Chapter 2: Microorganisms: Friend and Foe-Class 8

🔬 Chapter 2: Microorganisms: Friend and Foe (Class 8) 🧑‍🔬

Hey explorers! Humare aas paas bahut saare living organisms hain jo humein dikhayi nahi dete 👀❌. These tiny organisms are called **Microorganisms** or **Microbes**. Let’s learn about these invisible neighbours! Hey explorers! Hamare aas paas bahut saare jeevit prani hain jo humein dikhayi nahi dete. In chhote praniyon ko **Sukshmajeev (Microorganisms)** ya **Microbes** kehte hain. Chalo in adrishya padosiyon ke baare mein jaanein!

🦠 What are Microorganisms? (Sukshmajeev Kya Hain?)

Microorganisms (Microbes): Very small living organisms that cannot be seen with the naked eye. They can only be seen through a magnifying glass or a microscope 🔬.

Sukshmajeev (Microorganisms/Microbes): Bahut chhote jeevit prani jinhe nangi aankhon se nahi dekha ja sakta. Unhe kewal magnifying glass ya microscope se dekha ja sakta hai.

Major Groups of Microorganisms (Sukshmajeevon Ke Mukhya Samooh):

Microorganisms are mainly classified into four major groups (plus viruses, which are special!):

Sukshmajeevon ko mukhya roop se chaar pramukh samooh mein vargikrit kiya gaya hai (aur virus bhi hain, jo khaas hain!):

Bacteria bacterium : Single-celled organisms. They have different shapes like rod-shaped (bacilli), spherical (cocci), spiral (spirilla). Ek-koshikiy jeev. Alag-alag aakar ke hote hain jaise rod-shaped (bacilli), gol (cocci), spiral (spirilla).
Examples: Lactobacillus (helps make curd), E. coli, Salmonella (causes Typhoid).
Fungi 🍄: Mostly multicellular (except yeast). They are non-green, saprophytic (feed on dead organic matter) or parasitic. Zyadatar bahu-koshikiy (yeast ko chhodkar). Yeh hare nahi hote, saprophytic (sade gale padarthon par nirbhar) ya parasitic (doosron par nirbhar) hote hain.
Examples: Yeast (used in bread/alcohol), Bread mould (Rhizopus), Penicillium (source of antibiotic), Mushroom (some are edible).
Protozoa 🦠: Single-celled animal-like organisms. Many are aquatic and some cause diseases. Ek-koshikiy janwar jaise jeev. Kai paani mein rehte hain aur kuch bimari failate hain.
Examples: Amoeba, Paramoecium, Plasmodium (causes Malaria).
Algae 🌿: Simple, plant-like organisms. Mostly aquatic. Can be single-celled or multicellular. Contain chlorophyll and make their own food (photosynthesis). Saral, paudhe jaise jeev. Zyadatar paani mein rehte hain. Ek-koshikiy ya bahu-koshikiy ho sakte hain. Chlorophyll hota hai aur apna khana khud banate hain.
Examples: Chlamydomonas, Spirogyra, Blue-green algae (Cyanobacteria).

Viruses 🧬: They are also microscopic but different from other microbes. They reproduce only inside the cells of a host organism (plant, animal, or bacterium). Outside a host, they are non-living! Virus: Yeh bhi sukshm hote hain lekin dusre microbes se alag hain. Yeh sirf ek host organism (paudha, janwar, ya bacterium) ki koshikaon ke andar hi reproduce karte hain. Host ke bahar, yeh nirjeev (non-living) hote hain!

Examples: Influenza virus (causes flu 🤧), Polio virus, Coronavirus, HIV (causes AIDS).

🌍 Where Do Microorganisms Live? (Sukshmajeev Kahan Rehte Hain?)

Microorganisms are found **everywhere**! They are cosmopolitan. Sukshmajeev **har jagah** paaye jaate hain! Ve sarvavyapi hain.

They can survive in all types of environments, from icy cold climate 🥶 to hot springs ♨️.
They are found in deserts 🏜️ and marshy lands (daldali zameen).
They live in water (freshwater and saltwater 🌊), soil मिट्टी , and air 🌬️.
They are also found inside the bodies of other organisms, including humans 🧍!
Some live alone (like Amoeba), while others live in colonies (like fungi and bacteria). Ve sabhi prakar ke vatavaran mein jeevit reh sakte hain, barfile thande mausam se lekar garam jharano tak. Ve registan aur daldali zameen mein paaye jaate hain. Ve paani, mitti aur hawa mein rehte hain. Ve manushyon sahit anya jeevon ke sharir ke andar bhi paaye jaate hain! Kuch akele rehte hain (jaise Amoeba), jabki anya colonies mein rehte hain (jaise fungi aur bacteria).

