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.
Influenza type A viruses are very similar in structure to influenza viruses types B and C. The virus particle (also called the virion) is 80â120 nanometers in diameter and usually roughly spherical, although some rare filamentous forms can occur.nfluenza A virus causes influenza in birds and some mammals, and is the only species of influenza virus A. Influenza virus A is a genus of the Orthomyxoviridae family of viruses. Strains of all subtypes of influenza A virus have been isolated from wild birds, although disease is uncommon.