2.2.3: Chapter Summary

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Page ID: 37038

Melissa Ha, Maria Morrow, & Kammy Algiers
Yuba College, College of the Redwoods, & Ventura College via ASCCC Open Educational Resources Initiative

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Prokaryotes are unicellular organisms with circular DNA that lack a nucleus or other membrane-bound organelles. These organisms can be divided into two distinct evolutionary lineages: Bacteria and Archaea. Though Bacteria and Archaea share many traits, Archaea are considered more closely related to eukaryotes due to their cellular processes. Both groups of prokaryotes have complex and essential roles in ecosystems across the globe.

With regard to plants, Bacteria are particularly important for their role in converting atmospheric nitrogen into plant-available forms. Some of these nitrogen-fixing bacteria can be found in root nodules or other specialized compartments (e.g. cephalodia), while others are free-living. Additionally, without the original endosymbiotic event of a photosynthetic bacterial ancestor, "plants" would not exist!

Viruses are biological entities that are not classified as organisms because they are not composed of cells. They have an obligate intracellular relationship with their hosts. Most viruses that we are aware of are disease-causing, such as the Tobacco Mosaic Virus. However, as we learn more about virology, other outcomes are emerging, such as the heat tolerance observed in some grasses.

After completing this chapter, you should be able to...

Explain the distinguishing characteristics of prokaryotic cells
Describe common cell morphologies and cellular arrangements typical of prokaryotic cells and explain how cells maintain their morphology
Describe internal and external structures of prokaryotic cells in terms of their physical structure, chemical structure, and function
Compare the distinguishing characteristics of bacterial and archaean cells
Describe why the Archaea have been difficult to place on the tree of life
Explain what it means to be an extremophile
Describe some of the important ecological roles performed by bacteria
Explain a few ways bacteria interact with plants
Differentiate between oxygenic and anoxygenic photosynthesis
Explain the role of Cyanobacteria in changing Earth's atmosphere
Describe a few mutualistic relationships formed with Cyanobacteria
Distinguish between different Cyanobacterial cell types and describe their functions
Describe the root nodule symbiosis between plants and bacteria
Explain why plants cannot get nitrogen from the nitrogen-rich atmosphere
Describe the general characteristics of viruses
Describe the range of effects viral infections can have on plants

Attribution

Content by Maria Morrow, CC-BY-NC