In this post, we have provided solutions to all the Pause and Ponder Questions from NCERT Class 9 Science Chapter 2 – Cell: The Building Block of Life. These answers are prepared according to the latest NCERT syllabus and help students understand important concepts such as cell structure, cell organelles, and the differences between plant and animal cells.
Written in simple and easy-to-understand language, these solutions are useful for homework, quick revision, and exam preparation. Each answer is explained clearly to help students build a strong understanding of the chapter.
CH :- 02 - Cell: The Building Block of Life
Page No. :- 08 - Think it over
Ques 1:- Where does a cell come from ?
Ans:- A cell comes from a pre-existing cell through the process of cell division. Existing cells grow and divide to produce new cells, passing genetic material from parent cells to daughter cells.
Ques 2:-How have technological interventions facilitated the creation of new knowledge in understanding the world beyond the naked eye ? ?
Ans:- Technological tools like microscopes have enabled scientists to study cells, tissues, and microorganisms that are invisible to the naked eye. Improved microscopes and imaging techniques have revealed detailed structures and processes inside cells, helping us gain new knowledge about life and diseases.
Ques 3:- How is the cell structural and functional unit of life ?
Ans:- A cell is the structural unit as all organisms are made of cells. It is the functional unit because all vital activities- metabolism, respiration, growth, and reproduction-occur within cells. Thus, cells form the building blocks and carry out essential life processes.
Ques 4:- How does a cell multiply?
Ans:- Cells multiply through a process called cell division. There are two main types of cell division: mitosis and meiosis.
• In mitosis, one cell divides to form two identical daughter cells.
This helps in growth, repair, and replacement of worn-out cells.
• In meiosis, one cell divides to form four daughter cells with
half the number of chromosomes. Meiosis occurs in reproductive organs and produces sperm and egg cells for reproduction.
Cells multiply through a process called cell division.
• In mitosis, one cell divides to form two identical daughter cells,
helping in growth and repair.
• In meiosis, one cell produces four cells with half the number of chromosomes, which form sperm and egg cells for reproduction.
Page No.:- 14 - Pause and Ponder
Ques 1:- What argument would you give for the necessity of a cell wall in plants usually fixed in one place versus in animals usually moving from one place to the other?
Ans:- Plants are fixed in one place, so they need a rigid cell wall for support, protection, and maintaining their shape. Animals move from one place to another and require flexibility; therefore, their cells lack a cell wall, allowing them to change shape and perform movement-related functions.
Ques 2:- What consequences would you predict for a plant cell if its cell wall were to become as flexible as a cell membrane?
Ans:- If the cell wall became as flexible as the cell membrane :-
• The plant cell would lose its fixed shape.
• It could burst easily when water enters due to osmotic pressure.
• The plant would lose support and strength, causing wilting.
• Plants would not be able to remain upright properly.
Therefore, the rigid cell wall is essential for maintaining the shape, support and protection of plant cells.
Ques 3:- Why is it important to cut the two potato pieces in roughly equal size and measure their initial weight before placing them in different liquids?
Ans:- It is important to cut the two potato pieces to roughly equal size and measure their initial weight because :-
• Equal-sized pieces have similar surface area and volume, allowing a fair comparison.
• Measuring the initial weight helps determine the exact weight change after osmosis.
• This ensures that any difference in weight is due to the liquid's effect and not because the potato pieces were different sizes.
Therefore, these steps make the experiment fair and the results reliable.
Page No.:- 19 - Pause and Ponder
Ques 4:- Do white flowers contain any pigment? Give reasons.
Ans:- Yes, white flowers contain pigments. They may contain colourless or very faint pigments, but they generally lack coloured pigments such as anthocyanins. Their white appearance is due to the reflection of almost all wavelengths of visible light by the petal cells, making them appear white.
For 2 MarksYes, white flowers contain pigments. They appear white because they lack coloured pigments or have them in very small amounts, and their petals reflect most of the light falling on them.
Ques 5:- Draw a well-labelled schematic diagram of a plant or an animal cell using these clues-
(i) Nucleus appears as a dark and round body inside the cell.
(ii) ER spreads like a network of extended nuclear envelope.
(iii) Mitochondria and chloroplasts are rod shaped.
The well-labelled schematic diagram of a Plant Cell is shown below:
Page No.:- 22 - Pause and Ponder
Ques 6:- Instead of many small ones, why does a cell not have a single giant mitochondrion? How does this relate to the concept of surface area?
Ans:- A cell has many small mitochondria instead of one giant mitochondrion because many small mitochondria provide a larger total surface area. This gives more space for cellular respiration and ATP (energy) production. A larger surface area helps the cell produce energy more efficiently than a single large mitochondrion.
Ques 7:- If the skin cells start dividing by meiosis instead of mitosis, what do you think will happen to a cut on the skin?
Ans:- It would not heal properly.
Reason: Meiosis produces cells with half the number of chromosomes and forms non-identical cells meant for
reproduction. Skin repair requires identical diploid cells, which are produced by mitosis. Therefore, a cut on the skin would
not heal properly.
We hope these NCERT Class 9 Science Chapter 2 – Cell: The Building Block of Life Pause and Ponder solutions have helped you understand the key concepts of the chapter. By studying these answers, students can strengthen their knowledge of cell structure, cell organelles, and the differences between plant and animal cells. Regular revision of these solutions will help in completing assignments, preparing for examinations, and building a strong foundation in Biology.
Frequently Asked Questions (FAQs)
1. What is the basic unit of life?
The cell is the basic structural and functional unit of life. All living organisms are made up of one or more cells.
2. Who discovered the cell?
The cell was first discovered by Robert Hooke in 1665 while observing a thin slice of cork under a microscope.
3. What are cell organelles?
Cell organelles are specialized structures present inside a cell that perform specific functions, such as the nucleus, mitochondria, and vacuoles.
4. What is the difference between a plant cell and an animal cell?
Plant cells have a cell wall, chloroplasts, and a large central vacuole, whereas animal cells do not have a cell wall or chloroplasts and usually contain smaller vacuoles.
5. Why are NCERT solutions important for Class 9 Science?
NCERT solutions help students understand concepts clearly, complete homework accurately, and prepare effectively for school examinations.
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