Biology ~ Viruses

Both viruses and organisms contain what?

DNA or RNA. These are needed for the genetic code of proteins. Without an information code, viruses and organisms cannot copy themselves and continue.

Bacteria

One celled organisms that reproduce by fission

7 criteria for life

Organization, Metabolism, Growth, Homeostasis, Response to Stimuli, Adaptation, Reproduction

What part of the cell theory MOST implies that viruses, for all of their similarities to living cells, cannot be considered a life form according to definition?

all living things are made of cells

DNA

This holds an organisms hereditary information

1) Ability to reproduce independently 2) Can have a DNA genome 3) May mutate and evolve 4) Not made of cells 5) Protein coat instead of membrane 6)The ability to grow which ones are only living organism characteristics?

1) ability to reproduce independently (asexual) (remember viruses rely on hosts to give them energy to reproduce) 6) the ability to grow

1) Ability to reproduce independently 2) Can have a DNA genome 3) May mutate and evolve 4) Not made of cells 5) Protein coat instead of membrane 6)The ability to grow which ones are both virus and living organism characteristics?

2) Can have a DNA genome 3) May mutate and evolve

1) Ability to reproduce independently 2) Can have a DNA genome 3) May mutate and evolve 4) Not made of cells 5) Protein coat instead of membrane 6)The ability to grow which ones are only virus characteristics?

4) Not made of cells 5) Protein coat instead of membrane

nucleic acid

A macro molecule that holds cell information in a coded form. (ex. DNA and RNA)

VIRUS

A microscopic parasite that infects cells in biological organisms.

This question is debated among scientists throughout the world.Viewpoint #1 - Man's initial interest in viruses began with their association with disease. The word "virus" has its origins in the Latin term for "poison." In the late 19th century, scientific researchers discovered agents that behaved like bacteria causing diseases such as rabies and hoof-and-mouth, but were much smaller. Like bacteria, viruses contain one of two nucleic acids: DNA or RNA It was apparent that these particles could be spread from one person to another, with serious consequences: illness and death. At this time it became the general view that viruses were biologically "alive," the simplest of all life on Earth.An important characteristic of life is the response to stimuli. Scientists noted that viruses may exist in two distinct states. When not in contact with a host cell, the virus remains entirely dormant. Today, this is called the lysogenic cycle. During this time there are no biological activities occurring and the virus is nothing more than a static particle. Viruses can remain in this non-living state for extended periods of time, waiting to come into contact with the appropriate host. When the virus comes into contact with the appropriate host, it becomes active, reacts to its environment and/or host and directs all its efforts toward self-replication. This cycle is referred to as the lytic cycle. The viral goal now is to produce more viruses that then attack more host cells.Viewpoint #2 - In 1935 scientists discovered and crystalized the virus responsible for the tobacco mosaic virus. They further demonstrated that the particles lacked any mechanisms necessary for metabolic function. Researchers were also able to determine, at this time, that viruses consisted of a nucleic acid, either DNA or RNA, surrounded by a protein shell. Once again, the scientific view changed: viruses may be complex biochemical mechanisms but they are not alive.Viruses apparently parasitize the biomolecular aspects of life. They depend on the host cell for the raw materials and energy necessary for nucleic acid and protein synthesis, as well as all other biochemical activities that allow the virus to multiply and spread. Most simple life forms use cell division to reproduce, while viruses spontaneously assemble within cells. One might then conclude that even though these processes come under viral direction, viruses are simply nonliving parasites of other life forms.The simple question of whether or not viruses are alive, has defied a simple answer because it raises the fundamental issue: What defines life? Herpes simplex virus 1 (HSV-1), infects humans and produces most cold sores. The virus is contagious. Herpes simplex can be spread through contact with saliva, such as sharing drinks. HSV-1 persists in the body by becoming latent and hiding from the immune system in the cell bodies of neurons. After the initial or primary infection, some infected people experience sporadic episodes of viral reactivation or outbreaks. How would scientists with Viewpoint #1 respond to the description the herpes virus?

