BACTERIA AND VIRUSES

Simplest living organism What are bacteria? Simplest living organism Background Video Smaller or bigger than a human cell? How many cells? Do they have nucleus? Do they have a cell wall? What are flagella used for?

Are bacteria helpful or harmful? Helpful bacteria video Harmful bacteria video

What does this have to do with natural selection? Antibiotic resistant bacteria video

What are viruses? What are viruses? Non-living molecules that can’t reproduce without a living cell Intro to viruses video In order to reproduce, a virus needs a living cell.

Virus Structure Structure – Contain and inner core of DNA or RNA and an outer coat made of protein. Viruses vary in shape but are approximately 10 – 20 nanometers. This is 1000x smaller than human cells. They specifically infect particular host cells Examples: Influenza infects cells the lungs. Tobacco mosaic virus infects tobacco leaves. Hepatitis infects the liver

Virus Lifecycle ATTACHMENT – Virus binds to cell membrane INVASION – Virus enters cell UNCOATING – Virus sheds protein coat

Virus Lifecycle REPLICATION – Virus uses cell to make more protein coat and DNA ASSEMBLY – Coats and DNA are put together RELEASE – 1000’s of virus break out of cell

VIRUS EXAMPLES

Can viruses be killed by antibiotics? NO! Antibiotics only kill bacteria.

WHAT DOES THIS HAVE TO DO WITH NATURAL SELECTION? Viruses have very high mutation rates. Some mutations may be favorable, while others may be lethal. A successful mutation does not necessarily mean that the virus does a better job of killing its host. EBOLA VIDEO