Cell: Structure and Functions unit ke topics pe poori practice: cell ki discovery (Robert Hooke), ek cell aur bahut cell wale organism, cells ke alag-alag shape aur size, cell ke parts (cell membrane, cytoplasm, nucleus, cell wall, chloroplast, vacuole) aur unke functions, plant aur animal cell ka difference, prokaryote aur eukaryote, aur cell se tissue, organ, organ system tak ka safar. Pehle chhota recap (saare naye word wahin samjhaaye hain), phir MCQs, fill in the blanks, true/false, short aur long answer, HOTS, aur aakhir mein answer key, sab ke hal Hinglish mein step by step. Isse apne current chapter Ch 2: The Invisible Living World ke saath padhiye (yeh chapter is unit ka kuch part padhata hai). 🔬
🧠 Concept Recap: Pehle Yeh Yaad Kar Lo
📖 Current chapter: Ch 2: The Invisible Living World (yeh chapter is unit ka kuch part padhata hai). Is chapter ka hub page jald aa raha hai; tab tak Class 8 Science (saare chapters) dekho.
📏 Pehle yeh word samjho (aage yahi word use honge):
- Cell (koshika) = har organism ki sabse chhoti unit jo khud living hai, jaise wall ki ek brick. Har organism ka body cells se bana hai.
- Microscope (sukshmdarshi) = lens wala instrument jo cheez ko kai sau times bada karke dikhata hai. Magnification = kitne times bada dikha: eyepiece (eye wala lens) 10 times aur objective (cheez ke paas wala lens) 40 times ho to total 10 × 40 = 400 times.
- Unicellular = sirf ek cell ka organism (amoeba, paramecium, bacteria). Woh ek hi cell food, breathing, hilna-dulna aur count increase karna, sab karta hai. Multicellular = bahut saari cells se bana (mango tree, insect, hum humans).
- Metre aur mm (millimetre) = length measure karne ki units. 1 metre lagbhag ek bade man ke ek long step jitna hota hai. 1 metre ke 1000 equal parts karo to ek part = 1 mm; scale (ruler) pe sabse chhota box 1 mm ka hota hai.
- Point wale numbers (decimal) = poore number se chhote parts dikhaane ka method. 2.8 padho “do point aath”: 2 poore aur ek ke 10 parts mein se 8 parts (yaani 3 se thoda kam). 0.007 = ek ke 1000 parts mein se sirf 7 parts, yaani bahut hi chhota.
- Micrometre (µm) = length ki bahut chhoti unit: 1 mm = 1000 µm (1 mm ke 1000 equal parts karo, ek part = 1 µm).
- Oxygen = air mein maujood ek gas jo breathing pe hamare andar jaati hai; iske bina organism zinda nahi reh sakte. Energy (oorja) = kaam karne ki power: cells food ko oxygen ki madad se tod kar energy banaati hain, jisse hum chalte, khelte aur sochte hain.
- Cell membrane (koshika jhilli) = cell ko gherne wali thin, flexible layer. Yeh kuch cheezon (water, oxygen, food) ko andar-bahar jaane deti hai aur kuch ko rokti hai.
- Cytoplasm (koshika dravya) = cell membrane aur nucleus ke beech bhara jelly jaisa substances, jisme cell ke chhote parts tairte hain.
- Nucleus (kendrak) = cell ke beech ka gol, ghana part jo cell ke saare functions ko control karta hai (cell ka “mind” ya “control room”). Iske all four or nuclear membrane hoti hai, andar ek chhota ghana ball nucleolus aur thread jaise chromosomes.
- Chromosome aur gene = chromosomes pe genes hote hain; gene parents se children tak traits (jaise eye ka colour) pahunchaate hain. Is pahunchne ko inheritance (vanshaagati) kehte hain.
- Protoplasm (jeevdravya) = cell ke andar ka saara living substances: cytoplasm + nucleus.
- Cell wall (koshika bhitti) = sirf plants (aur bacteria, fungi) ki cells mein, cell membrane ke bahar ek strong, rigid layer. Plants mein yeh cellulose (ek strong chemical jo wood aur cotton mein bhi hota hai) se bani hoti hai.
- Plastids aur chloroplast = plastids plants ki cells mein milne wale chhote parts. Hare plastids ko chloroplast kehte hain; inme hara colour chlorophyll hota hai jo sunlight se food (photosynthesis) banaane mein kaam aata hai.
