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Biology Revision Presentation

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In any species there
exist groups of
individuals called


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breed among themselves more
than witht the other individual
members of the population.

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is the process by which an new
species with its own distinct gene
pool forms.

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Isolating Mechanisms
are barriers to the passage of
genetic material between demes.
In the long term this can lead to
groups so different that they can be
called separate species.

A new species is unable to breed with
the old species+.
OK, so you can have hybrids which are…

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There are a number of
different isolating
Geographic Isolation & Reproductive Isolation

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Geographic Isolation occurs when a
population is physically split into two or
more demes.

A physical barrier can be anything from a
river to a mountain and everything in

This kind of speciation is allopatric speciation,
it is very likely to occur.

Deme 1
Deme 2

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Reproductive isolation occurs when there are
no physical barriers but two demes cannot
interbreed. This form of speciation is
sympatric speciation.

Numerous mechanisms can cause
reproductive isolation.

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This occurs when
animals which have
Behavioral elaborate
isolation behaviours cannot
elicit the required
response in their
potential partner.

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Mechanical Occurs where
mating pairs are

isolation. unable to couple




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