Precambrian The first 4 billion years, make up the Precambrian. This is nearly 90 percent of Earth's entire history, stretching, from the formation of Earth to the Paleozoic era about 542 mya. The Precambrian was an important time. Earth formed and life first appeared. Eventually, autotrophic prokaryotes, much like cyanobacteria that made the stromatolites, enriched the atmosphere with oxygen. Eukaryotic cells also emerged, and by the end of the Precambrian, life was flourishing and the first of the animals had appeared. Extensive glaciation marked the second half of the Precambrian. This might have delayed further evolution of life until the ice receded at the beginning of the Ediacaran (ee Dee UH kur uhn) period. The Ediacaran period was added to the time scale in 2004. It is the first new period added to the time scale since 1891 and reflects new knowledge of Earth's history. The Ediacaran period lasted from about 630 mya to about 542 mya, representing about three quarters of a meter on the time scale at the end of the Precambrian.
The Paleozoic era A drastic change in the history of animal life on Earth marked the start of the Paleozoic (pay lee uh ZOH ihk) era. In the space of just a few million years, the ancestors of the most major animal groups diversified in what scientists call the Cambrian explosion. Not all major groups of organisms evolved rapidly at this time, and paleontologists still do not know when the rapid changes started or ended. Major changes in ocean life occurred during the Paleozoic. More importantly, it seems the first life on land emerged during this era. Life in the oceans continued to evolve through the Cambrian period. Fish, land plants, and Insects appeared during the Ordovician and Silurian periods. Organisms of many kinds, including huge Insects, soon flourished in swampy forests that dominated the land. Tetrapods, the first land vertebrates (animals with backbones), emerged in the Devonian period. By the end of the Carboniferous period, the first reptiles were roaming the forests. A mass extinction ended the Paleozoic era at the end of the Permian period. A mass extinction is an event in which many species become extinct in a short time. Mass extinctions have occurred 26 to 30 years on average. Between 60 and 75 percent of the species alive went extinct in each of these events. During the Permian mass extinction, about 90 percent of marine organisms disappeared. Geologist disagree about the cause of the Permian extinction, but most agree about the cause of the Permian extinction, but most agree that geologic forces, including increased volcanic activity, would have disrupted ecosystems or changed the climate.
The Mesozoic era At the beginning of the Triassic period, the ancestors of early mammals were the dominant land animals. Mammals and dinosaurs first appeared late in the Triassic period, and flowering plants first appeared late in the Triassic period, and flowering plants evolved from nonflowering plants. Birds evolved from a group of predatory dinosaurs in the middle Jurassic period. For the rest of the Mesozoic, reptiles such as dinosaurs, were the dominant organisms on the planet. Then, about 65 mya, a meteorite struck Earth. The primary evidence for this meteorite impact is found in a layer of material between the rocks of the Cretaceous (krih STAY shus) and rocks of the Paleogene period, the first period of the Cenozoic era. Paleontologists call this the K-T boundary. Within this layer, scientists find of an element called iridium. Iridium is rare on Earth, but relatively commodity in meteorites. Therefore, the presence of iridium on Earth indicates a meteorite impact. Many scientists think that impact is related to the mass extinction at the end of the Mesozoic era, which eliminated all dinosaurs except birds, most marine reptiles, many marine invertebrates, and numerous plant species. The meteorite itself did not wipe all of these species, but debris from the impact probably stayed in the atmosphere for months or even years, affecting global climate. Those species that could not adjust to the changing climate disappeared.
The Cenozoic era The most recent era is the one in which mammals became the dominant land animals. At the beginning of the Cenozoic (sen uh ZOH ihk) era, which means “recent life,” most mammals were small and resembled shrews. After the mass extinction at the end of the Mesozoic era, mammals began to diversify into distinct groups, including primates—the group to which you belong. Humans appeared very recently, near the end of the geologic time scale, in the current Neogene period. Humans survived the last ice age, but many species of mammals did not.
Notes: I do not mean to cause religious arguments, plus any argument in general. This thread is for users that are currently learning Biology. Perhaps it could be a discussion thread. Don't start a argument over Creation vs. Evolution.
*Mya = Million years ago. *Bya (although it isn't mentioned.) = Billion years ago. To younger users who don't know what Continental Drift. I suggest looking up Alfred Wagner and Plate Tectonics. I also will be posting some Cenozoic videos, if I can find a good one. By the way we are still in the Cenozoic era. Hence "Age of Mammals."
Videos:
Living Fossils, Evolution, and Cryptids video: https://youtu.be/ebb47QvvAKg
Earth's History video: https://youtu.be/rWp5ZpJAIAE
Rapid Evolution video: https://youtu.be/NArlXzSFt2Y
Permian Extinction | Mammal-like Reptiles video: https://youtu.be/cAzSHP7ETPQ
Continental Drift video:https://youtu.be/ovT90wYrVk4
Did Tyrannosaurs Rex have bad eyesight?: https://youtu.be/3rtQPo4HKLY
13 Prehistoric Fights That Really Happened video: https://youtu.be/ixv-Esx5D4c
Homo sapiens vs. Homo neanderthalensis | The Evolution of Language video: https://youtu.be/c9KnOjsc0g4
I used to post astronomy a lot on here. Users would comment their ideas. I just wanted to know some people's ideas. This isn't from Wikipedia. I found a lot of my old tests and then watched a lot of videos. Wikipedia isn't a reliable source. Never was. I could look up astronomy and, find a ton of errors in it. Such as the Moon is a planet or Jupiter is a star.
No need to cheat. Study for the test or exam etc, geography is a pretty interesting topic.
Earth Science? I did have a teacher that ruined it for me. I had to correct her so much. She would say Canzoic era, like who says that. So one day I just said f**** this it's Cenozoic era. I didn't get in trouble but, did get yelled at for correcting her.
I had to go through a lot files to remember.