- Vacuole (rikti) = cell ke andar empty jaisi dikhne wali bag jisme water aur ghule substances bhare rehte hain. Plant cell mein bahut bada, animal cell mein chhote ya na ke equal.
- Prokaryote = jinki cell mein nuclear membrane nahi hoti (nucleus ka items cytoplasm mein khula pada rehta hai, ise nucleoid kehte hain), jaise bacteria aur blue-green algae. Eukaryote = jinki cell mein nuclear membrane wala asli nucleus hota hai (plants, animals, fungi, amoeba).
- Pseudopodia (koot paad, “nakli pair”) = amoeba ke body ke projections jo baar-baar bante-mitte hain; inse woh chalta aur food pakadta hai.
- Tissue (oottak) = ek jaisi cells ka group jo milkar ek hi function kare (jaise muscle tissue). Organ (ang) = alag tissues se bana part jo ek khaas function kare (heart, stomach, leaf). Organ system (ang tantra) = kai organs jo milkar ek bada function karein (jaise digestive system: mouth, stomach, intestine). Organism (jeev) = poora living animal ya plant.
- Stain (rang) = cell ke parts ko saaf dikhaane wala colour, jaise methylene blue (neela) ya iodine ka solution. Slide = glass ki thin patti jispe sample rakh kar microscope se dekhte hain. Glycerine = gaadha, bina colour ka dravya jo sample ko sookhne nahi deta.
1. Cell ki discovery aur cell kya hai
1665 mein Robert Hooke ne cork (ek trees ki bark ka halka part) ki thin layer microscope se dekhi. Usme honeycomb jaise chhote-chhote food dikhe; unhone inhe “cell” (chhote room) name diya. Baad mein Antonie van Leeuwenhoek ne apne banaaye microscope se water mein tairte living ek-cell wale organism dekhe. Aaj hum jaante hain: har organism cells se bana hai, aur cell hi organism ki structure aur function ki sabse chhoti unit hai.
2. Cells ki count, shape aur size
| Baat | Example |
|---|---|
| Ek cell wale (unicellular) | Amoeba, paramecium, bacteria, Chlamydomonas (ek hari algae) |
| Bahut cell wale (multicellular) | Humans (karodon-arbon cells), mango tree, ant |
| Shape kaam ke hisaab se | Nerve cell long aur shaakhaon wali (message door tak le jaati hai, humans mein 1 metre tak long ho sakti hai). Muscle cell dono sire thin, beech mein moti (sikud-phail kar hilaati hai). Red blood cell (RBC) gol, beech mein dabi disc jaisi (blood ke saath oxygen le jaati hai). Amoeba ka koi tay shape nahi, baar-baar badalta hai. |
| Size | Zyada tar cells microscope se hi dikhti hain. Sabse chhoti bacteria ki cells lagbhag 0.1 se 0.5 µm. Sabse badi akeli cell ostrich ke eggs ki maani jaati hai. Humans ki RBC lagbhag 7 µm. |
| Bada organism = badi cells? Nahi! | Elephant ki cells mice ki cells se badi nahi hoti; elephant mein bas cells zyada hoti hain. |
3. Cell ke parts aur unke functions
| Part | Kahan | Function |
|---|---|---|
| Cell membrane | Har cell | Cell ko gherti hai, shape deti hai; kuch cheezon ko andar-bahar jaane deti hai, kuch ko rokti hai |
| Cytoplasm | Har cell | Jelly jaisa bhara part; cell ke chhote parts isme rehte hain aur yahin kai functions hote hain |
| Nucleus | Har eukaryote cell (prokaryote mein nuclear membrane nahi) | Saare functions ka control; chromosomes ke genes parents ke traits children tak le jaate hain |
| Cell wall | Plant cell (aur bacteria, fungi) | Bahar ki rigid layer: strength aur protection (heat-cold, air ke jhonke, tez sunlight) |
| Chloroplast | Plants ki hari cells | Chlorophyll se sunlight ki madad se food banaana |
| Vacuole | Plant cell mein bada; animal cell mein chhote | Water aur ghule substances jama rakhna; plant cell ko bhara-bhara (tana hua) rakhna |
4. Cell se poore organism tak
Cell → Tissue → Organ → Organ system → Organism. Example: muscle cells milkar muscle tissue, alag tissues milkar heart (organ), heart aur blood vessels milkar circulatory system (blood ghumaane wala tantra), aur saare systems milkar poora humans.
