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Viruses cannot change without a host

Viruses don't have the capability to reproduce

Viruses cannot get rid of waste

Since they need a host organism to reproduce– they are subject to evolutionary pressures which can cause change.

Viruses make more of themselves, but the only known way a virus can make more of itself is by taking over the host cell.

Over time a host cells immune system can learn from these encounters and develop strategies to prevent reinfection. So to survive, viruses must adapt or evolve, changing its surface proteins enough to trick the host cell into allowing it to attach.

Without a host cell to activate the change, the virus would not be able to change or evolve.

Viruses are acellular

Cellular metabolism - the set of chemical reactions that occur in living organisms in order to build up and break down cellular components in a balanced fashion.

DNA and RNA is a product of cell metabolism, but in order for metabolic pathways to occur, enzymes are required, which are not present in viruses.

Virus molecules attack a host cell and insert their DNA into the cell two different ways.

One way:

  • Just insert their virus into the cell and use the host cell's "machinery" to re-write it's genes. Therefore it's the actual host cell replicating the virus.
  • Then after the host cell replicates the virus, the virus can leave the host cell and then they go look for another host cell to use.

Second Way:

  • Insert their DNA into the host cell and actual insert their DNA into the current host cell re-writes it's DNA with the virus in it; mutating the cell.
  • This means when the cell replicates, it will replicate the virus over and over again therefore causing the virus to spread.

Acellular- not composed of cells ( = "bodies of protoplasm made discrete by an enveloping plasma membrane

Viruses have a basic structure.

All viruses contain nucleic acid, either DNA or RNA (but not both), and a protein coat, which encases the nucleic acid.

Questions . . .

Based on class discussions ...

Characteristics of Individual Living Organisms

(Foothold Principle: Something living needs to meet all of these.)

The six kingdoms are as follows: Archebacteria, Eubacteria, Protista, Fungi, Plantae, and Animalia. Which kingdom would you classify viruses into?

1. Need energy/nutrients/water and a place to get them

2. Change over time

3. Have the capability to reproduce

4. Get rid of waste

5. React to stimuli

6. Are made of cells

How do viruses obtain energy, replicate, and reproduce when they are not within a host?

Can you walk us through how a virus reproduces outside of a host cell?

You claimed the virus gets energy from the host, what does it use its energy for?

Like a computer “virus”, on its own, sitting there it is not living- it is activated once inside a live host.

Definitions of Life

Viruses do not have the ability to obtain energy, nutrients and water on their own.

A virus does not not even need energy, nutrients, or water. Viruses have only one need: to find a host cell. Without attaching to a host cell (bacteria, plant or animal), viruses do not have any effect. Therefore, without a host, a virus ceases to exist and our immune system can catch it.

Merriam-Webster.com:

Matter characterized by the ability to metabolize nutrients, grow, reproduce, and respond and adapt to environmental stimuli. All known life-forms possess either DNA or RNA.

Oxford Dictionary.com:

The condition that distinguishes animals and plants from inorganic matter, including the capacity for growth, reproduction, functional activity, and continual change preceding death.

Biology-Online.org:

A distinctive characteristic of a living organism from dead organism or non-living thing, as specifically distinguished by the capacity to grow, metabolize, respond (to stimuli), adapt, and reproduce.

Viruses are NOT alive

References

http://answers.webmd.com/answers/1198131/what-are-the-differences-between-bacteria

http://www.preservearticles.com/201101092882/characteristics-of-viruses.html

http://science.howstuffworks.com/life/cellular-microscopic/virus-human7.htm

http://www.uvm.edu/~biology/Classes/011/alive.pdf

http://people.eku.edu/ritchisong/301notes1.htm#metabolism

http://people.ysu.edu/~crcooper01/3702Ch16(S05).pdf

http://faculty.ccbcmd.edu/courses/bio141/lecguide/unit3/viruses/charvir.html

http://www.miamisci.org/youth/unity/Unity1/Lubens/pages/characteristic.html

http://www.biology-online.org/dictionary/Acellular

http://www.ncbi.nlm.nih.gov/books/NBK8174/

http://www.oswego.org/webpages/rfavuzzi/files/VIRUS%20PKT.CH2%20BP.pdf

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