🤝 Microorganisms and Us (Sukshmajeev Aur Hum)

Microorganisms play a very important role in our lives. Some are beneficial (friends 😊), while some are harmful (foes 😟).

Sukshmajeev hamare jeevan mein bahut mahatvapurna bhoomika nibhate hain. Kuch faydemand (dost 😊) hain, jabki kuch nuksaandayak (dushman 😟) hain.

😊 Friendly Microorganisms (Faydemand Sukshmajeev – Hamare Dost!)

These microbes help us in many ways:

Making Curd and Bread 🥛🍞:
- Bacterium Lactobacillus promotes the formation of curd from milk. (Lactobacillus bacteria doodh se dahi banata hai).
- Yeast (a fungus) is used in baking industry for making bread, pastries, cakes. It reproduces rapidly and produces Carbon Dioxide 💨 during respiration, which makes the dough rise (volume increase). (Yeast (ek fungus) bread, cake banane mein use hota hai. Yeh tezi se badhta hai aur CO2 gas banata hai jisse maida (dough) phool jaata hai).
Commercial Use (Vyavsayik Upyog) 🏭:
- Yeast is used for large-scale production of alcohol, wine, and acetic acid (vinegar). (Yeast ka istemal bade paimane par alcohol, sharab aur sirka banane mein hota hai).
- This process of conversion of sugar into alcohol by yeast is called Fermentation (discovered by Louis Pasteur). (Yeast dwara sugar ko alcohol mein badalne ki prakriya ko Fermentation kehte hain).
Medicinal Use (Dawai Ke Liye) 💊💉:
- Antibiotics: Medicines produced from bacteria and fungi that kill or stop the growth of disease-causing microbes. (Bacteria aur fungi se banne wali dawaiyan jo bimari failane wale microbes ko maarti hain ya rok deti hain).
  Examples: Streptomycin, Tetracycline, Erythromycin. Penicillin was the first antibiotic discovered by Alexander Fleming from Penicillium fungus.
  
  Precaution: Antibiotics should be taken only on the advice of a qualified doctor and the course must be completed. Wrong dose/unnecessary use makes them less effective and can kill useful bacteria too! (*Savdhani:* Antibiotics doctor ki salah par hi leni chahiye aur course poora karna chahiye. Galat dose ya bewajah use se yeh kam asardar ho jate hain aur faydemand bacteria ko bhi maar sakte hain!).
- Vaccines 💉: Weakened or dead microbes introduced into the body to stimulate the immune system to produce antibodies. These antibodies protect the body from the actual disease later. (Kamzor ya mare hue microbes ko sharir mein dala jaata hai taaki hamara immune system antibodies bana le. Yeh antibodies baad mein asal bimari se bachate hain).
  Vaccination prevents diseases like Cholera, Tuberculosis (TB), Smallpox, Hepatitis, Polio. Edward Jenner discovered the vaccine for Smallpox. Pulse Polio Programme in India aims to eradicate polio.
Increasing Soil Fertility ✨:
- Some bacteria (like Rhizobium) and blue-green algae can fix atmospheric Nitrogen into usable nitrogen compounds in the soil, increasing its fertility. These microbes are called biological nitrogen fixers. (Discussed more in Nitrogen Fixation section). (Kuch bacteria (jaise Rhizobium) aur neeli-hari shaival hawa ki Nitrogen ko mitti mein istemal hone wale compounds mein badal kar uski urvarta badhate hain. Inhe biological nitrogen fixers kehte hain).
Cleaning the Environment ♻️🧹:
- Microorganisms (bacteria, fungi) act as decomposers. They break down dead organic waste (dead plants/animals, feces) into simpler, harmless substances, cleaning up the environment and returning nutrients to the soil. (Sukshmajeev (bacteria, fungi) decomposers ka kaam karte hain. Woh mare hue organic kachre (mare paudhe/janwar, mal) ko saral, hanirahit padarthon mein tod dete hain, vatavaran ko saaf karte hain aur poshak tatvon ko mitti mein wapas bhejte hain).

😟 Harmful Microorganisms (Nuksaandayak Sukshmajeev – Hamare Dushman!)

Some microbes are harmful and cause problems:

Disease-Causing Microbes (Pathogens) 🦠💀: Microbes that cause diseases in humans, plants, or animals are called Pathogens. (Manushyon, paudhon ya janwaron mein bimari failane wale microbes ko Pathogens kehte hain).

Diseases in Humans: Pathogens enter our body through air 🌬️, water 💧, food 🍔, or direct/indirect contact 🤝, or through carriers (like insects).

