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B3 ­ Life on Earth ­ Answers
1. The basic theory of evolution is that all the different species on Earth have evolved from simple life forms that could
copy or replicate themselves. These simple life forms first developed more than 3500 million years ago (the Earth is
about 4500…

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9. The Peppered Moths as an example of natural selection:
Peppered moths are naturally pale and speckled so they are well camouflaged against silver birch trees. However,
some moths were naturally darker due to their genes ­ this is variation within a species.
Darker coloured and paler moths had to…

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16. An involuntary or reflex nervous action, which does not require the involvement of the brain. Reflex actions are rapid
and we don't need to think about them.
Removing your hand from a pin is an example of a reflex nervous action:
receptor detects a stimulus i.e. a pin

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21. Having a larger brain would give individuals an advantage making them more likely to survive.
At first, scientists also thought that the development of big brains allowed the development of being able to stand up
right. They needed more evidence to agree with the explanation to increase confidence in…

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27. Mass Extinctions: When species disappear in a relatively short time. These occur when environmental change happens
so quickly that animals and plants can't adapt fast enough.
28. Human activity has been responsible in the extinction of some species because:
The introduction of new predators or competition
Industrial activities that…


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