B1.6

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How old is the earth?
4.5 billion years old
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How long ago did life on earth begin?
3.5 billion years ago
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Why can’t scientists exact about when life began on earth?
Because there is little repeatable or reproducible evidence
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What are fossils?
Fossils are the remains of organisms from many years ago which are found in rocks.
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How can fossils be dated?
Carbon dating can work out the age using the half-life and the amount of layers in a rock can be used to approximate how old the rock is.
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Why don’t most organisms leave a fossil?
Because they don’t have the right conditions for fossil formation. Many early forms had soft bodies so few traces where left behind. Some traces might have been destroyed by geological activity. E.g earth quakes.
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What does extinction mean?
It means that a species which once existed has completely died out.
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What can cause extinction?
It always involves a change in circumstances; New disease, environmental change, a new predictor may evolve/be introduced into the area- new species-have little to eat. A catastrophic event that destroys the habitat. Natural changes in species over t
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How could a change in climate lead to the extinction of a species?
When an animal is adapted to live is a specific climate, if the climate is changed it may become extinct in that climate. This could have been caused by insufficient food or it not being the correct climate for the species to breed.
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Give reasons as to why dinosaurs have become extinct.
A Collison of an asteroid which cause fires, earthquakes, landslides and tsunamis dust rose which caused global temperatures to fall so plants didn’t grow. A new disease was introduced. The temp of c reduced less plankton/food
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What could cause a new species to arise?
Isolation- 2 pops become separated geographically. Genetic variation-each population has alleles that control their characteristics. Natl select- in each population the alleles that control the charatiswhich help the organism to survive are selected
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Explain the process in which a new species could arise through geographical isolation?
Two groups become isolated there is genetic variation in the 2 population #s alleles are selected which give advantage, interbreeding is no longer possible as population diverge therefore a new species has been formed.
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How do know if speciation has occurred?
The two populations are unable to interbreed successfully
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How might a new competitor cause the extinction of a species?
The original species may be left with too little to eat.
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Explain Darwin’s theory of evolution by natural selection using V.M.S.S.B.P.G
Variation due to mutation struggle to survive organisms which more suited characteristic breed and pass on their genes to offspring
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Why is there a natural variation in a population?
Because there is a wide range of alleles in a population
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Card 2

Front

How long ago did life on earth begin?

Back

3.5 billion years ago

Card 3

Front

Why can’t scientists exact about when life began on earth?

Back

Preview of the front of card 3

Card 4

Front

What are fossils?

Back

Preview of the front of card 4

Card 5

Front

How can fossils be dated?

Back

Preview of the front of card 5
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