Class 9 · Advanced ScienceNCERT 2026 Revised Syllabus

Chapter 9: Microscope and Microscopy

Science Advanced

Compound microscope, magnification and resolution, calculating actual size, temporary vs permanent slides, and electron microscopes (TEM and SEM).

Find complete NCERT solutions for Class 9 Advanced Science, Science Advanced Chapter 9. Every question has a clear, step-by-step answer.

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Activity 9.1 (Let Us Think and Write)(1 questions)

If you could shrink yourself and travel inside a leaf, what would you see? Write 3-4 lines.

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Solution:- Rows of green box-like cells packed with round chloroplasts. - Thin transparent cell walls. - Tiny pore-like stomata for gas exchange. - Vein-like vascular tissue carrying water and nutrients.Answer: Green box-like cells with chloroplasts, cell walls, stomata, and vascular tissue.

Activity 9.2 (A Timeline Strip)(1 questions)

Draw a horizontal line. Mark at least 5 important dates in microscopy and add a tiny sketch or symbol for each (e.g., cork cells, bacteria, electron beam etc.).

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Use milestones from the chapter in chronological order: 1590 Janssen; 1665 Hooke; 1670s Leeuwenhoek; 1878 Ernst Abbe; 1938 Ernst Ruska; and 1953 Frits Zernike. Add a small symbol for each milestone.

Activity 9.3 (Let us examine a compound microscope)(1 questions)

Identify the key parts of a compound microscope: eyepiece, objectives, nosepiece, stage with clips, coarse/fine focus, condenser, iris diaphragm, illuminator, arm, and base.

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Solution:Identify and label the eyepiece, objective lenses, revolving nosepiece, stage and clips, condenser, substage diaphragm, coarse adjustment knob, fine adjustment knob, illuminator/mirror, arm, and base. The objective lenses form the real magnified image; the eyepiece further magnifies it.Answer: Label all the listed microscope parts and their roles as described in the book.

Activity 9.4 (Leaf Peels of Monocot and Dicot Leaves)(1 questions)

Take peels from both upper and lower epidermis of a monocot leaf (Rhoeo/maize/lily) and a dicot leaf (Bryophyllum/petunia/balsam). Prepare their temporary mounts. Observe them under the microscope, compare their structure and draw labelled diagrams. Record similarities and differences, if any. Now correlate the points noted by you in Activity 9.1 with your observations.

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Solution:- Monocot leaf: epidermal cells are elongated with a regular parallel pattern; stomata are distributed evenly on both surfaces. - Dicot leaf: cells are irregular, jigsaw-shaped; stomata are mainly on the lower surface.Answer: Monocot - parallel cells, stomata on both surfaces; Dicot - jigsaw cells, stomata mainly on the lower surface.

Activity 9.5 (Permanent Slides)(1 questions)

Observe permanent slides of leaf peel of a monocot and dicot. Compare them with the temporary mounts and note the differences in clarity and preservation.

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Solution:- Permanent slides show clearer, sharper, well-stained cell walls and guard cells. - Two consistent features across both: 1. Distinct guard cell shape around stomata. 2. Visible cell wall boundaries.Answer: Permanent slides are clearer; both show distinct guard cells and visible cell walls.

Let Us Find Out(3 questions)

Hard

If a cell measures 5 mm on a 100X image, calculate its actual size.

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Solution:Actual size $= \dfrac{\text{image size}}{\text{magnification}} = \dfrac{5}{100} = 0.05 \text{ mm} = 50 \mu\text{m}$ Answer: Actual size = 0.05 mm (50 µm).

Hard

If you use a 15X eyepiece and a 10X objective, what will be the total magnification?

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Solution: $M = m_o \times m_e = 10 \times 15 = 150\times$ Answer: Total magnification = 150X.

Hard

If 4 cells fit across a 0.8 mm field of view, what will be the approximate size of one cell?

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Solution:Size of one cell $= \dfrac{0.8}{4} = 0.2 \text{ mm}$ Answer: Approximate size of one cell = 0.2 mm.

Think(1 questions)

Why do you think electron microscopes are usually found in big research centres and not in normal school laboratories?

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Solution:- Extremely costly. - Require a vacuum environment. - Need complex sample preparation. - Demand skilled operation.Answer: Cost, vacuum requirement, complex preparation, and skilled operation make them impractical for schools.

