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Premium CBSE/KV Question Bank | Class 8 Science Ch-1 | Page 2 TABLE OF CONTENTS Student Instructions Section A – Multiple Choice Questions (MCQs) .............. 20 Qs Section B – Very Short Answer Questions .................... 10 Qs Section C – Short Answer Questions – I (2 Marks) ......... 8 Qs Section D – Short Answer Questions – II (3 Marks) ........ 8 Qs Section E – Long Answer Questions (5 Marks) .............. 6 Qs Section F – Competency-Based Questions ................... 8 Qs Section G – Assertion & Reason Questions ................. 6 Qs Section H – Case-Based Questions ......................... 3 Cases Section I – Source-Based Questions ....................... 3 Sets Section J – HOTS (Higher Order Thinking Skills) .......... 6 Qs Prepared By / Credits Difficulty Distribution: Moderate ~70% | Difficult ~30% Total Questions: Approximately 80 high-quality competency-based items

Premium CBSE/KV Question Bank | Class 8 Science Ch-1 | Page 3 STUDENT INSTRUCTIONS 1. Read every question carefully before answering. 2. For MCQs, choose the most appropriate option (A/B/C/D). 3. Write answers in clear, concise language using NCERT terminology. 4. For short and long answers, use bullet points where helpful and highlight key terms. 5. Time management: Allocate time according to marks (approx. 1–1.5 min per mark). 6. Assertion–Reason: Select the correct option based on both statements. 7. Case-based and source-based questions test interpretation – read the passage fully. 8. HOTS questions require critical thinking; support answers with scientific reasoning. 9. This question bank follows the latest CBSE 2026–27 competency-based pattern and KVS guidelines. 10. Focus on the spirit of investigation: observation, controlled variables, and systematic enquiry. Bloom's Taxonomy Levels: Remember | Understand | Apply | Analyse | Evaluate | Create

Premium CBSE/KV Question Bank | Class 8 Science Ch-1 | Page 4 SECTION A – MULTIPLE CHOICE QUESTIONS (20 Questions) Each question carries 1 mark. Choose the correct option. Marks: 1 | Difficulty: Moderate | Bloom: Understand | Topic: Root & Kite Symbolism Q1. In the Curiosity textbook, the image of a root at the bottom of left-hand pages symbolises: (a) Soaring imagination (b) Deep foundation of knowledge connected to environment and heritage (c) Flight of a kite (d) Only traditional knowledge Answer: (b) Deep foundation of knowledge connected to environment and heritage Explanation: The root represents the solid foundation of knowledge that keeps us connected to environment, traditions and heritage. Marks: 1 | Difficulty: Moderate | Bloom: Understand | Topic: Root & Kite Symbolism Q2. The kite on the right-hand pages reminds us that: (a) We should only stay grounded (b) Curiosity must take flight to explore the unknown (c) Science needs no creativity (d) Observations are unnecessary Answer: (b) Curiosity must take flight to explore the unknown Explanation: The kite symbolises that curiosity must soar while remaining grounded in careful observation. Marks: 1 | Difficulty: Moderate | Bloom: Understand | Topic: Nature of Investigation Q3. Investigation in science means: (a) Only memorising facts (b) Asking focused questions, designing simple experiments and improving understanding from observations (c) Avoiding questions (d) Looking at something without asking questions Answer: (b) Asking focused questions, designing simple experiments and improving understanding from observations Explanation: Grade 8 emphasises becoming investigators who ask focused questions and experiment thoughtfully. Marks: 1 | Difficulty: Moderate | Bloom: Remember | Topic: Overview of Journey Q4. According to the chapter, the journey of Grade 8 science begins with examining: (a) Stars and galaxies only (b) Something as small as a single drop of water and tiny organisms (c) Only climate change (d) Only electric current Answer: (b) Something as small as a single drop of water and tiny organisms Explanation: The investigative adventure starts from tiny microbes invisible to the naked eye. Marks: 1 | Difficulty: Moderate | Bloom: Remember | Topic: Electricity Overview Q5. The heating effect of electric current is used to: (a) Run motors only (b) Keep us warm (c) Generate magnetic fields only (d) Produce light only Answer: (b) Keep us warm Explanation: The chapter mentions dependence on the heating effect of electric current to keep us warm. Marks: 1 | Difficulty: Moderate | Bloom: Understand | Topic: Forces Q6. Understanding forces helps explain why: (a) Sugar dissolves in tea (b) A ball thrown up falls back to the ground or a car stops when brakes are applied (c) The Moon has phases (d) Microbes cause infections Answer: (b) A ball thrown up falls back to the ground or a car stops when brakes are applied Explanation: Forces make objects speed up, slow down or change direction; gravity and friction are examples. Marks: 1 | Difficulty: Moderate | Bloom: Understand | Topic: Pressure & Weather Q7. A small difference in air pressure can result in:

Premium CBSE/KV Question Bank | Class 8 Science Ch-1 | Page 5 (a) Only cyclones (b) A gentle breeze (c) Only solid particles moving (d) No movement of air Answer: (b) A gentle breeze Explanation: Small pressure difference → gentle breeze; stronger difference → strong winds or cyclones. Marks: 1 | Difficulty: Moderate | Bloom: Remember | Topic: Nature of Matter Q8. In solids, particles: (a) Move around freely (b) Cannot move much (c) Are completely absent (d) Only vibrate in gases Answer: (b) Cannot move much Explanation: In solids particles cannot move much; in gases they move freely. Marks: 1 | Difficulty: Moderate | Bloom: Remember | Topic: Classification of Matter Q9. Materials can be classified into: (a) Only mixtures (b) Elements, compounds and mixtures (c) Only elements and solutions (d) Only pure substances Answer: (b) Elements, compounds and mixtures Explanation: Elements are pure substances; compounds are bonded elements; mixtures can be separated physically. Marks: 1 | Difficulty: Moderate | Bloom: Remember | Topic: Light Q10. Light rays bend when passing through: (a) Only flat mirrors (b) Lenses (c) Only the Moon (d) Only rough surfaces Answer: (b) Lenses Explanation: Light reflects off mirrors and bends (refracts) when passing through lenses. Marks: 1 | Difficulty: Moderate | Bloom: Understand | Topic: Moon Phases Q11. The phases of the Moon arise because of: (a) Changes in the Moon’s size (b) Relative positions of the Earth, Moon and Sun (c) Only Earth’s rotation (d) Clouds covering the Moon Answer: (b) Relative positions of the Earth, Moon and Sun Explanation: Different parts of the Moon are illuminated depending on the relative positions of Earth, Moon and Sun. Marks: 1 | Difficulty: Moderate | Bloom: Remember | Topic: Calendars & Moon Q12. Watching the periodic cycles of the Moon’s phases allowed humans to create: (a) Microscopes (b) The first calendars (c) Electric motors (d) Vaccines Answer: (b) The first calendars Explanation: Observations of lunar cycles, sunrises and sunsets led to various calendars. Marks: 1 | Difficulty: Moderate | Bloom: Understand | Topic: Earth & Life Q13. Earth is ‘just right’ for life mainly because: (a) It is the largest planet (b) It lies at the perfect distance from the Sun so water remains liquid and has a protective atmosphere (c) It has no atmosphere (d) It is closest to the Moon Answer: (b) It lies at the perfect distance from the Sun so water remains liquid and has a protective atmosphere Explanation: Distance allows liquid water; atmosphere provides oxygen and shields from harmful UV rays. Marks: 1 | Difficulty: Moderate | Bloom: Apply | Topic: Scientific Investigation Q14. In the puri investigation, the things we can change or control are called:

Premium CBSE/KV Question Bank | Class 8 Science Ch-1 | Page 6 (a) Observations only (b) Variables we control (c) Results only (d) Conclusions Answer: (b) Variables we control Explanation: Thickness of dough, type of flour, oil temperature, way of dropping are controllable variables. Marks: 1 | Difficulty: Moderate | Bloom: Apply | Topic: Controlled Experiments Q15. While doing experiments it is better to: (a) Change many things at the same time (b) Change only one thing at a time while keeping other conditions same (c) Never record observations (d) Avoid questions Answer: (b) Change only one thing at a time while keeping other conditions same Explanation: Changing one variable at a time helps us clearly see the effect of that variable. Marks: 1 | Difficulty: Difficult | Bloom: Evaluate | Topic: Nature of Science Q16. Even the simple everyday observation of a puri puffing is: (a) Completely understood by all scientists (b) Not really completely understood by scientists today (c) Impossible to investigate (d) Unrelated to science Answer: (b) Not really completely understood by scientists today Explanation: The chapter notes that even this simple phenomenon is not fully understood, showing science is still evolving. Marks: 1 | Difficulty: Moderate | Bloom: Understand | Topic: Science Everywhere Q17. The kitchen at home is described as: (a) Unsuitable for science (b) A wonderful place to observe and ask questions (c) Only for cooking (d) A place where experiments cannot be done Answer: (b) A wonderful place to observe and ask questions Explanation: Science is everywhere; a fancy laboratory is not always needed for simple experiments. Marks: 1 | Difficulty: Difficult | Bloom: Analyse | Topic: Climate Challenge Q18. Human activities can cause small changes in Earth’s temperature, leading to: (a) No effect on climate (b) Disruption of climate patterns with dangerous consequences (c) Only cooling of the planet (d) Increase in Moon’s size Answer: (b) Disruption of climate patterns with dangerous consequences Explanation: Human influence on climate is highlighted; science must guide protective actions. Marks: 1 | Difficulty: Difficult | Bloom: Analyse | Topic: Scientific Method Q19. What is the correct sequence of the investigative approach described for the puri? (a) Conclusion → Experiment → Question (b) Ask scientific question → Identify variables & observations → Experiment systematically → Record & ask further questions (c) Only observe without questioning (d) Change all variables together Answer: (b) Ask scientific question → Identify variables & observations → Experiment systematically → Record & ask further questions Explanation: This mirrors systematic investigation used in all scientific experiments. Marks: 1 | Difficulty: Moderate | Bloom: Understand | Topic: Ecosystems Q20. Ecosystems are formed by: (a) Only non-living things (b) Relationships between living organisms and their environments (air, water, sunlight and other organisms) (c) Only plants (d) Only animals Answer: (b) Relationships between living organisms and their environments (air, water, sunlight and other organisms) Explanation: Every living being depends on and responds to air, water, sunlight and other organisms.

