The Invisible Living World: Beyond Our Naked Eye — Class 8 MCQs with Answers
Class 8 CBSE Science · Chapter 2
72 practice questions · 24 Easy · 24 Medium · 24 Hard · Updated
Practise the most important Class 8 CBSE Science questions from Chapter 2, "The Invisible Living World: Beyond Our Naked Eye". You get 9 timed quizzes made from 72 NCERT-based MCQs, with answers and explanations. The questions are split into 24 Easy, 24 Medium and 24 Hard. Warm up on the basics, then move on to the exam-level questions that top scorers in CBSE Board exams get right.
To score well in "The Invisible Living World: Beyond Our Naked Eye", focus on clear concepts in physics, chemistry and biology basics. Each MCQ here is timed and uses exam-style marking (+4 correct, −1 wrong, 0 skipped). This helps you stay accurate when time is short, just as real papers need. Every question has a short explanation, so a wrong answer becomes a quick lesson. It is the fastest way to fix gaps before a test.
Use this chapter for focused revision. Start with the Easy set to check your basics on The Invisible Living World: Beyond Our Naked Eye, then move to Medium and Hard to practise applying them. Your accuracy, streaks and XP save automatically. This chapter also adds to your overall Class 8 Science mastery score. 14 sample questions are solved in full below, with the answer and a worked explanation. Sign in free to start practising.
The Invisible Living World: Beyond Our Naked Eye — important questions & MCQs with answers (Class 8 Science)
14 solved questions from this chapter's difficulty levels, each with its answer and explanation.
- Q1Easy
Living things too small to be seen with the naked eye are called:
A.insectsB.large plantsC.microorganisms✓ CorrectD.only animalsAnswer: C. microorganisms
Explanation: Microorganisms are living things too small to see unaided — insects, large plants and animals are all visible without help, so tiny-yet-alive is the defining trait, not being non-living.
- Q2Easy
Which of these is a group of microorganisms?
A.mammalsB.reptilesC.bacteria✓ CorrectD.birdsAnswer: C. bacteria
Explanation: Bacteria form one of the main microorganism groups, alongside fungi, protozoa and algae — mammals, reptiles and birds are visible multicellular animals, not microbes.
- Q3Easy
The microorganism used to make curd from milk is:
A.a virusB.Lactobacillus (a bacterium)✓ CorrectC.an algaD.a protozoanAnswer: B. Lactobacillus (a bacterium)
Explanation: Lactobacillus bacteria ferment milk sugar into lactic acid, curdling the milk — it is a living microbe doing the work, not a virus, alga or protozoan.
- Q4Easy
Some microorganisms are harmful because they:
A.clean the airB.are always helpfulC.make manureD.cause diseases and spoil food✓ CorrectAnswer: D. cause diseases and spoil food
Explanation: Not every microbe is helpful — some cause diseases in the body or spoil stored food, which is why hygiene and food preservation matter.
- Q5Easy
To see microorganisms, we need a:
A.telescopeB.microscope✓ CorrectC.magnifying stoneD.plane mirrorAnswer: B. microscope
Explanation: A microscope uses lenses to magnify tiny objects thousands of times, revealing microbes invisible to the naked eye — a telescope magnifies distant objects, not nearby tiny ones.
- Q6Easy
Yeast is a type of:
A.fungus✓ CorrectB.bacteriumC.virusD.algaAnswer: A. fungus
Explanation: Yeast is a single-celled fungus, valued for the fermentation it drives in bread and brewing — it is not a bacterium, virus or alga.
- Q7Medium
A bacterial cell differs from a plant cell in that it has:
A.a nucleoid instead of a true nucleus✓ CorrectB.no cell wall at allC.chloroplasts alwaysD.many nucleiAnswer: A. a nucleoid instead of a true nucleus
Explanation: A bacterium keeps its genetic material in a nucleoid region with no surrounding membrane, unlike a plant cell's true, membrane-bound nucleus — bacteria do have a cell wall and lack chloroplasts by default.
