What is the purpose of the plasma membrane

The influenza virus cause the flu, but not other diseases. why?

Apopulation of black bears depends on salmon from a stream for food. if a drought causes the stream to run dry one year, how will this likely impact the black bear population?

Which of the following is most likely the result of an organism having lipids in its body a) water cannot be absorbed through the surface of a leaf b)human eats fruits to get a quick source of energy c) a sheep sleeps for more hours in the winter d) a warm river is filled with fish and algae