Check Your Understanding(15 questions)

Hard

A microscope has a 10X eyepiece and a 40X objective. (a) What is its total magnification? (b) At this setting, the field of view is 0.4 mm; if 4 cells fit across, estimate the size of one cell.

a.(a) What is its total magnification?
b.(b) At this setting, the field of view is 0.4 mm; if 4 cells fit across, estimate the size of one cell.

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Solution:(a) Total magnification $= 10 \times 40 = 400\times$ .(b) Size of one cell $= \dfrac{0.4}{4} = 0.1 \text{ mm}$ .Answer: (a) 400X. (b) 0.1 mm.

(a) You want to watch live protozoa moving in pond water. Which microscope is best and why? (b) Neha wants to study the 3D surface of a pollen grain. Which microscope should she choose and why?

a.(a) You want to watch live protozoa moving in pond water. Which microscope is best and why?
b.(b) Neha wants to study the 3D surface of a pollen grain. Which microscope should she choose and why?

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Solution:(a) Phase-contrast microscope - enhances contrast in living cells without chemical stains that would kill them.(b) Scanning Electron Microscope (SEM) - gives 3D-like surface images.Answer: (a) Phase-contrast. (b) SEM.

Riya sees a sharp onion cell image at 100X, but when she switches to 400X, the image is bigger but very blurred. Name the concept causing this problem and explain.

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Solution:- This is due to limited resolution. - Increasing magnification beyond the microscope's resolving power only enlarges the blur. - Resolution, not magnification, determines the clarity of fine detail.Answer: Limited resolution - magnification beyond resolving power only enlarges the blur.

Draw a ray diagram of a compound microscope.

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Solution:- The objective lens (short focal length) forms a real, inverted, magnified image just beyond its focal point. - This image becomes the object for the eyepiece. - The eyepiece further magnifies it into a final upright, virtual image.Answer: Objective forms a real inverted image; the eyepiece magnifies it into an upright virtual image.

Design a simple poster ‘How to take care of a microscope?’ with three do’s and three don’ts.

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Solution:Do's: - Always carry it by the arm while supporting the base. - Clean lenses only with lens paper. - Store it covered in a dust-free place.Don'ts: - Never touch lenses with bare fingers. - Never force the focus knob. - Never tilt it while viewing a wet mount.Answer: Three do's and three don'ts as above.

Hard

At 40X total magnification, the field diameter is 4 mm. Predict the field diameter at 400X magnification (assume it is inversely proportional to magnification).

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Solution:Field diameter at 400X $= 4 \times \dfrac{40}{400} = 0.4 \text{ mm}$ Answer: Field diameter at 400X = 0.4 mm.

A student accidentally traps many air bubbles while placing the cover slip. How will this affect observation? Suggest two ways to avoid bubbles next time.

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Solution:- Air bubbles appear as dark circular outlines that obscure specimen details. - To avoid them: 1. Lower the cover slip gradually at an angle. 2. Use a sufficient, evenly spread drop of mounting fluid.Answer: Bubbles obscure details; lower the cover slip at an angle and use enough mounting fluid.

Compare TEM and SEM in terms of: (a) type of image (b) best use (internal vs surface).

a.(a) type of image
b.(b) best use (internal vs surface)

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Solution:(a) TEM produces two-dimensional images showing internal structures (organelles, viruses). SEM produces three-dimensional-like images.(b) TEM - best for internal cell details. SEM - best for external surface features.Answer: TEM - 2D internal images; SEM - 3D-like surface images.

Plan a brief investigation using a school light microscope to compare the purity of three water samples (tap water, RO-purified water, and pond water). Outline the main steps and predict your expected observations.

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Solution:- Prepare wet mounts of each water sample. - Observe under the same magnification, counting visible microorganisms or particles. - Expected result: pond water shows the most organisms, followed by tap water, with RO water showing the least.Answer: Count organisms in wet mounts at the same magnification; pond > tap > RO.

Can we rely on electron microscopes for studying living cells? Explain the reason.

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Solution:- No. The vacuum environment and metal coating or staining required kill living specimens. - They are unsuitable for observing life processes.Answer: No - the vacuum and coating kill living specimens.

List two ways how microscopes are used in hospitals and one way they are used in industries that manufacture mobile phones.

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Solution:Hospitals: - Diagnosing diseases such as malaria from blood smears. - Examining tissue biopsies for cancer.Mobile phone industry: - Inspecting microchip circuits for manufacturing defects using electron microscopes.Answer: Two hospital uses (malaria, biopsies) and one phone-industry use (microchip inspection).

