BIOL113 M2 L9

• Life is...

  a self-sustaining chemical system capable of Darwinian evolution
• Viruses are not included in the phylogenetic trees that we have that describe all of life. Explain this.

  Viruses do not have ribosomes and rely on host cells machinery for protein synthesis. Because of this they don't have the same genes, such as the 16s rRna, that we use as a bench mark for molecular relatedness between cells.
• The SARS-CoV-2 virus and the HIV virus share what traits ?

  They are both RNA based viruses. ,

  They are both membrane encapsulated. ,

  They both infect humans. 
• Why are viruses generally considered to be non-living ?

  because they require a host cell to reproduce
• virus of bacteria

  bacteriophage or 'phage'
• virus of plants

  viroid
• virus of animals

  virus
• Describe a prokaryotic virus

  Prokaryotic viruses, such as bacteriophages, typically have a simpler structure compared to eukaryotic viruses. They contain a nucleic acid core, which can be either DNA or RNA, surrounded by a protein coat called a capsid. Bacteriophages often have a tail-like structure used for attaching to and injecting their genetic material into bacterial cells.
• Eukaryotic viruses

  Viruses that infect eukaryotic cells, such as the tobacco mosaic virus, adenovirus, and influenza virus
• Eukaryotic viruses

  • Have more complex structures than prokaryotic viruses
  • Contain a nucleic acid core, which can be DNA or RNA
  • Can have additional components such as an outer lipid envelope derived from the host cell membrane
  • The nucleic acid core is surrounded by a protein coat, or capsid, which may have various shapes and arrangements depending on the virus
  • May have additional structures such as spikes or glycoproteins protruding from the capsid or envelope, which play a role in attachment to host cells and entry into them
• relate viruses to the definition of life

  Viruses challenge the definition of life because, although they can evolve like living organisms, they cannot multiply or reproduce on their own. They rely on host cells for replication, blurring the line between living and non-living entities.