Characteristics of life &viruses Classification Characteristics of life &viruses
Objectives Identify the characteristics of living organisms Differentiate between viruses and living organisms Explain the structure of viruses Explain the function of viruses
Living or non-living?
Living or non-living?
Living or non-living?
Living or non-living?
Living or non-living?
Pull out your “characteristics of life” list from Monday What were some of the characteristics your group came up with?
When is an organisms living? For something to be described as living, that something must display all seven characteristics of life. Although many different people have many different opinions about what "living" means, the following characteristics were designated "characteristics of living things" with the consensus of the scientific community.
When is an organisms living? Living things are: Made up of cells Respond to environment /Maintain Homeostasis Use energy Grow and develop Reproduce
Are Viruses Living? Virus- An infectious particle that cannot grow or reproduce apart from a living cell.
Are viruses living? This is a very interesting question which has instigated many heated debates in scientific circles. Why are viruses such a big deal? Well, viruses are interesting because they are neither inanimate nor living; a virus is "midway between brute matter and living organism" (Wolfhard Weidel).
Are viruses living? Living characteristics “Not living” characteristics Respond to environment Not composed of cells Evolve Do not use energy (on their own) Reproduce Do not reproduce (on their own) Contain proteins and nucleic acids Can form crystals and remain dormant for long periods of time So are viruses living? NO!
Virus structure Parts: Nucleic acid- DNA or RNA Caspid- protein shell surrounding a virus; proteins determine shape of virus Viral envelope- protective coating formed from host cell membrane Spikes- used to recognize and attach to the cell it attacks
Viruses come in many shapes
Viruses come in many shapes
How do viruses reproduce? Viral Replication: Attaches to a healthy cell Injects its DNA or RNA into the cell Viral DNA is added to host DNA Viral DNA is copied with the host DNA every time the cell divides Now viral DNA is passed on to every new daughter cell!
Function of viruses A virus that causes little or no harm to the host Benign viruses Virulent viruses A virus that causes little or no harm to the host Cause disease Difficult to cure: Replicate quickly Undergo frequent mutations Medicines made to destroy viruses often attack and harm healthy cells
Viruses Video!! Be sure to answer the 10 questions! http://player.discoveryeducation.com/index.cfm?guidAssetId=8819B0AE-8366-4E0F-938F-1B9FC9D57EA7&blnFromSearch=1&productcode=US