Premium CBSE/KV Question Bank | Class 8 Science Ch-1 | Page 7

Premium CBSE/KV Question Bank | Class 8 Science Ch-1 | Page 8 SECTION B – VERY SHORT ANSWER QUESTIONS (10 Questions) Answer in one word or one sentence. Each carries 1 mark. Marks: 1 | Difficulty: Moderate | Bloom: Understand | Topic: Symbolism Q1. What do the root and the kite together invite students to do? Answer: Stay grounded in real observations while allowing ideas to soar towards new horizons. Explanation: Balance careful observation with creative thinking. Marks: 1 | Difficulty: Moderate | Bloom: Remember | Topic: Investigation Q2. Name one everyday example of investigation mentioned in the chapter. Answer: Why does dough rise? / Why is one side of a puri thinner than the other? Explanation: Everyday life questions are starting points for scientific investigation. Marks: 1 | Difficulty: Moderate | Bloom: Remember | Topic: Electricity Q3. What does the magnetic effect of electric current help in? Answer: It helps motors run and machines function. Explanation: Mentioned as a useful effect of electric current. Marks: 1 | Difficulty: Moderate | Bloom: Understand | Topic: Pressure Q4. Define pressure in the context of the chapter. Answer: How the force is distributed over an object. Explanation: Force and pressure concepts also explain air movement. Marks: 1 | Difficulty: Moderate | Bloom: Remember | Topic: Solutions Q5. Give one example of a solution mentioned in the chapter. Answer: Sugar dissolving in tea to make it sweet. Explanation: Illustrates how particles mix in solutions. Marks: 1 | Difficulty: Moderate | Bloom: Remember | Topic: Light Q6. What do rough surfaces and the Moon do with light? Answer: They reflect light. Explanation: Not only polished mirrors reflect; rough surfaces and the Moon also reflect light. Marks: 1 | Difficulty: Moderate | Bloom: Remember | Topic: Earth Q7. What shields us from harmful ultraviolet rays? Answer: Earth’s atmosphere. Explanation: Atmosphere provides oxygen and UV protection. Marks: 1 | Difficulty: Moderate | Bloom: Apply | Topic: Investigation Q8. In experiments, what should we keep notes of? Answer: Everything that we see and sense (e.g., oil splatters, smell, smoke). Explanation: Recording observations is essential in systematic investigation. Marks: 1 | Difficulty: Moderate | Bloom: Apply | Topic: Variables Q9. Name two things that can be controlled while investigating puri puffing. Answer: Thickness/size of dough, type of flour, oil temperature, way of dropping dough (any two). Explanation: These are controllable variables. Marks: 1 | Difficulty: Difficult | Bloom: Evaluate | Topic: Climate Q10. What is at the heart of both the climate problem and its possible solution? Answer: Us (human beings) – we influence climate and can use science to guide actions. Explanation: Humans are both the cause and the potential solution.

Premium CBSE/KV Question Bank | Class 8 Science Ch-1 | Page 9 SECTION C – SHORT ANSWER QUESTIONS – I (8 Questions | 2 Marks) Answer in 3–4 lines. Marks: 2 | Difficulty: Moderate | Bloom: Understand | Topic: Symbolism Q1. Why does the textbook use the symbols of root and kite? Model Answer: • The root symbolises deep, solid foundation of knowledge linked to environment, traditions and heritage. • The kite reminds us that curiosity must take flight to explore the unknown. • Together they invite us to stay grounded in observation while letting ideas soar. Marks: 2 | Difficulty: Moderate | Bloom: Understand | Topic: Investigation Q2. What is meant by ‘investigation in science’ in Grade 8? Model Answer: • It means more than looking and asking simple questions. • Students learn to ask focused questions, design simple experiments, observe carefully and improve understanding. • Each student becomes an investigator exploring real-world puzzles. Marks: 2 | Difficulty: Moderate | Bloom: Remember | Topic: Overview Q3. List any three topics that Grade 8 science journey will cover. Model Answer: • Tiny microbes and health (food, exercise, medicines, vaccines) • Electric current, forces, pressure and weather (winds, cyclones) • Particles of matter, classification, solutions, light, Moon phases, ecosystems and Earth’s climate Marks: 2 | Difficulty: Moderate | Bloom: Understand | Topic: Pressure & Weather Q4. How are force and pressure related to weather events? Model Answer: • Force distributed over an area is pressure. • Small air-pressure difference → gentle breeze. • Stronger pressure difference → strong winds and sometimes cyclones that affect daily life and safety. Marks: 2 | Difficulty: Moderate | Bloom: Understand | Topic: Classification Q5. Why is classifying materials into elements, compounds and mixtures important? Model Answer: • Classification is a key feature of science. • Elements are pure substances; compounds are bonded elements; mixtures can be separated physically. • It helps us understand how particles combine or mix (e.g., sugar in tea). Marks: 2 | Difficulty: Moderate | Bloom: Understand | Topic: Moon & Calendars Q6. How did observations of the Moon help humans? Model Answer: • Periodic cycles of Moon phases were carefully observed. • Combined with sunrises and sunsets, these observations led to the first calendars. • Calendars that guide our routines are linked to motions of celestial objects. Marks: 2 | Difficulty: Moderate | Bloom: Understand | Topic: Earth & Life Q7. What makes Earth suitable for life according to the chapter? Model Answer: • Perfect distance from the Sun so that water remains liquid. • Atmosphere that provides oxygen and shields from harmful ultraviolet rays. • These conditions support the complex ecosystems of living organisms. Marks: 2 | Difficulty: Moderate | Bloom: Apply | Topic: Experimental Practice Q8. State two good practices while performing a scientific experiment. Model Answer: • Change only one variable at a time, keeping other conditions the same. • Keep detailed notes of everything observed and sensed (sight, smell, sound, etc.).

Premium CBSE/KV Question Bank | Class 8 Science Ch-1 | Page 10 SECTION D – SHORT ANSWER QUESTIONS – II (8 Questions | 3 Marks) Answer in about 5 lines with structured points. Marks: 3 | Difficulty: Moderate | Bloom: Understand | Topic: Progression of Science Learning Q1. Explain how Grade 8 science builds upon Grades 6 and 7. Model Answer: • Grade 6: Science begins with wonder and simple “Why?” and “How?” questions. • Grade 7: Science is always evolving; each answer opens new questions; ideas change as we explore deeper. • Grade 8: Wonder and evolution come together; students learn to investigate – ask focused questions, design experiments and explain observations. Marks: 3 | Difficulty: Moderate | Bloom: Understand | Topic: Electricity Q2. Describe the role of electric current as introduced in the chapter. Model Answer: • Electric current makes lives easier in many ways. • Heating effect keeps us warm. • Magnetic effect helps motors run and machines function. • These phenomena depend on fundamental forces, leading into the study of forces themselves. Marks: 3 | Difficulty: Moderate | Bloom: Apply | Topic: Particles of Matter Q3. How does understanding particles help explain everyday phenomena? Model Answer: • Everything is made of tiny particles. • In solids particles cannot move much; in gases they move freely. • This explains pressure of air, boiling of water, and how substances dissolve (e.g., sugar in tea). • Classification into elements, compounds and mixtures follows from particle behaviour. Marks: 3 | Difficulty: Moderate | Bloom: Understand | Topic: Light Q4. Outline the path of light studies described in the chapter. Model Answer: • Light reflects off flat and curved mirrors. • Light bends (refracts) when passing through lenses. • This explains images in a shiny spoon and how corrective glasses help us see clearly. • Rough surfaces and the Moon also reflect light, leading to phases of the Moon. Marks: 3 | Difficulty: Moderate | Bloom: Understand | Topic: Ecosystems Q5. What is the significance of ecosystems in the Grade 8 journey? Model Answer: • Living organisms (from insects to whales, grass to trees) depend on and respond to air, water, sunlight and other organisms. • These relationships form ecosystems that support life. • Understanding ecosystems prepares us to recognise Earth’s delicate balance and the challenges it faces. Marks: 3 | Difficulty: Difficult | Bloom: Apply | Topic: Scientific Investigation Q6. Using the puri example, explain the idea of controllable variables and observations. Model Answer: • Controllable variables: thickness/size of dough, type of flour, oil temperature, way of dropping dough. • Observations/measurements: whether it puffs (yes/no), time to puff (seconds), whether thick dough still gives a thin side. • Changing only one variable at a time while keeping others constant allows clear conclusions. Marks: 3 | Difficulty: Difficult | Bloom: Evaluate | Topic: Nature of Science Q7. Why is systematic investigation important even for simple everyday phenomena? Model Answer: • It is the method used in all scientific experiments, simple or complex. • Asking focused questions, controlling variables, recording observations and generating further questions leads to reliable understanding. • Even the puffing of a puri is not fully understood, showing that careful investigation continues to be needed. Marks: 3 | Difficulty: Difficult | Bloom: Evaluate | Topic: Climate & Science Q8. How can science help address the climate challenges mentioned in the chapter? Model Answer: • Human activities influence Earth’s temperature and climate patterns.

Premium CBSE/KV Question Bank | Class 8 Science Ch-1 | Page 11 • The same principles – observing, measuring, experimenting – help us understand these changes. • Science can guide our actions to protect the delicate balance on which life depends. • Students are encouraged to try solving these problems with Curiosity as guide.