5. Cell khud kaise dekhein?
Onion peel: onion ki andar wali thin layer slide pe rakho, water ki drop aur iodine ka solution daalo, cover slip (bahut thin glass) dhako. Brick jaisi line mein lagi square cells dikhengi, har ek mein nucleus. Cheek cells: saaf toothpick se cheek ke andar halke se khurcho, slide pe water aur methylene blue ki drop, phir glycerine ki drop (taaki sookhe nahi). Gol-matol cells, beech mein neela nucleus, aur koi cell wall nahi.
— 📌 charumam.com
📝 Section A: 10 MCQs
Har sawaal ke 4 options mein se ek sahi chuno. Pehle khud socho, phir “Hal dekho” kholo.
Q1. Cell ko sabse pehle dekh kar “cell” name kisne diya?
Hal (step by step) dekho
Sahi jawab: (a) Robert Hooke
1665 mein Robert Hooke ne cork ki thin layer mein honeycomb jaise food dekhe aur unhe “cell” kaha. Leeuwenhoek ne baad mein living ek-cell wale organism dekhe. Jenner (vaccine) aur Pasteur (pasteurisation) ka kaam doosra tha.
Q2. Cell ka kaunsa part uske saare functions ko control karta hai?
Hal (step by step) dekho
Sahi jawab: (c) Nucleus
Nucleus cell ka “control room” hai: chromosomes ke genes batate hain ki cell kya banaye aur kaise kaam kare. Cell wall protection deti hai, vacuole water store karta hai, cytoplasm bhara hua jelly jaisa part hai.
Q3. Inme se kya plant cell mein hota hai par animal cell mein nahi?
Hal (step by step) dekho
Sahi jawab: (b) Cell wall
Cell wall sirf plant cell (aur bacteria, fungi) mein hoti hai, cell membrane ke bahar. Cell membrane, nucleus aur cytoplasm dono tarah ki cells mein hote hain.
Q4. Inme se kaunsa organism unicellular (ek cell wala) hai?
Hal (step by step) dekho
Sahi jawab: (b) Amoeba
Amoeba sirf ek cell ka bana hai; wahi ek cell food, breathing aur chalna sab karti hai. Ant, neem aur earthworm mein bahut saari cells hain (multicellular).
Q5. Long aur shaakhaon wali cell jo body mein message le jaati hai, kaunsi hai?
Hal (step by step) dekho
Sahi jawab: (c) Nerve cell
Nerve cell long hoti hai aur uske ends pe shaakhaayein hoti hain, taaki message door tak aur kai cells tak pahunche. Cell ka shape uske kaam ke hisaab se hota hai.
Q6. Chloroplast hara kyun dikhta hai?
Hal (step by step) dekho
Sahi jawab: (b) Usme chlorophyll hota hai
Chloroplast mein hara colour chlorophyll hota hai. Yahi sunlight ki roshni pakad kar plants ko food banaane mein madad karta hai. Cellulose cell wall mein hota hai.
Q7. Prokaryote cell (jaise bacteria) mein kya nahi hota?
Hal (step by step) dekho
Sahi jawab: (c) Nuclear membrane
Prokaryote mein nuclear membrane nahi hoti: nucleus ka items (chromosome wala) cytoplasm mein bina layer ke pada rehta hai (nucleoid). Cell membrane aur cytoplasm to hote hain.
Q8. Cell membrane aur nucleus ke beech bhara jelly jaisa substances kya kehlaata hai?
Hal (step by step) dekho
Sahi jawab: (a) Cytoplasm
Yeh cytoplasm hai. Isme cell ke chhote parts (jaise chloroplast, vacuole) tairte rehte hain. Cytoplasm + nucleus = protoplasm.
Q9. Body ke organisation ka sahi order kaunsa hai?
Hal (step by step) dekho
Sahi jawab: (b) Cell → Tissue → Organ → Organ system
Sabse chhota cell; ek jaisi cells milkar tissue; alag tissues milkar organ (jaise heart); kai organs milkar organ system; saare systems milkar poora organism.
