Documented Examples of Natural Selection at Work
Natural Selection and the Peppered Moths
The Industrial Revolution in England (1850’s) caused mass amounts of soot to be
released in the air.
This caused the trees in the area around the factories to become dark, as their bark
absorbed the soot.
This, in turn, affected the peppered moths of the area, which had two known
varieties - light and dark. Moths that were not camouflaged against the tree
were eaten by predators.
How did changing the environment change the frequencies of light to dark moths in
these areas? ____________________________________________________________________________
___________________________________________________________________________________________
Natural Selection and Darwin’s Finches
Darwin’s Finches have been studied by Peter and Rosemary Grant for over 30
years. The average beak size within the population changed depending on
how the climate changes on the Galapagos Island called Daphne Major.
Since each island of the Galapagos has different environmental conditions, each
flock of birds whose migration lead them to a different island had to adapt
to whatever food source was present.
What would happen to beak size in this population of finches if each year after
1984 were dry again? Why? ____________________________________________________
_________________________________________________________________________________
Documented Examples of Natural Selection at Work
Natural Selection and the Peppered Moths
The Industrial Revolution in England (1850’s) caused mass amounts of soot to be
released in the air.
This caused the trees in the area around the factories to become dark, as their bark
absorbed the soot.
This, in turn, affected the peppered moths of the area, which had two known varieties light and dark. Moths that were not camouflaged against the tree were eaten by
predators.
How did changing the environment change the frequencies of light to dark moths in
these areas? ____________________________________________________________________________
___________________________________________________________________________________________
Natural Selection and Darwin’s Finches
Darwin’s Finches have been studied by Peter and Rosemary Grant for over 30
years. The average beak size within the population changed depending on
how the climate changes on the Galapagos Island called Daphne Major.
Since each island of the Galapagos has different environmental conditions, each
flock of birds whose migration lead them to a different island had to adapt to
whatever food source was present.
What would happen to beak size in this population of finches if each year after
1984 were dry again? Why? _________________________________________________________
__________________________________________________________________________________________
Natural Selection and Sickle Cell Anemia
Heterozygous carriers of sickle-cell have an advantage. They are able to
survive malaria at higher rates.
Homozygous normal and homozygous sickle-celled individuals do not have
this protection.
Thus, the frequency of the sickle-cell gene in those areas affected most by
malaria increased.
How could the sickle-cell gene be considered both a helpful and harmful
mutation? ______________________________________________
______________________________________________________
Natural Selection and Antibiotic Resistance
Antibiotics, at first, kill off the weak bacteria. If treatment stops too early, the more resistant
bacteria take over.
Tuberculosis or TB is a disease caused by bacteria that are evolving to become resistant to
most of all current antibiotics used today. TB consumes the lungs.
How could you prevent the evolution of antibiotic resistance bacteria and viruses?
_______________________________________________________________
_____________________________________________________________________
Natural Selection and Sickle Cell Anemia
Heterozygous carriers of sickle-cell have an advantage. They are able to
survive malaria at higher rates.
Homozygous normal and homozygous sickle-celled individuals do not have
this protection.
Thus, the frequency of the sickle-cell gene in those areas affected most by
malaria increased.
How could the sickle-cell gene be considered both a helpful and harmful
mutation? ______________________________________________
______________________________________________________
Natural Selection and Antibiotic Resistance
Antibiotics, at first, kill off the weak bacteria. If treatment stops too early, the more resistant
bacteria take over.
Tuberculosis or TB is a disease caused by bacteria that are evolving to become resistant to
most of all current antibiotics used today. TB consumes the lungs.
How could you prevent the evolution of antibiotic resistance bacteria and viruses?
_______________________________________________________________
_____________________________________________________________________