-
Archaen Eon 3.4-4 billion years ago
Archaean Eon
The Archaean Eon spanned for about 1.5 billion years, and it was divided into 4 separate eras the Neoarchean (2.8 to 2.5 billion years ago), Mesoarchean (3.2 to 2.8 billion years ago), Paleoarchean (3.6 to 3.2 billion years ago), and Eoarchean (4 to 3.6 billion years ago).The atmosphere of the Archaean Eon likely contained an atmosphere of unbreathable air, that contained methane, ammonia, and other toxic gases. During this period the earth's crust cooled so rocks and continental -
Proterozoic Eon 2.5 billion years ago
The first traces of life appear nearly 3.5 billion years ago, in the early Archaean. However, clearly identifiable fossils remain rare until the late Archaean, when stromatolites, layered mounds produced by the growth of microbial mats, become common in the rock record. Stromatolite diversity continued to increase through most of the Proterozoic. Until about 1 billion years ago, they flourished in shallow waters throughout the world. Stromatolites that have been silicified often preserve exquisi -
Proterozoic Eon: Ediacaran Time Period
The Ediacara Fauna. During this time was the assemblage of soft-bodied organisms . This period marks the when the first clearly multicellular life appears in fossil record. These animals had no shells or skeletons and some of the impressions they left were difficult to interpret because of their jelly like structure. -
Phanerozoic eon: 542 million- present day
The Phanerozoic, the eon of visible life, is divided into three major spans of time largely on the basis of characteristic assemblages of life-forms: the Paleozoic (542 million to 251 million years ago), Mesozoic (251 million to 65.5 million years ago), and Cenozoic (65.5 million years ago to the present) eras. -
Phanerozoic eon: Paleozoic era 542million years ago-251 million years ago
However the at the end of the Paleozoic era ended in a mass extinction of approximately 90% of all marine animal species. Yet the causes of these event are unclear.
Two of the great groups of the animals dominated the seas during the Paleozoic Era. These were the Cambrian fauna, and the seas were dominated by trilobites, extinct marine arthropods with a carapace over the forepart, and a segmented hind part divided longitudinally into three lobes. The diversity declined after the Ordovician time -
Phanerozoic eon: Paleozoic era 542million years ago-251 million years ago
Later Paleozoic seas were dominated by crinoid and blastoid echinoderms, articulate brachiopods, graptolites, and tabulate and rugose corals.
Near the end of the Ordovician period life expanded from the seas and onto land. Plants had begun to take over the landscape, and eventually into the Silurian segment invertebrates as well, and in the later Devonian segment vertebrates emerged. By the Paleozoic Era reptiles had evolved from early amphibious creatures. -
Phanerozoic eon: Paleozoic era 542million years ago-251 million years ago
By the end of the Devonian, forests of progymnosperms dominated the land. The Permian extinction, 251.4 million years ago, devastated the marine fauna: tabulate and rugose corals, blastoid echinoderms, graptolites, the trilobites, and most crinoids died out. One lineage of crinoids survived, but never again would they dominate the marine environment.The Paleozoic is divided into six periods: the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian. -
Phanerozoic eon: Paleozoic era 542million years ago-251 million years ago
The Paleozoic Era, which ran from about 542 million years ago to 251 million years ago, was a time of great change on Earth. The era began with the breakup of one supercontinent and the formation of another. Plants became widespread. And the first vertebrate animals colonized land.
During the Paleozoic Era multicelled animals underwent a dramatic explosion of diversity, and almost all of the oceanic animals within a few million years. -
Paleozoic Era: Permian Period 299 to 251 million years ago
The rest of the surface area of the Earth was occupied by a corresponding single ocean, known as Panthalassa, with a smaller sea to the east of Pangea known as Tethys.
The models indicate that the interior regions of the Permian Period were probably dry, but had many seasonal changes in weather due to the lack of nearby bodies of water. Only some portions of this interior region received rainfall throughout the year. There is little known about the Panthalassic Ocean itself. -
Paleozoic Era: Permian Period 299 to 251 million years ago
There is little known about the Panthalassic Ocean itself. There are notions that the climate of the Earth shifted during the Permian, with decreasing glaciation as the interiors of continents became drier. -
Paleozoic Era: Permian Period 299 to 251 million years ago
The Permian period lasted from 299 to 251 million years ago* and was the last period of the Paleozoic Era. The distinction between the Paleozoic and the Mesozoic is made at the end of the Permian in recognition of the largest mass extinction recorded in the history of life on Earth. It affected many groups of organisms in many different environments, but it affected marine communities the most by far, causing the extinction of most of the marine invertebrates of the time. -
Paleozoic Era: Permian Period 299 to 251 million years ago
Some groups survived the Permian mass extinction in greatly diminished numbers, but they never again reached the ecological dominance they once had, clearing the way for another group of sea life. On land, a relatively smaller extinction of diapsids and synapsids cleared the way for other forms to dominate, and led to what has been called the "Age of Dinosaurs." -
Paleozoic Era: Permian Period 299 to 251 million years ago
Also, the great forests of fern-like plants shifted to gymnosperms, plants with their offspring enclosed within seeds. The gymnosperms first appear in the fossil record of the Permian. The Permian was a time of great changes and life on Earth was never the same again.
Massive areas of land and water is the major effect of the Permian. The crustal plates of the Earth had been fused at this point into Pangea.Most of the present-day continents were in contact and connected. -
Mesozoic era: 251-65.5 million years ago
The angiosperms are a large group and include herbaceous plants, shrubs, grasses, and most trees.) had appeared and began to diversify, largely taking over from the other plant groups. -
Mesozoic era: 251-65.5 million years ago
The Mesozoic Era is divided into three time periods: the Triassic (251-199.6 million years ago), the Jurassic (199.6-145.5 million years ago), and the Cretaceous (145.5-65.5 million years ago).*
The definition the Mesozoic Era means middle animals. The animals fauna changed drastically from the the animal fauna seen in the Paleozoic. Dinosaurs started to appear and they were the most popular organisms of of the Mesozoic, involved in the Triassic and became more diverse in the Jurassic. -
Mesozoic era: 251-65.5 million years ago
Dinosaurs became extinct at the end of the Cretaceous, except for birds.
The Mesozoic was also a time of great change in the terrestrial vegetation. The early Mesozoic was dominated by ferns, cycads, ginkgophytes, bennettitales, and other unusual plants. Modern gymnosperms, such as conifers, first appeared in their current recognizable forms in the early Triassic. By the middle of the Cretaceous, the earliest angiosperms(a plant that has flowers and produces seeds enclosed within a carpel. -
Cenozoic era: 65 million years ago
The Cenozoic spans only about 65 million years, from the end of the Cretaceous Period and the extinction of non-avian dinosaurs to the present. The Cenozoic is sometimes called the Age of Mammals, because the largest land animals have been mammals during that time. However, the diversity of life during the Cenozoic is far wider than mammals. The Cenozoic also included flowering plants, insects, teleost fish, and birds. -
Cenozoic era: 65 million years ago
The cenozoic era is divided into neogene and paleogene periods, and, the Paleocene ( radiation of mammals, birds, and pollinating insects), Eocene (Angiosperm dominance, continued radiation of most present day mammals), Oligocene(Origins of primate groups, including apes), Miocene (Continued radiation of mammals and angiosperms, ancestors of humans appear), Pliocene (Origin of Genus Homo - Humans), Pleistocene(Ice ages; humans appear), Holocene(HIstorical time).
