✅ True or False (10 Questions)

(CBSE Class 8 Standard | Good Quality)

1. The human eye can see very tiny microorganisms without any tool.
   False
   (Microorganisms cannot be seen with naked eye.) hecu102

2. A lens helps small objects appear bigger.
   True hecu102

3. Robert Hooke first used the word “cell” after observing cork.
   True hecu102

4. Antonie van Leeuwenhoek is known as the Father of Microbiology.
   True hecu102

5. All living organisms are made up of cells.
   True hecu102

6. Plant cells do not have a cell wall.
   False
   (Plant cells have a cell wall.) hecu102

7. Cytoplasm is the region where most life processes occur in a cell.
   True hecu102

8. Bacteria have a well-defined nucleus like plant cells.
   False
   (Bacteria have nucleoid, not true nucleus.) hecu102

9. Yeast is a microorganism used in making bread and cakes fluffy.
   True hecu102

10. Microorganisms help in decomposing waste and cleaning the environment.
    True

✅ Fill in the Blanks (10 Questions)

(CBSE Class 8 Standard | Good Quality)

1. Tiny organisms that cannot be seen with naked eyes are called __________.
   Answer: microorganisms hecu102

2. The instrument used to observe very small objects is called a __________.
   Answer: microscope hecu102

3. Robert Hooke discovered cells while observing a thin slice of __________.
   Answer: cork hecu102

4. The basic structural and functional unit of life is the __________.
   Answer: cell hecu102

5. The jelly-like substance present inside the cell is called __________.
   Answer: cytoplasm hecu102

6. The control centre of the cell is the __________.
   Answer: nucleus hecu102

7. Plant cells have an extra outer covering called cell ________.
   Answer: wall hecu102

8. Microorganisms like yeast are used in the process of __________ to make bread.
   Answer: fermentation hecu102

9. The bacterium __________ helps in nitrogen fixation in leguminous plants.
   Answer: Rhizobium hecu102

10. Microalgae help maintain the oxygen and carbon dioxide __________ in nature.
    Answer: balance

✅ Multiple Choice Questions (15 MCQs)

(CBSE Class 8 Standard | Good Quality)

1. Microorganisms can be seen with the help of a:

A. Telescope
B. Microscope
C. Thermometer
D. Barometer
✅ Answer: B hecu102

2. Robert Hooke observed cells in:

A. Leaf
B. Cork
C. Water
D. Blood
✅ Answer: B hecu102

3. The basic unit of life is:

A. Tissue
B. Organ
C. Cell
D. System
✅ Answer: C hecu102

4. The control centre of the cell is:

A. Cytoplasm
B. Nucleus
C. Cell wall
D. Vacuole
✅ Answer: B hecu102

5. Plant cells differ from animal cells because plant cells have:

A. Nucleus
B. Cytoplasm
C. Cell wall
D. Cell membrane
✅ Answer: C hecu102

6. Bacteria belong to which group of microorganisms?

A. Fungi
B. Protozoa
C. Prokaryotes
D. Algae
✅ Answer: C hecu102

7. Yeast is used in making:

A. Plastic
B. Bread
C. Glass
D. Salt
✅ Answer: B hecu102

8. The process of converting sugar into alcohol by yeast is called:

A. Photosynthesis
B. Fermentation
C. Respiration
D. Germination
✅ Answer: B hecu102

9. Rhizobium bacteria are found in:

A. Roots of leguminous plants
B. Human stomach
C. Oceans
D. Deserts
✅ Answer: A hecu102

10. Which microorganism helps in decomposition?

A. Virus
B. Bacteria and fungi
C. Only algae
D. Only protozoa
✅ Answer: B hecu102

11. Which of the following is NOT a microorganism?

A. Amoeba
B. Mushroom
C. Elephant
D. Bacteria
✅ Answer: C hecu102

12. The outer boundary of an animal cell is:

A. Cell wall
B. Cell membrane
C. Cytoplasm
D. Nucleus
✅ Answer: B hecu102

13. Microalgae are important because they:

A. Cause diseases
B. Maintain oxygen balance
C. Destroy crops
D. Produce plastic
✅ Answer: B hecu102

14. Antonie van Leeuwenhoek is known for:

A. Discovering gravity
B. Inventing microscope and studying microbes
C. Making vaccines
D. Discovering electricity
✅ Answer: B hecu102

15. Cells combine to form:

A. Organs directly
B. Tissues
C. Microbes
D. Atoms
✅ Answer: B

✅ Assertion–Reason Questions (10)

(CBSE Class 8 Standard | Good Quality)

Directions: Choose the correct option:

A. Both A and R are true and R is the correct explanation of A
B. Both A and R are true but R is not the correct explanation of A
C. A is true but R is false
D. A is false but R is true

1.

Assertion (A): Microorganisms cannot be seen with naked eyes.
Reason (R): They are extremely small in size.
✅ Answer: A hecu102

2.

