When two different populations of the same species
change; usually to adapt to new environmental
conditions, until they are so different they cannot
interbreed anymore
Step 1-The population of
the species is separated
into 2 by a physical barrier.
eg. a mountain, a river
The two popualtions cannot
interbreed now as they cannot
cross the barrer
Step 2-In each of the population, there will be variation.This is because of a
wide range of alleles which lead to different characteristics. Also, different
mutations will occur in each of the populations. This increases variation.
Step 3-Each separate group will evolve
differently as conditions are different in their
environments. It is the survival of the fittest and
so only those who adapt to their new
environments the best will pass on their
advantageous characteristics and alleles to
the next generation. This means the longer the
two groups are apart the more different they
become.
Step 4-The two sub-populations have changed so much that they can no
longer interbreed. They are now closely related but different species