What are the characteristics of living organisms

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What are the characteristics of living organisms?
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Characteristics of living organisms

• Maintain homeostasis
• Reproduction
• Cellular organization
• Metabolism (use energy)
• Contain genetic information (DNA, RNA, nucleic
  acids)

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What about viruses?
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How are viruses transmitted?
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Airborne
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Contaminated food or water
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Vectors or infected animal bite
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Sexual contact
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Contaminated blood products
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Is a Virus Alive?

• No. They are non-living.
• Viruses are NOT cells
• Viruses ARE segments of nucleic acid (DNA or RNA)
  wrapped in a protein coat
• Smaller than bacteria

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Pathogen

• Viruses are pathogens.
• They cause DISEASE

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Why are viruses considered non-living?

• They cannot carry out life processes without a
  HOST cell.

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2 cycles of reproduction

• Lytic Cycle
• Lysogenic cycle

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Lytic Cycle

• 1. virus attaches to a cell and injects its DNA
• 2. Host cell will replicate the viral DNA
• 3. Host cell breaks open and releases the new
  viruses.

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Lysogenic Cycle

• 1. Virus attaches to a cell and injects its DNA
• 2. Viral DNA integrates with the host cells
  DNA.
• 3. Host cell divides normally
• replicates WITHOUT destroying the host cell

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Environmental factors can cause a cell to enter
the lytic cycle.

• Example virus that causes cold sores