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Isolation and the
Evolution of New
Species
Learning Objectives
1. To know how new species arise.
1. To understand how a population becomes
isolated.
1. To know whether new species form at
the same rate.
1. To know how speciation takes place in an
isolated population. (Higher)
How have these fossils formed?
Isolation and the Evolution of New Species
• After a mass
extinction, a huge
number of new
species appear in
the fossil records.
• This is evolution in
action.
Isolation and the Evolution of New Species
• Natural selection takes place and new organisms
adapted to different conditions evolve.
Isolation and the Evolution of New Species
• Any population of
living organisms
contain genetic
variation.
• If one population
becomes isolated
they will probably
be living in
different
conditions.
Isolation and the Evolution of New Species
• Two populations might change so much over time
that they can not interbreed.
• This is a new species.
Isolation and the Evolution of New Species
• The most
common way
species become
isolated is by
geographical
isolation.
• This is when
two populations
become
physically
isolated ie, a
new river or
mountains.
Isolation and the Evolution of New Species
• An example;
• Australia became
separated from
other continents
over 5 million years
ago.
• Marsupial mammals
(carry babies in
pouches) became
isolated.
• Natural selection
caused many marsupials
to evolve.
• Across the rest of the
world competition
resulted in other
mammals evolving with
more efficient
reproductive systems.
• Marsupials remain
dominant in Australia.
Isolation and the Evolution of New Species
• When species evolve in isolation and found in only
one place in the world, it is said to be endemic.
• Places like Borneo have many endemic species.
Isolation and the
Evolution of New
Species
• Mount Bosavi is a
crater of an extinct
volcano in Papua
New Guinea.
• The animals and
plants that live
inside it have
evolved differently
to those outside
the crater.
Isolation and the Evolution of New Species
• Speciation when
original species
can no longer
interbreed with
the new
species.
Isolation and the
Evolution of New
Species
• Ways for speciation to happen Higher tier
• New species can also arise as a
result of:
• Genetic variation - where each
population has a wide range of
alleles that control their
characteristics.
• Natural selection - where the
alleles which help an organism
to survive are selected in each
population.
• Speciation - where the
populations become so
different that successful
interbreeding cannot happen
anymore.