Pavlov's dog learned to anticipate food whenever he was presented with stimuli associated with food. pavlov knew that his dog associated specific stimuli with food because the was elicited by the stimuli conditioned response

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.