Premium CBSE/KV Question Bank | Class 8 Science Ch-1 | Page 12 SECTION E – LONG ANSWER QUESTIONS (6 Questions | 5 Marks) Answer in a structured manner (about 8 lines / points). Marks: 5 | Difficulty: Moderate | Bloom: Understand | Topic: Chapter Overview Q1. Describe the overall investigative journey planned for Grade 8 Science as outlined in Chapter 1. Model Answer: • Starts with tiny microbes in a drop of water – helpful and harmful; health, food, exercise, medicines, vaccines. • Electric current – heating and magnetic effects; then fundamental forces that change motion. • Pressure and its link to air movement, winds and cyclones. • Particles of matter, classification (elements, compounds, mixtures) and solutions. • Light – reflection, refraction, lenses, Moon phases and calendars. • Ecosystems and relationships between organisms and environment. • Finally, Earth as a habitable planet and climate challenges; science as a guide to protect life. Marks: 5 | Difficulty: Difficult | Bloom: Apply | Topic: Puri Investigation Q2. Explain the scientific approach to investigating why a puri puffs up, based on the chapter. Model Answer: • Start with a focused scientific question: What factors change the way a puri puffs? • Identify controllable variables: dough thickness/size, flour type, oil temperature, dropping method. • Decide what to observe/measure: does it puff? time taken? thickness of sides? • Change only one variable at a time, keep others constant. • Record all observations (sight, smell, sound, smoke, etc.). • After one round, generate further questions (fresh vs stored dough, pricking a hole, etc.). • This systematic method is how all scientific experiments are done. Marks: 5 | Difficulty: Difficult | Bloom: Evaluate | Topic: Philosophy of Investigation Q3. Discuss the importance of balancing ‘roots’ and ‘kite’ in scientific investigation. Model Answer: • Roots: Careful observation, connection to environment, traditions and cultural/natural heritage – the solid ground of knowledge. • Kite: Curiosity that takes flight, creative thinking, exploration of the unknown. • Investigation works best when both are balanced – grounded observation + freedom of creative ideas. • Without roots, ideas lack evidence; without the kite, learning remains limited to known facts. • Grade 8 aims to develop young scientists who observe carefully and think creatively. Marks: 5 | Difficulty: Difficult | Bloom: Analyse | Topic: Light & Moon Q4. How does the study of light in Grade 8 connect everyday objects to celestial phenomena? Model Answer: • Reflection from flat/curved mirrors and refraction through lenses explain images in spoons and corrective glasses. • Rough surfaces also reflect light – so does the Moon. • Relative positions of Earth, Moon and Sun illuminate different parts of the Moon → phases. • Observing these periodic phases, together with sunrises and sunsets, led to the first calendars. • Thus everyday optics is linked to motions of celestial objects that shape our time-keeping. Marks: 5 | Difficulty: Difficult | Bloom: Evaluate | Topic: Earth & Climate Q5. Explain why Earth is described as ‘just right’ for life and what threatens this balance. Model Answer: • Perfect distance from the Sun keeps water liquid. • Atmosphere supplies oxygen and shields from harmful UV rays. • Complex ecosystems of interdependent organisms thrive under these conditions. • Human activities can cause small temperature changes, disrupting climate patterns with dangerous consequences. • Humans are both the source of the problem and the possible solution; science must guide protective action. Marks: 5 | Difficulty: Difficult | Bloom: Create | Topic: Science in Everyday Life Q6. “Science is everywhere – you don’t need a fancy laboratory.” Justify this statement with examples from the chapter and suggest how a student can begin investigating at home. Model Answer: • The chapter uses the kitchen and the puffing of a puri/phulka/batura as a scientific puzzle. • Controllable variables and observable outcomes can be studied with everyday materials. • Simple questions (“What happens if…?”) start the process.

Premium CBSE/KV Question Bank | Class 8 Science Ch-1 | Page 13 • Student can begin by choosing one variable (e.g., oil temperature), keeping dough identical, recording puff time and appearance, and asking follow-up questions. • Careful notes and changing one factor at a time turn the kitchen into a laboratory of curiosity.

Premium CBSE/KV Question Bank | Class 8 Science Ch-1 | Page 14 SECTION F – COMPETENCY-BASED QUESTIONS (8 Questions) Real-life situations testing application, reasoning and decision-making. Marks: 3–4 | Difficulty: Difficult | Bloom: Create | Topic: Investigation Design Q1. Your younger sibling asks why one side of a puri is thinner. How would you turn this into a scientific investigation at home? List the steps. Model Answer: • Frame a question: What factors affect how a puri puffs and which side becomes thinner? • List variables to control (thickness, flour, oil temperature, dropping method). • Decide observations (puff yes/no, time, thickness of sides). • Change one variable at a time; record everything. • Compare results and ask further questions. Marks: 3–4 | Difficulty: Difficult | Bloom: Create | Topic: Controlled Experiment Q2. A student wants to test whether oil temperature affects puri puffing. Design a fair test. Model Answer: • Keep dough thickness, size, flour type and dropping method identical. • Prepare three oil temperatures (e.g., moderately hot, hot, very hot). • Fry identical dough circles one by one; record time to puff and final appearance. • Compare results to see the effect of temperature alone. Marks: 3–4 | Difficulty: Moderate | Bloom: Evaluate | Topic: Nature of Science Q3. During a class discussion a student says “Science is only about memorising facts.” How would you respond using ideas from Chapter 1? Model Answer: • Chapter emphasises learning how to find new facts, not only learning existing ones. • Investigation = focused questions + experiments + observations that improve understanding. • Even simple phenomena (puri puffing) are not fully understood – science is evolving. • Students become young investigators exploring real-world puzzles. Marks: 3–4 | Difficulty: Moderate | Bloom: Apply | Topic: Pressure & Weather Q4. You notice a gentle breeze on some days and strong winds on others. How does the chapter’s idea of pressure help explain this? Model Answer: • Air movement is driven by pressure differences. • Small difference → gentle breeze. • Larger difference → strong winds; still larger → possible cyclones. • Understanding force distributed over area (pressure) explains these weather events. Marks: 3–4 | Difficulty: Moderate | Bloom: Apply | Topic: Moon & Calendars Q5. A calendar on the classroom wall shows dates linked to lunar months. Connect this to the chapter’s discussion of the Moon. Model Answer: • Moon phases arise from relative positions of Earth, Moon and Sun. • Periodic observation of these phases (with sunrises/sunsets) allowed humans to create the first calendars. • Thus everyday time-keeping is linked to celestial motions studied through careful observation. Marks: 3–4 | Difficulty: Difficult | Bloom: Evaluate | Topic: Climate Q6. Your family is discussing climate change news. Using the chapter, explain why science is important in this context. Model Answer: • Human activities can change Earth’s temperature and disrupt climate patterns. • Observing, measuring and experimenting – the core of science – help us understand these changes. • Science can guide actions to protect the balance that makes Earth habitable. • We are both the problem and the possible solution. Marks: 3–4 | Difficulty: Difficult | Bloom: Create | Topic: Symbolism in Practice Q7. Suggest two ways a Class 8 student can practise ‘staying rooted’ and two ways to let the ‘kite soar’ while studying science. Model Answer:

Premium CBSE/KV Question Bank | Class 8 Science Ch-1 | Page 15 • Rooted: Careful observation of everyday events; recording data accurately; linking learning to local environment and heritage. • Kite: Asking new “what if” questions; designing simple experiments; imagining solutions to larger problems such as climate challenges. Marks: 3–4 | Difficulty: Difficult | Bloom: Evaluate | Topic: Role of Young Scientists Q8. Why does the chapter say that challenges ahead won’t always be easy, yet still encourage students to try? Model Answer: • Climate and planetary challenges are complex and urgent. • The same scientific principles (observe, measure, experiment) are key to understanding and protecting life’s balance. • With Curiosity as guide, students can contribute to solutions – becoming investigators rather than only learners.

Premium CBSE/KV Question Bank | Class 8 Science Ch-1 | Page 16 SECTION G – ASSERTION & REASON (6 Questions) Directions: Assertion (A) is followed by Reason (R). Choose: (a) Both A and R true and R explains A (b) Both A and R true but R does not explain A (c) A true, R false (d) A false, R true Marks: 1 | Difficulty: Moderate | Bloom: Understand | Topic: Symbolism Q1. Assertion (A): The root symbol on left-hand pages represents the foundation of knowledge. Reason (R): It keeps us connected to our environment, traditions and cultural and natural heritage. Answer: (a) Explanation: Both true; R correctly explains the meaning of the root symbol. Marks: 1 | Difficulty: Moderate | Bloom: Apply | Topic: Controlled Experiments Q2. Assertion (A): Investigation in science requires changing many variables at the same time. Reason (R): Changing only one variable at a time helps us see the effect of that variable clearly. Answer: (d) Explanation: A is false; R is true – fair tests change one factor while keeping others constant. Marks: 1 | Difficulty: Moderate | Bloom: Understand | Topic: Earth Q3. Assertion (A): Earth’s atmosphere protects us from harmful ultraviolet rays. Reason (R): The atmosphere also provides the oxygen we breathe. Answer: (b) Explanation: Both statements true, but R does not explain the UV-shielding role; both are separate benefits. Marks: 1 | Difficulty: Moderate | Bloom: Understand | Topic: Moon Phases Q4. Assertion (A): Phases of the Moon are caused by clouds covering different parts of the Moon. Reason (R): Relative positions of Earth, Moon and Sun determine which part of the Moon is illuminated. Answer: (d) Explanation: A is false; R is true and gives the correct explanation. Marks: 1 | Difficulty: Moderate | Bloom: Apply | Topic: Science Everywhere Q5. Assertion (A): Science is everywhere and does not always need a fancy laboratory. Reason (R): Even the kitchen can be a place for careful observation and simple experiments. Answer: (a) Explanation: Both true; the kitchen example supports the assertion. Marks: 1 | Difficulty: Difficult | Bloom: Evaluate | Topic: Climate Q6. Assertion (A): Human activities have no effect on Earth’s climate. Reason (R): Small changes in temperature caused by humans can disrupt climate patterns. Answer: (d) Explanation: A is false; R is true – the chapter stresses human influence and responsibility.

