Top News : ARE VIRUSES PLANTS OR ANIMALS ?

    Last week a question about slime molds took us down to creatures that populate a borderline world between the animal and plant kingdoms. The viruses take us deeper into this strange region. Their invisible world verges between the realm of life and nonliving chemical molecules.

     Plant viruses are viruses that affect plants. Like all other viruses, plant viruses are obligate intracellular parasites that do not have the molecular machinery to replicate without a host. Plant viruses can be pathogenic to higher plants.

 

 

    Are there any plant viruses?

    Plant viruses are highly prevalent in plants worldwide, including vegetables and fruits, and represent a serious threat to cultivated plants and agriculture production [1]. Nonetheless, in virology, interest has mainly been focused on viruses that cause diseases in humans and other vertebrates.

 

 

    Why are viruses not classified as either plants or animals?

     Viruses are not made out of cells, they can't keep themselves in a stable state, they don't grow, and they can't make their own energy. Even though they definitely replicate and adapt to their environment, viruses are more like androids than real living organisms.

 

 

 

    How has viruses been classified?

   Viruses are classified on the basis of morphology, chemical composition, and mode of replication.

 

 

    What is a virus made up of?

   A virus is made up of genetic code surrounded by a protein coat.

 

 

    What best describes a virus?

   Viruses are microscopic biological agents that invade living hosts and infect their bodies by reproducing within their cell tissue. Viruses are tiny infectious agents that rely on living cells to multiply. They may use an animal, plant, or bacteria host to survive and reproduce.

 

 

      Viruses are parasites that attack the living tissues of both palms and animals. No doubt there are more varieties, but the 50 or so known to science are all bandit microbes. A generation ago, some scientists were sure that the infinitesimal objects were not really living things at all. In dormant stages they may endure for decades under temperatures and other hardships that would destroy any plant or animal cell permanently. What's more, when they enter a suitable living cell they are aroused to activities that are very different from the normal processes of life.

       In the past, it seemed logical to suspect that viruses may be non living chemicals that cause destructive reactions in living tissues. Many poisons, of course, are destructive, inorganic or nonliving chemicals.

      And some experts suspected the viruses were toxic chemicals of this sort. These scientists refused to classify the viruses as living things, either plants or animals.

      Even modern scientists have not settled this problem definitely. Chemists who study.' the medical aspects of viruses, tend to think of them as nonliving chemical substances. , Biologists who study the life processes of the infinitesimal parasites regard and treat viruses as living things with basic qualities that make them unique in the realm of life. But they do not know enough about them to classify them as plants or animals.

      It takes at least a million of the miniature microbes to measure an inch. Aft electron microscope is needed to study their shadowy shapes. Their activates are studied by intricate equipment that appears to be borrowed from some weird science lab of the far future. The infinitesimal microbes may resemble bats or balls, sausages or commas. In suitable surroundings, they move and multiply and, like living cells, the teeming multitudes can mutate, or alter their structures.

       Each virus is a wad of simple chemicals, the very same chemicals in the tiny nucleus at the heart of every living cell. All plants and animals, of course, are built from living cells and each cell is organized and run by its tiny nucleus. Its key chemicals are nucleic acids known as DNA and RNA. And a miniscule virus is a wad of these complex organic chemicals. It seems to be identical with the vital core of a living cell. This is why microbiologists treat it as a form of life, though the evidence is much too scanty to assign it to the plant or animal kingdom.

      In the nucleus of a healthy cell, the DNA molecules. carry the blueprint for the busy .life processes. They issue orders that are obeyed and handed on by RNA molecules. A virus is small enough to filter through the tissues of a suitable plant or animal. It reaches the. nucleus and takes over the duties of the DNA. It forces these blueprint molecules to issue different orders of its own.. The cell must neglect its normal duties to produce copies of the virus. In some virus infections, a p ant or animal can fight back and. bring the disease under control. But sometimes the living organism is completely destroyed by the swarming invasion of a virus parasite.

   Viruses may have arisen from mobile genetic elements that gained the ability to move between cells. They may be descendants of previously free-living organisms that adapted a parasitic replication strategy. Perhaps viruses existed before, and led to the evolution of, cellular life.

 

 

    Do viruses use energy?

   Outside of a host cell, viruses do not use any energy. They only become active when they come into contact with a host cell. Once activated, they use the host cell's energy and tools to make more viruses. Because they do not use their own energy, some scientists do not consider them alive.

 

 

    Why are viruses considered to be alive?

    First seen as poisons, then as life-forms, then biological chemicals, viruses today are thought of as being in a gray area between living and nonliving: they cannot replicate on their own but can do so in truly living cells and can also affect the behavior of their hosts profoundly.

 

 

   What was the first virus on earth?

   Two scientists contributed to the discovery of the first virus, Tobacco mosaic virus. Ivanoski reported in 1892 that extracts from infected leaves were still infectious after filtration through a Chamberland filter-candle. Bacteria are retained by such filters, a new world was discovered: filterable pathogens.