The earth was formed about 4.6 billion years ago.
The frist life a pierd about billion years later.
The frist plants didn't appear until around 2 billion years ago.
Until about 580 million ago life forms were small and microscopic.
Since that time life has evolved into many different types or species.
However,Scientists ask me that more than 99% of them are none extinct.
There have been severl extinction events in the history of the earth.
In the extinction event many life forms or species of life died out.
The causes of mast extinction event are unsoft history.
These events are not predictable and can happen at any time.
Scientists think that some of them were study by asking or vercanic by actions
Event like these can change the global conditions that the life depends on .
One majoy extinction event happen about 66 million years ago.
That event may have been started by a large asteroid that hit the earth.
As a result,the and about a half of all species on the planet died out.
When the asteroid hit the earth it started a chain of events.
An asteroid hit the Earth and 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 caused a huge cloud of dust to enter the atmosphere.
The cloud of the dust blocked the sun,and darkened the earth for many months.
Without enough sunlight plants and plant-eating animals quickly died.
With the deaths of so many plants and animals.the food chain collapsed.
This lade to the death some many more species.
Mast extinction event have play the important part in the evolustion of life.
Infect some extinction events have has to salety evolution.
For example,some mamals live to age of but they couldn't compete.
When the dinosaurs were removed the mammals were able to compete more successfully.
Once they could compate manmals the a higher state.
Without extinction events perherps we wouldn't be here today.
Scientists ask me there have been at least 5 max extinction in the last 540 million years.
They also believe that we have entered a new extinction event.
Species are becoming extinct at a much faster rate than before.
Instead of asteroids or volcanic eruptions,the current event is the result of human activities.
Human activties for example have glad to global warming.
Global warming is the result of an increase in carbon gases in our atmosphere .
These gases trap heat from the sun so the earth is getting warmer.
As a result,sea levels are rising and weather patterns are changing.
In addition we humans are distroying the habitats of many plants and animals.
Cutting down forests and polluting rivers destroys the habitats of many forms of life.
There is no longer any doubt that this is happening
Species of life are disappear at increasing rate.
Global temprature are rising and weather patterns are changing.
Scientists are warming us that fast action is necessary to save our future.
If we don't act we may go the way of the dinosaurs.
Mammals couldn't compete successfully with the dinosaurs,so their evolution was blocked.
