Biology
Biology, 14.11.2019 20:31, demij

This question is debated among scientists throughout the world. viewpoint #1 - man’s initial interest in viruses began with their association with disease. the word “virus” has its origins in the latin term for “poison.” in the late 19th century, scientific researchers discovered agents that behaved like bacteria causing diseases such as rabies and hoof-and-mouth, but were much smaller. like bacteria, viruses contain one of two nucleic acids: dna or rna it was apparent that these particles could be spread from one person to another, with serious consequences: illness and death. at this time it became the general view that viruses were biologically "alive," the simplest of all life on earth. an important characteristic of life is the response to stimuli. scientists noted that viruses may exist in two distinct states. when not in contact with a host cell, the virus remains entirely dormant. today, this is called the lysogenic cycle. during this time there are no biological activities occurring and the virus is nothing more than a static particle. viruses can remain in this non-living state for extended periods of time, waiting to come into contact with the appropriate host. when the virus comes into contact with the appropriate host, it becomes active, reacts to its environment and/or host and directs all its efforts toward self-replication. this cycle is referred to as the lytic cycle. the viral goal now is to produce more viruses that then attack more host cells. viewpoint #2 - in 1935 scientists discovered and crystalized the virus responsible for the tobacco mosaic virus. they further demonstrated that the particles lacked any mechanisms necessary for metabolic function. researchers were also able to determine, at this time, that viruses consisted of a nucleic acid, either dna or rna, surrounded by a protein shell. once again, the scientific view changed: viruses may be complex biochemical mechanisms but they are not alive. viruses apparently parasitize the biomolecular aspects of life. they depend on the host cell for the raw materials and energy necessary for nucleic acid and protein synthesis, as well as all other biochemical activities that allow the virus to multiply and spread. most simple life forms use cell division to reproduce, while viruses spontaneously assemble within cells. one might then conclude that even though these processes come under viral direction, viruses are simply nonliving parasites of other life forms. the simple question of whether or not viruses are alive, has defied a simple answer because it raises the fundamental issue: what defines life?

herpes simplex virus 1 (hsv-1), infects humans and produces most cold sores. the virus is contagious. herpes simplex can be spread through contact with saliva, such as sharing drinks. hsv-1 persists in the body by becoming latent and hiding from the immune system in the cell bodies of neurons. after the initial or primary infection, some infected people experience sporadic episodes of viral reactivation or outbreaks. how would scientists with viewpoint #1 respond to the description the herpes virus?
a) a virus is alive because it causes disease.
b) a virus is not living; it responds to chemical changes in the environment. c) a virus is alive; it can respond and/or adapt to changes in the environment. d) a virus is not living; it has no genetic material and does not undergo division.

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