Rifka: February 2011

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Status of bacteria and virus :

Status of bacteria :
Bacteria are placed in a separate kingdom called Monera due to following reasons.

  (1) The main reason is their primitive nucleus.
  (2) Lack of membranous organelles.
  (3) Unorganized genetic material.
  (4) Genetic material occurs as a circular unit of nucleoprotein mass.
  (5) Any types of Membraneous organelles are absent.

Cocci Bacilli Spirillum

  (6) Possess a different kind of ribosomes.
  (7) Constitution of Cellwall is also different.
  (8) Cyclosis (is the circulation or streaming of the
cytoplasm within some living cells) does not occur.
  (9) Constant modification in their subclassification occurs as a new discoveries are made.

Status of virus: In the five kingdom classification of Whittaker there is no mention
of some acellular organisms like viruses.
Hence, viruses are considered a link between living and nonliving.

Bacteriophage

They have DNA or RNA and a protein wall surrounding them.

They do not carry out any metabolic activities.
They enter into other living cells, degrade their genetic material and using these constituents
T hey produce new viruses using the constituents of the host cell. This process is called reproduction.
Hence, they are considered a ‘connecting link’ between living and nonliving.