Assertion (A): Robert Hooke used the term “cell” for the first time.
Reason (R): He observed honeycomb-like structures in cork.
✅ Answer: A hecu102

3.

Assertion (A): The nucleus is called the control centre of the cell.
Reason (R): It controls all activities of the cell.
✅ Answer: A hecu102

4.

Assertion (A): Plant cells have a cell wall.
Reason (R): Cell wall provides shape and protection to plant cells.
✅ Answer: A hecu102

5.

Assertion (A): Bacteria are prokaryotic organisms.
Reason (R): They do not have a well-defined nucleus.
✅ Answer: A hecu102

6.

Assertion (A): Yeast is useful in making bread.
Reason (R): Yeast causes fermentation and releases carbon dioxide.
✅ Answer: A hecu102

7.

Assertion (A): Rhizobium bacteria help plants grow better.
Reason (R): They fix nitrogen in root nodules of leguminous plants.
✅ Answer: A hecu102

8.

Assertion (A): Microorganisms help in decomposition.
Reason (R): They break down dead plants and animals into simpler substances.
✅ Answer: A hecu102

9.

Assertion (A): Microalgae are important for the environment.
Reason (R): They help maintain oxygen and carbon dioxide balance.
✅ Answer: A hecu102

10.

Assertion (A): Cells form tissues and tissues form organs.
Reason (R): Living organisms show levels of organisation.
✅ Answer: A

✅ Very Short Answer Questions (10 Questions)

(2 Marks Each | CBSE Class 8 Standard | Good Quality)

1. What are microorganisms?

Answer:
Microorganisms are very tiny living organisms that cannot be seen with naked eyes and can be observed only with a microscope. hecu102

2. Who discovered cells and how?

Answer:
Robert Hooke discovered cells in 1665 while observing a thin slice of cork under a microscope. hecu102

3. What is the basic unit of life?

Answer:
The cell is the basic structural and functional unit of life. hecu102

4. Name the three main parts of a cell.

Answer:
The three main parts of a cell are cell membrane, cytoplasm, and nucleus. hecu102

5. What is the function of nucleus?

Answer:
The nucleus controls all activities of the cell and contains hereditary material. hecu102

6. What is the difference between plant and animal cells?

Answer:
Plant cells have a cell wall, while animal cells do not have a cell wall. hecu102

7. What is fermentation?

Answer:
Fermentation is the process in which yeast converts sugar into alcohol and carbon dioxide. hecu102

8. Name one microorganism useful in making curd.

Answer:
Lactobacillus bacteria are useful in making curd. hecu102

9. What is the role of Rhizobium bacteria?

Answer:
Rhizobium bacteria fix atmospheric nitrogen in the roots of leguminous plants, improving soil fertility. hecu102

10. Why are microorganisms called invisible living world?

Answer:
Microorganisms are called invisible living world because they are too small to be seen with naked eyes but are living organisms present everywhere.

✅ Short Answer Questions (10 Questions)

(3 Marks Each | CBSE Class 8 Standard | Good Quality)

1. Explain why microorganisms are called invisible living organisms.

Answer:
Microorganisms are called invisible living organisms because they are extremely small and cannot be seen with naked eyes. They can only be observed using a microscope. Despite being invisible, they perform important life activities. hecu102

2. Describe Robert Hooke’s discovery of cells.

Answer:
Robert Hooke observed a thin slice of cork under a microscope in 1665. He saw small box-like structures resembling honeycomb and named them “cells.” This led to the discovery of cells as the basic unit of life. hecu102

3. Differentiate between plant and animal cells.

Answer:
Plant cells have a cell wall and usually large vacuoles, giving them a fixed shape. Animal cells do not have a cell wall and have smaller vacuoles, making their shape irregular. Both have nucleus and cytoplasm. hecu102

4. What are the levels of organisation in living organisms?

Answer:
Living organisms show levels of organisation as:
Cell → Tissue → Organ → Organ System → Organism.
Cells combine to form tissues, tissues form organs, and organs work together in organ systems. hecu102

5. What are useful microorganisms? Give examples.

Answer:
Useful microorganisms help humans and environment. Examples:

• Lactobacillus helps in making curd.
• Yeast is used in bread making.
• Rhizobium fixes nitrogen in soil.
  They play important roles in food and agriculture. hecu102

6. Explain fermentation and its importance.

Answer:
Fermentation is the process in which yeast converts sugar into alcohol and carbon dioxide. It is important in making bread, cakes, and beverages. Carbon dioxide makes dough rise and become fluffy. hecu102

7. How do microorganisms help in decomposition?

Answer:
Microorganisms like bacteria and fungi break down dead plants and animals into simpler substances. This process is called decomposition and it helps in cleaning the environment and recycling nutrients back into soil. hecu102

8. What is nitrogen fixation? Name the microorganism involved.

Answer:
Nitrogen fixation is the process of converting atmospheric nitrogen into usable forms for plants. Rhizobium bacteria present in root nodules of leguminous plants perform nitrogen fixation. hecu102

9. Why are microalgae important for the environment?

Answer:
Microalgae are important because they produce oxygen during photosynthesis and help maintain the balance of oxygen and carbon dioxide in the atmosphere. They support aquatic life and ecosystem stability. hecu102

10. Mention three main functions of cell membrane.

Answer:
Cell membrane:

• Covers the cell and gives protection
• Controls movement of substances in and out of the cell
• Maintains the shape of the cell
  Thus, it acts as a selectively permeable barrier.