- Q8Medium
Fungi that grow as a fuzzy mass on stale bread are called:
A.single-celled yeastsB.bacteriaC.moulds✓ CorrectD.algaeAnswer: C. moulds
Explanation: Moulds are the fuzzy, multicellular fungi that grow on stale food — yeasts are single-celled, and bacteria and algae look and grow differently.
- Q9Medium
In the yeast-and-sugar balloon experiment, the balloon inflates because yeast:
A.heats the airB.makes water vapourC.produces a gas (carbon dioxide)✓ CorrectD.reacts with the balloonAnswer: C. produces a gas (carbon dioxide)
Explanation: Yeast ferments the sugar and releases carbon dioxide gas, which fills and inflates the balloon — it is not from heating the air or forming water vapour.
- Q10Medium
Food spoils faster in warm, moist conditions because microbes:
A.grow and multiply quickly there✓ CorrectB.die immediatelyC.stop movingD.turn into manureAnswer: A. grow and multiply quickly there
Explanation: Warmth and moisture are ideal growth conditions for microbes, so they multiply rapidly and spoil food faster — they do not die immediately or stop moving in such conditions.
- Q11Medium
Which part is found in a plant cell but not in an animal cell?
A.the nucleusB.the cytoplasmC.the cell membraneD.cell wall and chloroplast✓ CorrectAnswer: D. cell wall and chloroplast
Explanation: A rigid cell wall and chloroplasts for photosynthesis are found in plant cells but not animal cells; the nucleus, cytoplasm and cell membrane are common to both.
- Q12Hard
Ranking a virus, a bacterium and a human by cell number, the human is:
A.single-celledB.non-livingC.multicellular, made of many cells✓ CorrectD.a fungusAnswer: C. multicellular, made of many cells
Explanation: A human body is built from trillions of cells and is multicellular, a bacterium is a single cell, and a virus is not even made of cells at all.
- Q13Hard
A pond turns green in summer. This is most likely due to a rapid growth of:
A.virusesB.cowsC.saltD.algae✓ CorrectAnswer: D. algae
Explanation: A green bloom on a pond's surface signals rapid growth of algae, which multiply quickly in warm, nutrient-rich water — not viruses, cows or salt.
- Q14Hard
A farmer grows beans to enrich the soil with nitrogen. This works because bean roots host:
A.Rhizobium, a nitrogen-fixing bacterium✓ CorrectB.harmful fungiC.algaeD.virusesAnswer: A. Rhizobium, a nitrogen-fixing bacterium
Explanation: Bean roots host Rhizobium, a bacterium that fixes nitrogen from the air into a plant-usable form and enriches the soil — not harmful fungi, algae or viruses.
Key concepts: The Invisible Living World: Beyond Our Naked Eye (Class 8 Science)
This chapter opens the hidden world of microorganisms — living things too small to see without a microscope. You meet the main groups (bacteria, fungi, protozoa, algae and viruses) and learn which are single-celled and which are many-celled. Microbes are both friends and foes: they decompose waste into manure, fix nitrogen in legume roots (Rhizobium), and ferment food (yeast makes dough rise with carbon dioxide, Lactobacillus makes curd and idli batter), yet some spoil food or cause disease — which is why we preserve food with salt, sugar, drying and cold.
- Microorganism
- A living thing too small to be seen with the naked eye; a microscope is needed to view it. Microbes live almost everywhere — in soil, water, air and inside our bodies.
- Unicellular vs multicellular
- Unicellular organisms are made of a single cell (bacteria, protozoa, yeast); multicellular ones have many cells (moulds, algae, plants, animals).
- Bacteria
- Single-celled microbes that keep their genetic material in a nucleoid rather than a membrane-bound nucleus; some are helpful (curd, manure) and some are harmful.
- Fungi
- Microbes that can be single-celled, like yeast, or many-celled, like the moulds that grow on stale bread.
- Protozoa and algae
- Protozoa such as Amoeba and Paramecium are single-celled; algae are simple, often green microbes of ponds and water that can clean water and make biofuel.