Premium CBSE/KV Question Bank | Class 8 Science Ch-1 | Page 17 SECTION H – CASE-BASED QUESTIONS (3 Cases) Read the passage carefully and answer the questions that follow. Case Study 1 – The Puri Puzzle A student noticed that a puri puffs up like a balloon in hot oil and one side becomes thinner. She decided to investigate. She listed possible factors: thickness of dough, type of flour, temperature of oil, and the way the dough is dropped. She decided to change only the oil temperature while keeping dough thickness and dropping method the same. She recorded whether the puri puffed, the time taken, and any smoke or smell. Marks: 1–2 | Difficulty: Moderate | Bloom: Apply | Topic: Investigation Q1.1. Which scientific practice is the student following by changing only oil temperature? Answer: Controlling variables / fair test – changing one factor at a time while keeping others constant. Marks: 1–2 | Difficulty: Moderate | Bloom: Apply | Topic: Investigation Q1.2. Name two observations she planned to record. Answer: Whether the puri puffed (yes/no); time taken to puff; presence of smoke or smell (any two). Marks: 1–2 | Difficulty: Difficult | Bloom: Create | Topic: Investigation Q1.3. Suggest one further question she could ask after the first round of experiments. Answer: Do puris puff better when made from fresh dough or stored dough? / What happens if a hole is pricked before frying? (any valid follow-up) Case Study 2 – Root and Kite On every left-hand page of the textbook a root is drawn; on every right-hand page a kite soars. The authors explain that investigation works best when we balance the solid ground of careful observation with the freedom of creative thinking. Marks: 1–2 | Difficulty: Moderate | Bloom: Understand | Topic: Symbolism Q2.1. What does the root symbolise? Answer: Deep, solid foundation of knowledge connected to environment, traditions and cultural/natural heritage. Marks: 1–2 | Difficulty: Moderate | Bloom: Understand | Topic: Symbolism Q2.2. What does the kite remind students to do? Answer: Allow curiosity to take flight and explore the unknown while staying grounded in observation. Marks: 1–2 | Difficulty: Difficult | Bloom: Evaluate | Topic: Symbolism Q2.3. Why is the balance between root and kite important for a young scientist? Answer: Without careful observation (root) ideas lack evidence; without creative curiosity (kite) learning stays limited. Both together produce reliable and imaginative science. Case Study 3 – Earth and Climate The final part of the chapter notes that Earth lies at the perfect distance from the Sun, has liquid water and a protective atmosphere. Yet human activities can cause small temperature changes that disrupt climate patterns. The text states that we are at the heart of both the problem and any possible solution. Marks: 1–2 | Difficulty: Moderate | Bloom: Understand | Topic: Earth & Climate Q3.1. Give two reasons why Earth is described as ‘just right’ for life. Answer: Perfect distance from Sun keeps water liquid; atmosphere provides oxygen and shields from harmful UV rays. Marks: 1–2 | Difficulty: Difficult | Bloom: Analyse | Topic: Earth & Climate Q3.2. What is meant by ‘we are at the heart of both the problem and the solution’? Answer: Humans influence climate through activities (problem) but can also use science to understand changes and guide protective actions (solution). Marks: 1–2 | Difficulty: Moderate | Bloom: Apply | Topic: Earth & Climate Q3.3. Which scientific practices does the chapter say will help protect Earth’s balance? Answer: Observing, measuring and experimenting – the same principles that guide the middle-school science journey.

Premium CBSE/KV Question Bank | Class 8 Science Ch-1 | Page 18 SECTION I – SOURCE-BASED QUESTIONS (3 Sets) Study the given information and answer the questions. Source Set 1 – Journey Overview “This year, our investigative adventure will take us on a journey from the tiny microbes we can’t see to planet-wide challenges we can’t ignore… We will start by examining something as small as a single drop of water… Then electric current… forces… pressure… particles… light… Moon phases… ecosystems… and finally what makes Earth ‘just right’ for life.” Marks: 1 | Difficulty: Moderate | Bloom: Remember | Topic: Overview Q1.1. What is the starting point of the Grade 8 science journey? Answer: Examining tiny microbes in a single drop of water (invisible living world). Marks: 1 | Difficulty: Moderate | Bloom: Remember | Topic: Overview Q1.2. Name three intermediate topics listed in the journey. Answer: Electric current / forces / pressure / particles of matter / light / Moon phases / ecosystems (any three). Marks: 1 | Difficulty: Moderate | Bloom: Understand | Topic: Overview Q1.3. What is the final focus of the journey? Answer: Understanding what makes Earth suitable for life and recognising the climate challenges it faces. Source Set 2 – Systematic Investigation “It is better to change only one thing at a time while keeping the other conditions same… It is also a good idea to keep notes of everything that you see and sense… After doing one round of experiments, you may think of more questions… This is exactly how all scientific experiments, from simple to the most complicated are done.” Marks: 1–2 | Difficulty: Moderate | Bloom: Understand | Topic: Scientific Method Q2.1. Why should only one variable be changed at a time? Answer: So that the effect of that single variable can be clearly observed and conclusions remain reliable. Marks: 1–2 | Difficulty: Moderate | Bloom: Apply | Topic: Scientific Method Q2.2. What should be recorded during an experiment? Answer: Everything seen and sensed – e.g., appearance, time, smell, smoke, sound, etc. Marks: 1–2 | Difficulty: Difficult | Bloom: Analyse | Topic: Scientific Method Q2.3. What happens after one round of experiments according to the text? Answer: New questions arise, leading to further investigation – the process is continuous. Source Set 3 – Science and Society “At the heart of both the problem—and any possible solution—is us. We are the ones influencing Earth’s climate. But we are also the ones who can—and must—use science to understand these changes and guide our actions… We hope some of you will try to solve these difficult problems with Curiosity as your guide.” Marks: 1–2 | Difficulty: Moderate | Bloom: Remember | Topic: Climate & Responsibility Q3.1. Who is described as being at the heart of both the climate problem and its solution? Answer: We / human beings. Marks: 1–2 | Difficulty: Moderate | Bloom: Understand | Topic: Climate & Responsibility Q3.2. What role must science play according to the passage? Answer: Help us understand climate changes and guide our actions to protect Earth’s balance. Marks: 1–2 | Difficulty: Difficult | Bloom: Evaluate | Topic: Climate & Responsibility Q3.3. What invitation does the chapter extend to students? Answer: To try to solve difficult planetary problems with Curiosity (the spirit of investigation) as their guide.

Premium CBSE/KV Question Bank | Class 8 Science Ch-1 | Page 19 SECTION J – HOTS (6 Questions) These questions require critical thinking, analysis and evaluation. Marks: 4–5 | Difficulty: Difficult | Bloom: Evaluate | Topic: Nature of Science Q1. “Even the simple everyday observation of a puri puffing is not really completely understood by scientists today.” What does this statement tell us about the nature of science? Model Answer: • Science is an ongoing process; many everyday phenomena still hold unanswered questions. • Complete understanding is not always available; investigation continues. • Students are invited to participate in this open-ended enquiry rather than only memorise finished answers. • Humility and curiosity remain essential even for professional scientists. Marks: 4–5 | Difficulty: Difficult | Bloom: Analyse | Topic: Learning Progression Q2. Compare the approach of Grade 6, Grade 7 and Grade 8 to science learning as described in the chapter. How does each stage prepare students for the next? Model Answer: • Grade 6: Wonder and simple why/how questions – builds curiosity. • Grade 7: Science evolves; answers open new questions – builds flexibility of thought. • Grade 8: Focused questions + experimental design + explanation – builds investigative skill. • Each stage scaffolds the next, moving from wonder → evolving ideas → systematic investigation. Marks: 4–5 | Difficulty: Difficult | Bloom: Create | Topic: Experiential Learning Q3. Design a short classroom activity that helps students experience both the ‘root’ and the ‘kite’ aspects of investigation. Model Answer: • Root: Observe a local phenomenon carefully (e.g., how a leaf floats or how ice melts) and record detailed notes. • Kite: Brainstorm creative “what if” questions and design one simple test of a new idea. • Share findings and reflect on how observation and imagination worked together. • Emphasise that both careful data and creative questions are needed. Marks: 4–5 | Difficulty: Difficult | Bloom: Evaluate | Topic: Pedagogy of the Chapter Q4. Why might the authors have chosen the puffing of a puri as the central example of scientific investigation rather than a laboratory experiment? Model Answer: • It is familiar, accessible and requires no special equipment – science is everywhere. • It shows that complex science can start from everyday observation. • It models variable control and systematic recording in a context students can replicate at home. • It demonstrates that even “simple” phenomena can be scientifically deep and not fully solved. Marks: 4–5 | Difficulty: Difficult | Bloom: Analyse | Topic: Science & Society Q5. The chapter links calendars on Earth to motions of the Moon and Sun. What larger message about science does this connection convey? Model Answer: • Everyday human practices (time-keeping) are rooted in careful observation of nature. • Science connects local experience to celestial phenomena. • Observation + pattern recognition → practical tools (calendars). • Encourages students to look for similar hidden connections between daily life and larger natural systems. Marks: 4–5 | Difficulty: Difficult | Bloom: Create | Topic: Curiosity & Investigation Q6. If you were to write one new “Probe and ponder” question for the first page of this chapter, what would it be and why? Model Answer: • Example: “What everyday object in your home could become the starting point of a scientific investigation, and what one variable would you change first?” • Reason: It invites personal ownership of enquiry, applies the chapter’s method immediately, and balances root (observation of home) with kite (creative choice of variable).

