Part of your A-Level Biology specification (AQA & OCR) is to understand about natural selection as the mechanism of evolution. You will have come across the sequence of events that leads to allele frequencies changing.

The occurrence of a random mutation that offers the individual a selective advantage for the selection pressure, so that they survive and reproduce. They pass on this new advantageous mutation to their offspring and over many generations the frequency of this mutation increases as it gets established as a new allele. Studying this mechanism in animals is tricky as generation times are very long, but using microbes like yeast or bacteria means that we can study evolution happening before our eyes with generation times being as little as a few days.

Bacteria evolve quickly not just because of their short generation times but also because they reproduce asexually by binary fission. This means the whole population produced from one bacterium with the advantageous mutation will have that advantageous phenotype too.

What also drives natural selection is the presence of the selection pressure. If there is no selection pressure, then the mutation isn’t advantageous and won’t be selected for and become established.

The article I have chosen this week looks at the evolution of antibiotic resistance. We all know that we must reduce the selection pressure driving this evolution – the use of antibiotics. We must finish the course and take a dose high enough so that all the bacteria are killed. Antibiotics must not be prescribed unless it is a clear bacterial infection.

However, this isn’t the only use of antibiotics. In farming for meat, antibiotics can be used as a preventative to stop animals living in crowded conditions from being infected by bacteria. Disease would cause their growth to slow and reduce profits. Curiously giving antibiotics to animals makes them grow faster, so profits increase. This has led to the widespread use of antibiotics in farming and there is a cost to pay.

By keeping the selection pressure firmly in place, more bacteria are becoming resistant to more antibiotics. The article gives the example of colistin resistance – an antibiotic that was saved, under lock and key to treat people who had not responded to other antibiotics. Sadly, this antibiotic has been used in farming and now there are many resistant strains of bacteria out there.

It takes about a decade to get a new antibiotic to be available so we cannot afford to lose any more to resistance.

I am please to see that in the UK our use of colistin is less than 0.5% of all sales of antibiotics. The EU bloc also does well in its reduction of antibiotic use in farming. This isn’t the situation for other countries.

We are all globally linked so what happens in one country affects another. There is a clear link between food production methods, our health and also the climate.

I hope better decisions are made in the future to protect the antibiotics we have left.

Download the article from the Guardian page here