Q10. Amoeba chalne aur food pakadne ke liye kya use karta hai?
Hal (step by step) dekho
Sahi jawab: (c) Pseudopodia
Amoeba ke body se projections nikalte hain jinhe pseudopodia (“nakli pair”) kehte hain. Yeh baar-baar bante-mitte hain, isliye amoeba ka shape bhi badalta rehta hai.
— 📌 charumam.com
✍️ Section B: Fill in the Blanks
Empty jagah (_____) mein sahi word ya number bharo.
Q1. Organism ki structure aur function ki sabse chhoti unit _____ hai.
Jawab aur reason
Jawab: cell (koshika)
Jaise wall bricks se banti hai, waise hi har organism cells se banta hai, aur har cell khud living hai.
Q2. Ek jaisi cells ka group jo milkar ek kaam kare, _____ kehlaata hai.
Jawab aur reason
Jawab: tissue
Jaise muscle cells milkar muscle tissue banaati hain, jo sikud kar hands-feet hilaata hai.
Q3. Genes nucleus ke andar thread jaise _____ pe hote hain.
Jawab aur reason
Jawab: chromosomes
Chromosomes pe genes hote hain jo parents ke traits (jaise hair ka colour) children tak pahunchaate hain (inheritance).
Q4. Plant cell mein ek _____ vacuole hota hai, jabki animal cell mein chhote vacuole hote hain.
Jawab aur reason
Jawab: bada
Plant cell ka bada vacuole water se bhara rehta hai aur cell ko firm (bhara-bhara) rakhta hai.
Q5. Cheek cells dekhne ke liye neela stain _____ use karte hain.
Jawab aur reason
Jawab: methylene blue
Methylene blue nucleus ko gehra neela kar deta hai, isliye woh saaf dikhta hai.
Q6. Protoplasm = cytoplasm + _____
Jawab aur reason
Jawab: nucleus
Cell ke andar ka saara living substances protoplasm hai: cytoplasm aur nucleus milkar.
Q7. Nucleus ke andar ka chhota, ghana ball _____ kehlaata hai.
Jawab aur reason
Jawab: nucleolus
Nucleus ke andar ek ya zyada chhote ghane gole hote hain; unhe nucleolus (bahuvachan: nucleoli) kehte hain.
Q8. 1 mm = _____ µm (micrometre)
Jawab aur reason
Jawab: 1000
Micrometre bahut chhoti unit hai: 1 mm ko 1000 equal parts mein divide karo, ek part = 1 µm. Cells measure karne ke liye yahi unit use hoti hai.
— 📌 charumam.com
✅❌ Section C: True / False
Batao statement sahi (True) hai ya galat (False). Galat ho to use sahi karke likho.
Q1. Saare organism multicellular (bahut cell wale) hote hain.
Jawab aur reason
❌ False
Galat. Amoeba, paramecium aur bacteria sirf ek cell ke hote hain (unicellular). Sahi: “Kuch organism ek cell ke, kuch bahut cells ke hote hain.”
Q2. Elephant ki cells mice ki cells se bahut badi hoti hain.
Jawab aur reason
❌ False
Galat. Cells ka size organism ke size pe nirbhar nahi karta. Elephant bada hai kyunki usme cells ki count bahut zyada hai, cells badi nahi.
Q3. Animal cell mein cell wall hoti hai.
Jawab aur reason
❌ False
Galat. Animal cell ke bahar sirf thin, flexible cell membrane hoti hai. Cell wall plant cell (aur bacteria, fungi) mein hoti hai.
Q4. Bacteria ki cell mein nuclear membrane wala asli nucleus nahi hota.
Jawab aur reason
✅ True
Sahi. Bacteria prokaryote hain: unka nucleus ka items bina layer ke cytoplasm mein pada rehta hai (nucleoid).
Q5. Red blood cell (RBC) ek akeli cell hai.
Jawab aur reason
✅ True
Sahi. Blood mein laakhon RBC hoti hain, aur har RBC ek alag cell hai jo oxygen le jaati hai.
Q6. Ek hi organism ki saari cells ka shape ek jaisa hota hai.
Jawab aur reason
❌ False
Galat. Humans mein hi nerve cell long, muscle cell beech mein moti, RBC gol disc jaisi hoti hai. Shape kaam ke hisaab se alag hota hai.
