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Comparative studies of natural groups of organisms

               mosaic  in  plants, and newcastle  in  3.3   Kingdom Monera
               poultry.                                Task 3.2
           (b) Some viruses can cause chronic          Use internet sources and the library to
               infections; for example, the virus can   search for information on the kingdom
               replicate  the  entire  life  of the  host,   Monera and write short notes.
               regardless of the presence of the host’s
          FOR ONLINE READING ONLY
               defence mechanisms. This is common     The kingdom Monera consists of unicellular
               in Hepatitis viral infection and in HIV.  prokaryotes. Literally, the term prokaryote

           (c) A host with chronic viral infections   is a combination of two Greek words,
               can be a carrier of an infectious virus   pro meaning ‘before’ and karyo meaning
               for lifetime.  It can sometimes kill   ‘nucleus,’ which simply means before
               many cells,  causing the organism to   nucleus or without a true nucleus. Although
               suffer ill effects.                    prokaryotes have no true nucleus, they still
                                                      have diffuse area(s) of nucleoplasm called

              Exercise 3.1                            nucleoid, containing genetic materials with
                                                      no distinct nuclear membrane or envelope.
             1. A teacher explained to students that it is  This is a very unique feature unifying all
                difficult to classify viruses into a specific   prokaryotes. It makes them distinct from

                kingdom.  To illustrate this point, the   species of the other four kingdoms, which
                teacher showed a video demonstrating the   have membrane enclosed nuclei. Lack
                                                      of  membrane bounded nucleus makes
                structure of the organism. As a biologist,   prokaryotic organisms evolutionarily the
                provide examples and explanations to   most primitive life forms. It is believed
                support the teachers’ statement.      that the oldest prokaryote evolved about

             2.  Explain,  with   examples,    how    3.5 billion years ago. Moreover, most
                certain  microorganisms can  be       organisms under this kingdom have a cell
                                                      wall containing peptidoglycan (Refer to
                invaded  by others, leading  to rapid   Figure 1.3).
                multiplication inside the host's body.
                Support your explanation with the  Prokaryotic organisms are diverse, and they
                case of bacteriophage  T4 infecting  constitute the largest group, in terms of

                Escherichia coli (E. coli) bacteria.  abundance. Studies show that a gram of
                                                      soil may contain approximately 2.5 billion
             3.  Briefly explain why vaccines against   bacteria, while a cubic centimeter of milk

                many viral diseases are currently  may have more than 3 billion bacteria.
                available but HIV vaccination is still  Organisms belonging to this kingdom are
                a challenge to medical biologists.    very minute (ranging between 1 µm and 10
                                                      µm) organisms that cannot be seen without
             4.  Giving  reasons,  briefly  explain  the   the aid of a microscope, and are thus termed
                phase  of life cycle  in  which  HIV   as microscopic. This is the reason why
                replication occurs.                   kingdom Monera was not among the two


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