Extinction events 1
The earth was formed about 4.6 billion years ago.
The first life appeared about a billion years later.
The first plant didn't appeared until around 2 billion years ago.
Until about 580 million years ago. Life forms for small and microscopic.
Since that time life evolved into many different types or species.
However scientists estimate that more than 99% of them are extinct.
There has been several extinction events in the history of the earth.
In the extinction event, many life form or species of life die out.
The causes of mass extinction events are unsolved mysteries.
These events are not predictable and can happen at any time.
Scientists think that some of them started by asteroid impacts or volcanic eruption.
Events like these can change the global conditions that life depends on.
It's when asteroid collided with something.
One major extinction event happened about 66million years ago.
That event may have been started by a large asteroid that hit the earth.
As a result, the dinosaurs and about half of all species on the planet. Dead out .
When the asteroid hit the earth, it started a chain of events.
A chain of events is a series of events linked together like a chain.
This particular chain of events. happened over a period of months and years.
When the asteroid hit the earth. It cause a huge cloud of dust to enter the atmosphere.
This cloud of dust blocked the sun and darken the earth for many months.
Without enough sunlight plant and plant eating animals quickly died.
With the death of so many plants and animals, the food chain collapsed.
This let to death many more species.
Mass extinction events have played an important part in the evolution of life.
In fact, some extinction event have helped to accelerate evolution.
For example, some mammals lived through the age of dinosaurs, but they couldn't compete.
When the dinosaurs were removed, the mammals were able to compete more successfully.
Once they could compete mammals evolved to a higher state.
Without extinction events perhaps we wouldn't be here today.
Extinction event 2
Scientists estimate that there have been at least five mass extinction in the last 540 million years.
They also believed that we have entered a new extinction event.
Species are becoming extinct at a much faster rate than before.
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