Q7. Chromosomes pe genes hote hain jo traits ek generation se doosri tak le jaate hain.
Jawab aur reason
✅ True
Sahi. Isi wajah se child mein parents jaise kuch traits (jaise eye ka colour) aate hain.
Q8. Animal cell mein plant cell jitna bada vacuole hota hai.
Jawab aur reason
❌ False
Galat. Animal cell ke vacuole chhote hote hain (ya na ke equal); bada vacuole plant cell ki pehchaan hai.
— 📌 charumam.com
🟢 Section D: Short Answer Questions
2 se 3 marks wale sawaal. Har step likhne ki habit daalo.
Q1. Plant cell aur animal cell mein teen difference likho.
Step-by-step hal
1. Cell wall: plant cell mein cell membrane ke bahar cell wall hoti hai; animal cell mein nahi.
2. Chloroplast: plant ki hari cells mein chloroplast (chlorophyll) hota hai; animal cell mein nahi, isliye animals apna food khud nahi banaate.
3. Vacuole: plant cell mein ek bada vacuole; animal cell mein chhote vacuole.
Q2. Cell ko organism ki “structure aur function ki unit” kyun kehte hain?
Step-by-step hal
Structure: har organism ka body cells se bana hai, jaise place bricks se. Ek-cell wale organism mein to poora body hi ek cell hai.
Function: food pachaana, breathing (energy banaana), waste nikaalna, increase hona, apni count increase karna: yeh saare life ke functions cell ke andar hi hote hain. Isliye cell sabse chhoti living unit hai.
Q3. Cell membrane ke do functions likho. Agar yeh har cheez ko andar aane de, to kya mushkil hogi?
Step-by-step hal
Function 1: cell ko gherti hai aur shape deti hai, andar ke items ko bahar bikharne nahi deti.
Function 2: zaroori cheezein (water, oxygen, food) andar aane deti hai aur waste bahar jaane deti hai, par bahut si cheezon ko rokti hai.
Mushkil: agar har cheez andar aa jaaye, to nuksaandeh substances aur germs bhi cell mein ghus jaayenge, aur cell ka andar ka balance bigad jaayega.
Q4. Prokaryote aur eukaryote mein difference ek-ek example ke saath likho.
Step-by-step hal
Prokaryote: cell mein nuclear membrane nahi; nucleus ka items cytoplasm mein khula (nucleoid). Example: bacteria, blue-green algae.
Eukaryote: cell mein nuclear membrane se ghira asli nucleus. Example: onion ki cell, cheek cell, amoeba.
Q5. Nerve cell long aur shaakhaon wali kyun hoti hai, aur muscle cell beech mein moti aur ends pe thin kyun?
Step-by-step hal
Nerve cell: iska function message (jaise “garam hai, hand remove karo!”) door tak le jaana hai. Long hone se message door tak jaata hai, aur shaakhaon se ek saath kai cells tak pahunchta hai.
Muscle cell: iska function sikudna aur phailna hai. Is shape se kai muscle cells ek-doosre ke saath kas kar judi rehti hain aur milkar zor se sikud kar hands-feet hilaati hain.
Seekh: cell ka shape uske kaam ke hisaab se hota hai.
Q6. Onion peel dekhte time iodine aur cheek cells mein glycerine kyun daalte hain?
Step-by-step hal
Iodine (stain): cell lagbhag paardarshi (aar-paar dikhne wali) hoti hai. Iodine nucleus aur cell ke kinaare ko colour deta hai, to woh saaf dikhte hain.
Glycerine: sample air mein jaldi sookh jaata hai aur cells sikud jaati hain. Glycerine gaadha hai aur sample ko moist rakhta hai.
— 📌 charumam.com
📘 Section E: Long Answer Questions
4 se 5 marks wale sawaal. Hal mein har step ka reason bhi likha hai.
Q1. Ek table banao jisme cell ke 6 parts (cell membrane, cytoplasm, nucleus, cell wall, chloroplast, vacuole) ke name, woh plant/animal cell mein hain ya nahi, aur unka function ho.
