 76% of species lost, including all of the ammonites, mosasaurs, ichthyosaurs, plesiosaurs, pterosaurs, and nonavian dinosaurs