Communicable Diseases: Microbial diseases that can spread from an infected person to a healthy person. (Failne wali bimariyaan jo ek vyakti se doosre mein failti hain). Examples: Common cold, Cholera, Chickenpox, Tuberculosis (TB).
How they Spread? (Kaise Failti Hain?): Through air (sneezing 🤧 – common cold), contaminated water/food (cholera, typhoid), direct contact (skin infections), carriers (insects/animals).
Carriers: Some insects and animals carry disease-causing microbes. Examples:
- Housefly 🪰: Sits on garbage/excreta, pathogens stick to its body. When it sits on uncovered food, it transfers the pathogens. (Makhi kachre par baithti hai, bimari ke kitanu uske sharir par chipak jaate hain. Jab woh khule khane par baithti hai, toh kitanu transfer kar deti hai).
- Female Anopheles mosquito 🦟: Carries the parasite of Malaria (Plasmodium).
- Female Aedes mosquito 🦟: Acts as a carrier of Dengue virus.
Prevention Tip: Keep surroundings clean, don’t let water collect (mosquito breeding!), keep food covered. (Tip: Aas paas safai rakho, paani jama na hone do, khana dhak kar rakho).

Common Human Diseases caused by Microorganisms

Disease	Causative Microorganism	Mode of Transmission
Tuberculosis (TB)	Bacteria	Air
Measles	Virus	Air
Chicken Pox	Virus	Air/Contact
Polio	Virus	Air/Water
Cholera	Bacteria	Water/Food
Typhoid	Bacteria	Water
Hepatitis B	Virus	Water
Malaria	Protozoa (Plasmodium)	Mosquito (Anopheles)

Diseases in Animals 🐄💀: Microbes cause diseases in animals too. Example: Anthrax is a dangerous bacterial disease affecting humans and cattle. Foot and mouth disease is caused by a virus in cattle.

Diseases in Plants 🌾🍂: Microbes cause diseases in plants like wheat, rice, potato, etc., reducing crop yield. Example Diseases:

Common Plant Diseases caused by Microorganisms

Plant Disease	Microorganism	Mode of Transmission
Citrus Canker	Bacteria	Air
Rust of wheat	Fungi	Air, Seeds
Yellow vein mosaic of bhindi (Okra)	Virus	Insect

Food Poisoning 🤢🍔: Occurs due to consumption of food spoiled by some microorganisms. These microbes grow on food and produce toxic substances, making the food poisonous. Causes vomiting, pain, etc. (Microbes dwara kharab kiya gaya bhojan khane se hota hai. Microbes bhojan par ug kar zehreele padarth banate hain, jisse bhojan zehreela ho jata hai. Ulti, dard aadi hota hai).

Therefore, preserving food is very important! (Isliye, bhojan ko surakshit rakhna bahut zaroori hai!). See Food Preservation section.

🥫🧂 Food Preservation (Bhojan Ka Sanrakshan)

Spoiled food smells bad, tastes bad, and can cause illness. Food preservation means preventing food from getting spoiled by microbial growth. Kharab bhojan se badbu aati hai, swad kharab hota hai, aur bimari ho sakti hai. Bhojan sanrakshan ka matlab hai bhojan ko sukshmajeevon ki vridhhi se kharab hone se bachana.

Common Methods (Aam Tareeke):

Chemical Method 🧪: Using chemicals called **preservatives** that check microbial growth. **Preservatives** namak rasayanon ka upyog karna jo sukshmajeevon ki vridhhi ko rokte hain.
Common preservatives: Sodium benzoate and Sodium metabisulphite (used in jams, squashes).
Preservation by Common Salt 🧂: Salt draws out water from food items, preventing microbial growth. Used to preserve meat, fish, amla, raw mangoes, tamarind. Namak bhojan se paani nikal deta hai, jisse microbes nahi badh pate. Maans, machhli, amla, kacche aam, imli ko preserve karne mein istemal hota hai.
Preservation by Sugar 🍬: Sugar reduces moisture content which inhibits microbial growth. Used in jams, jellies, squashes. Cheeni nami ki matra kam karti hai jo microbes ki vridhhi ko rokti hai. Jams, jellies, squashes mein istemal hoti hai.
Preservation by Oil and Vinegar 🏺: Bacteria cannot live in such an environment. Used for preserving pickles, vegetables, fruits, fish, meat. Bacteria aise vatavaran mein nahi reh sakte. Achar, sabziyan, phal, machhli, maans ko preserve karne ke liye istemal hota hai.
Heat and Cold Treatments 🔥❄️:
- *Boiling:* Kills many microorganisms. (Ubalne se kai microbes mar jate hain).
- *Refrigeration:* Low temperature inhibits the growth of microbes. (Kam तापमान microbes ki vridhhi rokta hai).
- Pasteurization 🥛: Heating milk to about 70°C for 15-30 seconds and then suddenly chilling and storing it. Prevents microbial growth. Discovered by Louis Pasteur. Used for milk. (Doodh ko lagbhag 70°C par 15-30 second tak garam karke fir achaanak thanda karke store karna. Microbes ki vridhhi rokta hai. Milk ke liye istemal hota hai).
Storage and Packing 📦💨: Drying food properly and then storing in air-tight packets prevents microbial attack. Used for dry fruits, vegetables etc. Bhojan ko theek se sukha kar fir hawa-band packet mein store karne se microbes ka attack rukta hai. Dry fruits, sabziyon aadi ke liye istemal hota hai.

