Introducing
Your new presentation assistant.
Refine, enhance, and tailor your content, source relevant images, and edit visuals quicker than ever before.
Trending searches
Name: Jessica McCabe Student Number: n8836051
Viruses are not classified as living things, although many opinions will vary from this. This is from solid evidence to support that they do not hold the characteristics to be deemed as alive. Viruses do hold some traits such as their molecular make up, similar to cells, but not much else. The main argument to prove that viruses are not alive is the way of “borrowing life” to reproduce. All living things on the tree of life hold a degree of traits that make them living, and viruses are not included in this.
Viruses were first accepted as “missing links between the inert world and living organisms” (1), but after further research and solid evidence, it has been decided that viruses are not apart of the tree of life (1). Many scientific outlets still argue this fact, but this poster presentation will provide the evidence to convince that viruses do not hold enough living characteristics to title them as a living thing.
LIVING THINGS A “living thing” is an organism that possesses the characteristics of life (2). Some living things are bacteria, protozoa, plants, fungi, animals and humans. These characteristics are: Having an organized structure - being made up of cells Requires energy to survive or sustain an existence Ability to reproduce Ability to grow Ability to metabolize Ability to respond to stimuli Ability to adapt to the environment Ability to move Ability to respire A virus is a “non-living thing” (7). This means that before they are outside their host, they are basically inactive and inanimate (3), however the line is blurred as to whether to classify them as living or not, as they do hold some “living” traits.
VIRUSES The word virus literally translates as “poison” (3). This is often associated with disease and thus bacteria; which are considered as “living”, but this is an incorrect train of thought. When viruses were first discovered, it was thought that they were living because they behaved similar to bacteria however were much smaller. After more research into viruses and how they are composed, it was discovered that they are made up of similar molecules as those found in cells and have the capacity to evolve, when attached to a host, they are often considered to be alive (4).
The main focus reason for viruses not being alive comes down to numerous points that have arisen from various arguments throughout time. These can include such reasons (8): Lack of an essential metabolic system Lack any form of energy Do not replicate or evolve but are evolved by cells Do not produce waste product Do not react to stimuli These are all very supportive points in the non-living virus argument however, the most valid and strongest reason is that viruses need cells in order to survive.
Viruses lead a “borrowed life”(5). This means that when a viruses reproduces it needs the support from a cell. It goes through a chemical reaction by shedding its protein coat, bares its genes and finally takes on the cell’s reproducing system and replicates it’s own RNA or DNA. It also creates more viral protein based on the nucleic acid involved in the process. (6).
This table that shows the comparison between cells and viruses. Cells are the most fundamental building block for all living organisms and hold a certain amount of recognizable traits to justify that they are living. When looking at the viral traits, there are some similarities such as information content, but all the other traits differ to the cells. Information content refers to the composition of the virus, which are similar molecules of those in cells such as nucleic acid, proteins, lipids and complex sugars (5). This can explain why it was thought that viruses were similar to cells before there were more solid evidence on such topic.
Moveria. D., Lopez-Garcia.P. Ten Reasons to Exclude Viruses from the Tree of Life (Internet). Nature Reviews Microbiology. 2009. (cited 2013 Oct 26); 7: (page 306-311)Available from: http://www.nature.com/nrmicro/journal/v7/n4/full/nrmicro2108.htmlDoi: 10.1038 Villarreal. L.P. Are Viruses Alive? (Internet). Scientific American. 2004. (cited 2013 Oct 26); 269(1): (pages 1-3)Avaiable from: http://www.uvm.edu/~biology/Classes/011/alive.pdfFree text full article Haberle. W., Horber. J.K.H., Ohnesorge. F., Smith. D.P.E., Binning. G. In Situ Investigations of Single Living Cells Infected by Viruses (Internet). Ultramicrosopy. 1992. (cited 2013 Oct 26); 42: (pages 1161-1167)Available from: http://www.sciencedirect.com/science/article/pii/030439919290418JFree text full article
Brussow. H. The Not So Universal Tree of Life or the Place of Viruses in the Living World (Internet). Biological Sciences. 2009. (cited 2013 Oct 26); 364(1527): (pages 2263-2265)Available from: http://rstb.royalsocietypublishing.org/content/364/1527/2263.shortDoi: 10.1098
Lanier. L.L. Evolutionary Struggles Between NK Cells and Viruses (Internet). Nature Reviews Immunology. 2008. (cited 2013 Oct 26); 8: (pages 259-268)Availble from: http://www.nature.com/nri/journal/v8/n4/full/nri2276.htmlDoi: 10.1038
Suttle. C.A. Viruses in the Sea (Internet). Nature. 2005. (cited 2013 Oct 26); 437: (pages 356-361)Available from: http://www.nature.com/nature/journal/v437/n7057/abs/nature04160.htmlDoi: 10.1038
Racaniello. V. Are Viruses Alive? (Internet). Virology Blog; 2004 (cited 2013 Oct 26).Avaiable from: http://www.virology.ws/2004/06/09/are-viruses-living/ University of Arizona. Viruses (Internet). The Biology Project; 2004 (cited 2013 Oct 26)Available from: http://www.biology.arizona.edu/cell_bio/tutorials/pev/main.html Moveria. D., Lopez-Garcia.P. Table 1| Comparison of Cellular and Viral Traits (Internet). Nature Reviews Microbiology. 2009. (cited 2013 Oct 26); 7: (page 306-311)Available from: http://www.nature.com/nrmicro/journal/v7/n4/full/nrmicro2108.htmlDoi: 10.1038
Moveria. D., Lopez-Garcia.P. Definition of Life or Living Beings (Internet). Nature Reviews Microbiology. 2009. (cited 2013 Oct 26); 7: (page 306-311)Available from: http://www.nature.com/nrmicro/journal/v7/n4/full/nrmicro2108.htmlDoi: 10.1038