Kingdom Monera

  

•What is Systematics?

•“The study of kinds and diversity of organisms and their comparative and evolutionary relationship is called systematics.” (G. Simpson, 1961)

•There is great diversity of organisms around us.

•Since time immemorial, we humans have been exploiting this wealth for our own benefit.

•During this process man tried to differentiate between and identify the organisms.

•Eventually this evolved into a branch of biology known as systematics or classification.

•The methods of classification dates back to ancient time when Indian, Greek and Roman philosophers have contributed their might to systematize science.

•

•What is five kingdom system of classification?

- R. H. Whittaker(1969)  proposed Five Kingdom  system of classification.

- This system shows the

phylogenetic relationship

between the organisms.

- The five kingdoms are

  1. Kingdom Monera

  2. Kingdom Protista

  3. Kingdom Plantae

  4. Kingdom Fungi

  5. Kingdom Animalia

•

•2.13 Salient features of Five Kingdoms:

1. Kingdom Monera :

•Monera includes unicellular prokaryotic organisms.

•These are omnipresent.

•They are found in all types of environment which are not generally inhabited by other living beings.

•Few are photoautotrophs or chemoautotrophs; but majority are heterotrophic in nature.

•These organisms do not have well defined nucleus.

•DNA exists as a simple double stranded circular single chromosome called as nucleoid.

•Smaller circular molecules of DNA as extrachromosomal genetic elements called plasmids are often present.

•Cell wall is made up of peptidoglycan (also called murein) which is a polymer of sugars and amino acids.

•Membrane bound organelles e.g. mitochondria, chloroplast, endoplasmic reticulum are absent.

•Ribosomes are smaller in size (70S) than in eukaryotic cells.

•The mode of reproduction in Monera is

–asexual or

–with the help of binary fission or

–budding.

•Very rarely, sexual reproduction is by conjugation method.

•Morphologically, bacteria are categorized into four groups,

–the spherical- Coccus,

–the rod-shaped bacillus,

–the comma or kidney shaped- vibrio and

–the spiral- spirillum.

•On the basis of evolution, bacteria can be classified as Archaebacteria and Eubacteria

a. Archaebacteria :

•These are differentiated from other bacteria on the basis of their different cellular features.

•These bacteria are mostly found in the extreme environments; hence termed extremophiles.

•They are found in a variety of places from volcanic craters to salty lakes and hot springs.

•Their ability to withstand such hostile environment speaks of their capacity to survive in very severe conditions.

•Bacteria that can withstand high salinities are called halophiles while those that withstand extreme temperature are known as thermophiles.

•A very common example is of methanogenic bacteria found in gut of ruminants (cows and buffaloes).

•–These bacteria help in production of methane in biogas plants.

b. Eubacteria :

•These are commonly referred as true bacteria.

•They have cell wall of peptidoglycan.

•They are found as autotrophs and heterotrophs.

•The autotrophs can be

–Photosynthetic like

•Chlorobium (Green sulphur bacteria) and 

•Chromatium or

–Chemosynthetic like Sulphur bacteria.

•These are mostly multicellular filamentous forms living in fresh water.

•The body is covered by mucilaginous sheath.

•The genetic material is typical prokaryotic.

•Chl-a, Chl-b, carotenes and xanthophylls are the photosynthetic pigments.

•Filaments show heterocyst which helps in nitrogen fixation.

•

•Heterotrophs are the most abundant.

•Most of them are decomposers and known for breaking down large molecules in simple molecules or minerals.

•They can be anaerobes helping in

– curdling of milk (Lactobacilli),

– fixation of nitrogen (Azotobacter),

–antibiotic production (Streptomyces),

– composting and

–degrading oil.

•Some of them are pathogens i.e. causing disease (typhoid, cholera, tuberculosis, tetanus).

•Can you tell?

•1. What are salient features of Monera?

•2. What will be the shape of a bacillus and      coccus type of bacteria?

•3. Write a note on useful and harmful  bacteria.

•Mycoplasma :

•These are smallest of the living forms.

•They do not have cell wall.

•Many forms are pathogenic.

•They are found resistant to common antibiotics due to absence of cell wall.

                                                       Mycoplasma

-Created by-

Shri. Deshmukh A. B.