✨ Nitrogen Fixation (Nitrogen Sthirikaran)

Atmosphere has lots of nitrogen gas (N₂) (about 78%), but plants cannot use it directly in gaseous form! They need it in the form of soluble compounds. Vayumandal mein bahut sari nitrogen gas (N₂) hai (lagbhag 78%), lekin paudhe ise seedhe gas roop mein istemal nahi kar sakte! Unhe yeh ghulansheel compounds ke roop mein chahiye.

Nitrogen Fixation: The process of converting atmospheric nitrogen gas (N₂) into usable nitrogen compounds (like nitrates, nitrites, ammonia) in the soil.

Nitrogen Sthirikaran: Vayumandaliy nitrogen gas (N₂) ko mitti mein upyogi nitrogen compounds (jaise nitrates, nitrites, ammonia) mein badalne ki prakriya.

How does it happen? (Kaise hota hai?)

By Bacteria bacterium : Bacterium called Rhizobium lives in the root nodules of leguminous plants (peas, beans, pulses 🌱). It fixes nitrogen for the plant (symbiotic relationship). Rhizobium नामक bacterium faliidar paudhon (matar, beans, daal) ki jadon ki gaanthon (root nodules) mein rehta hai. Yeh paudhe ke liye nitrogen fix karta hai (sahajeevi sambandh).
By Blue-Green Algae (Cyanobacteria) 🌿: Certain blue-green algae present in the soil also fix atmospheric nitrogen. Mitti mein maujood kuch neeli-hari shaival bhi vayumandaliy nitrogen ko fix karti hain.
By Lightning ⚡: During lightning, the high temperature and pressure convert atmospheric nitrogen into oxides of nitrogen, which dissolve in rainwater and reach the soil as nitric acid. Bijli chamakne ke dauran, uchh taapman aur dabav vayumandaliy nitrogen ko nitrogen ke oxides mein badal dete hain, jo baarish ke paani mein ghul kar nitric acid ke roop mein mitti tak pahunchte hain.

🔄 Nitrogen Cycle (Nitrogen Chakra)

The amount of nitrogen in the atmosphere remains more or less constant. How? This happens through the Nitrogen Cycle. Vayumandal mein nitrogen ki matra lagbhag sthir rehti hai. Kaise? Yeh Nitrogen Chakra ke madhyam se hota hai.

Nitrogen Cycle: The circulation of nitrogen between the atmosphere, soil, plants, and animals.

Nitrogen Chakra: Vayumandal, mitti, paudhon aur janwaron ke beech nitrogen ka chakriya pravah.

Steps in the Cycle (Chakra Ke Kadam):

Atmospheric nitrogen (N₂) exists freely. 🌬️ Vayumandaliy nitrogen (N₂) mukt roop se maujood hai.
Nitrogen Fixation: Atmospheric N₂ is converted into nitrogen compounds (usable form) by:
- Biological Nitrogen Fixers (Rhizobium, blue-green algae). bacterium 🌿
- Lightning ⚡.
Nitrogen Sthirikaran: Vayumandaliy N₂ ko nitrogen compounds mein badla jaata hai: Biological Nitrogen Fixers dwara ya Bijli dwara.
Nitrogen compounds are now in the soil मिट्टी .
Assimilation: Plants absorb these nitrogen compounds from the soil through their roots and use them to make proteins and other compounds 🌱➡️💪. Assimilation: Paudhe mitti se in nitrogen compounds ko apni jadon se sokh lete hain aur unka upyog protein aur anya compound banane mein karte hain.
Animals get nitrogen by eating plants or other animals 🐄➡️🍖. Janwar paudhon ya anya janwaron ko khakar nitrogen prapt karte hain.
Ammonification/Decomposition: When plants and animals die 💀, or when animals excrete waste 💩, bacteria and fungi in the soil decompose the nitrogenous waste into simpler nitrogen compounds (like ammonia). 🦠🍄 Ammonification/Apghatan: Jab paudhe aur janwar mar jaate hain, ya jab janwar mal tyag karte hain, toh mitti mein bacteria aur fungi nitrogenous kachre ko saral nitrogen compounds (jaise ammonia) mein tod dete hain.
Nitrification: Other bacteria convert these compounds (ammonia) first into nitrites and then into nitrates, which plants can use again. 🔄 Nitrification: Doosre bacteria in compounds (ammonia) ko pehle nitrites aur fir nitrates mein badalte hain, jinhe paudhe fir se istemal kar sakte hain.
Denitrification: Some other bacteria (denitrifying bacteria) convert some of the nitrogen compounds back into nitrogen gas (N₂), which goes back into the atmosphere. 💨 Denitrification: Kuch anya bacteria (denitrifying bacteria) kuch nitrogen compounds ko wapas nitrogen gas (N₂) mein badal dete hain, jo vayumandal mein wapas chali jaati hai.

