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The most primitive of monerans are
A) Rickettsiae
B) Actinomycetes
C) Progenote
D) Archaebacteria

Last updated date: 13th Jun 2024
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Hint: The most ancient group of organisms on the earth is monera. This kingdom includes mycoplasma,bacteria, actinomycetes and cyanobacteria. Monera is the only prokaryotic kingdom .These organisms are single celled and have no true nucleus. Monerans are the most numerous of all living organisms on the earth.

Complete Answer:
>Option a is Rickettsiae which is a gram negative ,non spore forming and nonmotile bacteria. It is belongs to rickettsiaceae family.hence option a is wrong
>Option b is actinomycetes which are unicellular gram positive bacteria.Members of this group are found in different habitats across the world.They can produce different kinds of spores. So option b is also wrong.
>Option c is progenote. It was the last common ancestor of archaebacteria and eukaryotic.It is also called the last universal common ancestor. So option c is also wrong
>Option d is given to archaebacteria. They are the oldest living form on the earth.They belong to kingdom monera.So option d is correct.

Additional information:
Characters of archaebacteria
->Cell membrane of archaebacteria is made of lipids.
->The cell wall of archaebacteria is rigid which provides it shape and support.
->Its nutritional requirement is fulfilled by thick cytoplasm.
->They do not possess membrane bound organelles.
->Archaebacteria can live in a variety of environments so they are called extremophiles.
->They can withstand a very high pressure of more than 200 atmospheres.

Note:Archaebacteria able to do photosynthesis. They can reproduce asexually. They show a high level of horizontal gene transfer between lineage.They do not produce spores like other bacteria. They can live in extreme environments.