Viruses

Are they living things?!?

Review

• Which correctly identifies the organization of living things from least complex to most complex?

• A. Community, Organism, Cell, Atom• B. Tissue, Ecosystem, Cell, Organ System• C. Molecule, Tissue, Population, Community• D. Atom, Organ, Community, Population

Review

• What 8 characteristics define living things?

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What do viruses look like?

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• All Viruses– Capsid

– DNA or RNA

• Some viruses– Envelop

Comparison with a bacteria

• Bacteria– Made up of cells

– Get energy (metabolize)

– Respond to stimuli

– Reproduce asexually

– Evolve

• Virus– Not a cell--no cell

membrane, ribosomes

– No metabolism

– ?Response to stimuli?

– Reproduce using the cells machinery as a host

– Evolve

Bacteria vs. Viruses

• Bacteria can be treated with antibiotics that destroy the cell’s wall. – Ex. Penicillin to get rid of Strep throat!

• Would antibiotics work on a sore throat caused by the common cold virus?

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Virus Reproduction

• Lytic: Uses cell and destroys cell. • Lysogenic: Uses cell and hangs out inside until

the right time to strike!

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Chicken Pox

• Varicella virus• Lytic cycle--pox• Lysogenic cycle--can

remain dormant and come back as shingles.

• What does the vaccine do?

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Vaccines

• Trick your immune system into producing a response to an antigen and make antibodies.

• Can be for a virus or bacteria.

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What do antibodies do?

• Antibodies make it easier for your body’s immune system to recognize and destroy pathogens before you get “sick”

• “Memory”

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Why vaccinate? Why not just treat the symptoms?

• If there is no host, the virus may no longer be able to exist.

• Smallpox was eradicated in 1977 through a world-wide vaccination program.

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Types of Vaccines

• Live, attenuated– Chicken Pox– MMR– Polio “drink”

• Killed– Flu– Polio shot

• Component– Hepatitis

• Toxins– Tetanus – DPT (whooping cough)

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“Tricky” Vaccines

• Influenza--– Why do we have to get

a new one every year?

– Why doesn’t it always work?

• HIV--Why don’t we have one?

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Virus Question

• Peer edit:– How many characteristics of life did they mention?– How many characteristics of life did they relate to the

virus?– How many characteristics of life did they explain using

example from a virus why the virus does or does not display the characteristic?

– What could they add from what we talked about today to support 1-2 characteristics of life?

What makes a good open response?