- Viruses
- On the borderline of living and non-living: a virus can only multiply inside a living host cell and is inert outside it.
- Decomposers and manure
- Bacteria and fungi break down dead plants and animals into simple, nutrient-rich manure, returning nutrients to the soil and cleaning the environment.
- Nitrogen fixation
- Rhizobium bacteria live in the root nodules of legumes (peas, beans, lentils) and trap nitrogen from the air, increasing soil fertility.
- Fermentation
- Yeast ferments dough and releases carbon dioxide, making bread rise; Lactobacillus ferments milk into curd and batter for idli and dosa.
- Biogas
- When microbes decompose waste without air, they produce biogas, a mixture mainly of methane and carbon dioxide that can be used as a fuel.
- Harmful microbes
- Some microorganisms spoil food or cause diseases and infections, which spread through contaminated food, water and air.
- Food preservation
- Salting, adding sugar, drying and refrigeration all preserve food by making conditions too harsh for microbes to grow.
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What are the key concepts in Class 8 Science The Invisible Living World: Beyond Our Naked Eye?+
This chapter opens the hidden world of microorganisms — living things too small to see without a microscope. You meet the main groups (bacteria, fungi, protozoa, algae and viruses) and learn which are single-celled and which are many-celled. Microbes are both friends and foes: they decompose waste into manure, fix nitrogen in legume roots (Rhizobium), and ferment food (yeast makes dough rise with carbon dioxide, Lactobacillus makes curd and idli batter), yet some spoil food or cause disease — which is why we preserve food with salt, sugar, drying and cold. Key ideas include Microorganism, Unicellular vs multicellular, Bacteria, Fungi, Protozoa and algae, Viruses.
What does Class 8 Science Chapter 2 (The Invisible Living World: Beyond Our Naked Eye) cover on XamBaaz?+
It has 72 NCERT-based MCQs on "The Invisible Living World: Beyond Our Naked Eye": 24 Easy, 24 Medium and 24 Hard. Together they make 9 timed quizzes, and you never get the same set twice. Every question has an instant explanation. They help you prepare for CBSE Board exams.
Are these "The Invisible Living World: Beyond Our Naked Eye" questions free to practise?+
Yes. Sign in with Google to practise "The Invisible Living World: Beyond Our Naked Eye" free. Full unlimited access is ₹999/year. One year from the day you pay. You stay in Class 8 till 31 March; on 1 April your account moves up to Class 9 and the rest of your year carries over. No chapter is charged separately.
How should I revise "The Invisible Living World: Beyond Our Naked Eye" for the exam?+
Start with the Easy quiz to check your basics, then try Medium and Hard to practise applying them. There are 9 timed quizzes on this chapter, so you can come back for a fresh set instead of one you have seen. Read each explanation, retry the questions you miss, and track your accuracy until it stays high.
Are these "The Invisible Living World: Beyond Our Naked Eye" MCQs available with answers?+
Yes. 14 sample questions are shown here in full, each with the correct option and a step-by-step "Why" explanation. Sign in free with Google to start practising, with instant scoring.
Is there negative marking in the "The Invisible Living World: Beyond Our Naked Eye" quizzes?+
Yes. The timed quizzes use exam-style marking: +4 for a right answer, −1 for a wrong one and 0 for a skip. MHT-CET and CBSE board papers have no negative marking. Our mocks for those are scored their way.
What are the important questions from The Invisible Living World: Beyond Our Naked Eye (Class 8 Science)?+
The questions that matter most test Microorganism, Unicellular vs multicellular, Bacteria, Fungi, Protozoa and algae, Viruses. This page shows 14 solved important MCQs with answers and explanations. Sign in to practise all 72 questions on the chapter as timed quizzes.
Is there an online quiz for The Invisible Living World: Beyond Our Naked Eye?+
Yes — Class 8 Science The Invisible Living World: Beyond Our Naked Eye has timed online quizzes at Easy, Medium and Hard levels, with instant scoring and a worked explanation on every question. The first quiz on the chapter is free.