In development of life on the planet some types appeared, others disappeared. Most often living organisms died out gradually, and the formed niche also gradually was filled with new beings. But there were in the history of Earth several tragic pages when disappearance of types happened almost instantly. One of such pages - extinction of dinosaurs.
According to one of the most widespread versions, the death of large reptiles occurred because of the big asteroid which faced Earth 65 million years ago. Presumably this asteroid had a diameter of 10-15 kilometers and moved with a speed of 60 km/s. The pebble of such sizes was capable to destroy a half of the Asian continent. The raising in the atmosphere of millions of tons of dust and steam became a consequence of blow. Destructive earthquakes, huge tsunami swept away everything on the way. All live, being in close proximity to accident epicenter, died instantly. The others died slow and painful death of hunger and cold. The first died from a lack of heat and sunlight of a plant. Tree ferns, many species of the horsetails and club mosses dominating at that time on the planet died out. Herbivorous dinosaurs, such as Diplodocuses, tritseratopsa, stegozavra, lost the food. After disappearance of herbivorous giants there was no food and at predators (tyrannosaurs, velotseraptor, allozavra) – they died too. Only at deathbirds of food was in prosperity, but also they soon died out. Many bird species and small small animals survived. According to the same scenario the tragedy was played also in waters of the World Ocean. At first beings who were at the very bottom of a food chain, and then larger, including plesiosauri, mozazavra, bazilozavra died. Together with dinosaurs, ammonites which fine sinks in a large number are found by paleontologists worldwide in the thickness of breeds relating to the end of the Mesozoic Era died out. It is possible to think that all this occurred for only a few weeks. But such large-scale processes required about several thousands of years. However scientists recreated only accident consequences, for certain the reason is known by nobody. Proceeding from it, various hypotheses, guesses and theories are under construction. Asteroid – the most known. But there is some other which also have the right for existence. On one of them instead of an asteroid the comet could face Earth, on another – change of geographical poles resulted from a natural precession of a terrestrial axis. From exotic theories the most interesting and noteworthy – capture we weed attractions of Earth of a large space body (Moon). Therefore there were those climate and geographical changes which led to extinction of dinosaurs. But it, in turn, gave the chance to develop freely a mammal, and subsequently to appear to the person.