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Geologic & Evolutionary History of Earth

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Evolution of Life on Earth

Tree of Life - Phylogenetic systematics. Geologic & Fossil Resources. Extinctions. Evolutionary history of life. The evolutionary history of life on Earth traces the processes by which living and fossil organisms have evolved since life appeared on the planet, until the present day.

Evolutionary history of life

Earth formed about 4.5 Ga (billion years ago) and life appeared on its surface within 1 billion years. The similarities between all present-day organisms indicate the presence of a common ancestor from which all known species have diverged through the process of evolution.[1] More than 99 percent of all species, amounting to over five billion species,[2] that ever lived on Earth are estimated to be extinct.[3][4] Estimates on the number of Earth's current species range from 10 million to 14 million,[5] of which about 1.2 million have been documented and over 86 percent have not yet been described.[6] Outline[edit]

Hadean Eon: 4.57 to 3.85 billion years ago

Archean Eon: 3.85 to 2.5 billion years ago. Proterozoic Eon: 2.5 billion years ago to 542 mya. Phanerozoic Eon: 542 - 0 mya. Timeline of evolutionary history of life. Timeline of natural history. History of the Earth. Geological history of Earth. Geologic time represented in a diagram called a geological clock, showing the relative lengths of the eons of Earth's history and noting major events The geological history of Earth follows the major events in Earth's past based on the geologic time scale, a system of chronological measurement based on the study of the planet's rock layers (stratigraphy).

Geological history of Earth

Earth formed about 4.54 billion years ago by accretion from the solar nebula, a disk-shaped mass of dust and gas left over from the formation of the Sun, which also created the rest of the Solar System. As the surface continually reshaped itself over hundreds of millions of years, continents formed and broke apart. They migrated across the surface, occasionally combining to form a supercontinent. Roughly 750 million years ago, the earliest-known supercontinent Rodinia, began to break apart. Geologic time scale. The geologic time scale (GTS) is a system of chronological measurement that relates stratigraphy to time, and is used by geologists, paleontologists, and other earth scientists to describe the timing and relationships between events that have occurred throughout Earth's history.

Geologic time scale

The table of geologic time spans presented here agrees with the nomenclature, dates and standard color codes set forth by the International Commission on Stratigraphy. Evidence from radiometric dating indicates that the Earth is about 4.54 billion years old. The geology or deep time of Earth's past has been organized into various units according to events which took place in each period. Different spans of time on the GTS are usually delimited by changes in the composition of strata which correspond to them, indicating major geological or paleontological events, such as mass extinctions. Terminology[edit] International Chronostratigraphic Chart. Permian Time Scale. Ordovician Chronostratigraphic Chart. Profiles of over 300 known dinosaurs! Evolutionary history of plants. A late Siluriansporangium.

Evolutionary history of plants

Green: A spore tetrad. Blue: A spore bearing a trilete mark – the -shaped scar. The spores are about 30-35 μm across Cladogram of plant evolution The evolution of plants has resulted in increasing levels of complexity, from the earliest algal mats, through bryophytes, lycopods, ferns to the complex gymnosperms and angiosperms of today. In the Ordovician period, around 450 million years ago, the first land plants appeared.[1] These began to diversify in the late Silurian Period, around 420 million years ago, and the results of their diversification are displayed in remarkable detail in an early Devonian fossil assemblage from the Rhynie chert.

By the middle of the Devonian Period, most of the features recognised in plants today are present, including roots, leaves and secondary wood. Colonization of land[edit] Plants were not the first photosynthesisers on land; weathering rates suggest that organisms[which?] Charcoalification is an important taphonomic mode. Timeline of plant evolution. This article attempts to place key plant innovations in a geological context.

Timeline of plant evolution

It concerns itself only with novel adaptations and events that had a major ecological significance, not those that are of solely anthropological interest. The timeline displays a graphical representation of the adaptations; the text attempts to explain the nature and robustness of the evidence. Plant evolution is an aspect of the study of biological evolution, involving predominantly evolution of plants suited to live on land, greening of various land masses by the filling of their niches with land plants, and diversification of groups of land plants.

Earliest classifiable plants[edit] In the strictly modern sense, the name plant refers to the biological classification kingdom Plantae.