Virus different living organisms

Viruses are microscopic parasites responsible for a host of familiar — and often fatal — diseases, including the flu, Ebola, measles and HIV. They are made up of DNA or RNA encapsulated in a protein shell and can only survive and replicate inside a living host, which could be any organism on earth.

All viruses are obligate parasites; that is, they lack metabolic machinery of their own to generate energy or to synthesize proteins, so they depend on host cells to carry out these vital functions.

Viruses are considered by some biologists to be a life form, because they carry genetic material, reproduce, and evolve through natural selection, although they lack the key characteristics, such as cell structure, that are generally considered necessary criteria for defining life. A virus is made up of a core of genetic material, either DNA or RNA, surrounded by a protective coat called a capsid which is made up of protein.

Sometimes the capsid is surrounded by an additional spikey coat called the envelope. Viruses are capable of latching onto host cells and getting inside them. Like bacterial infections, many viral infections are also contagious.

They can be transmitted from person to person in many of the same ways, including: coming into close contact with a person who has a viral infection. They are not considered as living organisms since they show more non-living characteristics than living characteristics. Similarly, they do not contain ribosomes and enzymes to synthesize proteins. Hence, they need a living organism host to multiply.

Furthermore, they cannot be observed under the light microscopes, and they cannot be filtered out by Chamberland filters. Moreover, they are not culturable in nutrient media. The difference between virus and prion is mainly due to their composition. Viruses consist of nucleic acids and proteins while prions consist only of proteins. Likewise, there are several differences between virus and prion which this article will discuss.

Overview and Key Difference 2. What is Virus 3. What is Prion 4. Similarities Between Virus and Prion 5. Virus is a nanometer size infectious particle composing a protein coat and nucleic acids. Nucleic acids can be single or double-stranded. Furthermore, they can be linear or circular or segmented. Structurally, nucleic acids remain protected within the protein capsid. Protein capsid may contain spikes and tails. These spikes and tails help the viruses to attach with the host cells.

Based on the protein capsid arrangement, viruses have different shapes such as helical, icosahedral, polyhedral and complex structures. Other than the nucleic acids and protein capsid, some viruses possess an envelope that encloses the nucleocapsid.

Thus, there are enveloped virus while others are naked virus. Using these nucleic acids, viruses multiply inside a living organism host via five steps; attachment, penetration, replication and synthesis, assembly and release. There are very few if any forms of life on Earth that could survive in a world in which all chemical requirements were present but no other life. So, what does define life? Some have argued that the possession of ribosomes is a key ingredient.

This draws a neat distinction between viruses and obligate intracellular parasites such as Chlamydia and Rickettsia. This definition also confers the status of life on mitochondria and plastids, however. The endosymbiosis that led to mitochondria is thought to have given rise to eukaryotic life.

Mitochondria have metabolic activity on which we depend, they have machinery to manufacture proteins and they have genomes. Most would accept that mitochondria are part of a life form, but they are not independent life. I would argue that the only satisfactory definition of life therefore lies in the most critical property of genetic heredity: independent evolution.

Life is the manifestation of a coherent collection of genes that are competent to replicate within the niche in which they evolve d.

Viruses fulfil this definition. It is estimated that there are 10 31 virus particles in the oceans — they vastly outnumber all other organisms on the planet. Alive or not, viruses are doing rather well! University of Edinburgh [email protected]. Bamford, D. Evolution of viral structure. Theor Popul Biol 61, — Boyer, M. Phylogenetic and phyletic studies of informational genes in genomes highlight existence of a 4 th domain of life including giant viruses.

Moreira, D. Ten reasons to exclude viruses from the tree of life. Nat Rev Microbiol 7, — and associated commentary. Nasir, A. A phylogenomic data-driven exploration of viral origins and evolution. Sci Adv , e Rybicki, E. A top ten list for economically-important plant viruses. Arch Virol.