Biology Virus Essay

Biology Virus Essay A virus is a microorganism that cannot reproduce without a host. As a result of this, there has been a lot of controversy on whether or not a virus is a living or non-living organism. The dictionary. com definition for life is, â€Å"the condition that distinguishes organisms from inorganic objects and dead organisms, being manifested by growth through metabolism, reproduction, and the power of adaptation to environment through changes originating internally. Viruses have characteristics of both living and non-living organisms, for example, a living characteristic includes reproduction. A non-living characteristic of a virus is that they cannot have both DNA and RNA. The living characteristics of viruses state that viruses can reproduce, but viruses can only reproduce with the help of a host. As a result of viruses not being able to replicate on their own, viruses are not living organisms. Viruses are small infectious particles that have nucleic acid. They can come in many different shapes and sizes. Although viruses vary in shape the common virus has four main parts, the head, DNA or RNA, tail sheath, and tail fiber. The head of a virus is a protein shell that protects the DNA inside it also known as the genome. In comparison, viruses and living organisms both are made up of smaller units that form up to make something larger. The physical appearance of a virus and living organisms are different and what a virus is made up of is different in comparison to a living organism. Viruses are made up of proteins and nucleic acid. The protein comes together to form an encasing shell for the nucleic acid. The protein shell is called a capsid. The nucleic acid inside a capsid can either be DNA or RNA, but never both. Viruses can be classified depending on the features they have, for example the various shapes of a capsid can determine the type of virus. A capsid can be a simple or complex structure. The most complex capsid is found in bacteria called bacteriophages. A virus can also have a viral envelope which contains protein and lipids. Based on shape and structure viruses can infect bacteria, animals and plants. The way in which viruses can infect theses organisms is different. The viruses that infect bacteria are the most common. The life cycle of viruses that infect bacteria are put into two categories known as the lysogenic and lytic cycles. In the lytic cycle, the virus injects its DNA or RNA into the bacteria and makes the bacteria create all the different components that form an entire virus. These parts come together to create individual viruses and as a result of this mass production of individual viruses, the cell bursts. Viruses that go through the lytic cycle are called virulent phages. Phages that go through the lysogenic cycle are known as temperate phages. In the lysogenic cycle the virus injects its DNA or RNA into the host in the same way as the lytic cycle does except the injected DNA or RNA sits and stays inside the host. As a result the virus doesn’t create more individual viruses and the host’s cell doesn’t burst. Although the nucleic acid sits and stays inside the genome, a reaction could occur and the virus could go from the lysogenic to the lytic cycle. In conclusion, viruses have characteristics of both living and non-living organisms. Like non-living organisms, viruses can’t have both DNA and RNA. They can reproduce like living organisms but that is with the help of a host. Without the help of a host viruses can’t perform the characteristics of a living organism. Due to the lack of living characteristics, this shows that viruses are not living organisms.