Class 8 Science Chapter 2 – The Invisible Living World: Beyond Our Naked Eye from NCERT Curiosity with easy Notes and complete Book Solutions. Get simple explanations, important concepts, questions and answers, and revision material for effective learning, practice and exam preparation.
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Class 8 Science Worksheet
Chapter 2 – The Invisible Living World: Beyond Our Naked Eye
Subject: Science | Class: 8
NCERT / Curiosity
Name: __________________________
Class & Section: __________________
Date: __________________________
Instructions: Read each question carefully. Answer all questions in the space provided or in your notebook.
A. Multiple Choice Questions
1. Who first observed tiny organisms using a microscope?
2. The basic structural and functional unit of life is the:
3. Which part of the cell controls most activities of the cell?
4. Which structure is present in plant cells but absent in animal cells?
5. Which organelle helps green plants prepare food?
6. Which of the following is a microorganism?
7. Which microorganism is commonly used in making bread?
8. Which gas is produced by yeast during fermentation?
9. Rhizobium is commonly found in the:
10. Which microorganism helps in setting curd?
B. Fill in the Blanks
1. The study of microorganisms is called __________________________.
2. Robert Hooke observed tiny box-like structures in a thin slice of __________________________.
3. The jelly-like substance inside a cell is called __________________________.
4. The outer boundary of an animal cell is called the __________________________.
5. The rigid outer covering of a plant cell is called the __________________________.
6. Green plastids containing chlorophyll are called __________________________.
7. Bacteria do not have a well-defined __________________________.
8. The DNA-containing region in a bacterial cell is called the __________________________.
9. The process in which microorganisms break down organic matter is called __________________________.
10. __________________________ helps in fixing nitrogen in the soil.
C. True or False
1. All living organisms are made up of cells. __________
2. Animal cells have a cell wall. __________
3. Plant cells generally have chloroplasts. __________
4. Bacteria are always harmful to humans. __________
5. Yeast is a microorganism. __________
6. Microorganisms can be useful in making food. __________
7. Rhizobium is associated with leguminous plants. __________
8. Microorganisms have no role in decomposition. __________
9. A microscope helps us observe objects that are too small to be seen clearly with the naked eye. __________
10. Viruses can multiply independently outside living cells. __________
D. Match the Following
| Column A | Column B |
|---|---|
| 1. Robert Hooke | a. Curd formation |
| 2. Yeast | b. Nitrogen fixation |
| 3. Rhizobium | c. Cork cells |
| 4. Lactobacillus | d. Bread making |
| 5. Chloroplast | e. Photosynthesis |
E. Very Short Answer Questions
1. What is a cell?
2. What is a microorganism?
3. Name any two microorganisms.
4. What is the function of the cell membrane?
5. What is the function of the cell wall?
6. What is the role of chloroplasts?
7. What is fermentation?
8. Name the microorganism used in bread making.
9. What is the role of Rhizobium?
10. Why are microorganisms called microscopic organisms?
F. Short Answer Questions
1. Why could people not see microorganisms before the invention of the microscope?
2. What did Robert Hooke observe when he examined cork under a microscope?
3. Why is a cell called the basic unit of life?
4. Write two differences between plant cells and animal cells.
5. Why do cells have different shapes and structures?
6. What are the different levels of organisation in a multicellular organism?
7. How are microorganisms useful in our daily lives?
8. How do microorganisms help in decomposition?
9. Why does bread dough rise when yeast is added?
10. Why is curd usually kept in a warm place while setting?
G. Give Reasons
1. We need microscopes to study microorganisms.
2. Plant cells have a cell wall.
3. Bread becomes soft and fluffy when yeast is used.
4. Food gets spoiled when microorganisms grow on it.
5. Farmers growing leguminous crops may need less nitrogen fertiliser.
H. Complete the Table
| Microorganism / Group | One Useful Role |
|---|---|
| Bacteria | |
| Yeast | |
| Lactobacillus | |
| Rhizobium | |
| Microalgae |
I. Cell-Based Questions
1. Name the three main structures found in most plant and animal cells.
2. Which cell structure contains the genetic material in a typical plant or animal cell?
3. Which structure is found outside the cell membrane in a plant cell?
4. What is the function of cytoplasm?
5. Why can a bacterial cell be considered different from a typical plant or animal cell?
J. Microorganisms Around Us
1. Name four major groups of microorganisms.
2. Where can microorganisms be found?
3. How can microorganisms help in cleaning the environment?
4. What happens to fruit and vegetable peels when they are left with suitable moisture and air?
5. What is biogas and how is it related to microorganisms?
K. Application-Based Questions
1. A student keeps two slices of bread. One is kept near the kitchen sink and the other in a refrigerator. After three days, the slice near the sink has more mould. Explain why.