Imagine you are Robert Hooke. Write a 5-6 line diary entry about what you felt when you first saw ‘little boxes’ (cells) in cork.

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Solution:Today I observed thin slices of cork bark under my microscope and was astonished to see tiny hexagonal, box-like spaces resembling a honeycomb pattern; I have decided to name these small units 'cells'.Answer: Diary entry describing the first sight of cork 'little boxes' (cells).

Ananya says, ‘If we add more and more lenses, we can see anything, even atoms, with a school microscope.’ Use the idea of resolution to correct this statement.

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Solution:- This is incorrect. - Adding more lenses only increases magnification, not resolution. - Light microscopes cannot resolve details smaller than about 0.2 µm, which is far larger than an atom.Answer: More lenses increase magnification, not resolution; light microscopes cannot resolve atoms.

Nishant wants to observe the effect of a concentrated salt solution on cells of a Rhoeo leaf and also wants to keep slides for future reference. (a) Which type of mount should be used for this purpose? Give reason. (b) Will the same slide be suitable for long-term storage? Elucidate the reason.

a.(a) Which type of mount should be used for this purpose? Give reason.
b.(b) Will the same slide be suitable for long-term storage? Elucidate the reason.

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Solution:(a) A temporary mount should be used first, since the immediate live cellular reaction (plasmolysis) must be observed fresh.(b) No. The same slide is not suitable for long-term storage - temporary mounts dry out and cells distort over time. A separate permanent mount must be prepared.Answer: (a) Temporary mount. (b) No - prepare a separate permanent mount.

Why is it important to fix and dehydrate cheek cells before mounting in Canada Balsam for school laboratory storage? Predict the consequences if a student inadvertently skipped the fixation and dehydration steps.

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Solution:- Fixing preserves the cell's structure. - Dehydration removes water so the mounting medium can properly seal the specimen. - Skipping these steps would cause the cells to rot, distort, or dissolve, ruining the permanent slide.Answer: Fixing and dehydration preserve the cells; skipping them ruins the permanent slide.

Quick Check(3 questions)

What is biotechnology?

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Solution:Biotechnology is the judicious use of living organisms or their cellular components to produce substances beneficial to humans.Answer: Biotechnology is the judicious use of living organisms or their cellular components to produce useful substances.

Give two examples from your daily life demonstrating the use of biotechnology.

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Solution:- Making curd from milk using bacteria. - Baking bread using yeast fermentation.Answer: Making curd and baking bread are two everyday examples.

Why are microorganisms important in biotechnology?

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Solution:- Grow rapidly. - Need minimal space and simple nutrients. - Their DNA can be easily manipulated.Answer: Rapid growth, simple needs, and easy DNA manipulation make microbes ideal tools.

Quick Check (Traditional vs Modern Biotechnology)(5 questions)

Uses natural microbial processes | Uses ______ techniques.

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Solution:Modern biotechnology uses genetic engineering / recombinant DNA techniques.Answer: Genetic engineering / recombinant DNA techniques.

Used since times | Developed in times.

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Solution:- Traditional biotechnology has been used since ancient times. - Modern biotechnology was developed in recent/modern times.Answer: Ancient times / recent (modern) times.

Example: Making curd and bread | Example: Production of ______ using bacteria.

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Solution:Modern biotechnology example: production of insulin using bacteria.Answer: Production of insulin using bacteria.

Has limited control over | Provides greater control over .

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Solution:- Traditional biotechnology has limited control over the genetic makeup of organisms. - Modern biotechnology provides greater control over genetic traits.Answer: Genetic makeup / genetic traits.

Does not involve gene transfer | Involves ______ modification.

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Solution:Modern biotechnology involves genetic modification.Answer: Genetic modification.

Quick Check (Fermenters)(3 questions)

Why is temperature control important in fermenters?

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Solution:- Microbial growth and enzyme activity are temperature-sensitive. - Excess heat produced during growth can kill the microbes if not controlled by cooling.Answer: Excess heat can kill microbes, so temperature must be controlled.

What happens if contamination occurs?

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Solution:- Unwanted microorganisms compete for nutrients. - They may produce harmful by-products. - They spoil the desired product, reducing yield and quality.Answer: Contamination reduces yield and quality by spoiling the product.

Explain sterilization and its importance in microbial growth.

