The fear of wolves is caused by high levels of stress hormones in the blood. But some wolves have relatively low levels of these hormones due to natural variation → are not very afraid of people → evolved into dogs (15000-20000 years)
//quote encyclopedia // Geological age Paleozoic (an ancient biological age, lasting about 300 million years: 1. Cambrian 2. Ordovician 3. Silurian //// 1-3 collectively referred to as the Early Paleozoic (invertebrate Animal Age 4. Devonian 5. Carboniferous 6. Permian ////4-6 collectively called Late Paleozoic (Fish and Amphibian Age
//quote Encyclopedia // The cataclysm that destroyed the world (five times in 500 million years 1. Ordovician mass extinction // The first mass extinction time : started 500 million years ago and lasted 65 million years Results: 85% of species extinct Paleontologists: Global climate is cooling
In 2005, scientists from NASA and the University of Kansas jointly researched the results: a gamma-ray burst released by a supernova (an aging star 6,000 light-years away from the earth) was caused by a gamma-ray burst that lasted for 10 seconds and destroyed 30% of the earth's surface. The ozone layer makes the ultraviolet rays penetrate directly → a large number of organisms die on the ground and offshore → destroy the food chain
2. Late Devonian Extinction Event // The second mass extinction, mainly marine species extinction, the earliest terrestrial vertebrate, the Haina salamander , landed on land. There would be no human beings today without the axolotl.
3. Permian-Triassic extinction event About 250 million years ago , it was the largest of the five mass extinction events, so it is officially called The Great Dying. It started in what is now Siberia, when the earth had only one supercontinent and one huge ocean. Volcanic eruptions lasting 100,000 years → Melting rocks ignite coal deposits → Earth heats up, preventing the circulation of ocean currents → Toxic bacteria erupts and nearly all other life in the ocean dies → Dirty waters release deadly hydrogen sulfide into the air Gas → Most land animals suffocate to death → 90% of species on Earth go extinct (recovered after 10 million years) Trilobites (the first animals to evolve imageable eyes) . After 270 million years, the earth was their world. Extinct in mass extinction.
4. Triassic-Jurassic extinction event Time : It started 250 million to 203 million years ago and lasted for about 50 million years. Pangaea is about to split, and magma activity is extremely intense, forming huge pressure in it → a large number of magma spurts (in the eastern United States and the Caribbean) → a 2500km, 50m wide crack forms on the surface, cutting the continent in half → destroying the foundation of the food chain, a large number of animals Extinction. Volcanic eruption → a large amount of toxic gas + carbon dioxide → global temperature rises dramatically (16 ° C ↑ 30 ° C) → destroys most of the remaining plants → famine is more serious → atmospheric oxygen content drops rapidly → destroys many animals. Water vapor and SO2 in the atmosphere react to form acid rain (lasting for tens of thousands of years) → further reduction of plants and acidification of soil. 200,000 years after the disaster, the magma stopped erupting. But the volcanic ash formed by the eruption obscures the sky, and the earth receives only 50% of the usual solar energy. After the heat formed by the volcanic eruption was exhausted, the earth entered a large-scale ice age→30℃↓10℃→The eggs of a large number of animals could not hatch, so they became extinct
5. Cretaceous-Tertiary extinction event
Titan // Titan: The largest of Saturn's moons and the second largest in the solar system. The temperature is -200°C The atmosphere is mainly composed of nitrogen (4 times the concentration of the earth's atmosphere), there is no oxygen in the air, and it is colder than anywhere on the earth. With rivers and coastlines and hundreds of lakes. In the solar system, rainfall is only present on Earth and Titan. The difference is that all the ocean and rain on Titan is not water, but methane and ethane (these molecules on Earth make up natural gas).
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