Viruses - not a life-form!
Viruses are no organisms; they are “parasitic chemicals”
Different forms with common structure:a core of DNA or RNA and a protein capsid
Animal viruses may have envelope of proteins, lipids, and glycoprotein around capsid
Genomes may be made of DNA or RNA; linear or circular; single- or double-stranded (Only one form per virus)
Reproduction only possiblewithin living cells
Occur in all organisms; bacteriophages are structurally distinct viruses that infect bacteria