Page 110 - Biology_F5

Comparative studies of natural groups of organisms

(g) Their cell wall is composed of a of their ability to survive in extreme
carbohydrate-protein complex called conditions, Archaebacteria are grouped
murein or peptidoglycan. into methanogens, which produce methane
(h) Most prokaryotes move using a beating by reducing carbon-dioxide, for example,
flagella, gas vesicles, and gliding methanogens (Methanobrevibacter
mechanisms. Flagella, if present, lack ruminantium) found in ruminants’
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an internal 9+2 fibril arrangement digestive system. The outer group is
pattern. extremothermophiles which are extreme

(i) They reproduce asexually by binary temperature loving archeans living in very
fission and sexually by conjugation. hot environment e.g hot springs or very
There is no mitotic and meiotic cold temperatures. The second group is
divisions, hence no spindle formation. acid loving archeans (acidophiles). They

are found in acidic conditions such as in
3.3.2 Classification of the kingdom phosphoric and arsenic ponds. The third
Monera
The microorganisms in kingdom Monera group is the extremohalophiles which
are salt loving archaeans found in salt
are considered as primitive organisms and lakes. Other classification systems treat
the most ancient living forms on earth. This Archaebacteria as a kingdom and place
kingdom is divided into two main groups the groups of archaea into distinct phyla or
which are Archaebacteria (Extremophiles) divisions. In this text, the entire group of
and Eubacteria (cyanobacteria and true Archaebacteria is regarded as a division.
bacteria). In this text, much emphasize
will be devoted to Eubacteria.
Division Eubacteria
These include the true bacteria and the
Division Archaebacteria
Under this group, bacteria are the most cyanobacteria, that are also known or blue-
primitive and ancient members of kingdom green algae, which are photosynthetic.
Monera. Their cell wall chemistry differs Members of this division lack true nuclei
from eubacteria, as they lack peptidoglycan. and they have a strong and rigid cell wall
Instead, they have lipids, which are different containing a polysaccharide called murein
in composition from other bacteria due to cross-linked by short chains of amino acids.

the presence of long chains of fatty acids They have a variety of shapes, ranging from
with glycerol attached to it by ester linkage. spherical, rod-like, to spiral and comma
Another unique feature of these bacteria is shaped. Additionally, some are heterotrophs,
their ability to inhabit extreme environments living as pathogenic parasites, while others
in which other organisms cannot survive. are free living autotrophs. Furthermore,
These habitats include environments with eubacteria have simple circular DNA which
extreme temperatures, saline, and acidic is not associated with proteins to form
conditions. Others can survive in oxygen chromosomes and they use mesosomes
deprived or anoxic conditions. Because for respiration.

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