Page 108 - Biology_F5
P. 108
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
Form Five Student’s Book
101