R Keith and Elliot have kids at the same Daycare facility Bo

R. Keith and Elliot have kids at the same Daycare facility. Both have read the exposure notice posted outside of their kids classroom warning them of an outbreak of head lice at the Daycare. Keith had heard that the most widely used shampoo to treat head lice, permethrin, is no longer effective. He explains to Elliot that the head lice have built up tolerance to the active ingredient in the shampoo in a similar way to a beer drinker building up alcohol tolerance. If you were Elliot how would you correct Keith’s misconception of natural selection? some natural selection stuff

Solution

This can be explained with the example of peppered moths of Great Britain. Here the moths existed in nature in both dark shade and light shades.

These moths mostly rests on tree barks and the dark moths were easily visible to the birds which preyed on them and therefore the dark moths population was low compared to the light shaded moths.

The moths with light shade couldn’t be easily distinguished from the bark and therefore was not preyed up on by the birds and their population increased. But during the industrial revolution the increase in air pollution led to deposition of soot released from the chimneys of factories on to the tree barks. This led to darkening of the tree barks and this made the light shaded moths easily visible to the birds than the dark shaded once, which blended with the backdrop, thus favouring the dark moths and their population steadily increased.

Similarly here also there could have been some lice which were naturally resistant to the shampoo containing permethrin, and when all the other head lice that were sensitive to permethrin were killed off, the resistant verity survived and multiplied causing this outbreak.