Class 9 Science | Chapter 5 | The Fundamental Unit Of Life | Important Questions And Answers
NCERT Class 9 Science Chapter 5 The Fundamental Unit of Life is about cells. You can find important questions and answers from this chapter here.
1. Who discovered the cell?
2. When was the cell discovered?
3. How was the discovery of cell made?
In 1665, Robert Hooke was examining a cork through a microscope he had designed. He noticed that while seen through a microscope, the cork resembled a honeycomb consisting of many compartments. He called these little compartments cells.
4. Which solution is used to examine onion peels under a microscope?
5. Who was the first person to discover free living cells in pond water?
6. The nucleus in a cell was discovered by …………………………… in 1831.
7. What is the name of the fluid substance in the cell?
8. Define the cell theory.
The cell theory proposes that the cell is the fundamental unit of life and that all plants and animals are made up of cells.
9. Which scientists proposed the cell theory?
Schleiden and Schwann
10. Give some examples of single cell organisms.
Amoeba, paramecium, bacteria and chlamydamonas
11. What are unicellular organisms?
These are organisms that have just one cell.
12. What are multicellular organisms?
These are organisms that have a number of cells living together in a single body and performing different functions. Examples are: plants, animals, fungi
13. Is fungi unicellular or multicellular?
Fungi is multicellular
14. What are cell organelles?
Cell organelles are the specific components within a cell.
15. Why is the cell called the structural and functional unit of life?
The cell is called the structural and functional unit of life because all organisms originated from a single cell. In fact, our bodies are all made up of cells.
16. What are the three main features of a cell?
Plasma membrane, nucleus and cytoplasm are the three main features of a cell.
17. What is the outermost covering of a cell called?
18. What separates the content of the cell from its external environment?
19. Why is the plasma membrane called a selectively permeable membrane?
The plasma membrane allows the entry or exit of some materials in and out of the cell. It also prevents the movement of some other materials. Hence, it is called a selectively permeable membrane.
20. How does oxygen or carbon dioxide move through the cell membrane?
Oxygen or carbon dioxide move through the cell membrane by a process called diffusion. Diffusion is the spontaneous movement of a substance from a region of high concentration to a region of low concentration. So, when the concentration of carbon dioxide inside the cell is higher than its concentration in the external environment, it moves out of the cell through the cell membrane. Similarly, when the concentration of oxygen inside the cell is lower than its concentration in the external environment, O2 moves in through the cell membrane.
21. What is osmosis?
Osmosis is the movement of water molecules through a selectively permeable membrane. It is the movement of water from a region of high water concentration to a region of low water concentration until equilibrium is achieved.
22. What is a hypotonic solution?
A hypotonic solution is a solution that has a lower concentration of dissolved particles than a normal cell. When a plant cell or animal cell is dipped in a hypotonic solution, water molecules will move into the cell through the cell membrane because the water concentration outside the cell is higher than the concentration of water inside the cell. As a result, the cell is likely to swell up.
23. What is an isotonic solution?
An isotonic solution is a solution that has the same water concentration as the cell put in it. In an isotonic solution, there is no net movement of water through the cell membrane. Of course, water will move in and out but the amount of water going out will be the same as the amount of water going in. Hence, the size of the cell will remain the same.
24. What is a hypertonic solution?
A hypertonic solution is a solution that has a higher concentration of dissolved particles than a normal cell. When a cell is put in a hypertonic solution, water will move out of the cell causing the cell to shrink.