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Natural selection. A Lesson from a Biologist Dinner Party. Dinner Party with Biologists. ?. I was reading about a new strain of antibiotic resistant Tuberculosis in the news today… What CAUSES antibiotic resistance anyway? Like, What Happens??. Friend # 1- Ms. Conception.

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Natural selection

Natural selection

A Lesson from a Biologist Dinner Party



?

I was reading about a new strain of antibiotic resistant Tuberculosis in the news today…

What CAUSES antibiotic resistance anyway?

Like, What Happens??


Friend 1 ms conception
Friend # 1- Ms. Conception

  • During treatment with an antibiotic, each individual bacterium tries to become resistant to the antibiotic. Only some are able to willingly become resistant, and these individuals survive to pass this trait to their offspring.


Friend 2 r u wong
Friend # 2- R. U. Wong

  • During treatment with an antibiotic, all of the bacteria gradually become more resistant to the antibiotic the more they are exposed to it. They all survive and pass this trait to their offspring.


Friend 3 di lusion
Friend # 3- Di Lusion

  • During treatment with an antibiotic, a population of bacteria usually dies. Sometimes by chance, all members of the population become resistant at once, survive, and pass their resistance to their offspring.


Friend 4 natur l selectiona
Friend # 4- NaturàlSelectiona

  • During treatment with an antibiotic, only those individual bacteria that already have a trait that helps them survive the effects of the antibiotic will live. Their offspring in the next generation will also have the trait.


After all the debate
After all the debate…

Confusion…

Wait! Maybe I’ll ask my students! They’ll know!



Friend 1 ms conception1
Friend # 1- Ms. Conception

  • During treatment with an antibiotic, each individual bacterium tries to become resistant to the antibiotic. Only some are able to willingly become resistant, and these individuals survive to pass this trait to their offspring.


Friend 2 r u wong1
Friend # 2- R. U. Wong

  • During treatment with an antibiotic, all of the bacteria gradually become more resistant to the antibiotic the more they are exposed to it. They all survive and pass this trait to their offspring.


Friend 3 di lusion1
Friend # 3- Di Lusion

  • During treatment with an antibiotic, a population of bacteria usually dies. Sometimes by chance, all members of the population become resistant at once, survive, and pass their resistance to their offspring.


Friend 4 natur l selectiona1
Friend # 4- NaturàlSelectiona

  • During treatment with an antibiotic, only those individual bacteria that already have a trait that helps them survive the effects of the antibiotic will live. Their offspring in the next generation will also have the trait.


Winner winner chicken dinner
Winner Winner Chicken Dinner

  • When it comes to matters of Natural Selection, NaturàlSelectiona is usually tops!

  • But what went wrong with the answers my other friends gave?


Story time it is the year 1840
Story Time! It is the year 1840…

We are all in England, drinking tea, and most likely fabulously dressed



Peppered moth watching
Peppered Moth Watching!

The moth ranges in color from a light mottled gray to dark black


Light moths
Light Moths

  • The light moths are by far more numerous, but more difficult to spot because they blend in so well with the tree trunks!

  • The trees are covered in a tree fungus called a Lichen that gives them light mottled gray appearance.


Yum!

We love to spot the dark moths because our real joy is to see a bird swoop in and eat the moths!

The black ones are more likely to be bird-gobbled!


1850

The factories are pumping pollution and soot into the air and our nearby moth-watching spot!

The pollution kills the lichens, and the soot covers the tree trunks.


Back to the countryside
Back to the Countryside

  • We all get a day off from our labors at the factory and decide to go out for some moth watching…

  • But to our surprise, our favorite sport looks very different than we remember!

  • The light gray moths are no longer the most plentiful…


A changed sport
A Changed Sport

  • And if we want to see a good bird-gobbling, we no longer look for our friends the dark moths, because it’s the lighter moths that are being seen and eaten!


What happened
What Happened?!?!

  • The environmental conditions changed!

  • In the previous environment of a light, lichen-covered tree trunk, the lighter moths were better camouflaged from flying predators, so they were not getting gobbled and therefore lived to reproduce. But in this current environment of a sooty lichen-less tree trunk, the darker moths were better camouflaged, so they were not bird-gobbled and were more likely to survive and reproduce.



Survival and reproduction
Survival and Reproduction!

  • So, out of the original 10 moths on the tree…

  • 4 light moths live to reproduce

  • Only 1 dark moth lives to reproduce

  • The next generation of moths will be skewed in favor of light moths!

The next Generation of Moths


1952

Strict environmental regulations are put in place that restrict pollution and set clean air standards

What do you think is going to happen to the peppered moths?



The original question of antibiotic resistant tuberculosis
The original question of antibiotic-resistant Tuberculosis

  • Think of the Peppered Moths as the Bacteria

  • Think of the Hungry Birds and the Antibiotics

  • Now let’s revisit my friend’s answers to the question of antibiotic resistance and see what we can figure out!


Friend 1 ms conception2
Friend # 1- Ms. Conception

During treatment with an antibiotic, each individual bacterium tries to become resistant to the antibiotic. Only some are able to willingly become resistant, and these individuals survive to pass this trait to their offspring.


Friend 2 r u wong2
Friend # 2- R. U. Wong

  • During treatment with an antibiotic, all of the bacteria gradually become more resistant to the antibiotic the more they are exposed to it. They all survive and pass this trait to their offspring.


Friend 3 di lusion2
Friend # 3- Di Lusion

  • During treatment with an antibiotic, a population of bacteria usually dies. Sometimes by chance, all members of the population become resistant at once, survive, and pass their resistance to their offspring.


Friend 4 natur l selectiona2
Friend # 4- NaturàlSelectiona

  • During treatment with an antibiotic, only those individual bacteria that already have a trait that helps them survive the effects of the antibiotic will live. Their offspring in the next generation will also have the trait.


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