short note Term virus and elichen
Answers
The viruses are non-cellular obligate parasites that are characterized by having an inert crystalline structure outside the living cell.
Once the viruses infect a cell, they kill the host cell and take over the machinery of the host cell to replicate themselves.
The name virus that means venom or poisonous fluid was given by Pasteur. D.J. Ivanowsky.
J. Ivanowsky recognized certain microbes as causal organism of the mosaic disease of tobacco, which were found to be smaller than bacteria because they passed through bacteria-proof filters.
W. Beijerinek demonstrated that the extract of the infected plants of tobacco could cause infection in healthy plants and called the fluid as Contagium vivum fluidum.
M. Stanley showed that viruses could be crystallized and crystals consist largely of proteins, which are inert outside their specific host cell.
In addition to proteins viruses also contain genetic material that could be either RNA or DNA.
Viruses that infect plants have single stranded RNA and viruses that infect animals have either single or double stranded RNA or double stranded DNA.
Bacteriophages are usually double stranded DNA viruses.
The protein coat called capsid made of small subunits called capsomeres, protects the nucleic acid.
Viruses cause diseases like mumps, small pox, herpes and influenza, AIDS.
Lichens are symbiotic associations between algae and fungi.
The algal component is known as phycobiont and fungal component as
Algae prepare food for fungi and fungi provide shelter and absorb mineral nutrients and water for its partner.
Lichens are very good pollution indicators.
Explanation:
A virus is a small infectious agent that replicates only inside the living cells of an organism. Viruses can infect all types of life forms, from animals and plants to microorganisms, including bacteria and archaea
Lichens are symbiotic associations i.e. mutually useful associations, between algae and fungi. The algal component is known as phycobiont and fungal component as mycobiont. In this relationship, fungi get food from algae and in returen blue green algae get shelter.