Questions: The invisible living world

Q1. Why did people need a microscope to discover microorganisms?

Answer (English): The human eye can see only objects above a certain size, and microorganisms are far smaller than that limit. A curved lens makes small objects look larger, and better lenses gradually produced more powerful microscopes. With these instruments people could finally see bacteria, protozoa, algae and fungi that had been present all along. In that sense the microscope did not create the invisible world; it made the world visible.

Hinglish: Aankh sirf ek certain size se badi cheezein dekh sakti hai, aur microorganisms usse bahut chhote hain. Lens chhoti cheezon ko bada dikhata hai, aur behtar lens se zyada powerful microscopes bane. Inhi se log bacteria, protozoa, algae aur fungi dekh paaye jo pehle se hi aas-paas the. Microscope ne duniya banayi nahi, use dikhaya.

Q2. Who first used the word cell, and how did the word arise?

Answer (English): Robert Hooke first used the word cell in 1665 in his book Micrographia. He examined a thin slice of cork with a microscope that magnified objects about 200 to 300 times, and the slice looked like many small empty compartments packed together like a honeycomb. He called each compartment a cell, and the word became the scientific name for the basic unit of life. His careful drawing and skilled observation made the discovery possible, even though the spaces he saw were the empty walls of dead plant cells.

Hinglish: Robert Hooke ne 1665 mein Micrographia kitab mein pehli baar "cell" word use kiya. Unhone cork ki patli slice microscope se dekhi jo 200-300 guna bada karta tha, aur woh chhote khaali compartments jaise dikhi, honeycomb jaisi. Unhone har compartment ko cell kaha. Unki careful drawing aur observation se ye discovery hui, chahe woh dead plant cells ki khaali walls thi.

Q3. Name the three basic parts of a cell and state one function of each.

Answer (English): The three basic parts are the cell membrane, the cytoplasm and the nucleus. The cell membrane encloses the cell and controls which materials enter and leave. The cytoplasm is the jelly-like filling where most life processes take place, and it holds compounds such as carbohydrates, proteins and fats. The nucleus regulates the activities and growth of the cell.

Hinglish: Teen basic parts hain cell membrane, cytoplasm aur nucleus. Cell membrane cell ko ghere rehta hai aur andar-bahar aane-jaane wale materials ko control karta hai. Cytoplasm jelly jaisa filling hai jahan zyadatar life processes hote hain aur carbohydrates, proteins, fats jaise compounds hote hain. Nucleus cell ki activities aur growth regulate karta hai.

Q4. Differentiate between plant cells and animal cells.

Answer (English): Plant cells have a cell wall outside the cell membrane, while animal cells do not. Plant cells usually contain chloroplasts with chlorophyll, which animal cells lack, so plants can photosynthesise and animals cannot. Plant cells have a large vacuole while animal cells have small vacuoles or none. Plant cells are often rectangular and firm, whereas animal cells are often rounded and variable in shape.

Hinglish: Plant cells mein cell wall hoti hai, animal cells mein nahi. Plant cells mein chloroplast aur chlorophyll hote hain, isliye plants photosynthesis kar sakte hain; animal cells mein ye nahi. Plant cells mein badi vacuole hoti hai, animal cells mein chhoti ya nahi. Plant cells aksar rectangular aur firm hote hain, animal cells rounded aur shape mein badalte hain.

Q5. Why do cells have different shapes? Give two examples.

Answer (English): The shape of a cell is related to the work it does. Muscle cells are spindle-shaped, which helps them contract and relax, as they do when pushing food along the food pipe. Nerve cells are long and branched, which helps them carry messages quickly to different parts of the body. Cheek cells are thin and flat and form a protective lining, while some plant cells form long tubes that carry water. The list shows that structure follows function at the level of cells.

Hinglish: Cell ka shape uske kaam se juda hota hai. Muscle cells spindle jaisi hoti hain, jo unhe contract-relax karne mein help karti hai, jaise food pipe mein khana aage dhakelte waqt. Nerve cells lambi aur branched hoti hain, jo messages jaldi pahunchane mein help karti hain. Cheek cells patli aur flat hoti hain aur protective lining banati hain, aur kuch plant cells lambi tubes banati hain. Structure kaam ke hisaab se hota hai.

Q6. What are the levels of organisation in a living organism?

