In some democratic nations, citizens use a system of elections where if no one candidate gets more than 50 percent of the votes, everyone is eliminated except for the top two contenders. Citizens then vote again and may select either of the top two candidates. This is an example of a election system.

majority with run-off      

Explanation:

In some democratic nations, citizens use a system of elections where if no one candidate gets more than 50 percent of the votes, everyone is eliminated except for the top two contenders. Citizens then vote again and may select either of the top two candidates. This is an example of a majority with run-off election system.  In majority runoff election system, a candidate wins outright in the first round if she/he obtains  an absolute majority of the votes or else the two top contenders will be subjected to a second round of voting to decide a winner.

as university of miami psychologists debra lieberman and adam smith pointed out in a recent article in the journal current directions in psychological science, humans have social and psychological mechanisms to deter incest. with very few exceptions, marriages between brothers and sisters and between parents and their children are verboten in every human culture. the primary psychological anti-incest mechanism is the yuck response. even the idea of sex with their mom or dad, bro or sis is upsetting to most people. the psychologist jonathan haidt has found that nearly everyone is repelled by the prospect of brother-sister sex, even in hypothetical situations in which there is no chance of pregnancy).

the biological cost of incest

this raises an interesting question: just what’s so bad about incest? sure, having sex with your dad or your sister seems gross — but why? some anthropologists have argued that incest taboos are learned social conventions. this explanation, however, doesn’t make sense to me as it does not explain the widespread existence of anti-incest mechanisms in creatures ranging from cockroaches to chimpanzees. second, the incest taboo is about as close to a universal law as human moral rules get.

why should mechanisms to avoid incest be so widespread both in nature and across human societies? the answer is simple. the problem with having sex close with relatives is that there is an astonishingly high chance that your offspring will be born with a serious birth defect.

the invasive species was introduced due to commercial purpouses, as there was a demand for fur clothes and hence, a business opportunity connected to this product. actually, it was when the nutrias scaped, causing harm to the us ecosystems when they acquired the status of invasive species. in this case they have caused an environmental problem, but it could have affected also economic interests or even human health.