Premium CBSE/KV Question Bank | Class 8 Science Ch-1 | Page 20 PREPARED BY Ekaparna Sahu B.Sc., M.Sc., B.Ed., M.Ed. Premium KV & CBSE Competency-Based Question Bank Class 8 Science | Chapter 1 Exploring the Investigative World of Science Academic Session 2026–27 Based exclusively on NCERT Textbook – Curiosity (Science) Grade 8 Aligned with CBSE Competency-Based Assessment Pattern & KVS Guidelines NEP 2020 | Bloom's Taxonomy | CBE Framework Practice • Learn • Revise • Excel © For educational use | Original questions based on NCERT content

Premium CBSE/KV Question Bank | Class 8 Science Ch-2 | Page 2 TABLE OF CONTENTS Student Instructions Section A – Multiple Choice Questions (MCQs) .............. 20 Qs Section B – Very Short Answer Questions .................... 10 Qs Section C – Short Answer Questions – I (2 Marks) ......... 8 Qs Section D – Short Answer Questions – II (3 Marks) ........ 8 Qs Section E – Long Answer Questions (5 Marks) .............. 6 Qs Section F – Competency-Based Questions ................... 8 Qs Section G – Assertion & Reason Questions ................. 6 Qs Section H – Case-Based Questions ......................... 3 Cases Section I – Source-Based Questions ....................... 3 Sets Section J – HOTS (Higher Order Thinking Skills) .......... 6 Qs Prepared By / Credits Difficulty Distribution: Easy ~30% | Moderate ~50% | Difficult ~20% Total Questions: Approximately 80 high-quality competency-based items

Premium CBSE/KV Question Bank | Class 8 Science Ch-2 | Page 3 STUDENT INSTRUCTIONS 1. Read every question carefully before answering. 2. For MCQs, choose the most appropriate option (A/B/C/D). 3. Write answers in clear, concise language using NCERT terminology. 4. For short and long answers, use bullet points where helpful and highlight key terms. 5. Time management: Allocate time according to marks (approx. 1–1.5 min per mark). 6. Diagrams, if required, should be neat, labelled and drawn with pencil. 7. Assertion–Reason: Select the correct option based on both statements. 8. Case-based and source-based questions test interpretation and application – read the passage fully. 9. HOTS questions require critical thinking; support answers with scientific reasoning. 10. This question bank follows the latest CBSE 2026–27 competency-based pattern and KVS guidelines. Bloom's Taxonomy Levels used: Remember | Understand | Apply | Analyse | Evaluate | Create

Premium CBSE/KV Question Bank | Class 8 Science Ch-2 | Page 4 SECTION A – MULTIPLE CHOICE QUESTIONS (20 Questions) Each question carries 1 mark. Choose the correct option. Marks: 1 | Difficulty: Easy | Bloom: Remember | Topic: Discovery of Microorganisms Q1. Who is known as the Father of Microbiology? (a) Robert Hooke (b) Antonie van Leeuwenhoek (c) Louis Pasteur (d) Ananda Mohan Chakrabarty Answer: (b) Antonie van Leeuwenhoek Explanation: He was the first to clearly see and describe bacteria and blood cells using improved lenses. Marks: 1 | Difficulty: Easy | Bloom: Remember | Topic: What is a Cell? Q2. Robert Hooke coined the term ‘cell’ after observing a thin slice of: (a) Onion peel (b) Cork (c) Cheek cells (d) Leaf Answer: (b) Cork Explanation: In 1665, Hooke observed empty compartments in cork that reminded him of a honeycomb and called them cells. Marks: 1 | Difficulty: Easy | Bloom: Understand | Topic: Structure of Cell Q3. Which of the following is present in plant cells but usually absent or very small in animal cells? (a) Nucleus (b) Cell membrane (c) Large vacuole (d) Cytoplasm Answer: (c) Large vacuole Explanation: Plant cells have a large vacuole for storage and support; animal cells have small or no vacuoles. Marks: 1 | Difficulty: Easy | Bloom: Remember | Topic: Structure of Cell Q4. The outer layer that provides rigidity and strength to plant cells is the: (a) Cell membrane (b) Cell wall (c) Cytoplasm (d) Nucleus Answer: (b) Cell wall Explanation: The cell wall is an extra outer layer in plant cells that gives rigidity and strength. Marks: 1 | Difficulty: Easy | Bloom: Understand | Topic: Microorganisms and Food Q5. Yeast is used in baking because it produces: (a) Oxygen (b) Carbon dioxide (c) Nitrogen (d) Hydrogen Answer: (b) Carbon dioxide Explanation: Yeast breaks down food releasing COn which forms bubbles and makes dough soft and fluffy. Marks: 1 | Difficulty: Easy | Bloom: Remember | Topic: Microorganisms and Food Q6. Lactobacillus is useful in the preparation of: (a) Bread (b) Curd (c) Alcohol (d) Biogas Answer: (b) Curd Explanation: Lactobacillus ferments milk sugar (lactose) producing lactic acid which turns milk into curd. Marks: 1 | Difficulty: Easy | Bloom: Remember | Topic: Nitrogen Fixation Q7. Rhizobium bacteria live in the root nodules of:

Premium CBSE/KV Question Bank | Class 8 Science Ch-2 | Page 5 (a) Wheat (b) Rice (c) Legumes (peas, beans, lentils) (d) Maize Answer: (c) Legumes (peas, beans, lentils) Explanation: Rhizobium traps atmospheric nitrogen and makes it available to leguminous plants. Marks: 1 | Difficulty: Moderate | Bloom: Understand | Topic: Levels of Organisation Q8. The correct sequence of levels of organisation in a living organism is: (a) Tissue → Cell → Organ → Organ system → Organism (b) Cell → Tissue → Organ → Organ system → Organism (c) Organ → Tissue → Cell → Organism → Organ system (d) Cell → Organ → Tissue → Organism → Organ system Answer: (b) Cell → Tissue → Organ → Organ system → Organism Explanation: Cells form tissues; tissues form organs; organs form organ systems; organ systems form the organism. Marks: 1 | Difficulty: Moderate | Bloom: Understand | Topic: Bacterial Cell Q9. Which structure is found only in bacterial cells among the following? (a) Nucleus (b) Nucleoid (c) Chloroplast (d) Large vacuole Answer: (b) Nucleoid Explanation: Bacteria lack a well-defined nucleus and nuclear membrane; genetic material is in the nucleoid region. Marks: 1 | Difficulty: Moderate | Bloom: Understand | Topic: Microalgae Q10. Microalgae such as Spirulina are called superfoods mainly because they are rich in: (a) Fat (b) Protein and Vitamin Bnn (c) Sugar only (d) Cellulose Answer: (b) Protein and Vitamin Bnn Explanation: Spirulina has more than 60% protein and is a good source of Vitamin Bnn. Marks: 1 | Difficulty: Easy | Bloom: Remember | Topic: Role in Environment Q11. The process by which microorganisms break down complex substances of dead plants and animals into simpler nutrient-rich substances is called: (a) Photosynthesis (b) Fermentation (c) Decomposition (d) Respiration Answer: (c) Decomposition Explanation: Decomposers recycle nutrients back into the soil, helping plants grow and cleaning the environment. Marks: 1 | Difficulty: Moderate | Bloom: Apply | Topic: Variation in Cell Shape Q12. A nerve cell is long and branched mainly to: (a) Store food (b) Carry messages quickly to different parts of the body (c) Provide rigidity (d) Produce digestive juices Answer: (b) Carry messages quickly to different parts of the body Explanation: The elongated and branched structure of neurons helps them reach different body parts and transmit messages rapidly. Marks: 1 | Difficulty: Moderate | Bloom: Understand | Topic: Viruses Q13. Viruses are considered different from other microorganisms because they: (a) Have a cell wall (b) Are multicellular (c) Multiply only inside a living host cell (d) Perform photosynthesis Answer: (c) Multiply only inside a living host cell Explanation: Viruses are acellular and can reproduce only when they enter a living cell.

Premium CBSE/KV Question Bank | Class 8 Science Ch-2 | Page 6 Marks: 1 | Difficulty: Moderate | Bloom: Apply | Topic: Yeast in Baking Q14. In the experiment with dough, the volume of dough increases when yeast is added because: (a) Yeast absorbs water (b) Yeast produces carbon dioxide gas (c) Sugar expands on heating (d) Flour absorbs air Answer: (b) Yeast produces carbon dioxide gas Explanation: During respiration, yeast releases COn which forms bubbles making the dough rise and become fluffy. Marks: 1 | Difficulty: Moderate | Bloom: Analyse | Topic: Structure of Cell Q15. Which of the following is NOT a basic part common to most cells? (a) Cell membrane (b) Cytoplasm (c) Nucleus (d) Chloroplast Answer: (d) Chloroplast Explanation: Chloroplasts are present only in green plant cells (and some algae); they are not common to all cells. Marks: 1 | Difficulty: Moderate | Bloom: Remember | Topic: Be a Scientist Q16. Ananda Mohan Chakrabarty is remembered for developing a bacterium that could: (a) Produce curd (b) Fix nitrogen (c) Break down oil spills (d) Make bread soft Answer: (c) Break down oil spills Explanation: He developed a special bacterium (patented in 1980) that could clean oil spills, solving an environmental problem. Marks: 1 | Difficulty: Easy | Bloom: Remember | Topic: Size of Cells Q17. The largest known single cell in the living world is the yolk of: (a) Hen’s egg (b) Ostrich egg (c) Frog’s egg (d) Fish egg Answer: (b) Ostrich egg Explanation: The yolk of an ostrich egg measures about 130–170 mm in diameter and is the largest known cell. Marks: 1 | Difficulty: Moderate | Bloom: Understand | Topic: Biogas Q18. Biogas produced by microorganisms mainly contains: (a) Oxygen and nitrogen (b) Carbon dioxide and methane (c) Hydrogen and oxygen (d) Nitrogen and hydrogen Answer: (b) Carbon dioxide and methane Explanation: Anaerobic bacteria decompose organic waste releasing a mixture of COn and methane used as fuel. Marks: 1 | Difficulty: Difficult | Bloom: Analyse | Topic: Human Cheek Cells Q19. Cheek cells appear polygonal under the microscope mainly because: (a) They have a thick cell wall (b) They form a protective lining and are thin and flat (c) They contain chloroplasts (d) They are muscle cells Answer: (b) They form a protective lining and are thin and flat Explanation: Inner cheek cells are thin and flat to form a protective lining on the inner surface of the mouth. Marks: 1 | Difficulty: Difficult | Bloom: Evaluate | Topic: Importance of Microbes Q20. If microorganisms did not exist on Earth, which of the following would be most severely affected? (a) Only production of bread (b) Recycling of nutrients and cleaning of environment (c) Only formation of curd (d) Only oxygen production by plants Answer: (b) Recycling of nutrients and cleaning of environment

Premium CBSE/KV Question Bank | Class 8 Science Ch-2 | Page 7 Explanation: Without decomposers, dead matter would accumulate and nutrients would not return to the soil, disrupting ecosystems.