Answer (English): The levels begin with the cell, the basic unit of life. A group of similar cells forms a tissue, different tissues together form an organ, several organs work together as an organ system, and all the systems working together form a complete organism. A brick wall helps picture this: a brick resembles a cell, bricks join to make a wall, walls make rooms, and rooms make a building. The levels explain how simple cells build a complex living body.

Hinglish: Sabse pehle cell aata hai, jo life ki basic unit hai. Similar cells mil kar tissue banate hain, tissues mil kar organ, organs mil kar organ system, aur saare organ systems mil kar ek organism banta hai. Brick wall se samajh lo: brick cell jaisa, deewar tissue jaisi, kamre organ jaise, aur building poora organism.

Q7. What are microorganisms? Name the main groups and give one example of each.

Answer (English): Microorganisms are living organisms too small to be seen with the naked eye. They may be unicellular, such as bacteria and protozoa, or multicellular, such as some fungi and algae. The main groups are bacteria (for example, the rod-shaped bacteria in soil), protozoa (Amoeba and Paramecium), fungi (yeast and moulds), algae (microalgae such as Spirulina), and viruses, which are acellular and multiply only inside a living host.

Hinglish: Microorganisms woh living organisms hain jo naked eye se nahi dikhte. Ye unicellular ho sakte hain, jaise bacteria aur protozoa, ya multicellular, jaise kuch fungi aur algae. Main groups: bacteria (soil ke rod-shaped), protozoa (Amoeba, Paramecium), fungi (yeast, moulds), algae (Spirulina jaise microalgae), aur virus, jo cell nahi hain aur sirf living host ke andar multiply karte hain.

Q8. How do microorganisms help keep the environment clean?

Answer (English): Fungi and bacteria decompose fallen leaves, dead plants and animal waste, breaking complex materials into simpler substances rich in nutrients. These nutrients return to the soil and help plants grow, and the dark material formed is manure. Some microbes also work without oxygen and release biogas from waste, which can be used as fuel. Certain bacteria even break down oil spills, as the work of Ananda Mohan Chakrabarty showed, so microbes can help clean up pollution.

Hinglish: Fungi aur bacteria fallen leaves, dead plants aur animal waste ko decompose karke simple nutrient-rich substances banate hain. Ye nutrients soil mein wapas jaate hain aur plants ki growth mein help karte hain, aur bana dark material manure hota hai. Kuch microbes bina oxygen ke biogas banate hain jo fuel ki tarah use hota hai. Kuch bacteria oil spills bhi break karte hain, jaisa Ananda Mohan Chakrabarty ke kaam se pata chala.

Q9. How are microorganisms used in making food? Give two examples.

Answer (English): Yeast, a fungus, is used in baking. In warm conditions it respires and releases carbon dioxide, and the gas bubbles make dough rise and become soft and fluffy; a little alcohol also forms. Bacteria such as Lactobacillus ferment batter for idli, dosa and bhatura. In curd making, Lactobacillus feeds on the sugar in warm milk, multiplies, and produces lactic acid, which sets the milk and gives curd its sour taste.

Hinglish: Yeast ek fungus hai jo baking mein use hota hai. Warm conditions mein respire karke carbon dioxide chhodta hai, jiski bubbles se dough phoolta hai aur soft-fluffy ban jaata hai; thoda alcohol bhi banta hai. Lactobacillus jaise bacteria idli, dosa aur bhature ke batter ko ferment karte hain. Curd mein Lactobacillus warm doodh ki sugar par feed karke lactic acid banata hai, jisse doodh jamta hai aur curd khatta hota hai.

Q10. What are viruses, and how are they different from other microorganisms?

Answer (English): Viruses are microscopic but they are not cells, so they are described as acellular. They cannot multiply on their own and must enter a living host cell to reproduce. They may infect plants, animals or bacteria, and they often cause disease. Other microorganisms such as bacteria and protozoa are cells that can carry out their own life processes, which is the key difference.

Hinglish: Virus microscopic hain par cell nahi hain, isliye acellular kehlate hain. Woh apne aap multiply nahi kar sakte; unhe living host cell ke andar jaana padta hai. Woh plants, animals ya bacteria ko infect kar sakte hain aur aksar disease karte hain. Bacteria aur protozoa jaise baaki microbes cells hain jo apne life processes khud kar sakte hain, yahi main difference hai.

The quick check below has five multiple choice questions on microscopes, cell parts, plant and animal cells and helpful microorganisms. Each one comes with a short explanation, so take the quiz and see which topics need another read.