Now that we know about both prokaryotic and eukaryotic cells, let's look at the endosymbiosis theory. This theory suggests that mitochondria and plastids in eukaryotic cells were once independent prokaryotic cells.
Avian influenza (AI) is an infectious viral disease of birds (especially wild water fowl such as ducks and geese), often causing no apparent signs of illness. AI viruses can sometimes spread to domestic poultry and cause large-scale outbreaks of serious disease.
The influenza virus, conversationally called the flu, is an illness that's highly contagious and causes a number of different symptoms. There are many different types, or strains, of the influenza virus, including the seasonal flu virus and the H1N1 influenza virus (commonly called swine flu).