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Solution:- Sterilization removes all unwanted microorganisms from the equipment and medium beforehand. - It ensures only the desired culture grows without contamination.Answer: Sterilization removes unwanted microbes so only the desired culture grows.

Activity 5.4: Growth Simulation(4 questions)

Using the following hypothetical data, plot a graph using time (hours) on the X-axis and number of microorganisms on the Y-axis: Time (hours): 0, 2, 4, 6, 8, 10, 12, 14; Number of microorganisms: 10, 12, 25, 60, 120, 125, 123, 90.

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Solution:- The graph rises slowly at first. - Then increases steeply. - Flattens near its peak. - Finally declines.Answer: The graph forms a typical S-shaped microbial growth curve.

Identify and label the growth phases: lag, log, stationary, and death.

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Solution:From the data and growth curve: - Lag phase: about 0–2 h. - Log phase: about 2–8 h. - Stationary phase: about 8–10 h. - Death/decline phase: about 10–14 h.Answer: Label the graph with these four phases.

During which time period do microorganisms grow most rapidly?

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Solution:From 6 to 8 hours, the population increases from 60 to 120, an increase of 60 microorganisms, which is the largest increase over any 2-hour interval. Therefore the most rapid growth occurs during 6–8 hours, in the log/exponential phase.Answer: 6–8 hours (log phase).

Suggest one reason why the population decreases after a certain time.

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Solution:- Nutrients become depleted. - Toxic metabolic waste accumulates in the fermenter. - The death rate exceeds the reproduction rate.Answer: Nutrient depletion and toxic waste accumulation cause the population to decline.

Activity (Traditional Biotechnology Research)(2 questions)

Part A: Make a list of fermented foods used in your home or community and identify the responsible microorganism.

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Solution:- Curd - Lactobacillus bacteria. - Bread - yeast. - Idli and dosa batter - bacteria and yeast. - Pickles - lactic acid bacteria.Answer: Curd (Lactobacillus), bread (yeast), idli/dosa (bacteria + yeast), pickles (lactic acid bacteria).

Part B: Prepare kanji using carrot and beetroot and record observations over several days.

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Solution:- Ferment chopped carrot and beetroot with water, salt, and mustard powder in sunlight for 2-3 days. - Observe a sour aroma, colour change, and bubble formation. - This indicates lactic acid bacterial fermentation.Answer: Sour aroma, colour change, and bubbles indicate lactic acid fermentation.

Check Your Understanding(17 questions)

Define biotechnology. Explain how microorganisms act as ‘life’s engineers’ giving two examples.

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Solution:- Biotechnology uses living organisms to create useful products. - Microorganisms act as 'life's engineers' by: 1. Converting milk into curd (bacteria). 2. Producing insulin using genetically engineered bacteria.Answer: Biotechnology uses living organisms to create useful products; microbes act as 'life's engineers'.

Differentiate between traditional biotechnology and modern biotechnology using suitable examples.

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Solution:- Traditional biotechnology: uses natural microbial processes, e.g. fermentation for bread and curd. - Modern biotechnology: uses genetic engineering, e.g. producing insulin using genetically modified bacteria.Answer: Traditional - natural fermentation (bread, curd); Modern - genetic engineering (insulin).

Why are fermenters used instead of open containers for industrial production of useful substances? Give any two reasons.

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Solution:1. Fermenters maintain sterile, contamination-free conditions. 2. They allow precise control of temperature, pH, and aeration needed for optimal microbial growth.Answer: Sterility and precise control of temperature, pH, and aeration.

Explain the importance of maintaining sterility inside a fermenter. What problems may arise if sterility is not maintained?

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Solution:- Sterility ensures only the desired microorganism grows inside the fermenter. - Without it, contaminating microbes compete for nutrients, lower product yield, and may spoil the final product.Answer: Sterility ensures only the desired microbe grows; contamination lowers yield and spoils product.

Study the diagram of a fermenter. (A) Identify any two parts responsible for maintaining microbial growth. (B) What is the function of the stirrer in a fermenter? (C) Why is oxygen supply important in some fermenters?

a.(A) Identify any two parts responsible for maintaining microbial growth.
b.(B) What is the function of the stirrer in a fermenter?
c.(C) Why is oxygen supply important in some fermenters?

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Solution:(A) The stirrer (impeller) and the sparger - they distribute nutrients/oxygen and support aeration.(B) The stirrer agitates the broth so every microbial cell receives adequate nutrients and oxygen evenly.(C) Many microbes are aerobic and require oxygen for respiration to grow and form the desired product.Answer: (A) Stirrer and sparger. (B) Agitates broth for even nutrients/oxygen. (C) Aerobic microbes need oxygen.