Premium CBSE/KV Question Bank | Class 8 Science Ch-2 | Page 8 SECTION B – VERY SHORT ANSWER QUESTIONS (10 Questions) Answer in one word or one sentence. Each question carries 1 mark. Marks: 1 | Difficulty: Easy | Bloom: Remember | Topic: History of Microscopy Q1. Name the book published by Robert Hooke in 1665. Answer: Micrographia Explanation: It contained detailed drawings of tiny objects seen through a microscope. Marks: 1 | Difficulty: Easy | Bloom: Remember | Topic: What is a Cell? Q2. What is the basic structural and functional unit of life? Answer: Cell Explanation: All living organisms are made up of one or more cells. Marks: 1 | Difficulty: Easy | Bloom: Remember | Topic: Activity – Onion Peel Q3. Name the stain used to observe onion peel cells. Answer: Safranin Explanation: Safranin gives a pinkish colour to the cells making them clearly visible. Marks: 1 | Difficulty: Easy | Bloom: Remember | Topic: Activity – Cheek Cells Q4. Which stain is used for observing human cheek cells? Answer: Methylene blue Explanation: It increases contrast and improves visibility under the microscope. Marks: 1 | Difficulty: Easy | Bloom: Remember | Topic: Plastids Q5. Name the green pigment present in chloroplasts. Answer: Chlorophyll Explanation: Chlorophyll helps in photosynthesis by capturing sunlight. Marks: 1 | Difficulty: Easy | Bloom: Understand | Topic: Microorganisms Q6. What are unicellular organisms? Answer: Organisms made up of a single cell (e.g., bacteria, Amoeba). Explanation: They perform all life functions within one cell. Marks: 1 | Difficulty: Moderate | Bloom: Remember | Topic: Microorganisms and Food Q7. Name one microorganism used in the fermentation of idli and dosa batter. Answer: Lactobacillus (or bacteria involved in fermentation) Explanation: Certain bacteria help ferment the batter making it soft and fluffy. Marks: 1 | Difficulty: Moderate | Bloom: Understand | Topic: Structure of Cell Q8. What is the function of the nucleus in a cell? Answer: It regulates all activities of the cell and also regulates growth. Explanation: The nucleus is the control centre of the cell. Marks: 1 | Difficulty: Easy | Bloom: Understand | Topic: What are Microorganisms? Q9. Define microorganisms. Answer: Living organisms that are too small to be seen with the naked eye and can only be observed under a microscope. Explanation: They include bacteria, protozoa, fungi, some algae, etc. Marks: 1 | Difficulty: Easy | Bloom: Remember | Topic: Yeast Q10. Name the gas released by yeast that makes bread soft and fluffy. Answer: Carbon dioxide (COn) Explanation: COn forms bubbles in the dough during fermentation.

Premium CBSE/KV Question Bank | Class 8 Science Ch-2 | Page 9 SECTION C – SHORT ANSWER QUESTIONS – I (8 Questions | 2 Marks each) Answer in 3–4 lines. Marks: 2 | Difficulty: Easy | Bloom: Understand | Topic: Discovery of Cell Q1. Why did Robert Hooke call the compartments he saw in cork ‘cells’? Model Answer: • When Hooke observed a thin slice of cork under his microscope, he saw many small empty spaces. • These compartments reminded him of a honeycomb. • He called each small space a cell. This was the first use of the word ‘cell’ in science. Marks: 2 | Difficulty: Easy | Bloom: Understand | Topic: Plant vs Animal Cell Q2. List any two differences between plant cells and animal cells. Model Answer: • Plant cells have a cell wall; animal cells do not. • Plant cells usually have a large vacuole and plastids (chloroplasts); animal cells have small or no vacuoles and lack chloroplasts. Marks: 2 | Difficulty: Easy | Bloom: Understand | Topic: Cell Structure Q3. What is the role of the cell membrane? Model Answer: • The cell membrane encloses the cytoplasm and nucleus. • It is porous and allows entry of materials essential for life processes and exit of waste materials. • It separates one cell from another. Marks: 2 | Difficulty: Moderate | Bloom: Apply | Topic: Cell Shape and Function Q4. Why are muscle cells spindle-shaped? Model Answer: • Muscle cells are thin, flexible and spindle-shaped. • This shape allows them to contract and relax in a wave-like manner. • This helps in movements such as pushing food down the food pipe. Marks: 2 | Difficulty: Moderate | Bloom: Understand | Topic: Role of Microbes Q5. How do microorganisms help in cleaning the environment? Model Answer: • Bacteria and fungi act as decomposers. • They break down complex substances of dead plants and animals into simpler, nutrient-rich substances. • This process of decomposition recycles nutrients back to the soil and cleans the surroundings. Marks: 2 | Difficulty: Moderate | Bloom: Apply | Topic: Yeast in Baking Q6. What happens when yeast is added to flour dough with sugar and warm water? Model Answer: • Yeast grows well in warm conditions and respires, breaking down sugar. • It releases carbon dioxide which forms bubbles making the dough soft and fluffy. • A small amount of alcohol is also produced, giving a characteristic smell. Marks: 2 | Difficulty: Moderate | Bloom: Analyse | Topic: Curd Formation Q7. Why is curd formed in lukewarm milk but not (or very slowly) in cold milk when a little curd is added? Model Answer: • Lactobacillus bacteria present in curd grow well in warm conditions. • They ferment lactose producing lactic acid which turns milk into curd. • Cold temperature slows or stops their growth; hence curd does not form properly in cold milk. Marks: 2 | Difficulty: Moderate | Bloom: Understand | Topic: Microalgae Q8. State two uses of microalgae. Model Answer: • Microalgae produce more than half of Earth’s oxygen and serve as food for aquatic animals. • Some (e.g., Spirulina, Chlorella) are used as health supplements; they also help clean water and can be used to make biofuel.

Premium CBSE/KV Question Bank | Class 8 Science Ch-2 | Page 10 SECTION D – SHORT ANSWER QUESTIONS – II (8 Questions | 3 Marks each) Answer in about 5 lines with structured points. Marks: 3 | Difficulty: Easy | Bloom: Understand | Topic: Cell Structure Q1. Describe the three main parts of a cell and one function of each. Model Answer: • Cell membrane: Outer covering; encloses cytoplasm and nucleus; porous – allows entry of useful materials and exit of wastes. • Cytoplasm: Jelly-like substance between cell membrane and nucleus; contains other components; most life processes occur here. • Nucleus: Round structure in the centre; regulates all cellular activities and growth. Marks: 3 | Difficulty: Moderate | Bloom: Apply | Topic: Cell Shape & Function Q2. Explain how the shape of a nerve cell is related to its function. Model Answer: • Nerve cells (neurons) are very long and have branches. • The elongated shape and branched structure help them reach different parts of the body. • This enables them to carry messages quickly from one part of the body to another. • Thus, structure is adapted to the function of rapid message transmission. Marks: 3 | Difficulty: Moderate | Bloom: Understand | Topic: Levels of Organisation Q3. What are the levels of organisation in the body of a multicellular organism? Give one example for each level in humans. Model Answer: • Cell → e.g., muscle cell • Tissue → group of similar cells, e.g., muscle tissue • Organ → e.g., stomach • Organ system → e.g., digestive system • Organism → complete human being Sequence: Cell → Tissue → Organ → Organ system → Organism Marks: 3 | Difficulty: Moderate | Bloom: Apply | Topic: Nitrogen Fixation Q4. How do Rhizobium bacteria benefit leguminous plants and the soil? Model Answer: • Rhizobium lives in root nodules of legumes (peas, beans, lentils). • It traps nitrogen from the air and converts it into a form useful for plants. • This helps plants grow better without chemical fertilisers. • Farmers grow legumes in rotation to naturally increase soil nitrogen and keep soil healthy. Marks: 3 | Difficulty: Moderate | Bloom: Apply | Topic: Activity – Soil Suspension Q5. Describe the activity to observe microorganisms in soil suspension. Model Answer: • Collect moist soil in a beaker (use spoon/gloves). • Add water, stir and allow the mixture to settle (soil suspension). • Take a drop from the top layer with a dropper, place on a slide, cover with coverslip. • Observe under microscope – small moving organisms (microbes) can be seen. Marks: 3 | Difficulty: Easy | Bloom: Understand | Topic: Unicellular vs Multicellular Q6. Differentiate between unicellular and multicellular organisms with examples. Model Answer: • Unicellular: Made of a single cell; perform all life functions in one cell. Examples: bacteria, Amoeba, yeast. • Multicellular: Made of many cells; cells specialise and cooperate. Examples: plants, animals, humans, mould (some fungi). Marks: 3 | Difficulty: Moderate | Bloom: Evaluate | Topic: Cell as Basic Unit Q7. Why is the cell considered the basic unit of life? Model Answer: • All living organisms (plants, animals, microbes) are made of one or more cells. • A single cell contains components that help perform life functions. • In multicellular organisms, cells specialise yet cooperate for survival.

Premium CBSE/KV Question Bank | Class 8 Science Ch-2 | Page 11 • Even unicellular organisms carry out all necessary functions within one cell. • Hence the cell is the structural and functional unit of life. Marks: 3 | Difficulty: Moderate | Bloom: Understand | Topic: Biogas Q8. Explain how biogas is produced and state two of its uses. Model Answer: • Certain bacteria and fungi live in oxygen-free environments and decompose plant and animal waste. • During this process they release a mixture of gases called biogas (mainly COn and methane). • Uses: cooking, heating, generating electricity, and even running vehicles.

