What is a virus envelope in biology?

The Virus Envelope is where the capsid is surrounded by lipid bilayer that contains viral proteins, usually including the proteins that would enable the virus to bind to the host cells. and is derived from the host cell membranes. They may help viruses avoid the host immune system. The viral envelope then fuses with the host's membrane, allowing the capsid and viral genome to enter and infect the host.

genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).