Scientists have observed that when air pollution is significantly reduced, the frequency of the melanic form of peppered moths:.

The correct answer is : decreases

Explanation:

The development of the peppered moth is a transformative event of directional color change in the moth populace as a result of air contamination during the Industrial Revolution.

The melanic or dark color type of the peppered moth was not known before pollution level was low before 1811. Hence the decrease in pollution level in atmosphere will lowers the frequency of the melanic form of peppered moths.

Thus, the correct answer is : decreases.

the element that provides strength to the exoskeletons of clams and oysters is phosphorus.

this is so because calcium carbonate is the main component in the shells. calcium carbonate is strengthened by phosphorus.

explanation:

"1. it should be, it has been for about 20 years, and it's really not much different in the end than breeding animals to have particular traits. there are always concerns about genetically engineered animals/plants affecting the environment in unexpected negative ways, but i can't think of an example where the fears didn't turn out to be baseless.  

first, as you point out, it would be a great advance in pharmacology, to be able to tailor drugs and their doses to me. the pros involve better medical treatment. the cons involve privacy issues like insurance companies denying coverage to people with genetic risk factors. looking at dna markers wouldn't affect the frequency of genetic diseases, but it would allow detection of them earlier. and ok, actually i suppose that if people used this information to avoid having children with genetic diseases, some might decrease in frequency."