Premium CBSE/KV Question Bank | Class 8 Science Ch-2 | Page 12 SECTION E – LONG ANSWER QUESTIONS (6 Questions | 5 Marks each) Answer in a structured manner (about 8 lines / points). Marks: 5 | Difficulty: Moderate | Bloom: Understand | Topic: Plant & Animal Cell Q1. Describe the structure of a typical plant cell and an animal cell. Highlight the differences with the help of labelled points. Model Answer: • Common parts: Cell membrane, cytoplasm, nucleus, mitochondria. • Plant cell only: Cell wall (rigidity), large vacuole (storage & support), chloroplasts (photosynthesis). • Animal cell: No cell wall; vacuoles small or absent; no chloroplasts. • Plant cells are usually rectangular and compact; animal cells vary more in shape. • Both have cytoplasm where most life processes occur and a nucleus that controls activities. Marks: 5 | Difficulty: Moderate | Bloom: Understand | Topic: History of Microscopy Q2. Explain the contributions of Robert Hooke and Antonie van Leeuwenhoek to the discovery of the microscopic world. Model Answer: • Robert Hooke (1665): Published Micrographia; observed cork under microscope (200–300×); coined the term cell. • He made detailed drawings of tiny objects never seen before. • Antonie van Leeuwenhoek (1660s): Made better lenses and more useful microscopes. • First person to clearly see and describe bacteria and blood cells. • Known as the Father of Microbiology. • Together they opened the invisible living world to science. Marks: 5 | Difficulty: Moderate | Bloom: Apply | Topic: Uses of Microbes Q3. Describe how microorganisms are useful in the kitchen and in agriculture. Give suitable examples. Model Answer: • Kitchen: Yeast produces COn making bread, cakes soft; Lactobacillus turns milk into curd; bacteria help ferment idli/dosa batter and bhatura dough. • Agriculture: Rhizobium in root nodules of legumes fixes atmospheric nitrogen, enriching soil; decomposers convert plant/animal waste into manure increasing soil fertility. • Microbes thus help in food preparation and natural fertilisation without chemical fertilisers. Marks: 5 | Difficulty: Difficult | Bloom: Evaluate | Topic: Importance of Decomposers Q4. What would happen if decomposer microorganisms disappeared from the Earth? Discuss with scientific reasoning. Model Answer: • Dead plants and animals would not be broken down. • Waste would accumulate, making the environment unclean and unhealthy. • Nutrients locked in dead matter would not return to the soil. • Plants would suffer from lack of essential nutrients; food chains would be disrupted. • Manure formation and nutrient recycling would stop. • Overall ecosystem balance and life on Earth would be severely threatened. Marks: 5 | Difficulty: Moderate | Bloom: Apply | Topic: Onion Peel Mount Q5. Explain the steps involved in preparing a temporary mount of onion peel. Why is glycerin and stain used? Model Answer: • Cut onion, pull thin transparent peel with forceps. • Place peel in safranin for ~30 seconds (stain colours cells pink for visibility). • Rinse in water to remove extra stain. • Place peel on slide; add drop of glycerin (prevents drying, improves clarity). • Lower coverslip carefully (no air bubbles); wipe excess glycerin. • Observe under microscope – rectangular cells with cell wall, membrane, cytoplasm, nucleus. Marks: 5 | Difficulty: Difficult | Bloom: Analyse | Topic: Diversity of Microbes Q6. Discuss the diversity of microorganisms and their occurrence. How does this diversity benefit humans and the environment? Model Answer: • Microbes include protozoa, algae, fungi, bacteria; some unicellular, some multicellular.

Premium CBSE/KV Question Bank | Class 8 Science Ch-2 | Page 13 • Found everywhere – water, soil, air, inside bodies, extreme environments (hot springs, cold zones). • Benefits: Decomposition & nutrient recycling; nitrogen fixation; food production (curd, bread); biogas; oxygen from microalgae; cleaning oil spills (engineered bacteria); health supplements (Spirulina). • Diversity ensures multiple ecological and human benefits while maintaining environmental balance.

Premium CBSE/KV Question Bank | Class 8 Science Ch-2 | Page 14 SECTION F – COMPETENCY-BASED QUESTIONS (8 Questions) Real-life situations testing application, reasoning and decision-making. Marks: 3–4 | Difficulty: Moderate | Bloom: Apply | Topic: Conditions for Microbial Growth Q1. Riya left a slice of bread near the sink and another in the refrigerator. After three days the one near the sink had cotton-like growth while the refrigerated one did not. What does this observation tell us about the conditions needed for microbial growth? Suggest one way to prevent food spoilage at home. Model Answer: • Microorganisms (mould/fungi) need optimal temperature, moisture and air to grow. • Warm, moist conditions near the sink favoured growth; cold refrigerator slowed or stopped it. • Prevention: Store food in refrigerator / airtight containers / keep dry and cool. Marks: 3–4 | Difficulty: Moderate | Bloom: Analyse | Topic: Nitrogen Fixation Q2. A farmer grows wheat and adds nitrogen fertiliser. His neighbour grows beans and does not add nitrogen fertiliser yet gets healthy crops. Explain the scientific reason and advise the first farmer on a sustainable practice. Model Answer: • Beans are legumes; Rhizobium in their root nodules fixes atmospheric nitrogen, so external fertiliser is not needed. • Wheat does not have this association, hence needs fertiliser. • Advice: Practise crop rotation with legumes to naturally enrich soil nitrogen and reduce chemical fertiliser use. Marks: 3–4 | Difficulty: Moderate | Bloom: Apply | Topic: Pond Water Microbes Q3. During a school picnic, students collected pond water and observed it under a foldable paper microscope. They saw irregular moving structures and greenish cells. Identify the likely groups of microorganisms and state one role of each in nature. Model Answer: • Irregular moving structures: Protozoa (e.g., Amoeba) – part of aquatic food chain / consume bacteria. • Greenish cells: Algae / microalgae – produce oxygen via photosynthesis and serve as food for aquatic animals. Marks: 3–4 | Difficulty: Easy | Bloom: Apply | Topic: Curd Formation Q4. Your mother adds a spoon of curd to warm milk and keeps it overnight to set. Next morning the milk has turned into curd. Explain the process and why she insists on warm (not boiling hot or ice-cold) milk. Model Answer: • Lactobacillus from the curd multiplies and ferments lactose into lactic acid, turning milk into curd. • Warm temperature is optimal for bacterial growth. • Boiling hot milk would kill the bacteria; ice-cold milk would slow growth drastically – hence lukewarm milk is ideal. Marks: 3–4 | Difficulty: Moderate | Bloom: Apply | Topic: Manure Formation Q5. Gardeners collect dry leaves and put them into pits. After some weeks the material turns into dark nutrient-rich manure. Name the process and the organisms responsible. Why is moisture and temperature important? Model Answer: • Process: Decomposition / composting. • Organisms: Bacteria and fungi present in soil. • Optimal temperature and moisture allow these microbes to grow and efficiently break down complex substances into simpler nutrient-rich manure. Marks: 3–4 | Difficulty: Difficult | Bloom: Create | Topic: Yeast Experiment Q6. A student wants to demonstrate that yeast produces a gas. Design a simple classroom experiment using balloons, sugar solution and yeast. What result is expected and how can the gas be identified? Model Answer: • Take two test tubes with sugar solution; add yeast only to one; attach balloons. • Keep in warm place. Balloon on yeast tube inflates due to COn. • Pass the gas through lime water – it turns milky, confirming carbon dioxide. Marks: 3–4 | Difficulty: Moderate | Bloom: Apply | Topic: Spirulina Q7. Spirulina farming is being promoted as a livelihood. List three conditions needed to grow Spirulina and two benefits of promoting its cultivation. Model Answer:

Premium CBSE/KV Question Bank | Class 8 Science Ch-2 | Page 15 • Conditions: Clear tank in bright place (not direct sun), moderate temperature, pond water with living Spirulina; stir twice a week; harvest after 3–6 weeks by filtering. • Benefits: Nutritious superfood (protein, Vitamin Bnn); income opportunity; helps food security and oxygen balance. Marks: 3–4 | Difficulty: Difficult | Bloom: Apply | Topic: Bioremediation Q8. An oil tanker spill has polluted a coastal area. How can knowledge of microorganisms help in cleaning? Name the scientist who worked on this idea. Model Answer: • Special bacteria can be used to break down oil (bioremediation). • Ananda Mohan Chakrabarty developed such a bacterium and received a patent in 1980. • Microbes offer an eco-friendly way to solve pollution problems.

Premium CBSE/KV Question Bank | Class 8 Science Ch-2 | Page 16 SECTION G – ASSERTION & REASON (6 Questions) Directions: In the following questions, a statement of Assertion (A) is followed by a statement of Reason (R). Mark the correct option: (a) Both A and R true and R explains A (b) Both A and R true but R does not explain A (c) A true, R false (d) A false, R true Marks: 1 | Difficulty: Easy | Bloom: Understand | Topic: Cell Wall Q1. Assertion (A): Plant cells have a rigid outer covering called the cell wall. Reason (R): The cell wall provides rigidity and strength to plants and keeps cells compact. Answer: (a) Explanation: Both statements are true and the reason correctly explains the assertion. Marks: 1 | Difficulty: Moderate | Bloom: Understand | Topic: Yeast Q2. Assertion (A): Yeast is used in the preparation of bread. Reason (R): Yeast produces oxygen which makes the dough rise. Answer: (c) Explanation: A is true; R is false – yeast produces carbon dioxide, not oxygen. Marks: 1 | Difficulty: Moderate | Bloom: Understand | Topic: Bacterial Cell Q3. Assertion (A): Bacteria do not have a well-defined nucleus. Reason (R): Bacterial genetic material is present in a region called nucleoid. Answer: (a) Explanation: Both true; nucleoid is the region containing genetic material without a nuclear membrane. Marks: 1 | Difficulty: Easy | Bloom: Evaluate | Topic: Beneficial vs Harmful Q4. Assertion (A): All microorganisms are harmful to humans. Reason (R): Microorganisms cause diseases in plants and animals. Answer: (d) Explanation: A is false (many microbes are beneficial); R is true but only for some microbes. Marks: 1 | Difficulty: Moderate | Bloom: Apply | Topic: Cell Shape Q5. Assertion (A): Nerve cells are long and branched. Reason (R): The shape of a cell is related to the function it performs. Answer: (a) Explanation: Both true; elongated branched shape helps neurons transmit messages to distant body parts. Marks: 1 | Difficulty: Difficult | Bloom: Analyse | Topic: Viruses Q6. Assertion (A): Viruses are considered living organisms under all conditions. Reason (R): Viruses can multiply only inside a living host cell. Answer: (d) Explanation: A is false (viruses are acellular and show living characteristics only inside host); R is true.