A virus is alive; it can respond and/or adapt to changes in the environment

What part of the cell theory most implies that viruses, for all of their similarities to living cells, cannot be considered a life form according to definition?

All living things are made of cells

Are viruses alive? This question is debated among scientists throughout the world. Consider the following passage. Scientific researchers discovered agents that behaved like bacteria causing diseases such as rabies and hoof-and-mouth, but were much smaller. Viruses exist in two distinct states. When not in contact with a host cell, the virus remains entirely dormant. During this time there are no biological activities occurring and the virus is nothing more than a static organic particle. In this state viruses can remain for extended periods of time, waiting to come into contact with the appropriate host. When the virus comes into contact with the appropriate host, it becomes active, reacts to its environment and/or host and directs its efforts toward self-replication. The viral goal now is to produce more viruses to attack host cells. The debate regarding viruses continue. According to this passage, some consider viruses to be alive because they A)reproduce.B)cause disease.C)respond to stimuli.D)contains DNA or RNA.

C) respond to stimuli

Are viruses alive? This question is debated among scientists throughout the world. Consider the following passage. Scientific researchers discovered agents that behaved like bacteria causing diseases such as rabies and hoof-and-mouth, but were much smaller. At this time it became the general view that viruses were biologically "alive." This perception changed in 1935 when the tobacco mosaic virus was crystallized and scientists demonstrated that the particles lacked any mechanisms necessary for metabolic function. It was determined that viruses consisted of a nucleic acid, DNA or RNA, surrounded by a protein shell and the scientific view changed: viruses are complex biochemical mechanisms but not alive. According to the passage, the MOST IMPORTANT evidence supporting the opinion that viruses are not alive is that they...

Do not have cellular structure

How does a viruses lytic cycle occur?

It occurs when the virus replicates in a host cell

How does a viruses lysogenic cycle occur?

It occurs when viral DNA incorporates itself into the cell"s DNA and multiplies when the cell multiplies

Can viruses reproduce on their own?

No. They reproduce only by invading and controlling other cells and controlling other cells, as they lack the cellular machinery for self reproduction.

A virus is referred to as a particle rather than a cell because structurally it is a...

RNA or DNA core surrounded by a protein coat

A virus is referred to as a particle rather than a cell because, structurally it is a...

RNA or DNA surrounded by a protein coat

cell

The structural and functional unit of all living organisms

Why aren't viruses living?

They aren't cellular, they cant keep themselves in a stable state, they don't grow, and they can't make their own energy.

Why do some scientist believe that virus responds to the environment.

They believe that a virus responds to its environment when it changes from a dormant to an active form.

Are viruses alve?Viewpoint #1 - The word virus has its origins in the Latin term for poison. In the late 19th century, scientists discovered agents that behaved like bacteria causing diseases such as rabies and hoof-and-mouth, but were much smaller. Like bacteria, viruses contain one of the two nucleic acids: DNA or RNA. The scientists noticed that these particles could be spread from one person to another, with serious consequences: illness and death. At this time it became the general view that viruses were biologically alive, the simplest of all life on Earth.An important characteristic of life is the response to stimuli. Scientists noted that viruses may exist in two distinct states. When they are not in contact with a host cell, the virus remains dormant. Today, this is called the lysogenic cycle. During this time there are no biological activities occurring and the virus is really just a particle. Viruses can remain in this dormant, non-living state for extended periods of time, waiting to come into contact with a host cell. When the virus comes into contact with the host, it becomes active, reacts to its environment and/or host and directs all its energy toward reproduction. This cycle is referred to as the lytic cycle. The viral goal now is to produce more viruses that then attack more host cells.Viewpoint #2 - In 1935 scientists discovered and crystalized the virus responsible for the tobacco mosaic virus. They discovered that viruses consisted of a nucleic acid, either DNA or RNA, surrounded by a protein shell. Viruses did not have a cellular structure; a key characteristic of life. Scientist suggested that viruses may be complex biochemical particles but they are not alive.Viruses depend on the host cell for the raw materials and energy necessary for nucleic acid and protein synthesis, as well as all other biochemical activities that allow the virus to multiply and spread. Most simple life forms use cell division to reproduce, while viruses spontaneously assemble within cells. They concluded that even though reproduction occurs under viral direction, viruses are simply nonliving parasites of other life forms. The simple question of whether or not viruses are alive, has defied a simple answer because it raises the fundamental issue: What defines life? choose all that apply a) Some scientists support the idea that viruses are alive because they contain a nucleic acid. b) One key argument against viruses not being alive is that they do not have a cellular structure. c)A virus can reproduce asexually via cell division. d)Because viruses can spread disease from one organism to another, they are in fact reproducing. e) Some scientists believe that a virus responds to its environment when it changes from a dormant to an active form. f) Living in a host cell as a parasite qualifies an organism as alive.

