Understanding antibiotic resistance
Understanding antibiotic resistance

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Understanding antibiotic resistance

3.1 Evolution and natural selection

In 1858, the British naturalists Charles Darwin and Alfred Russel Wallace both independently proposed the theory of evolution through natural selection to explain how organisms change over time.

Evolution is a change over time in the inherited characteristics or traits in a population. This change is largely brought about by natural selection. This is the process by which a particular trait that confers a survival advantage for an individual becomes more frequent in the population.

Although Darwin and Wallace were unaware of the existence of DNA, we now know that natural selection is the process by which genetic mutations that increase the ability of an organism to survive are selectively passed on to subsequent generations.

Now listen to Audio 1 in which Professor Steve Jones from University College London explains Darwin’s theories of evolution and natural selection.

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Transcript: Audio 1 Darwin’s theories of evolution and natural selection.

What was the crux of Darwin's ideas?
Darwin described his own theory in a pretty tight nutshell. Evolution, he said, is descent with modification. Descent – the passage of information, we would say, today, from one generation to the next and modification – the fact that that passage is imperfect. Over time, those changes will build up and you will get change. It's inevitable. It's bound to happen. But we can rephrase that in slightly more telling terms today. We can say, evolution is genetics plus time. If you've got genetics, DNA, all that stuff – if it copies itself with mistakes, that's mutations. And if you've got time – and we got three and a half thousand million years since the origin of life– evolution is absolutely inevitable. So that's the core of Darwin's theory. It's extraordinarily simple. But Darwin had a second idea, and that's really where he was so smart, because he realised that what's being copied in biology is itself a copying machine, so that if one version inherits a change, a mutation, which makes it more likely that it will survive and reproduce itself, then that change will become more common and will spread. And over time, those differences will build up and new forms of life will emerge by what he called natural selection – inherited differences in the chances of reproducing. So that's Darwinism in one minute.
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Audio 1 Darwin’s theories of evolution and natural selection.
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In the next section, you will see how our use of antibiotics contributes to the evolution of resistance.


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