This completes the cycle, ensuring nitrogen levels in the atmosphere stay balanced!

Isse chakra poora hota hai, vayumandal mein nitrogen ka star santulit bana rehta hai!

❓ Sawal Jawab (Questions & Answers)

🤏 Very Short Answer Questions (Ati Laghu Uttariy Prashn)

1. What are microorganisms?

Very small organisms, cannot be seen with naked eye. (Bahut chhote jeev, nangi aankhon se nahi dikhte).

2. Name the four major groups of microorganisms.

Bacteria, Fungi, Protozoa, Algae. (Bacteria, Fungi, Protozoa, Algae).

3. How are viruses different from other microbes?

They reproduce only inside a host cell. (Woh sirf host koshika ke andar hi reproduce karte hain).

4. Name the bacterium that helps make curd.

Lactobacillus.

5. Name the microbe used for large scale alcohol production.

Yeast (a fungus). (Yeast (ek fungus)).

6. What is fermentation?

Conversion of sugar into alcohol by yeast. (Yeast dwara sugar ko alcohol mein badalna).

7. Name the first antibiotic discovered.

Penicillin.

8. What is a vaccine?

Weakened/dead microbes used to stimulate immunity. (Kamzor/mare microbes jo immunity badhane ke liye use hote hain).

9. What are pathogens?

Disease-causing microorganisms. (Bimari failane wale sukshmajeev).

10. Name a disease caused by Protozoa.

Malaria.

11. Name an insect that acts as a carrier for malaria.

Female Anopheles mosquito. (Maada Anopheles machhar).

12. Name a plant disease caused by fungi.

Rust of wheat.

13. What is food preservation?

Preventing food spoilage by microbial growth. (Bhojan ko microbes se kharab hone se bachana).

14. What is Pasteurization used for?

Preserving milk. (Doodh ko preserve karne ke liye).

15. Name the process that converts atmospheric nitrogen into nitrogen compounds.

Nitrogen Fixation. (Nitrogen Sthirikaran).

📝 Short Answer Questions (Laghu Uttariy Prashn)

1. Where are microorganisms found?

Microorganisms are found everywhere (cosmopolitan). (Har jagah paye jaate hain).
In all environments: ice cold 🥶, hot springs ♨️, deserts 🏜️, marshy lands.
In air 🌬️, water 💧, and soil मिट्टी .
Inside bodies of other organisms, including humans 🧍.

2. Write a short note on the usefulness of Yeast.

Yeast is a single-celled fungus. (Yeast ek-koshikiy fungus hai).
Used in baking (bread 🍞, cakes 🎂) – makes dough rise due to CO₂ production during respiration. (Baking mein istemal – CO2 se maida phoolta hai).
Used in commercial production of alcohol and wine by fermentation. 🍷(Alcohol/wine banane mein fermentation dwara).
Also used in making Idlis and Bhaturas.

3. What are antibiotics? What precautions must be taken while taking them?

Antibiotics are medicines produced by microbes (bacteria/fungi) that kill or stop the growth of other disease-causing microbes. (Microbes se bani dawaiyan jo dusre bimari wale microbes ko marti hain).
Examples: Streptomycin, Penicillin.
Precautions: Take only on doctor’s advice, complete the full course, wrong dose/use makes them ineffective and harms useful bacteria. (Savdhani: Doctor ki salah par lein, course poora karein, galat dose se beasar aur nuksaandayak).

4. How do vaccines work?

Vaccines contain weakened or dead microbes of a particular disease. (Vaccine mein bimari ke kamzor ya mare hue microbes hote hain).
When introduced into a healthy body, the body’s immune system produces antibodies to fight these invaders. (Jab sharir mein jaate hain, immune system antibodies banata hai).
These antibodies remain in the body. (Yeh antibodies sharir mein reh jaati hain).
If the actual disease microbes enter later, the body is already prepared with antibodies to fight and prevent the disease. 🛡️(Agar baad mein asal microbes aate hain, toh sharir antibodies se ladne ke liye taiyar rehta hai).

