Natural selection is one of many
concepts for Evolution. Evolution is change over time. In order for natural
selection to happen, over population, variation, and competition has to occur. After
all these conditions have been met, Charles Darwin suggests that the fittest
will survive. Fittest doesn’t necessary mean the strongest. Organism with
variation that will benefit them in survival over the others will triumph, and
will survive and reproduce.
The
snails in the article are an excellent example of natural selection. Cepaea
nemoralis is the snails that are being studied for evolution. These snails
are highly variable as their shells can be yellow, pink or brown. Their shells
can also be banded, which are genetically inherited. This variability is spread
out over many regions as their color allows them to survive in different
environment. Snails are able to possess different colors of shell because shell
color is controlled by a single gene with three alternative alleles. On the
other hand, the band in the snail’s shell is controlled by a single gene with
two alleles. Researches have shown that darker shells, which are brown or pink,
will be able to absorb more solar radiation than yellow shells. Therefore they
can adapt to cooler climates, as they can keep themselves warm. Snails that
inherited the yellow shell will prefer the warmer climate as they can bathe in
sunshine without dying of heat. Their environment also plays a role. If the
snails lived in a open grassland, where grasses are yellow, the snails with
yellow shells will be able to camouflage among the grasses while the snails with
darker shells get eaten by predators. The environment and the climate supports
the snails that are best adapted to it, while killing off the rest. The ones
that survive grow up and eventually pass on their advantageous gene by
reproducing. This is natural selection.
Another
case of natural selection, which is rapidly becoming a problem today, is the
evolution of antibiotic resistance in bacteria. Due to random mutation, a few
bacteria will become resistant to the antibiotic. Once a few bacteria are able
to resist the antibiotic, it can pass on its gene to other bacteria by plasmid
exchange. Antibiotic was first introduced by the usage of penicillin, which was
first discovered by Alexander Fleming in 1928. Since then, bacteria have
mutated due to over-prescription of antibiotics by the physician, or patient’s
incompetence to follow the antibiotic prescription instructions. Antibiotics
kill off bacteria which isn’t able to resist it, giving the bacteria’s
environment pressure. As a result, only the bacteria with the antibiotic
resistant gene are able to survive. With their competition eliminated, they can
divide freely, and their population will rise. They can then reproduce and pass
on their traits to their offspring. This natural selection of the bacteria
eventually produces bacteria that have several antibiotic resistant genes
called superbug. This is becoming a major problem as places that are sanitary
like hospitals are slowly generating superbug.