a) Some scientists support the idea that viruses are alive because they contain a nucleic acid. b) One key argument against viruses not being alive is that they do not have a cellular structure. e) Some scientists believe that a virus responds to its environment when it changes from a dormant to an active form.

which criteria of life do viruses meet?

adaptation, and organization. The two possibilities are reproduction and metabolism. The unknown is response to stimuli.

Scientific researchers discovered agents that behaved like bacteria causing diseases such as rabies and hoof-and-mouth, but were much smaller. It became the general view that viruses were biologically "alive." This perception changed in 1935 when the tobacco mosaic virus was crystallized and scientists demonstrated that the particles lacked any mechanisms necessary for metabolic function. It was determined that viruses consisted of a nucleic acid, DNA or RNA, surrounded by a protein shell. Viruses exist in two distinct states. When not in contact with a host cell, the virus remains entirely dormant. During this time there are no biological activities occurring and the virus is nothing more than a static organic particle. Viruses can remain like this for extended periods of time, waiting to come into contact with the appropriate host. When the virus comes into contact with a host, it becomes active, reacts to its environment and/or host and directs its efforts toward self-replication. The viral goal now is to produce more viruses to attack host cells. The characteristics of life: many are listed in the passage describing viruses. One important piece of evidence arguing against life for viruses is implied by the passage; not stated directly. Viruses are not living, because, as implied by the passage, they......

are not cellular

Viruses have all of the characteristics of living things EXCEPT

cells

According to cell theory...

even primitive cells, like the prokaryote, can carry out the functions of life.

Virus? Living or not? If we use the image as an indicator, we might say living because...

it contains nucleic acid

Scientific researchers discovered agents that behaved like bacteria causing diseases such as rabies and hoof-and-mouth, but were much smaller. At this time it became the general view that viruses were biologically "alive." This changed in 1935 when the tobacco mosaic virus was crystallized and scientists demonstrated that the particles lacked any mechanisms necessary for metabolic function. It was determined that viruses consisted of a nucleic acid, DNA or RNA, surrounded by a protein shell and the scientific view changed: viruses are complex biochemical mechanisms but not alive. When not in contact with a host, the virus remains dormant. During this time there are no biological activities occurring and the virus is nothing more than a static organic particle. In this state viruses can remain for extended periods of time, waiting to come into contact with the appropriate host. When in contact with a host, it becomes active, reacts to its environment and/or host and directs its efforts toward self-replication. The viral goal now is to produce more viruses to attack host cells. According to the passage all BUT ONE is a reason to classify viruses as living. That is they...

lack mechanisms for metabolic function

Which statement describes ALL living things? A)They must reproduce sexually.B)They are composed of one or more cells.C)They are capable of making their own food.D)They have organ systems to carry out the processes of life.

they are composed of one or more cells