This PSEB 8th Class Science Notes Chapter 2 Microorganisms: Friend and Foe will help you in revision during exams.
PSEB 8th Class Science Notes Chapter 2 Microorganisms: Friend and Foe
→ Micro-organisms are very small organisms that can be seen with the help of a microscope.
→ Micro-organisms can survive in almost all kinds of environments like hot springs, ice-cold water, saline water, desert soil or even in marshy land.
→ Micro-organisms are classified as bacteria, fungi, protozoa, algae, and viruses.
→ Micro-organisms exist in all types of habitats.
→ Generally, they are single-celled (unicellular) sometimes occur in a chain or group of cells.
→ Micro-organisms play an important role in our life.
→ Bacteria are present almost everywhere and are smaller in size.
→ The average size of bacteria is 1.25 times one-thousandth of a millimeter in diameter.
→ Bacteria are divided into three types
- Bacillus or rod-shaped
- Coccus or round-shaped
- Spirillum or spiral
→ Bacteria are autotrophic as well as heterotrophic in nutrition.
→ Bacteria reproduce by cell division or binary fission.
→ There are many similarities between algae and bacteria.
→ They are called cyanobacteria. They are helpful in fixing atmospheric nitrogen and in increasing soil fertility.
→ Diatoms are microscopic algae that occur in springs, estuaries, sediments, and the ocean.
→ Fungi are saprophytic or parasitic in their mode of nutrition.
→ Some fungi damage and spoil food products, leather, paper, and textile whereas others are pathogenic to crops and animals.
→ Yeasts are unicellular and saprophytic fungi used in fermentation to produce beer, wine, and other beverages.
→ Viruses are the smallest parasitic organisms that have the ability to replicate inside the living cells.
→ Protozoans are unicellular organisms that cause serious diseases like dysentery and malaria.
→ Food poisoning is due to the consumption of food spoilt by some microorganisms.
→ Micro-organisms that grow on our food produce toxic substances.
→ The common methods used to preserve our food are chemical methods, salting, sugar, oil, and vinegar, by heat and cold treatments.
→ Protozoa: These are single-celled microorganisms, which may cause some serious diseases like dysentery and malaria.
→ Fungi: Fungi are non-green plants (micro-organisms) that spoil most of the food items.
→ Virus: These are micro-organisms that are present on the borderline between living and non-living. They reproduce only inside the host organism.
→ Bacteria: Bacteria are microorganisms that are present almost everywhere ant) are smaller in size. They are autotrophic as well as heterotrophic in nutrition.
→ Yeast: Yeast is fungi that are unicellular used in fermentation to produce beer, wine, and other beverages.
→ Rhizobium: It is a bacteria that helps in the fixation of nitrogen. It is present in root nodules of leguminous plants.
→ Soil Fertility: It means enriching the soil with nutrients especially nitrogen. It is done by some bacteria and blue-green algae.
→ Micro-organisms: These are very small organisms that cannot be seen with the naked eye. They can only be seen under a microscope. They exist in all types of habitats.
→ Microbes: The other name of micro-organisms is a microbe.
→ Lactobacillus: The bacteria present in curd is called lactobacillus which promotes the formation of curd.
→ Carriers: Carriers are insects and other animals which carry the disease-carrying micro-organisms.
→ Antibodies: When a disease-carrying microbe enters our body, the body produces antibodies to fight the invader.
→ Antibiotics: These are the chemicals that are produced by micro-organisms and are used to kill harmful micro-organisms.
→ Vaccine: It is a dead or weakened microbe which is introduced into a healthy body.
→ Pathogen: The disease-causing micro-organism is called a pathogen.
→ Fermentation: The conversion of sugar into alcohol with the help of micro-organisms is called fermentation.
→ Nitrogen Fixation: The process of conversion of atmospheric nitrogen into nitrites and nitrates with the help of Rhizobium bacteria is called nitrogen fixation.
→ Nitrogen Cycle: When atmospheric nitrogen after going through various phenomenon like nitrogen fixation, nitrification, denitrification again enters the atmosphere, it is called the nitrogen cycle.