5. How do microorganisms clean the environment?

Microbes like bacteria and fungi act as decomposers. 🧹♻️ (Bacteria aur fungi jaise microbes decomposer ka kaam karte hain).
They break down dead organic waste (dead plants, animals, feces). (Woh mare hue organic kachre ko tod dete hain).
Convert complex organic matter into simpler, harmless substances. (Jatil organic cheezon ko saral, hanirahit cheezon mein badalte hain).
This cleans up waste and returns nutrients to the soil. (Isse kachra saaf hota hai aur poshak tatva mitti mein laut aate hain).

6. What are communicable diseases? Give two examples.

Diseases that can spread from an infected person to a healthy person. (Bimariyaan jo ek bimar vyakti se swasth vyakti mein fail sakti hain).
Spread through air, water, food, or direct contact/carriers. (Hawa, paani, bhojan, ya contact/carriers se failti hain).
Examples: Common cold (failta hai air se), Cholera (failta hai paani/food se), Chickenpox, TB.

7. How do houseflies spread diseases?

Houseflies 🪰 sit on garbage and animal excreta. (Makkhiyan kachre aur janwar ke mal par baithti hain).
Pathogens (disease microbes) stick to their bodies/legs. (Bimari ke kitanu unke sharir/pairon par chipak jaate hain).
When these flies sit on uncovered food, they transfer the pathogens to the food. (Jab yeh makkhiyan khule khane par baithti hain, woh kitanu transfer kar deti hain).
Consuming this contaminated food causes illness. (Yeh ganda khana khane se bimari hoti hai).

8. Write two methods of food preservation using chemicals.

Using preservatives like Sodium Benzoate and Sodium Metabisulphite. (Sodium Benzoate aur Sodium Metabisulphite jaise preservatives ka istemal). Used in jams, squashes to check microbial growth. (Jam, squash mein microbes rokne ke liye).
Using common salt 🧂 which draws out moisture, preventing microbial growth. Used for meat, fish, pickles. (Aam namak ka istemal jo nami sokhta hai. Maans, machhli, achar ke liye).
Using sugar 🍬 which reduces moisture, inhibiting microbes. Used for jams, jellies. (Cheeni ka istemal jo nami kam karti hai. Jam, jelly ke liye).
Using Oil and Vinegar 🏺 create an environment where bacteria can’t survive. Used for pickles. (Tel aur sirka aisa mahaul banate hain jahan bacteria nahi reh sakte. Achar ke liye).

*Note: Choose any two specific methods for the answer.*

9. Explain Pasteurization.

A method used to preserve milk 🥛, discovered by Louis Pasteur.
Milk is heated to about 70°C for 15 to 30 seconds. 🔥 (Doodh ko 70°C par 15-30 second tak garam karte hain).
Then it is suddenly chilled and stored ❄️. (Fir use achaanak thanda karke store karte hain).
This process kills most harmful microbes and prevents spoilage. (Isse zyadatar nuksaandayak microbes mar jaate hain aur kharab hone se bachta hai).

10. What is nitrogen fixation? Name two biological nitrogen fixers.

Nitrogen Fixation is converting atmospheric nitrogen gas (N₂) into usable nitrogen compounds in soil. (Hawa ki nitrogen ko mitti mein istemal hone wale compounds mein badalna).
Plants cannot use gaseous nitrogen directly. (Paudhe seedhe gas nitrogen nahi le sakte).
Biological Nitrogen Fixers are microbes that perform this. (Yeh kaam karne wale microbes biological nitrogen fixers kehlate hain).
Example 1: Rhizobium bacteria (in legume root nodules). bacterium (Rhizobium bacteria).
Example 2: Blue-green algae (Cyanobacteria). 🌿 (Neeli-hari shaival).

📜 Long Answer Questions (Dirgh Uttariy Prashn)

1. Describe the major groups of microorganisms with examples.

Microorganisms are mainly grouped into:

Bacteria bacterium : Single-celled, various shapes (rod, sphere, spiral). Ex: Lactobacillus (curd), Salmonella (Typhoid).
Fungi 🍄: Mostly multicellular (except Yeast). Non-green, saprophytes/parasites. Ex: Yeast (bread), Rhizopus (mould), Penicillium.
Protozoa 🦠: Single-celled, animal-like. Many aquatic. Ex: Amoeba, Paramoecium, Plasmodium (Malaria).
Algae 🌿: Simple, plant-like (have chlorophyll). Mostly aquatic. Ex: Chlamydomonas, Spirogyra.
Viruses 🧬: Different! Microscopic but reproduce *only inside host cells*. Non-living outside. Ex: Influenza virus, Polio virus.

