Viruses from the Latin "virus" meaning poison undoubtedly occupies a crucial role in the earth's biosphere. Yet they defy solid explanation by modern science and there is some question as to whether they are living organisms at all. Viruses exhibit characteristics of both organic life and inorganic, living and non-living. All viruses are capable of self replication, but so are crystals estimated to have been the first non-biological self-replicators. All viruses are parasites, they do not create their own cellular structures and are wholly dependant on host cells for normal cellular function; a cellular structure is one of the pre-requisites for organic life.

Viruses do not fit well into the classical scientific hierarchical taxonomy or tree classification system either. For this reason they are slotted straight in at number six, Family level, out of nine for classification and aside from a general Order of "virales" above Family, have no subsequently higher Class, Division/Phylum, Kingdom, and root Domain. Yet the all pervasive virus Family greatly affects every single organic organism on earth.

There are two main schools of thought as to how viruses evolved, the first maintains that small viruses, or viruses with small short genome's, could be runaway genes. The first candidate for runaway gene's is the processes of plasmid transference created by Plasmid's, which are not only capable of autonomous self-replication within host cells but travel freely around and even out of, multi cellular systems. The other, Transpons, Jumping Gene's or mobile genetic elements, can move freely up and down the genome chain. They leave their position by transcribing themselves into RNA and then back into DNA at a different genome position. 48% of the human genome is made up of Transpons.

The second maintains that large viruses, or viruses with larger longer genome's, were small cells that developed parasitical relationships with larger cells. Over time they streamlined their DNA by a process of reverse-evolution, or chucking out what you don't need, until they became wholly dependant on host cells.

There is a definite cloud of mystery over viruses and their true role in our biosphere, everyday new connections are being made between viruses and major diseases, physiological and psychological conditions, and even our very evolution.

There are five viruses that are thought to contribute to at least 15% of the world's cancers, 80% of which are liver and cervical

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