Using the given fermenter growth data: (a) During which time period does rapid microbial growth occur? (b) Identify the stationary phase from the data. (c) Suggest one reason why the microbial population decreases after a certain time.

a.(a) During which time period does rapid microbial growth occur?
b.(b) Identify the stationary phase from the data.
c.(c) Suggest one reason why the microbial population decreases after a certain time.

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Solution:(a) Rapid growth occurs during the middle hours - the log (exponential) phase - where numbers rise sharply.(b) The stationary phase occurs when counts level off near their peak value.(c) Accumulation of toxic waste and depletion of nutrients causes the death rate to exceed the growth rate.Answer: (a) Middle hours (log phase). (b) When counts level off near the peak. (c) Toxic waste and nutrient depletion.

Microbes are used in food production, medicine and environmental protection. Analyse how biotechnology helps improve human life using any three examples.

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Solution:1. Insulin production for diabetic patients using engineered bacteria. 2. Bt cotton providing pest-resistant crops for farmers. 3. Bioremediation using bacteria to clean up oil spills and industrial pollutants.Answer: Insulin, Bt cotton, and bioremediation are three examples.

A scientist wants to produce insulin using bacteria. Explain how modern biotechnology makes this possible. Why has traditional biotechnology not achieved this?

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Solution:- The human insulin gene is cut using restriction enzymes and inserted into a bacterial plasmid using DNA ligase. - The transformed bacteria then mass-produce insulin. - Traditional biotechnology lacked the gene-transfer technology required for this process.Answer: Recombinant DNA technology inserts the insulin gene into bacteria; traditional methods lacked gene transfer.

Biotechnology has helped increase food production, but some people have ethical concerns regarding GM crops. Evaluate both advantages and concerns.

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Solution:Advantages: - Pest resistance, higher yield, improved nutrition - as seen in Golden Rice.Concerns: - Gene flow creating herbicide-resistant 'super-weeds'. - Harm to beneficial insects. - Unequal access to seeds due to patent control.Answer: Advantages - pest resistance, yield, nutrition; Concerns - super-weeds, harm to insects, seed patents.

Design a simple biotechnology product that can help solve an environmental problem in your community. Describe the microorganism/enzyme used, the problem it solves, and how it benefits society.

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Solution:- Microorganism: oil-degrading Pseudomonas bacteria. - Problem it solves: bioremediation of contaminated soil or water. - How it benefits society: it naturally breaks down pollutants like hydrocarbons, restoring the ecosystem without harsh chemicals.Answer: Pseudomonas bacteria for bioremediation of contaminated soil/water.

Which of the following is an example of traditional biotechnology? (a) Production of insulin using bacteria (b) Preparation of curd from milk (c) Development of disease-resistant crops (d) Gene transfer between organisms

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Solution:Preparation of curd from milk is a natural microbial process - an example of traditional biotechnology.Answer: (b) Preparation of curd from milk.

Which microorganism is commonly used in bread making? (a) Bacteria (b) Virus (c) Yeast (d) Algae

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Solution:Yeast is commonly used in bread making (fermentation).Answer: (c) Yeast.

Which of the following conditions is necessary for proper functioning of a fermenter? (a) Contamination (b) Controlled temperature (c) Open environment (d) Absence of nutrients

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Solution:A fermenter requires controlled temperature for proper functioning.Answer: (b) Controlled temperature.

Genetic engineering mainly involves: (a) Mixing different foods (b) Transfer of genes between organisms (c) Increasing natural microbial growth (d) Removing microorganisms from food

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Solution:Genetic engineering mainly involves the transfer of genes between organisms.Answer: (b) Transfer of genes between organisms.

During which phase do microorganisms show maximum growth? (a) Lag phase (b) Log phase (c) Stationary phase (d) Death phase

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Solution:Microorganisms show maximum growth during the log (exponential) phase.Answer: (b) Log phase.

Assertion: Sterility must be maintained inside a fermenter. Reason: Contamination by unwanted microorganisms can reduce product quality.

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Solution:- Assertion: Sterility must be maintained inside a fermenter - true. - Reason: Contamination can reduce product quality - true. - The reason correctly explains the assertion.Answer: (a) Both assertion and reason are true, and the reason explains the assertion.

