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Bacteria Lecture - Mr Pauller

Tip: This isn't the place to ask a question because the teacher can't reply.

Key Questions

  • Answer:

    Prokaryotes are the simplest organisms.


    Prokaryotes are organisms without a nucleus and usually possess few organelles.
    One type of these organisms are bacteria. Their DNA is circular and is found in the cytosol . They divide through binary fisson.

    This is how DNA is present in bacteria:

    In contrast, eukaryotes(complex organisms), possess a nucleus and many organelles.
    The cells of these organisms are found in protists, plants, fungi, and animals. The cells of these organisms use mitosis and meiosis as forms of cell division.

    This is how DNA is present in eukaryotes(in chromatids inside the nucleus):
    Prokaryotes were the first life forms and therefore are much older on an evolutionary scale. Eukaryotes evolved through the fusion of prokaryotes as detailed in the endosymbiosis theory.

    Here is a video about bacteria.

    Video from: Noel Pauller

  • The biggest difference between these two groups is that bacteria are considered living things and are made of cells, whereas viruses are not (and aren't made of cells).

    Expanding on that, bacteria are unicellular organisms belonging to the domain Eubacteria but now called Bacteria and Archaea ,

    They are ubiquitous on Earth and while they often have a bad reputation for causing disease, many are harmless to humans and some are very helpful to us (for example, the E. coli in your gut helps you digest food).

    Viruses, on the other hand, are not in the organism classification scheme as they are not considered living things. They are not made of cells like organisms, instead they are generally composed of a protein coat surrounding genetic material (DNA or RNA). They do not respire the way organisms do, nor can they reproduce independently. Some have a lipid coat while others do not.

    Here are a few other differences:

    1. Though bacteria are small, viruses are much smaller still. They are said to be ultramicroscopic. Bacteria can be more than 10 to 100 times bigger than viruses!
    2. Viruses are generally parasitic in some way. Most tend to damage their hosts. Some bacteria do this, but many do not.
    3. Bacteria reproduce by binary fission, while viruses must use host cells to create more viruses.

    One more note-- viruses don't just attack large organisms. Viruses will even attack bacteria!

    Here is an image that helps compare the structure of the two (note that it is not to scale- the virus should be much smaller):
    ABC Science

  • Prokaryotes are single-celled organisms with no nucleus. Eukaryotic organisms have cells containing a nucleus.

    All bacteria are prokaryotes, such as E. coli , Streptococcus bacterium, Lactobacillus , Salmonella . It is important to note that only organisms belonging to the Kingdoms Archaebacteria and Eubacteria are prokaryotic. Single-celled Protists (such as euglenas and amoebas) and eukaryotic, as are multicelled members of Kindgoms Fungi, Plantae, and Animalia.

    Here is a video which discusses examples of bacteria and some of their important characteristics, uses, importance and evolutionary importance.

    Video from: Noel Pauller