2. Explain how microorganisms are useful to us (Friendly Microbes).

Microorganisms are our friends in many ways:

Food Making: Lactobacillus for curd 🥛; Yeast for bread/cake 🍞 (fermentation causes dough to rise).
Commercial Use: Yeast ferments sugar to produce alcohol, wine, vinegar 🍷🏭.
Medicines 💊💉: Production of Antibiotics (kill harmful microbes, e.g., Penicillin) and Vaccines (stimulate immunity to prevent diseases).
Soil Fertility ✨: Nitrogen fixation by Rhizobium/Blue-green algae converts atmospheric N₂ into usable compounds for plants.
Environment Cleaning ♻️🧹: Decomposers (bacteria/fungi) break down dead organic waste, cleaning surroundings and returning nutrients to soil.

3. Explain how microorganisms are harmful (Harmful Microbes).

Some microorganisms are harmful foes:

Cause Diseases (Pathogens) 🦠💀: Cause communicable diseases in humans (spread via air, water, food, contact, carriers) like Cholera, TB, Cold, Malaria. (Manushya mein bimari failate hain).
Carriers Spread Disease: Houseflies 🪰 spread pathogens from garbage to food. Mosquitoes 🦟 spread Malaria (Anopheles) & Dengue (Aedes). (Makkhi, Machhar bimari failate hain).
Cause Diseases in Animals 🐄: Example: Anthrax (bacterial) in cattle, Foot and mouth disease (viral). (Janwaron mein bimari failate hain).
Cause Diseases in Plants 🌾🍂: Reduce crop yields. Ex: Citrus canker (bacteria), Rust of wheat (fungi). (Paudhon mein bimari failakar fasal kam karte hain).
Spoil Food (Food Poisoning) 🤢🍔: Microbes grow on food, produce toxins, making it poisonous. Causes illness. (Khane ko kharab karte hain, zehreele padarth banate hain, jisse bimari hoti hai).

4. What are communicable diseases? How can we prevent them?

Communicable diseases are microbial diseases that spread from an infected person to a healthy person.

Sancharaniy rog ve sukshmajeev janit rog hain jo sankramit vyakti se swasth vyakti mein failte hain.

Modes of Transmission (Failne Ke Tareeke):

Air (sneezing/coughing 🤧 – common cold, TB)
Contaminated Water/Food (cholera, typhoid)
Direct Contact (skin infections)
Carriers (insects 🦟🪰 like mosquitoes, flies)

Prevention Measures (Roktham Ke Upay):

Maintain personal hygiene (washing hands 🧼).
Keep surroundings clean.
Drink clean, boiled water 💧.
Eat properly cooked and covered food 🍲.
Vaccination 💉 for preventable diseases.
Avoid contact with infected persons or their belongings.
Control carriers like mosquitoes (don’t let water collect 🚫💧).

5. Describe common methods of food preservation.

Methods to prevent microbial growth and food spoilage:

Chemicals 🧪: Preservatives like Sodium benzoate stop microbe growth (Jams, squashes).
Common Salt 🧂: Removes water, inhibits microbes (Meat, fish, pickles).
Sugar 🍬: Reduces moisture, inhibits microbes (Jams, jellies).
Oil & Vinegar 🏺: Creates environment where bacteria can’t live (Pickles).
Heat 🔥: Boiling kills microbes.
Cold ❄️: Refrigeration slows microbe growth.
Pasteurization 🥛: Heating (70°C) then rapid cooling kills microbes in milk.
Storage & Packing 📦: Drying food & sealing in air-tight packets prevents entry/growth of microbes.

6. What is Nitrogen Fixation? Explain the role of Rhizobium and lightning.

Nitrogen Fixation is converting unusable atmospheric nitrogen gas (N₂) into usable nitrogen compounds (like ammonia, nitrates) in the soil.

Vayumandaliy nitrogen gas ko mitti mein upyogi nitrogen compounds mein badalna Nitrogen Fixation hai.

Role of Rhizobium bacterium :

Rhizobium bacteria live in root nodules of leguminous plants (peas, beans). (Rhizobium faliidar paudhon ki jadon ki gaanthon mein rehta hai).
They have a symbiotic relationship: Plant provides shelter/food, Rhizobium fixes N₂ into ammonia/nitrates for the plant. 🤝 (Sahajeevi sambandh: Paudha ghar/khana deta hai, Rhizobium paudhe ke liye N₂ fix karta hai).
This enriches the soil naturally with nitrogen compounds.