Step-by-step hal
| Part | Plant cell | Animal cell | Function |
|---|---|---|---|
| Cell membrane | Haan | Haan | Gherti hai; chuni hui cheezein andar-bahar jaane deti hai |
| Cytoplasm | Haan | Haan | Jelly jaisa bhara part; cell ke chhote parts isme rehte hain |
| Nucleus | Haan | Haan | Saare functions ka control; genes se traits aage jaate hain |
| Cell wall | Haan | Nahi | Strength aur protection |
| Chloroplast | Haan (hari cells mein) | Nahi | Chlorophyll se sunlight ki madad se food banaana |
| Vacuole | Haan, bada | Chhote | Water aur substances jama; cell ko firm rakhna |
Q2. Cell se poore organism tak ka organisation samjhao. Humans ke heart ka example lo, aur ek plants ka example bhi do.
Step-by-step hal
Step 1 (cell): sabse chhoti living unit, jaise heart ki muscle cell.
Step 2 (tissue): ek jaisi muscle cells milkar muscle tissue banaati hain jo sikud-phail sakta hai.
Step 3 (organ): muscle tissue aur doosre tissues milkar heart banaate hain, jo blood pump karta hai.
Step 4 (organ system): heart, blood vessels aur blood milkar circulatory system banaate hain, jo poore body mein oxygen aur food pahunchata hai.
Step 5 (organism): circulatory, digestive (pachan), respiratory (saans) jaise saare systems milkar poora humans.
Plants ka example: leaves ki hari cells → leaves ka tissue → leaf (organ, food banaata hai) → leaves, stem aur root milkar poora plant.
Q3. Cheek cells microscope se dekhne ka experiment step by step likho. Tumhe kya dikhega aur isse kya pata chalta hai?
Step-by-step hal
Step 1: mouth saaf water se kulla karo.
Step 2: saaf toothpick ke chapte sire se cheek ke andar halke se khurcho (zor se nahi).
Step 3: scraping ko saaf slide pe water ki ek drop mein phailao.
Step 4: methylene blue ki ek drop daalo (stain), phir glycerine ki ek drop (taaki sookhe nahi).
Step 5: dhyaan se cover slip dhako taaki air ke bulbule na banein; extra water tissue paper se sokh lo (tissue paper = naak ponchhne wala thin paper; iska cells ke group wale “tissue” se koi lena-dena nahi, sirf name milta hai).
Step 6: pehle kam magnification, phir zyada pe dekho.
Kya dikhega: chapti, gol-matol cells, beech mein gehra neela nucleus, all four or thin cell membrane, aur koi cell wall nahi.
Seekh: humans ka body cells se bana hai, aur animal cell mein cell wall nahi hoti.
Q4. Ek microscope mein eyepiece 10 times aur objective 40 times bada karta hai. Usme ek RBC ki breadth 2.8 mm dikhti hai. (a) Total magnification kitna hai? (b) RBC ki asli breadth mm aur µm mein nikaalo.
Step-by-step hal
(a) Step 1: total magnification = eyepiece × objective = 10 × 40 = 400 times.
(b) Step 1: microscope ne asli breadth ko 400 times bada dikhaaya. To asli = dikhne wali ÷ 400.
Step 2: 2.8 ÷ 400 = 0.007 mm.
Step 3 (µm mein): 1 mm = 1000 µm, to 0.007 × 1000 = 7 µm.
Check: 7 µm × 400 = 2800 µm = 2.8 mm ✅ (aur humans ki RBC lagbhag 7 µm hi hoti hai).
— 📌 charumam.com
🧩 Section F: HOTS (Soch Wale Sawaal)
HOTS matlab Higher Order Thinking Skills: aise sawaal jinme formula se aage thoda mind lagana padta hai.
Q1. Ek sample ki cells mein cell wall hai par chloroplast nahi. Kya yeh plant cell ho sakti hai? Reason do.
Soch aur hal dekho
Soch: chloroplast sirf plants ki hari cells mein hota hai, har plant cell mein nahi.
Onion peel ya root ki cells mein sunlight nahi pahunchti aur woh hari nahi hoti, isliye unme chloroplast nahi hota, par cell wall hoti hai. To haan, yeh plant cell ho sakti hai. (Fungi ki cell bhi ho sakti hai, kyunki unme bhi cell wall hoti hai par chloroplast nahi.)
Q2. Plants ko cell wall ki zaroorat hai par animals ko nahi. Kyun?
