Which is an example of a behavioral adaptation?
a. a beaver marks it territory with its scent.
b. an arctic fox has thick fur on its feet for warmth.
c. a hummingbird has a long bill to reach the flower's nectar.
d. an egret has long legs for wading in the mud.

this null effect is caused by a weak manipulation and ineffective internal validity. in a scientific study, as the one dr. morimoto is trying to perfom, internal validity refers to the confidence placed in the cause-effect relationship and to how well an experiment is done and able to eliminate confounding variables.        

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.