microbiology

Chapter 25: The Origin and Diversification of Eukaryotes Overview: Shape Changers Because eukaryotes have internal membranes, they can perform a wide variety of tasks that prokaryotes are unable to perform. An example is a Didinium eating a larger Paramecium The cytoskeleton allows the Didinium to change its shape enough to engulf the Paramecium Concept 25.1 Eukaryotes arose by endosymbiosis more than 1.8 billion years ago Endosymbiosis in Eukaryotic Evolution There is now considerable evidence that much protist diversity has its origins in endosymbiosis Endosymbiosis is the process in which a unicellular organism engulfs another cell, which becomes an endosymbiont and then organelle in the host cell Mitochondria evolved by endosymbiosis of an aerobic prokaryote

Chapter: 17 Viruses Overview: A Borrowed Life ? A virus is an infectious particle consisting of little more than genes packaged into a protein coat ? Viruses lead ?a kind of borrowed life?, existing in a shady area between life-forms and chemicals. ? Viruses called bacteriophages can infect and set in motion a genetic takeover of bacteria, such as Escherichia coli. ? A virus consists of a nucleic acid surrounded by a protein coat. ? Virus lack the metabolic machinery found in a cell, thus they can?t reproduce or carry out metabolism. Concept 17.1 A virus consist of a nucleic acid surrounded by a protein coat ? Virus smaller than a ribosome and even the largest virus is barely visible under light Microscope ? Some viruses can be crystalized