Premium CBSE/KV Question Bank | Class 8 Science Ch-2 | Page 17 SECTION H – CASE-BASED QUESTIONS (3 Cases) Read the passage carefully and answer the questions that follow. Case Study 1 A group of Class 8 students performed an activity. They took two bowls of flour, added sugar to both, and yeast only to bowl A. They kneaded both with warm water, covered them and kept them in a warm place. After 4–5 hours the dough in bowl A had risen, become fluffy and had a different smell, while bowl B showed little change. Marks: 1–2 | Difficulty: Easy | Bloom: Understand | Topic: Yeast & Fermentation Q1.1. Why did the dough in bowl A rise? Answer: Yeast respired and produced carbon dioxide gas which formed bubbles, making the dough rise and become fluffy. Marks: 1–2 | Difficulty: Moderate | Bloom: Apply | Topic: Yeast & Fermentation Q1.2. What is the role of sugar and warm water in this activity? Answer: Sugar is food for yeast; warm water provides optimal temperature for yeast growth and activity. Marks: 1–2 | Difficulty: Moderate | Bloom: Apply | Topic: Yeast & Fermentation Q1.3. Name one other food item that uses a similar microbial process and the microbe involved. Answer: Idli/dosa batter or bhatura – fermented by bacteria such as Lactobacillus; or bread/cakes – yeast. Case Study 2 Snehal dug two pits in her garden. In pit A she mixed fruit and vegetable peels with dried leaves. In pit B she put the same waste without dried leaves. She covered both with soil. After three weeks she observed differences in the contents of the two pits. Marks: 1–2 | Difficulty: Easy | Bloom: Understand | Topic: Decomposition Q2.1. What process is Snehal trying to demonstrate? Answer: Decomposition / formation of manure (composting) by microorganisms present in soil. Marks: 1–2 | Difficulty: Difficult | Bloom: Analyse | Topic: Decomposition Q2.2. Why might the waste in pit A decompose better than in pit B? Answer: Mixing with dried leaves improves aeration and carbon-nitrogen balance, helping microbes work more efficiently. Marks: 1–2 | Difficulty: Moderate | Bloom: Apply | Topic: Decomposition Q2.3. Name the organisms mainly responsible and one benefit of the end product. Answer: Bacteria and fungi. The manure is rich in nutrients and increases soil fertility. Case Study 3 In an experiment, Aanandi took two test tubes with sugar solution. She added yeast only to test tube B and attached incompletely inflated balloons to both. After 3–4 hours the balloon on B inflated. She then transferred the gas from balloon B into lime water, which turned milky. Marks: 1–2 | Difficulty: Moderate | Bloom: Apply | Topic: Yeast Experiment Q3.1. What gas inflated the balloon on test tube B? How do you know? Answer: Carbon dioxide. Lime water turning milky is the confirmatory test for COn. Marks: 1–2 | Difficulty: Easy | Bloom: Understand | Topic: Yeast Experiment Q3.2. Why did the balloon on the test tube without yeast not inflate? Answer: Without yeast there is no fermentation/respiration producing COn; hence no gas to inflate the balloon. Marks: 1–2 | Difficulty: Moderate | Bloom: Understand | Topic: Yeast Experiment Q3.3. Write the overall process occurring in test tube B in one sentence. Answer: Yeast breaks down sugar (respiration/fermentation) releasing carbon dioxide and a small amount of alcohol.

Premium CBSE/KV Question Bank | Class 8 Science Ch-2 | Page 18 SECTION I – SOURCE-BASED QUESTIONS (3 Sets) Study the given information / table and answer the questions. Source Set 1 – Organisms in Pond Water (based on Table 2.1) Students observed: (1) Amoeba – single cell, moving, irregular shape; (2) Paramecium – single cell, moves with specialised structures; (3) Algae – single cell, green pigment, movement with specialised structures. Marks: 1 | Difficulty: Easy | Bloom: Remember | Topic: Pond Microorganisms Q1.1. Which group do Amoeba and Paramecium belong to? Answer: Protozoa (unicellular microorganisms). Marks: 1 | Difficulty: Easy | Bloom: Understand | Topic: Pond Microorganisms Q1.2. Why do algae appear green? Answer: Presence of green pigment (chlorophyll) which helps in photosynthesis. Marks: 1 | Difficulty: Moderate | Bloom: Analyse | Topic: Pond Microorganisms Q1.3. What common feature is shared by all three organisms listed? Answer: All are single-celled (unicellular) and can be observed only under a microscope. Source Set 2 – Levels of Organisation The body of a living organism is organised as: Cell → Tissue → Organ → Organ system → Organism. A group of similar cells forms a tissue. Different tissues form an organ. Several organs work together as an organ system. Marks: 1–2 | Difficulty: Easy | Bloom: Remember | Topic: Levels of Organisation Q2.1. What is the basic unit of life in this hierarchy? Answer: Cell Marks: 1–2 | Difficulty: Moderate | Bloom: Apply | Topic: Levels of Organisation Q2.2. Give one example of an organ system in humans and the major function it performs. Answer: Digestive system – digests food and absorbs nutrients (or any correct organ system). Marks: 1–2 | Difficulty: Difficult | Bloom: Evaluate | Topic: Levels of Organisation Q2.3. Why is organisation into levels advantageous for multicellular organisms? Answer: It allows division of labour; specialised cells/tissues/organs perform specific functions efficiently while cooperating for survival of the organism. Source Set 3 – Snapshots from the Chapter Microorganisms are small-sized and not visible to the unaided eye. They can be unicellular or multicellular. Bacteria and protozoans are unicellular; fungi can be either; plants and animals are multicellular. A typical cell has cell membrane, cytoplasm and nucleus. Plant, fungal and bacterial cells have a cell wall. Bacteria lack a well-defined nucleus. Viruses multiply only inside a host organism. Marks: 1–2 | Difficulty: Moderate | Bloom: Remember | Topic: Cell & Microbes Summary Q3.1. Name one unicellular and one multicellular fungus. Answer: Unicellular: Yeast; Multicellular: Mould (or mushroom). Marks: 1–2 | Difficulty: Moderate | Bloom: Understand | Topic: Cell & Microbes Summary Q3.2. Which feature distinguishes bacterial cells from plant and animal cells regarding the nucleus? Answer: Bacteria lack a well-defined nucleus (have nucleoid instead of nucleus with nuclear membrane). Marks: 1–2 | Difficulty: Difficult | Bloom: Analyse | Topic: Cell & Microbes Summary Q3.3. Why are viruses placed separately from other microorganisms in the chapter? Answer: Viruses are acellular and can reproduce only inside a living host cell; they are different from cellular microorganisms.

Premium CBSE/KV Question Bank | Class 8 Science Ch-2 | Page 19 SECTION J – HOTS – HIGHER ORDER THINKING SKILLS (6 Questions) These questions require critical thinking, analysis and evaluation. Marks: 4–5 | Difficulty: Difficult | Bloom: Evaluate | Topic: Importance of Bacteria Q1. If all bacteria on Earth suddenly disappeared, discuss three major consequences for ecosystems and human life. Model Answer: • Decomposition would stop – dead matter would accumulate; nutrient cycles would collapse. • Nitrogen fixation would cease – soil fertility would decline drastically affecting agriculture. • Many food processes (curd, fermented foods) and biogas production would stop; some beneficial gut bacteria would be lost affecting digestion and health. Marks: 4–5 | Difficulty: Difficult | Bloom: Evaluate | Topic: Cell Shape & Function Q2. A scientist claims that ‘shape of a cell always determines its function’. Support or refute this statement with two examples from the chapter. Model Answer: • Supported by evidence: Nerve cells are long and branched to transmit messages; muscle cells are spindle-shaped to contract and relax. • Cheek cells are thin and flat to form a protective lining. • Thus, in many cases shape is adapted to function, though not the only determining factor. Marks: 4–5 | Difficulty: Difficult | Bloom: Create | Topic: Experimental Design Q3. Design a simple investigation to test whether moisture is necessary for the growth of bread mould. Write aim, materials, procedure and expected result. Model Answer: • Aim: To test if moisture is required for mould growth. • Materials: Two bread slices, two plates, water, dry place. • Procedure: Moisten one slice; keep both in similar temperature/light; observe after 3–4 days. • Expected: Mould appears on moist slice; dry slice remains largely free of mould – showing moisture is necessary. Marks: 4–5 | Difficulty: Difficult | Bloom: Analyse | Topic: Crop Rotation Q4. Why do farmers practise crop rotation with legumes even when chemical fertilisers are available? Analyse from environmental and economic viewpoints. Model Answer: • Environmental: Rhizobium fixes natural nitrogen; reduces chemical fertiliser use and pollution; improves soil health long-term. • Economic: Lowers fertiliser cost; maintains yield sustainability; healthier soil may reduce other input costs over time. Marks: 4–5 | Difficulty: Difficult | Bloom: Analyse | Topic: Fermentation Q5. Compare the role of yeast in baking and Lactobacillus in curd formation. What common principle do both processes illustrate? Model Answer: • Yeast: Anaerobic respiration/fermentation of sugar → COn (dough rises) + alcohol. • Lactobacillus: Fermentation of lactose → lactic acid (milk sets into curd). • Common principle: Microorganisms can transform food substances through fermentation, producing useful products under suitable conditions. Marks: 4–5 | Difficulty: Difficult | Bloom: Evaluate | Topic: Microalgae Conservation Q6. The chapter states that microalgae produce more than half of Earth’s oxygen. What could be the consequences of large-scale decline of microalgae due to pollution and climate change? Suggest one conservation measure. Model Answer: • Reduced oxygen production; disruption of aquatic food chains; loss of a nutritious food/supplement source; imbalance in global oxygen and carbon cycles. • Conservation: Reduce water pollution, protect aquatic habitats, promote sustainable microalgae cultivation (e.g., Spirulina farming).

Premium CBSE/KV Question Bank | Class 8 Science Ch-2 | Page 20 PREPARED BY Ekaparna Sahu B.Sc., M.Sc., B.Ed., M.Ed. Premium KV & CBSE Competency-Based Question Bank Class 8 Science | Chapter 2 The Invisible Living World: Beyond Our Naked Eye Academic Session 2026–27 Based exclusively on NCERT Textbook – Curiosity (Science) Grade 8 Aligned with CBSE Competency-Based Assessment Pattern & KVS Guidelines NEP 2020 | Bloom's Taxonomy | CBE Framework Practice • Learn • Revise • Excel © For educational use | Original questions based on NCERT content

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