When two salamander species, the red-backed salamander and the valley-and-ridge salamander, occur without the other present, their jaw structures are identical, and they consume the same prey. however, when the two species co-occur, the red-backed salamander has a slower-closing, stronger jaw, while the valley-and-ridge salamander has a faster-closing, smaller jaw, and the two species consume prey of different sizes. which of the following is suggested by these observations?

(a) competitive exclusion
(b) preemptive competition
(c) a trade-off between growing fast and competing well
(d) character displacement

regulation of gene expression. gene expression can be regulated by various cellular processes with the aim to control the amount and nature of the expressed genes. these regulatory proteins bind to dna and send signals that indirectly control the rate of gene expression

explanation:

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"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."