Describe the balance between internal validity and external validity with quasi-experiments.

answer: there were new carvings etched into the back of the sculpture and each shoulder was turned into a symbol of the birdman.

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.