Mass Extinctions Flashcards

1
Q

What is a mass extinction?

A

It is when many species die out over the same period of time

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2
Q

How many mass extinctions have occurred since the creation of life on earth?

A

Five

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3
Q

What are the five major mass extinctions?

A
End of Ordovician period
Late Devonian period
End of Permian period
End of Triassic period
End of Cretaceous period
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4
Q

When did the mass extinction at the end of the Ordovician period occur?

A

435 mya

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5
Q

What is special about the mass extinction at the end of the Ordovician period?

A

It is the second biggest mass extinction

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6
Q

What was a possible cause of the mass extinction at the end of Ordovician period?

A

Climatic changes (ice age, with a possible drop in sea level)

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7
Q

When did the mass extinction during the late Devonian period occur?

A

345 mya

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8
Q

What caused the mass extinction late in the Devonian period?

A

The exact cause is unknown

It may have been an ice age with a drop in sea level

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9
Q

When did the mass extinction at the end of the Permian period occur?

A

250 mya

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10
Q

What caused the mass extinction at the end of the Permian period?

A
Climatic changes
Ice age
Volcanic eruptions
Flood
Comet or asteroid
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11
Q

What was special about the mass extinction at the end of the Permian period?

A

It was the biggest mass extinction in history

About 90% of all life on earth was wiped out

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12
Q

When did the mass extinction at the end of the Triassic period occur?

A

190 mya

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13
Q

What caused the mass extinction at the end of the Triassic period?

A

It is uncertain

Could have been global warming, ice age or volcanic eruptions

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14
Q

What happened after the mass extinction late in the Devonian period?

A

Amphibians became terrestrial

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15
Q

What happened after the biggest mass extinction?

A

Reptiles replaced huge amphibians as the dominant group

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16
Q

What was life like before the mass extinction at the end of the Ordovician period?

A

Until this time, life was limited to the water, with very little life on land

17
Q

What is special about the mass extinction at the end of the Triassic period?

A

The last of the big amphibians became extinct

18
Q

What happened after the mass extinction at the end of the Triassic period?

A

Dinosaurs were abundant

19
Q

When did the mass extinction at the end of the Cretaceous period occur?

20
Q

What caused the mass extinction at the end of the Cretaceous period?

A

Possibly a meteorite collision with the earth

Volcanic eruptions

21
Q

Why do scientists think that a meteorite collision caused the mass extinction at the end of the Cretaceous period?

A

The Yucatan Peninsula seems to show evidence of the collision

22
Q

What is special about the mass extinction at the end of the Cretaceous period?

A

The dinosaurs became extinct

Marine ammonites became extinct

23
Q

What happened after the mass extinction at the end of the Cretaceous period?

A

Mammals increased and became the dominant group

24
Q

Why do scientists suspect volcanic eruptions caused the mass extinction at the end of the Cretaceous?

A

There is evidence of a high level of volcanic activity at that time

25
Where was the main concentration of these volcanic eruptions?
In the Deccan region of India
26
What probably caused this raised level of volcanic activity?
India was a separate mass of land drifting north | The collision with Asia probably caused it
27
Why could volcanic activity cause a mass extinction?
Dust and ash released into the air could block out the sun's rays This led to a cooling of the atmosphere Ice sheets were formed at the poles, sea levels dropped and the aquatic habitats decreased Less photosynthesis occurred O2 in the atmosphere decreased The surface of the earth becomes submerged in CO2 This intensifies global warming (greenhouse effect) Ice masses melt Terrestrial habitats are flooded and destroyed
28
What is a meteorite?
Mass of dust and rock moving through space
29
What is an asteroid?
A meteorite with a diameter of more than one kilometre
30
What is the asteroid impact theory?
A theory which speculates that the mass extinction at the end of the Cretaceous period was caused by an asteroid impact
31
Why would an asteroid cause a mass extinction?
Dust and rubble would have been released into the air It blocked the sun's rays, which could ave caused an ice age The heat of the impact would have led to the extinction of many plant and animal species including the dinosaurs Organisms could not adapt to the ch aged environment and died out Photosynthesis stopped: Plants became extinct When this food source was lost, many other animals died out O2 levels dropped
32
What other disasters would an asteroid impact have caused?
Worldwide fires Huge tsunamis Acid rain
33
Why do some scientists say that modern time is the sixth mass extinction?
The present rate of extinction is higher than any during any time in the past
34
How many species become extinct each year?
About 40 000
35
What is the cause of this "sixth mass extinction"?
The negative impact of humans on the environment
36
What is unique about this sixth mass extinction?
It is the only one with a biotic cause