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Anonymous asked in Science & MathematicsBiology · 9 months ago

A question about antibiotics and evolution...?

Antibiotics are medicines that are designed to kill disease-causing organisms, or pathogens. However, some pathogens evolve antibiotic resistance, where they gain traits that allow them to survive in the presence of antibiotics. The ability of bacteria to adapt to antibiotics so quickly has created a huge concern over whether antibiotics are being overused. What form of evolution is antibiotic resistance an example of, and why?

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  • 9 months ago
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    Natural selection. Any cause that reduces reproductive success in a portion of a population potentially exerts evolutionary pressure, selective pressure or selection pressure, driving natural selection. Antibiotics increase selective pressure in bacterial populations, causing vulnerable bacteria to die; this increases the percentage of resistant bacteria which continue growing.

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  • 9 months ago

    Very good question, and I was very interested in reading the answers.

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  • MARK
    Lv 7
    9 months ago

    It is natural selection.

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  • Anonymous
    9 months ago

    Antibiotics are chemicals that bacteria evolved to kill one another. Antibiotics therefore occur naturally in nature, just not in the same quantity as humans can make them. Antibiotics kill all kinds of bacteria, including good ones indiscriminantiy, not just disease causing ones. The evolution of antibiotic resistance is the result of natural selection. The environment determines or "selects" which individual organisms survive based on their heritable traits. So, even though the environment is not a living thing or a supernatural being, it does "select" which individuals live and which do not. Survival is not guaranteed. If organisms fail to adapt then they will become extinct. For example, the Dead Sea is such a harsh environment (it is so salty) that no living organism can adapt and survive in it. The same is true of the molten lava inside a volcano.

    Some bacteria just happens by chance to have mutations that allow them to survive, even though all other bacteria are killed. The survivors then are able to pass on the genes to future generations. If antibiotics continues to be used over and over again, then the only bacteria that can survive are those that are antibiotic resistant. No other genes matter much when that is the case. Because the abuse of antibiotics does not occur in nature, some people also use the term unnatural selection to describe the abuse of antibiotics.

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  • Ted K
    Lv 7
    9 months ago

    Development of antibiotic resistance in bacterial populations is an example of natural selection.

    Bacteria have small "rings" of double-stranded DNA floating around (called plasmids) that are separate from, and which can replicate independently of the bacterial genome. Many of these plasmids contain genes which code for resistance to antibiotics. In any given population of bacteria, there is going to be variability both in the bacterial genomes and the resident plasmids. As long as the antibiotic in question is not present, then all individuals will be fine. And in fact, during bacterial "sex" (i.e. conjugation, which bacteria do all the time), some individuals which do not have any bacterial resistance may acquire it via transfer of plasmids from another one which does, during the conjugation process. So, you have a bunch of bugs, some of which happen to have resistance genes, and others which don't.

    Now expose that population to the antibiotic. Those which don't carry the resistance gene will be killed, and become "extinct." Those which are resistant, survive. Now you have an "evolved" population, in which ALL bacteria are resistant to that antibiotic. That's classic natural selection.

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  • Dale-E
    Lv 7
    9 months ago

    Natural selection is a vague observation that sees organisms adjusting to their environment.

    The Galapagos turtles and Iguanas are famous examples.

    • Ted K
      Lv 7
      9 months agoReport

      "vague observation?" What the hell does THAT mean?

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  • Anonymous
    9 months ago

    What forms of evolution were you given in your class? I have seen different lists for different classes. It would be something along the lines of developmental gene changes. It could be convergent evolution too because bacteria of different evolutionary origins are developing similar traits (antibiotic resistance) as opposed to divergent evolution (when species have the same evolutionary ancestors that they diversified traits from).

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