The History of Life insect

The History of Life insect - The History of Life...

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12/19/11 The History of Life 1/8 Precambrian Geological Features The origin of Earth, Ch 4 of textbook The different spheres Relation between biosphere-hydrosphere-atmosphere Origin of the term Present status in the geologic time scale Subdivisions of the Precambrian: Proterozoic __ Archean Sumarry of important events Biological Features Classification of Organisms Extremophiles (1) Methanogens (2) Halophiles (3) Thermoacidophiles (4) Psychrophiles Paleontological Features Origin of Life Diversification of life The Domain Archaea Fossil types (1) The Euryarchaeota (2) TheCrenarchaeota (3) The Korarchaeota Important events in the history of life Paleogeographic Map < > PRECAMBRIAN: Precambrian means: "before the Cambrian System." During the eighteenth century geologists began mapping the rock sequences of the earth's crust. They frequently found a basement complex made of igneous and metamorphic rocks beneath the lowest sedimentary layers. These were called the "Primitive" or "Primary", although the term "Primary Era' later came to be applied to the oldest sedimentary stage (later to be called the Paleozoic). In 1835 the English geologist Adam Sedgwick used the name "Cambrian" for the oldest sedimentary strata. Thereafter the underlying rocks were term Precambrian - "before the Cambrian". Thus, the Precambrian was originally defined as the era that predated the appearance of life in the Cambrian System. In the last few decades geologists have found that there are some hard-to-discern fossils in some Precambrian rocks, so this period was now also known as the Cryptozoic Eon or "hidden life" (from the words "crypt" = "hidden," and "zoon" = "life"). During the twentieth century the term "Cryptozoic" - age of hidden life" - was used to designate this period, whereas the Phanerozoic - "age of obvious (or revealed) life" - was used for those periods from which fossils of multicellular organisms are known (i.e. the Cambrian period to the present- day). Although the term latter term "Cryptozoic" is still in use by some geologist, it formally disappeared in favor of the older and well established term Precambrian. This old, but still common term has not a formal status in the subdivisions of the geological time scale; however, we still use the term Precambrian as it was originally used: to refer to the whole period of earth's history before the formation of the oldest rocks with recognizable fossils in them. The Precambrian covers almost 90% of the entire history of the Earth, from 4,500 to about 443 mya (million years ago). The Precambrian would be regarded as a first order division of the geological time scale, that is, an Eonothem; however, as stated above, it is not considered as a formal division of the geologic time scale. Instead the Precambiran time is divided into three major parts that are considered as first order divisions: the Priscoan Eonothem (also known as the Hadean), the Archean Eonothem
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This note was uploaded on 12/19/2011 for the course HISTORY 1101 taught by Professor Josef.longoria during the Fall '10 term at FIU.

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The History of Life insect - The History of Life...

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