Which of the following is an example of a positive feedback loop?
the pituitary gland releasing prolactin for lactation to feed a newborn
the pancreas releasing insulin after eating a bowl of sugar based cereal
the pituitary gland releasing antidiuretic hormone in response to high osmotic pressure
the parasympathetic nervous system reacting to the sympathetic nervous system after an emergency

if the type of the food available changes, then the frequency of beak types will change, because birds with beaks more suited to the available food will be more successful over time.

"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."

i don't know. if i were you, i would search it up online : d