Assertion: Modern biotechnology allows production of insulin using bacteria. Reason: Modern biotechnology involves genetic modification techniques.

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Solution:- Assertion: Modern biotechnology allows insulin production using bacteria - true. - Reason: Modern biotechnology involves genetic modification techniques - true. - The reason correctly explains the assertion.Answer: (a) Both assertion and reason are true, and the reason explains the assertion.

Activities — How to Do(3 questions)

Activity 10.1: in what times or situations does curd take a long time to form?

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Curd sets slowly when it is cold (winter nights), the milk is cold, the starter (jaman) is weak or stale, or the vessel is moved/disturbed while setting. Lactobacillus multiplies fastest in warmth (~35–40 °C) — chill slows it sharply.

What conditions support the curdling of milk?

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Use lukewarm milk, stir in a spoon of fresh curd starter, cover and keep the vessel warm and undisturbed for 6–8 hours. Warmth speeds bacterial conversion of lactose to lactic acid, which curdles the protein; cold, disturbance or a dead starter prevents setting.

Think and Discuss (ethical principles): beneficence (doing good), non-maleficence (do no harm), autonomy (freedom of choice), justice and fairness — how do they evaluate biotechnologies like SynBio?

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Sort each technology by where its concern falls: Beneficence (does it heal or feed people?), Non-maleficence (could it harm health or ecosystems?), Autonomy (are consent and choice respected?), Justice (are benefits and risks shared fairly?). Classify SynBio and others accordingly, with one reason each.

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Chapter 9: Microscope and Microscopy

Activity 9.1 (Let Us Think and Write)(1 questions)

If you could shrink yourself and travel inside a leaf, what would you see? Write 3-4 lines.

Activity 9.2 (A Timeline Strip)(1 questions)

Draw a horizontal line. Mark at least 5 important dates in microscopy and add a tiny sketch or symbol for each (e.g., cork cells, bacteria, electron beam etc.).

Activity 9.3 (Let us examine a compound microscope)(1 questions)

Identify the key parts of a compound microscope: eyepiece, objectives, nosepiece, stage with clips, coarse/fine focus, condenser, iris diaphragm, illuminator, arm, and base.

Activity 9.4 (Leaf Peels of Monocot and Dicot Leaves)(1 questions)

Activity 9.5 (Permanent Slides)(1 questions)

Observe permanent slides of leaf peel of a monocot and dicot. Compare them with the temporary mounts and note the differences in clarity and preservation.

Let Us Find Out(3 questions)

If a cell measures 5 mm on a 100X image, calculate its actual size.

If you use a 15X eyepiece and a 10X objective, what will be the total magnification?

If 4 cells fit across a 0.8 mm field of view, what will be the approximate size of one cell?

Think(1 questions)

Why do you think electron microscopes are usually found in big research centres and not in normal school laboratories?

Check Your Understanding(15 questions)

A microscope has a 10X eyepiece and a 40X objective. (a) What is its total magnification? (b) At this setting, the field of view is 0.4 mm; if 4 cells fit across, estimate the size of one cell.

(a) You want to watch live protozoa moving in pond water. Which microscope is best and why? (b) Neha wants to study the 3D surface of a pollen grain. Which microscope should she choose and why?

Riya sees a sharp onion cell image at 100X, but when she switches to 400X, the image is bigger but very blurred. Name the concept causing this problem and explain.

Draw a ray diagram of a compound microscope.

Design a simple poster ‘How to take care of a microscope?’ with three do’s and three don’ts.

At 40X total magnification, the field diameter is 4 mm. Predict the field diameter at 400X magnification (assume it is inversely proportional to magnification).

A student accidentally traps many air bubbles while placing the cover slip. How will this affect observation? Suggest two ways to avoid bubbles next time.

Compare TEM and SEM in terms of: (a) type of image (b) best use (internal vs surface).

Plan a brief investigation using a school light microscope to compare the purity of three water samples (tap water, RO-purified water, and pond water). Outline the main steps and predict your expected observations.

Can we rely on electron microscopes for studying living cells? Explain the reason.

List two ways how microscopes are used in hospitals and one way they are used in industries that manufacture mobile phones.

Imagine you are Robert Hooke. Write a 5-6 line diary entry about what you felt when you first saw ‘little boxes’ (cells) in cork.

Ananya says, ‘If we add more and more lenses, we can see anything, even atoms, with a school microscope.’ Use the idea of resolution to correct this statement.