Role of Lightning ⚡:

The high energy (temperature/pressure) during lightning causes atmospheric N₂ and O₂ to react and form oxides of nitrogen (e.g., NO, NO₂). (Bijli ke dauran uchh urja N₂ aur O₂ ko react karakar nitrogen oxides banati hai).
These oxides dissolve in rainwater, forming nitric and nitrous acids. (Yeh oxides barish mein ghulkar nitric/nitrous acid banate hain).
These acids fall on earth with rain and react with soil minerals to form nitrates, adding usable nitrogen to the soil. (Yeh acid barish ke saath zameen par girte hain aur nitrates banakar mitti mein nitrogen jodte hain).

7. Draw a labelled diagram of the Nitrogen Cycle (or Describe the steps).

(Diagram cannot be drawn here, but the steps are described below):

Nitrogen Cycle Steps 🔄:

Nitrogen Fixation: Atmospheric N₂ converted to usable compounds by Rhizobium, blue-green algae, or lightning ⚡.
Assimilation: Plants absorb nitrogen compounds from soil 🌱; Animals eat plants 🐄.
Ammonification: Decomposers (bacteria/fungi 🦠🍄) break down dead organisms 💀 & waste 💩 into ammonia.
Nitrification: Bacteria convert ammonia into nitrites, then into nitrates (usable by plants again).
Denitrification: Denitrifying bacteria convert some nitrates back into N₂ gas, returning it to atmosphere 🌬️.

8. How are microbes used in making medicines?

Microbes are crucial in medicine production:

Antibiotics 💊: Certain bacteria and fungi (like Penicillium) produce chemicals (antibiotics) that kill or inhibit harmful bacteria. These are extracted and used as medicines like Penicillin, Streptomycin. (Kuch bacteria/fungi aise chemical banate hain jo doosre harmful bacteria ko maarte hain. Inhe nikal kar dawai banate hain).
Vaccines 💉: Weakened or dead pathogens (viruses/bacteria) are used to create vaccines. When injected, they trigger the body’s immune system to produce antibodies without causing the actual disease. This provides immunity against future infections by the same pathogen. (Kamzor/mare hue germs se vaccine banti hai jo body mein immunity paida karti hai).
Production of Vitamins/Enzymes: Some microbes are used commercially to produce certain vitamins (like B12) or enzymes used in medical applications. (Kuch microbes se vitamins ya enzymes banaye jaate hain).

9. Why is it important to preserve food? Explain preservation by salt and sugar.

Food preservation is important to:

Prevent spoilage by microorganisms 🦠🍄.
Increase the shelf-life of food items.
Reduce food wastage.
Maintain nutritional value for longer.
Ensure food availability during off-seasons or emergencies.

Bhojan sanrakshan zaroori hai: Microbes se kharabi rokne, shelf-life badhane, bhojan ki barbadi kam karne, poshan banaye rakhne, aur off-season mein bhojan uplabdh karane ke liye.

Preservation by Salt 🧂:

Common salt draws out moisture from food items by osmosis. (Namak osmosis dwara bhojan se nami kheench leta hai).
Lack of moisture inhibits the growth of bacteria and fungi. (Nami ki kami bacteria/fungi ki vridhhi rokti hai).
Used to preserve meat, fish, amla, raw mangoes, tamarind.

Preservation by Sugar 🍬:

High concentration of sugar also reduces the moisture content available to microbes. (Cheeni ki adhik sandrata bhi microbes ke liye uplabdh nami ko kam karti hai).
It inhibits the growth of spoilage bacteria. (Yeh kharab karne wale bacteria ki vridhhi ko rokti hai).
Used in the preparation of jams, jellies, and squashes.

10. How can we prevent diseases spread by mosquitoes and houseflies?

Preventing Mosquito-Borne Diseases (Malaria, Dengue 🦟):

Don’t let water collect in coolers, tyres, flower pots, etc. as mosquitoes breed in stagnant water 🚫💧. (Cooler, tyre, gamlon mein paani jama na hone dein).
Keep surroundings clean and dry. (Aas paas safai rakhein).
Use mosquito repellents and mosquito nets. (Machhar bhagane wale aur machhardani ka istemal karein).
Spray insecticides and control breeding in drains/ponds. (Keetnashak chidken aur naali/talab mein breeding rokein).

Preventing Fly-Borne Diseases (Cholera, Typhoid 🪰):

Keep food covered always 🍲🛡️. (Khana hamesha dhak kar rakhein).
Avoid consuming uncovered food items from markets. (Bazaar se khula khana na khayein).
Maintain personal hygiene (wash hands before eating 🧼). (Vyaktigat swachhta banaye rakhein).
Keep house and surroundings clean; dispose garbage properly. (Ghar aur aas paas safai rakhein; kachra theek se phenkein).

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Chapter 2: Microorganisms: Friend and Foe-Class 8