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Evolution…read more

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· When animals within a species are different.
· Variation has two causes
1. An organism's genes
2. An organism's environment…read more

Slide 3

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Genetic variation
· Different varieties of a gene for a particular
characteristic are called alleles.
· In sexually reproducing animals, alleles are
shuffled each time a new organism is
· It is possible for an entirely new combination
of alleles to be produced. This is done by
accident when DNA is being replicated. This is
called mutation.…read more

Slide 4

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Environmental variation
· E.g. Differences in skin tone, different sizes due
to diet.
· Differences like these arise during the
individual's lifetime.
· They cannot be passed onto the offspring
because they are not caused by DNA.
INHERITED.…read more

Slide 5

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Discontinuous and continuous
· Discontinuous variation is when there are certain
groups that the variation can belong too. There is
no in-betweens... E.g. Blood group.
· this is almost always caused by genes.
· Usually only one or two genes are involved, each of
them having only a few alleles.
· Continuous variation is when a variation doesn't
fall so easily into a category. E.g. Leaf length!
· It may be caused by the environment or your genes
(or both)…read more

Slide 6

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Charles Darwin and the theory of
natural selection
· In 1856 a theory was put forward by Charles
· His book was called The Origin of Species.
· Proposed a mechanism called natural
selection…read more

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