2. A farmer grows beans and wheat. The farmer uses less nitrogen fertiliser for beans. Give a scientific reason.
3. A child notices that curd becomes more sour when kept outside for a longer time. What could be the reason?
4. Why does lime water turn milky when carbon dioxide is passed through it?
5. Why does dough rise after yeast is added?
L. Experiment and Observation
1. Design a simple experiment to show that microorganisms need suitable temperature, air and moisture for their growth.
2. Complete the observation table.
| Condition | Prediction | Observation |
|---|---|---|
| Warm and moist | ||
| Cold and moist | ||
| Warm and dry | ||
| Warm with little air |
3. Write two safety precautions that should be followed while observing microorganisms.
M. Think and Answer
1. What would happen if microorganisms did not exist on Earth?
2. Why are microorganisms important even though most of them cannot be seen with the naked eye?
3. How can microorganisms be both useful and harmful to humans?
4. Why is the shape of a cell related to its function?
N. Case-Based Questions
Case Study 1
Aanandi takes two test tubes containing sugar solution. She adds yeast to one test tube and attaches balloons to both test tubes. After a few hours, the balloon attached to the test tube containing yeast becomes inflated.
Aanandi takes two test tubes containing sugar solution. She adds yeast to one test tube and attaches balloons to both test tubes. After a few hours, the balloon attached to the test tube containing yeast becomes inflated.
(a) Which microorganism is involved in this activity?
(b) Which gas causes the balloon to inflate?
(c) What process is taking place?
(d) How can the gas be tested?
Case Study 2
A farmer grows pulse crops in a field. The plants grow well even though the farmer does not add much nitrogen fertiliser.
A farmer grows pulse crops in a field. The plants grow well even though the farmer does not add much nitrogen fertiliser.
(a) Which microorganism may be present in the roots?
(b) What does this microorganism do?
(c) Why is this relationship useful to the plant?
Case Study 3
A student puts fruit and vegetable peels into a pit and mixes them with dry leaves. After some weeks, the waste changes into manure-like material.
A student puts fruit and vegetable peels into a pit and mixes them with dry leaves. After some weeks, the waste changes into manure-like material.
(a) Which organisms help in this process?
(b) What is this process called?
(c) How is the final material useful?
O. Challenge Questions
1. A microorganism is too small to be seen with the naked eye but has a very important role in nature. Explain how such an organism can affect the whole ecosystem.
2. Explain the sequence from a cell to an organism in a multicellular living organism.
3. Explain why microorganisms are important in both agriculture and food production.
4. If yeast is kept without sugar, will the same amount of gas be produced? Give a reason.
Answer Key
Section A – MCQs
| Q. | Answer |
|---|---|
| 1 | b |
| 2 | c |
| 3 | b |
| 4 | c |
| 5 | a |
| 6 | b |
| 7 | a |
| 8 | c |
| 9 | b |
| 10 | a |
Section B – Fill in the Blanks
| Q. | Answer |
|---|---|
| 1 | Microbiology |
| 2 | Cork |
| 3 | Cytoplasm |
| 4 | Cell membrane |
| 5 | Cell wall |
| 6 | Chloroplasts |
| 7 | Nucleus |
| 8 | Nucleoid |
| 9 | Decomposition |
| 10 | Rhizobium |
Section C – True or False
| Q. | Answer |
|---|---|
| 1 | True |
| 2 | False |
| 3 | True |
| 4 | False |
| 5 | True |
| 6 | True |
| 7 | True |
| 8 | False |
| 9 | True |
| 10 | False |
Section D – Match the Following
| Column A | Answer |
|---|---|
| 1. Robert Hooke | c. Cork cells |
| 2. Yeast | d. Bread making |
| 3. Rhizobium | b. Nitrogen fixation |
| 4. Lactobacillus | a. Curd formation |
| 5. Chloroplast | e. Photosynthesis |
Section E – Very Short Answers
| Q. | Key Answer |
|---|---|
| 1 | Basic structural and functional unit of life. |
| 2 | An organism too small to be seen clearly with the naked eye. |
| 3 | Any two: bacteria, fungi, protozoa, algae. |
| 4 | Controls movement of substances into and out of the cell. |
| 5 | Provides support and protection. |
| 6 | Helps green plants make food. |
| 7 | Breakdown of substances by microorganisms, such as yeast. |
| 8 | Yeast. |
| 9 | Helps in nitrogen fixation. |
| 10 | They are extremely small and usually require a microscope to observe. |
Sections F–O – Key Points
| Question Area | Key Answer |
|---|---|
| Cell basic unit | All basic life processes occur within cells. |
| Plant vs animal cells | Plant cells have a cell wall and usually chloroplasts; animal cells do not. |
| Levels of organisation | Cell → Tissue → Organ → Organ system → Organism. |
| Decomposition | Microorganisms break down dead organic matter and help form manure. |
| Yeast and dough | Yeast produces carbon dioxide during fermentation, causing dough to rise. |
| Curd | Lactobacillus helps convert milk into curd. |
| Rhizobium | Lives in root nodules of leguminous plants and helps fix nitrogen. |
| Bread mould | Warm and moist conditions favour faster microbial growth; refrigeration slows it. |
| Lime water test | Carbon dioxide turns lime water milky. |
| Case Study 1 | Yeast; carbon dioxide; fermentation; lime water test. |
| Case Study 2 | Rhizobium; nitrogen fixation; provides usable nitrogen to the plant. |
| Case Study 3 | Microorganisms; decomposition/composting; produces useful manure. |
Note: For descriptive questions, answers may be worded differently if the scientific meaning is correct.
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