Soch aur hal dekho
Plants: ek jagah khade rehte hain; tez air, sunlight, rain aur keedon se bach ke division nahi sakte, aur unke paas skeleton nahi. Har cell ki rigid cell wall unhe strength aur protection deti hai.
Animals: chal-phir sakte hain, unhe skeleton aur skin protection deti hai. Unki cells ko flexible rehna hai (jaise muscle cell sikudti hai), isliye rigid cell wall rukawat banti.
Q3. Ek bacterium 2 µm long hai. 1 mm long line mein aise kitne bacteria ek ke baad ek sama jaayenge?
Soch aur hal dekho
Step 1 (ek hi unit mein lao): 1 mm = 1000 µm.
Step 2: count = total length ÷ ek bacterium ki length = 1000 ÷ 2 = 500.
Jawab: 500 bacteria sirf 1 mm mein! Isliye inhe dekhne ke liye microscope chahiye.
Q4. Agar kisi cell se nucleus nikaal diya jaaye, to kya hoga? Socho aur do asar likho.
Soch aur hal dekho
Soch: nucleus cell ke functions ka control karta hai aur usme genes hote hain.
Asar 1: cell ke functions (kya banaana hai, kab increase hona hai) ka control khatam; dheere-dheere cell ke functions ruk jaayenge aur zyada tar cells kuch time baad mar jaati hain.
Asar 2: cell apni count (bant kar nayi cells) nahi bana paayegi, aur genes aage nahi jaayenge. (Dhyaan: humans ki RBC bina nucleus ke hi bani hoti hai, isliye woh lagbhag 120 days ji kar nayi RBC se badal di jaati hai aur khud bant nahi sakti.)
— 📌 charumam.com
🔑 Answer Key (Ek Nazar Mein)
Pehle saare sawaal khud karo, phir yahan milaao. Jahan mistake ho, upar us sawaal ka step-by-step hal dobara padho.
| Section | Answers |
|---|---|
| A. MCQ | 1: (a) · 2: (c) · 3: (b) · 4: (b) · 5: (c) · 6: (b) · 7: (c) · 8: (a) · 9: (b) · 10: (c) |
| B. Fill in the Blanks | 1: cell (koshika) · 2: tissue · 3: chromosomes · 4: bada · 5: methylene blue · 6: nucleus · 7: nucleolus · 8: 1000 |
| C. True / False | 1: F · 2: F · 3: F · 4: T · 5: T · 6: F · 7: T · 8: F |
| D. Short Answer | 1: Cell wall, chloroplast, bada vacuole (plant mein) · 2: Body cells se bana + life ke functions cells mein · 3: Gherna/shape; chuni hui cheezon ko andar-bahar jaane dena · 4: Nuclear membrane: prokaryote mein nahi (bacteria), eukaryote mein hai (onion) · 5: Shape kaam ke hisaab se · 6: Iodine parts rangta hai; glycerine sookhne nahi deta |
| E. Long Answer | 1: Table upar · 2: Cell → tissue → organ (heart) → circulatory system → humans · 3: Steps upar; gol cells, neela nucleus, cell wall nahi · 4: (a) 400 times (b) 0.007 mm = 7 µm |
| F. HOTS | 1: Haan (jaise onion/root ki cell) · 2: Plants hil nahi sakte, skeleton nahi; animals ki cells ko flexibility chahiye · 3: 500 · 4: Control khatam, cell bant nahi sakti (RBC jaisi kam age) |
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👩🏫 CharuMam Ka Tip
Cell ke sawaal mein ek chhota chitra banao (plant cell square, animal cell gol-matol) aur har parts pe name likho. Phir teen sawaal pucho: (1) yeh part kahan hai (plant, animal ya dono)? (2) iska kaam kya hai? (3) iske na hone pe kya hoga? Yaad rakho: cell wall, chloroplast, bada vacuole = plant ki pehchaan; nuclear membrane nahi = prokaryote (bacteria)! 🔬
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👉 Aage Kya?
Ch 2: The Invisible Living World ka hub page jald aa raha hai; tab tak Class 8 Science page (link neeche) se baaki chapters padho. Pichla practice unit Microorganisms: Friend and Foe bhi practice hub pe hai. Agla practice unit: Chemical Effects of Electric Current, jald aa raha hai!
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