Bacteria and evolution

[Sammy1024]

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When you have a bacteria inside of you, and you take an antibiotic, the bacteria that survives hasn't evolved right? It just was able to evade the medicine or was already superior?

I read a verbal passage and it was about tumors and how antioxidants can help get rid of them by stunting growth.

"Paragraph 5 discusses how antioxidants might weed out weaker cancer cells, leaving only the hearty ones to grow and reproduce (mitotically). In other words, antioxidants act as an evolutionary stress, and choice A is correct" but I thought that isn't how it works?

I knew D was a bad answer but I felt that it was the best out of the 4.

 

[sillyjoe]

When you have a bacteria inside of you, and you take an antibiotic, the bacteria that survives hasn't evolved right? It just was able to evade the medicine or was already superior?

I read a verbal passage and it was about tumors and how antioxidants can help get rid of them by stunting growth.

View attachment 184499
"Paragraph 5 discusses how antioxidants might weed out weaker cancer cells, leaving only the hearty ones to grow and reproduce (mitotically). In other words, antioxidants act as an evolutionary stress, and choice A is correct" but I thought that isn't how it works?

I knew D was a bad answer but I felt that it was the best out of the 4.

Well first off, you never want to bring outside information into verbal. Ever.

In terms of the science behind this, I believe it is because cancer cells become "stronger" when there are more mutations allowing for uncontrolled growth. Antioxidants will decrease genomic stress (mutations) and thus "weed out" the weaker cancer cells that don't have enough mutations to become completely uncontrolled.

 

[neurodoc]

Bacteria exposed to an antibiotic can "evolve" in that the antibiotic will "select for" bacteria that are
"resistant to" the antibiotic. Those bacteria that are "killed" by the antibiotic do not reproduce, while
those that are not do.This will lead an "evolved" population of antibiotic resistant bacteria. That is
certainly an example of genetic "evolution."

 

[NextStepTutor_1]

Right, as @neurodoc stated, the bacteria itself could not evolve in response to some adverse stimuli in order to continue to prosper. The adverse stimuli would select those bacteria that can cope and kill those that cannot. The difference between the two cells (one lives, one dies) may be a result of a mutation that is being selected for - or is able to prosper because it's providing some favorable outcome thus allowing the cell to live and pass on this mutation to it's progeny. This is a snapshot, a still frame, of evolution - it is inaccurate to say a single cell evolves. Evolution is a grand process that tracks and explains many generations, not an individual.

So when you mention antibiotics - the bacteria that do not die may have a mutation that allowed them to avoid the adverse effect (death) due to the antibiotic.

 

[Sammy1024]

Just to reiterate the mutation has occurred before ever being in the body and that's why the antibiotic didn't kill it. It is not possible for it to mutate within the body?

 

[neurodoc]

Just to reiterate the mutation has occurred before ever being in the body and that's why the antibiotic didn't kill it. It is not possible for it to mutate within the body?

You raise an interesting question about how "evolution" actually occurs. Natural selection, as proposed by Darwin and Wallace, holds that there is some genetic variability of organisms and that environmental conditions competitively "select" the "most fit" organisms for "survival," which is defined as the ability to survive and produce offspring that go on to reproduce at the expense of other organisms that do not. Such differential survival acting upon organismal genetic variation leads to "evolution by natural selection." Lamarck had a different idea, which allowed for organisms to change their physiology under the selective pressure of the environment, and to pass these physically "acquired characteristics" on to their progeny. The classic paradigm of such Lamarckian evolution was the idea that giraffes developed long necks (during their individual lives) by having to stretch their necks to compete to get at leaves higher and higher on trees and they somehow were able to pass on their "acquired characteristics (the longer neck) to their progeny.

Both hypotheses (Lamarck and Darwin) are intellectually plausible explanations for evolution. Currently we believe that the Darwinian hypothesis is correct.