Introduction
Q. What is Kingdom Monera?
Ans: The organisms in this group are
prokaryotes = do not have a defined nucleus or organelles.
unicellular = do any of them show multi-cellular body designs.
This group includes all Some well-known bacteria include blue-green algae or cyanobacteria (have cell walls), and mycoplasma (doesn’t possess a Cell Wall). They are the most abundant micro-organisms and live in extreme habitats. Some of them have cell walls (bacteria) while some do not (mycoplasma).The mode of nutrition of organisms in this group can be either by synthesizing their own food (autotrophic) or getting it from the environment (heterotrophic). Many of them live in or on other organisms as parasites.
- Bacteria are grouped under four categories based on their shape 1. The spherical Coccus 2. The rod-shaped Bacillus 3. The comma-shaped Vibrium 4. The spiral Spirillum
- Some of the bacteria are autotrophic, i.e., they synthesise their own food. They may be photosynthetic autotrophic or chemosynthetic autotrophic (metabolic synthesis of organic compounds by living organisms using energy derived from reactions involving inorganic chemicals).
Image: Longitudinal Section of kidney
Source: NCERT Text Books
Monera
- These bacteria are special since they live in some of the most harsh habitats such as:
- Extreme salty areas (halophiles),
- Hot springs (thermoacidophiles) and
- Marshy areas (methanogens) {Microbes In Human Welfare | Useful Microbes}.
- Archaebacteria differ from other bacteria in having a different cell wall structure and this feature is responsible for their survival in extreme conditions.
- Methanogens are present in the gut of several ruminant animals such as cows and buffaloes and they are responsible for the production of methane (biogas) from the dung of these animals.
- There are thousands of different eubacteria or ‘true bacteria’.
- They are characterized by the presence of a rigid cell wall, and if motile, a flagellum.
- The cyanobacteria (also referred to as blue-green algae) have chlorophyll a similar to green plants and are photosynthetic autotrophs.
- The cyanobacteria are unicellular, colonial, filamentous, freshwater/marine or terrestrial algae. The colonies are generally surrounded by gelatinous sheath.
- They often form blooms [algal blooms] in polluted water bodies.
- Some of these organisms can fix atmospheric nitrogen in specialized cells called heterocysts, e.g., Nostoc and Anabaena.
- Chemosynthetic autotrophic bacteria oxidise various inorganic substances such as nitrates, nitrites and ammonia and use the released energy for their ATP production.
- They play a great role in recycling nutrients like nitrogen, phosphorous, iron and sulphur.
- Heterotrophic bacteria are the most abundant in nature. The majority are important decomposers.
- Many of them have a significant impact on human affairs. They are helpful in making curd from milk, production of antibiotics, fixing nitrogen in legume roots, etc {Microbes In Human Welfare | Useful Microbes}.
- Some are pathogens causing damage to human beings, crops, farm animals and pets.
- Cholera, typhoid, tetanus, citrus canker are well-known diseases caused by different bacteria {Diseases Caused by Microorganisms, Diseases | Acute, Chronic, Communicable Diseases}.
- Bacteria reproduce mainly by fission.
- Sometimes, under unfavorable conditions, they produce spores.
- They also reproduce by a sort of sexual reproduction by adopting a primitive type of DNA transfer from one bacterium to the other.
- The Mycoplasma are organisms that completely lack a cell wall.
- They are the smallest living cells known and can survive without oxygen.
- Many mycoplasma are pathogenic in animals and plants.