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The Triassic is the first period of the Mesozoic Era.
Both the start and end of the period are marked by major extinction events.
The Scale of the Universe from Big to Small (youtube) The Scale of the Universe from Small to Big (youtube) NASA Astronomy Picture of the Day (APOD) The Scale of the Universe - Interactive (manual control scale) Sizes (nano) It is believed that our Universe began.
(Not sure if it was the first time or even the beginning of time? Reionization marks the point at which the hydrogen in the Universe became ionized.
A second, distinct mass extinction, the Hangenberg event, closed the Devonian period. A footprint of a reptile-like creature called an Isochirotherium - an ancestor of dinosaurs and crocodiles, that roamed the area 230 million years ago - was discovered in early April by a person out walking in Olesa de Montserrat, 40 kilometers (25 miles) north of Barcelona. Mammals Evolve - Dinosaurs Evolved and lived for 180 Million years (over 700 types).
Dinosaurs are a diverse group of Reptiles of the clade Dinosauria that first appeared during the Triassic period, which was a geologic period and system which spans 50.9 million years from the end of the Permian Period 252.17 million years ago (Mya), to the beginning of the Jurassic Period 201.3 Mya.
Land plants began to diversify in the Late Silurian, from around 430 million years ago, and the results of their diversification are displayed in remarkable detail in an early Devonian fossil assemblage from the Rhynie chert.
As a rule, to be considered a living fossil, the fossil species must be old relative to the time of origin of the extant clade. It has been defined as "short-term (hours or days to kyrs) locally, regionally, or interregionally pervasive changes in the ecological, biogeographical, and/or evolutionary character of biotas that are isochronous or nearly so throughout their range".
Bioevents either relate to diversification of a particular fossil group or a reduction, these may equate to speciation events or extinction events, or may only represent migration.
By 600 million years ago, the oxygen in the atmosphere reached about one-fifth of today’s level (21 percent).
(3.9 Billion Years since the Birth of Earth, and 2.9 Billion Years since Microorganisms Formed) Multicellular Organisms appear that consist of more than one cell, in contrast to unicellular organisms, which is an organism that consists of only one cell. Multicellularity has evolved independently at least 46 times. Snowball Earth Choanoflagellate are a group of free-living unicellular and colonial flagellate eukaryotes considered to be the closest living relatives of the animals.
The photo above is not to make you feel insignificant, it is only for reference and scale. Depending on your field of view, you would have to be around 100,000 light years away to see this Galaxy using the naked human eye.