The Origins of Viruses
Viruses do not have nuclei, organelles, or cytoplasm like cells do, and so they they can't keep themselves in a stable state, they don't grow, and they can't make . all the different aspects of living organisms they need to be able to develop.and how do i watch ncis online for free
Christina's SJC ePortfolio. Home English Narrative Paper. Are Viruses Alive? Digital Security. This paper is arguing that viruses should not be considered as 'alive. I Think Not. A question that has been asked for generations and generations turns out to not have the most clear cut easy answer, but is comprised with much supporting evidence leading towards one theory.
If you have read How Cells Work , you know how both bacteria cells and the cells in your body work. A cell is a stand-alone living entity able to eat, grow and reproduce. Viruses are nothing like that. If you could look at a virus, you would see that a virus is a tiny particle. Virus particles are about one-millionth of an inch 17 to nanometers long. Viruses are about a thousand times smaller than bacteria , and bacteria are much smaller than most human cells. Viruses are so small that most cannot be seen with a light microscope , but must be observed with an electron microscope.
Viruses are not living things. Viruses are complicated assemblies of molecules, including proteins, nucleic acids, lipids, and carbohydrates, but on their own they can do nothing until they enter a living cell. Without cells, viruses would not be able to multiply. Therefore, viruses are not living things. When a virus encounters a cell, a series of chemical reactions occur that lead to the production of new viruses. These steps are completely passive, that is, they are predefined by the nature of the molecules that comprise the virus particle.
Viruses reproduce by inserting genetic material into a host cell. Scientists are not sure whether viruses are living or non-living. In general, scientists use a list of criteria to determine if something is alive. Living things have cells. Viruses do not have cells.
Are viruses dead or alive?
Researchers at Chiron made virology history in when they discovered the hepatitis C virus HCV , not by isolating viral particles, but by cloning and sequencing its genome. Subsequently, scientists developed tests for HCV infection and deciphered aspects of its lifecycle.
This page has been archived and is no longer updated. The evolutionary history of viruses represents a fascinating, albeit murky, topic for virologists and cell biologists. Because of the great diversity among viruses, biologists have struggled with how to classify these entities and how to relate them to the conventional tree of life. They may represent genetic elements that gained the ability to move between cells. They may represent previously free-living organisms that became parasites.
No one knows exactly when viruses emerged or from where they came, since viruses do not leave historical footprints such as fossils. Modern viruses are thought to be a mosaic of bits and pieces of nucleic acids picked up from various sources along their respective evolutionary paths. Viruses are acellular, parasitic entities that are not classified within any domain because they are not considered alive. They have no plasma membrane, internal organelles, or metabolic processes, and they do not divide. Viruses infect all forms of organisms including bacteria, archaea, fungi, plants, and animals. Living things grow, metabolize, and reproduce.
At a basic level, viruses are proteins and genetic material that survive and replicate within their environment, inside another life form. In the absence of their host, viruses are unable to replicate and many are unable to survive for long in the extracellular environment. In many ways whether viruses are living or non-living entities is a moot philosophical point. There can be few organisms other than humans that have caused such devastation of human, animal and plant life. Smallpox, polio, rinderpest and foot-and-mouth viruses are all well-known for their disastrous effect on humans and animals. Less well known is the huge number of plant viruses that can cause total failure of staple crops. The gift-wrapping is virtually always a virus-encoded protein capsid and may or may not also include a lipid coat from the host.
Are viruses alive?