According to janet lever's observations of children at play, gender has little effect on young children. girls spend much more time at play than boys do. boys favor games with clear winners and losers. boys favor games that encourage communication and cooperation.

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.