Microbes as Biofertilizers – CBSE / NCERT Notes for Class 8 Science
Microbes as Biofertilizers Class 8 Science Online Notes –
Fertilizers are substances added to enhance soil fertility. This results in higher yields & healthier plants. Chemical fertilizers, however, have several disadvantages like they are toxic to various life forms, can cause an imbalance in soil ph, results in soil infertility, degrades ecosystem, plants become susceptible to many diseases, fruits & vegetables have high toxic residues. Excessive use of fertilizers can cause environmental pollution.
Use of biofertilizers is preferred as they do not include any of the disadvantages mentioned above. Biofertilizers are living organisms that enrich soil nutrient quality. Some of the sources of biofertilizers are bacteria, fungi, cyanobacteria, etc.
Rhizobium is an example of a nitrogen-fixing bacteria present in the root nodules of leguminous plants. Nitrogen is a macronutrient for the growth & development of plants. Rhizobium enriches the soil with nitrogen.
Mycorrhiza, a symbiotic association between fungi & certain plants, also enhance the phosphorus content which in turn helps in better growth & development of plants. They are resistant to pathogens.
The nitrogen cycle is all about the movement of nitrogen between various elements on Earth (like air, soil, living organisms, etc.) The amount of nitrogen in the atmosphere remains constant.
- The atmosphere has approx. 78% nitrogen.
- Atmospheric Nitrogen is fixed into the soil. N2fixing microbes convert atmospheric N2 into nitrogen compounds like NH3
- Plants utilize nitrogen from soil through their roots
- Animals utilize nitrogen, feeding on plants
- When Plants & animals die, Nitrogenous wastes are returned to soil
- Decomposers convert some part to nitrogen compounds to be used by plants
- Denitrifying bacteria convert into atm. N2
Decomposition is the process in which complex organic matter is broken down into simpler forms. This process breaks down dead & decaying organic matter into simple inorganic forms.
Organisms which help in decomposition are termed as ’Decomposers’. Bacteria & Fungi are important Decomposers
Decomposers help the environment to get rid of dead & decaying matter and also enrich the soil quality for better growth of plants.
There are many microbes which cause several diseases in plants, animals & human beings. Such disease-causing organisms are called Pathogens. Pathogens include bacteria, viruses, fungi & protozoa.
In this section, we will discuss the various diseases caused by various pathogens. ‘Disease’ is disturbed ease. Disease results in a change in either the functioning or the appearance of one or more systems of the body for worse.
Diseases in Humans: Typhoid
- Bacteria, Salmonella typhi
- Pathogen’s entry
- Contaminated food & water
- Primarily reach the small intestine
- High fever
- Loss of appetite
- Diagnosed using Blood culture/ Urine culture or Widal test
- Treated with a course of antibiotic medication
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