Species produce more
than the environment can
causing selection pressure. The
adapted individuals in a population survive to
, passing on the favourable charateristics that confer the selective advantage to their
The light moths have the selective
because they are
against the lichen-covered trees which helps them to avoid
The light moths had a greater chance of
and passing on the genes that made them dark.
This causes an increase in the proportion of light moths until the dark moths became very rare.
During the 19th century pollution killed off some of the lichens and soot deposits caused the tree bark to appear
The melanic dark moth has the selective
because it is better
against the dark tree. They can better avoid
Dark moths had a greater chance of
and passing on their favourable genes that made them dark
This caused a gradual increase in the proportion of dark moths until light moths became very rare in industrial areas.
bacteria arrives spontaneously in the population. Mutant bacteria that are resistant to antibiotics have the
and survive. These bacteria with the selective advantage
to make more resistant bacteria.
One of these bacteria may be resistant to a 2nd antibiotic.
These mutant bacteria have the
survive and reproduce to form more resistant bacteria.
A bacteria resistant to two bacteria
A bacteria resistant to one antibiotic
A bacteria resistant to almost all β-lactam antibiotics
To prevent species
A species is a group of organisms that can
Is the name given to the process where two new species are formed from one original species
Is the name given to the process where the best adapted organisms survive
Is the name given to a random change to an organisms genetic material
Population separated by an
for example a mountain.
occur in each new sub-population.
is displayed in each new population and natural selection occurs where those with the
will survive and
passing on their genes. After many generations, mutations and natural selection changing the gene pool of each population, even if the isolation barrier is removed, these sub-groups will no longer be able to
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