✅ Case-Based Questions (4 Cases)

(4 Marks Each | Sub-questions: 1 + 1 + 2 Marks)
CBSE Competency-Based Standard

Case 1: Discovery of Cells

Robert Hooke observed a thin slice of cork under a microscope and saw small compartments which he named cells.

Questions:

Q1. (1 Mark) Who discovered cells?
Answer: Robert Hooke hecu102

Q2. (1 Mark) In which material did he observe cells?
Answer: Cork hecu102

Q3. (2 Marks) Why are cells called the basic unit of life?
Answer:
Because all living organisms are made up of cells and all life processes occur inside cells. hecu102

Case 2: Plant and Animal Cells

A student observes plant cells and animal cells under a microscope. He finds that plant cells have an extra outer layer.

Questions:

Q1. (1 Mark) Name the extra outer layer present in plant cells.
Answer: Cell wall hecu102

Q2. (1 Mark) Which cell does not have a cell wall?
Answer: Animal cell hecu102

Q3. (2 Marks) State two differences between plant and animal cells.
Answer:
Plant cells have a cell wall and fixed shape, while animal cells lack cell wall and have irregular shape. hecu102

Case 3: Yeast and Fermentation

Yeast is used in baking industries to make bread soft and fluffy by releasing gas.

Questions:

Q1. (1 Mark) Which microorganism is used in bread making?
Answer: Yeast hecu102

Q2. (1 Mark) Name the process carried out by yeast.
Answer: Fermentation hecu102

Q3. (2 Marks) How does yeast help in making bread fluffy?
Answer:
Yeast releases carbon dioxide during fermentation, which makes the dough rise and become fluffy. hecu102

Case 4: Rhizobium and Nitrogen Fixation

Farmers grow leguminous plants because bacteria in their roots improve soil fertility.

Questions:

Q1. (1 Mark) Name the bacteria present in leguminous root nodules.
Answer: Rhizobium hecu102

Q2. (1 Mark) What process does Rhizobium perform?
Answer: Nitrogen fixation hecu102

Q3. (2 Marks) How does Rhizobium help plants and soil?
Answer:
Rhizobium converts atmospheric nitrogen into usable form for plants, increasing soil fertility and improving crop growth.

✅ Long Answer Questions (5 Questions)

(5 Marks Each | CBSE Class 8 Standard | High Quality Answers)

1. What are microorganisms? Explain why they are called the invisible living world.

Answer:
Microorganisms are very tiny living organisms that cannot be seen with naked eyes. They can only be observed with the help of a microscope.

They are called the invisible living world because:

• They are present everywhere in air, water, and soil.
• They perform important activities like decomposition and fermentation.
• They include bacteria, fungi, protozoa, and algae.

Thus, though invisible, microorganisms form an important part of life on Earth. hecu102

2. Describe the discovery of cells and explain the structure of a cell.

Answer:
Robert Hooke discovered cells in 1665 while observing a thin slice of cork under a microscope. He saw small box-like structures and named them cells.

Structure of a Cell:

• Cell membrane: outer covering controlling entry and exit of substances.
• Cytoplasm: jelly-like substance where life processes occur.
• Nucleus: control centre containing hereditary material.

Thus, cells are the basic building blocks of life. hecu102

3. Differentiate between plant cells and animal cells.

Answer:

Feature	Plant Cell	Animal Cell
Cell wall	Present	Absent
Shape	Fixed/regular	Irregular
Vacuoles	Large	Small
Chloroplast	Present	Absent

Both plant and animal cells contain nucleus, cytoplasm, and cell membrane but differ in structure. hecu102

4. Explain fermentation and the role of yeast in food industry.

Answer:
Fermentation is the process in which yeast converts sugar into alcohol and carbon dioxide.

Role of Yeast:

• Used in baking industries.
• Carbon dioxide released makes dough rise.
• Bread becomes soft and fluffy.
• Also used in making beverages.

Thus, yeast is an important useful microorganism in food production. hecu102

5. Explain nitrogen fixation and the importance of Rhizobium bacteria.

Answer:
Nitrogen fixation is the process of converting atmospheric nitrogen into a form usable by plants.

Role of Rhizobium:

• Lives in root nodules of leguminous plants.
• Fixes nitrogen and improves soil fertility.
• Helps plants grow better without chemical fertilisers.

Thus, Rhizobium plays an important role in agriculture and environment.