Nishant wants to observe the effect of a concentrated salt solution on cells of a Rhoeo leaf and also wants to keep slides for future reference. (a) Which type of mount should be used for this purpose? Give reason. (b) Will the same slide be suitable for long-term storage? Elucidate the reason.

Why is it important to fix and dehydrate cheek cells before mounting in Canada Balsam for school laboratory storage? Predict the consequences if a student inadvertently skipped the fixation and dehydration steps.

Quick Check(3 questions)

What is biotechnology?

Give two examples from your daily life demonstrating the use of biotechnology.

Why are microorganisms important in biotechnology?

Quick Check (Traditional vs Modern Biotechnology)(5 questions)

Uses natural microbial processes | Uses ______ techniques.

Used since ______ times | Developed in ______ times.

Example: Making curd and bread | Example: Production of ______ using bacteria.

Has limited control over ______ | Provides greater control over ______.

Does not involve gene transfer | Involves ______ modification.

Quick Check (Fermenters)(3 questions)

Why is temperature control important in fermenters?

What happens if contamination occurs?

Explain sterilization and its importance in microbial growth.

Activity 5.4: Growth Simulation(4 questions)

Using the following hypothetical data, plot a graph using time (hours) on the X-axis and number of microorganisms on the Y-axis: Time (hours): 0, 2, 4, 6, 8, 10, 12, 14; Number of microorganisms: 10, 12, 25, 60, 120, 125, 123, 90.

Identify and label the growth phases: lag, log, stationary, and death.

During which time period do microorganisms grow most rapidly?

Suggest one reason why the population decreases after a certain time.

Activity (Traditional Biotechnology Research)(2 questions)

Part A: Make a list of fermented foods used in your home or community and identify the responsible microorganism.

Part B: Prepare kanji using carrot and beetroot and record observations over several days.

Check Your Understanding(17 questions)

Define biotechnology. Explain how microorganisms act as ‘life’s engineers’ giving two examples.

Differentiate between traditional biotechnology and modern biotechnology using suitable examples.

Why are fermenters used instead of open containers for industrial production of useful substances? Give any two reasons.

Explain the importance of maintaining sterility inside a fermenter. What problems may arise if sterility is not maintained?

Study the diagram of a fermenter. (A) Identify any two parts responsible for maintaining microbial growth. (B) What is the function of the stirrer in a fermenter? (C) Why is oxygen supply important in some fermenters?

Using the given fermenter growth data: (a) During which time period does rapid microbial growth occur? (b) Identify the stationary phase from the data. (c) Suggest one reason why the microbial population decreases after a certain time.

Microbes are used in food production, medicine and environmental protection. Analyse how biotechnology helps improve human life using any three examples.

A scientist wants to produce insulin using bacteria. Explain how modern biotechnology makes this possible. Why has traditional biotechnology not achieved this?

Biotechnology has helped increase food production, but some people have ethical concerns regarding GM crops. Evaluate both advantages and concerns.

Design a simple biotechnology product that can help solve an environmental problem in your community. Describe the microorganism/enzyme used, the problem it solves, and how it benefits society.

Which of the following is an example of traditional biotechnology? (a) Production of insulin using bacteria (b) Preparation of curd from milk (c) Development of disease-resistant crops (d) Gene transfer between organisms

Which microorganism is commonly used in bread making? (a) Bacteria (b) Virus (c) Yeast (d) Algae

Which of the following conditions is necessary for proper functioning of a fermenter? (a) Contamination (b) Controlled temperature (c) Open environment (d) Absence of nutrients

Genetic engineering mainly involves: (a) Mixing different foods (b) Transfer of genes between organisms (c) Increasing natural microbial growth (d) Removing microorganisms from food

During which phase do microorganisms show maximum growth? (a) Lag phase (b) Log phase (c) Stationary phase (d) Death phase

Assertion: Sterility must be maintained inside a fermenter. Reason: Contamination by unwanted microorganisms can reduce product quality.

Assertion: Modern biotechnology allows production of insulin using bacteria. Reason: Modern biotechnology involves genetic modification techniques.

Activities — How to Do(3 questions)

Activity 10.1: in what times or situations does curd take a long time to form?

What conditions support the curdling of milk?

Think and Discuss (ethical principles): beneficence (doing good), non-maleficence (do no harm), autonomy (freedom of choice), justice and fairness — how do they evaluate biotechnologies like SynBio?

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