Fossils, Extinction and Speciation

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What are Fossils?
The hardened remains of Plants and Animals from many years ago found in rocks
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What are examples of ways fossils are formed?
From the hard parts of an animal that do not decay easily, from parts or organisms that have not decayed because one or more of the conditions needed for decay are absent, when parts of the organisms are replaced by other materials as they decay
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Why are fossils quite rare?
Many early life forms were soft-bodied and did not leave traces behind, also fossils have been destroyed by geological activity
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What can we learn from Fossils?
How much or how little different organisms have changed as life has developed on Earth
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What can cause Extinction?
Changes to the environment over geological time, new predators may arise, new diseases may arise, new, more successful, competitors may arise, a single catastrophic event, eg massive volcanic eruptions or collisions with asteroids.
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Define Extinction
Where all individuals of a species have died out
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What is Isolation?
When two populations of a species become geographically separated
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What is genetic variation?
This is where each population has a wide range of alleles that control their characteristics
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How does genetic variation lead to natural selection?
the individuals with characteristics that make them better suited to their environment are more likely to survive and breed passing on the alleles containing the beneficial characteristics to the next generation
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How do new species Arise?
because of Isolation of two populations and natural selection
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What happens to two separated populations over a period of time?
Individuals from the 2 populations will have changed so much they wont be able to breed with one another to produce fertile offspring and will have become separate species
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Why is it difficult for scientists to know exactly how life on Earth began?
There it little evidence that is valid
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What is Speciation?
The formation of a new species
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What are a Species?
A group of organisms that are capable of breeding together to produce fertile offspring.
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Card 2

Front

What are examples of ways fossils are formed?

Back

From the hard parts of an animal that do not decay easily, from parts or organisms that have not decayed because one or more of the conditions needed for decay are absent, when parts of the organisms are replaced by other materials as they decay

Card 3

Front

Why are fossils quite rare?

Back

Preview of the front of card 3

Card 4

Front

What can we learn from Fossils?

Back

Preview of the front of card 4

Card 5

Front

What can cause Extinction?

Back

Preview of the front of card 5
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