What are the similarities and differences of bacteria and viruses? Size, appearance, reproduction, structure?

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One similarity is that they are both small.  Viruses are a lot smaller than most bacteria, but they are both really small compared to your pen tip.  

Another similarity is that they both have the capability of making you sick.  

Appearance:  Viruses come in a variety of shapes and designs.  Most of the time they look completely foreign.  Some viruses are symmetrical, but some are not.  A bacteriophage virus, for example, looks like a space ship with legs.  Bacteria, on the other hand, do not widely vary in shape and appearance.  They are cells, so they are mostly roundish.  

Reproduction: Bacteria reproduce through binary fission, which is a form of asexual reproduction.  Viruses reproduce by either the lytic or lysogenic life cycle. They differ slightly, but viruses survive by hijacking a cell.  In that regard, viruses are parasitic.  

Structure: Both viruses and bacteria have an outer "shell."  The difference is that bacteria have a cell membrane and viruses have a protein shell coat. Both entities have DNA stored inside of the outer barrier. 

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