MRSA is a bacterium that has evolved to become resistant to antibiotics. With reference to Darwin’s theory of evolution by natural selection, explain how MRSA bacteria have evolved to become resistant to antibiotics – 10024

Q1.

MRSA is a bacterium that has evolved to become resistant to antibiotics.

With reference to Darwin’s theory of evolution by natural selection, explain how MRSA bacteria have evolved to become resistant to antibiotics.

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Rajiv Bansal says:

July 23, 2025 at 4:55 am

Bacteria can reproduce very quickly, often doubling in number in a few hours. This rapid reproduction means that large populations of bacteria can form in a short time.

Within any bacterial population, there is natural variation. This means that not all bacteria are exactly the same. Some of this variation is caused by random mutations in their genes during reproduction.

Occasionally, a mutation might give a bacterium resistance to a particular antibiotic. This means that the antibiotic no longer kills or harms that bacterium.

When antibiotics are used to treat an infection, they kill the non-resistant bacteria. However, any bacteria with the resistance mutation will survive. This is called selection pressure — only the bacteria with the useful characteristic (resistance) survive.

The resistant bacteria can now reproduce and pass on the resistant gene to their offspring. Over many generations, more and more bacteria in the population will inherit this resistance.

As a result, the overall level of antibiotic resistance in the bacterial population increases. This makes infections harder to treat because antibiotics become less effective.

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