Mass extinctions are caused by significant environmental changes. Sometimes these changes are man-made, such as a factor that begins to pollute the water source. Other times these changes are natural, such as a disease or temperature change. One example in the news today has to do with frogs. There is a bacterial infections that is killing the world's frog population in record numbers. So far, this bacteria does not seem to jump species nor do we really understand where it is coming from. All scientists know right now is that the disease is deadly to frogs and the loss of frogs is causing a hole in the ecosystem of many areas.
Mass extinctions have occurred many times during the course of Earth's history. Specifically, when most of life is wiped out, it is due to something environmental that occurs that most organisms are unable to adapt to. It could be due to climate change--periods of ice age, or periods of higher temperatures. It could be due to an event that causes other events to occur--example, if a large asteroid hit earth, the dust would darken the skies, photosynthesis would decrease, temperatures too would decrease, the food chains may begin to fail and many organisms could die off. This possibly occurred when dinosaurs died out 65 million years ago.
Mass extinction can be caused by natural disasters and/or human-made (like weapons of mass destruction). By creating weapons which could exterminate life, life on earth as we know it could end. That being said, the climatic changes which are taking place on the earth could be responsible for mass extinction as well.
It takes a significant environmental change for a mass extinction to occur. This change could be due to manmade circumstances or natural changes in the environment, such as changes in climate.
Sometimes extinctions are indirectly caused. If pollution drastically reduces one species that happens to be the food source for another species, the second species may be the one that becomes extinct.
I don't think we know in all cases. We think that the mass extinction of the dinosaurs was caused by the asteroid hitting. We're pretty sure that the mass extinction of various animals in the Americas and Australia were caused by human actions. But there's not one answer as to what causes mass extinctions in general.
This is a difficult question to answer, because there are many factors that could cause a mass extinction. However, the causes of a mass extinction can change over time. For example, with the dinosaurs, there are many different theories, but most of them are by natural disasters such as earthquakes, hurricanes, and meteors. There are also a few "possible" supernatural causes, but I don't personally believe in them.
However, with human advancement, mass extinction causes have altered slightly in the fact that now it is more mankind's fault as opposed to natural disasters. For example, with the Dodo bird, it was hunted by man into extinction in the 20th century.
Hope this helps!
'' Mass extinction ''
* It must be a rapid event
* during which significant part of all life on earth become extinct
* and the life forms that become extinct must have belonged to different phyla.
Mass extinctions result from different reasons for different species
2.Sudden change in the environment of the habitat
4.accumulation of pesticide in food chain(leading to formation of week egg shell reulting in breakage of egg while coming out)
Sudden environmental change causes mass extinctions.
The first major extinction event which we know about was caused by Stromatolites. They were a weird mutated life form that had evolved the strange ability to photosynthesise. But a by-product of this ability was that they pumped a killer chemical into the atmosphere. As they reproduced and lived and spread, they kept pumping more and more of this toxic, killer chemical into the atmosphere and almost all life, except stromatolites, were poisoned and wiped from the Earth.
Oh... the killer chemical... it was oxygen.