Important Questions for CBSE Class 9 Science Chapter 5 – The Fundamental Unit of Life

Important Questions Class 9 Science Chapter 5 – The Fundamental Unit of Life 

Science is an exciting subject which teaches students various concepts. However, there are times when students face difficulty understanding complex concepts. However, it is of utmost importance that students understand the underlying concepts of Biology, Chemistry, and Physics studied in previous classes.  Their interest and curiosity will not only encourage them to take active interest in the world around them and also help them decide which stream they would like to pursue in high school. For this, our subject matter experts have compiled a set of important questionnaires for class 9 Science chapter 5. It covers more than 30 questions of varying degree of difficulty such as multiple-choice, long, and short answer types. It will help students learn the various complicated topics related to the fundamental units of life. 

The questions are compiled from the NCERT book, CBSE sample papers, NCERT solutions, and NCERT exemplar. In addition, the questions are updated as per the latest CBSE syllabus and guidelines. Solving class 9 science chapter 5 extra questions and answers will help students to get step-by-step solutions to the numerical answers. Therefore, they don’t lose any extra marks for skipping a step. With the help of important questions, students can have an insight into the chapter without taking too much of their time.. 

The list of important questions in class 9 Science chapter 5 will give the students new confidence to crack their exams and score good marks without any  hassle. Students can also refer to other course material on our website, including NCERT solutions, past year questions papers, CBSE revision notes, and CBSE additional questions. 

Get Access to CBSE Class 9 Science Important Questions 2022-23 with Solutions

Also, get access to CBSE Class 9 Science Important Questions for other chapters too:

CBSE Class 9 Science Important Questions
Sr No Chapters Chapter Name
1 Chapter 1 Matter in Our Surroundings
2 Chapter 2 Is Matter Around Us Pure
3 Chapter 3 Atoms and Molecules
4 Chapter 4 Structure of Atom
5 Chapter 5 The Fundamental Unit of Life
6 Chapter 6 Tissues
7 Chapter 7 Diversity in Living Organisms
8 Chapter 8 Motion
9 Chapter 9 Force and Laws of Motion
10 Chapter 10 Gravitation
11 Chapter 11 Work and Energy
12 Chapter 12 Sound
13 Chapter 13 Why Do We Fall ill
14 Chapter 14 Natural Resources
15 Chapter 15 Improvement in Food Resources

The Fundamental Unit of Life Class 9 Science Chapter 5 Question Answer

Long Answer Questions 

Q1. Who discovered cells, and how?


Cells are the fundamental structural and functional units of living things. Robert Hooke, a British scientist, first used the term “cells” in 1665. Hooke was the first to examine living things under a microscope. He examined a thin slice of cork under a microscope and saw honeycomb-like structures. These structures were called cells by Robert Hooke.

Antonie Van Leuwenhoek soon made more discoveries when he invented his microscope lenses, which were much more potent than at the time. His microscope was the first to allow him to examine bacteria and cells of human beings.

More discoveries about cells were made with the help of microscopes. Seeing the intricate structures within cells with a light microscope was difficult. The electron microscope, a more robust microscope than the light microscope, was developed to allow for more straightforward observation of objects smaller than cells.

Q2. Why is the cell called the structural and functional unit of life?

Answer: A cell refers to the smallest unit of life that is responsible for all aspects of life. All living things are composed of cells. They are their structural, functional, and biological components. Further, a cell can reproduce itself independently. They are therefore known as the building blocks of  life.

Our most important unit for forming our bodies is the cell. Every organ of our body is made up of cells. Cells also divide and multiply to create new organs and gametes. A cell is a functional living unit because it can divide and multiply for the reasons mentioned above.

  • Because all living organisms are composed of cells, the cell is known as life’s structural and functional unit.
  • Cells are essential for many life processes, including maintaining life.
  • Cells also provide structure, form, nutrient processing, and energy conversion.
  • Multicellular organisms possess specialised cells that perform specific functions.

Q3. Explain why ozone is thermodynamically less stable than oxygen. 

Answer: Ozone is thermodynamically inelastic with oxygen because its decomposition results in the release of heat (DH is negative) and an increase in entropy (DS is positive). These two effects are mutually reinforcing and result in significant negative Gibbs energy changes (DG) that allow oxygen conversion.

Q4. What do you mean by cell organelles?


The cellular components of cells are called cell organelles. These cell organelles include both membrane-bound and non-membrane organelles. They are found in cells and have different shapes and activities. To allow cells to function normally, they must coordinate and work together. Most of them provide support and form, but others play a role in cell motility and reproduction. The presence or absence of a membrane can classify organelles into one of three types.

  • The cell wall, ribosomes and cytoskeleton are all examples of organelles in cells that don’t have a membrane.
  • Endoplasmic Reticulum and Lysosome are all single membrane-bound organelles. The reticulum is a single membrane-bound organelle found only in eukaryotic cell symbionts.
  • The only two membrane-bound organelles in eukaryotic cells are the nucleus, mitochondria, and chloroplast.

Q5. What happens to substances such as CO2 or water when moving in and out of a cell? Discuss.


CO2 is a substance that moves in and out of cells through diffusion, while water does this by osmosis. It’s the movement of particles from different substances from their highest to their lowest concentrations.

(i) More CO2 can be produced in a respiring cell. Its internal concentration increases as a result. Because the outside medium has a lower concentration of CO2, CO2 escapes from cells and is absorbed into the external medium.

(iii) CO2 in photosynthetic cells is being used for photosynthesis. Its intracellular concentration tends to be lower than that in the outside medium. CO2 diffuses outside the cell to the inside. Osmosis is water movement from the area of higher concentration (pure or dilute water) to the area of lower concentration (robust solution) when the two are separated with a semipermeable barrier. Semipermeable membranes are used to separate plasma membranes. 

Endosmosis is the process by which water enters a cell. This happens until wall pressure counterbalances this tendency. In addition, water would escape the cell if the external medium contained a robust solution. This phenomenon is known as exosmosis.

Q6. Perform the following experiment:

  1. Take four potato halves, and hollow them out to make potato cups. The boiled potato should make one of these potato cups.
  2. Place each potato cup into a trough with water.
  3. Pour the water into the trough.

(a) Keep cup A empty,

(b) Add one teaspoon of sugar to cup B.

(c) Add one teaspoon of salt to cup C.

(d) Add one teaspoon of sugar to a boiled cup D.

One must keep this set up for at least two hours. Next, examine the four potato cups. Then answer the following questions:

(i) Describe why water collects in B and C hollowed portions.

(ii) Why is potato A required for this experiment?

(iii). Explain why water doesn’t collect in the hollowed-out portion of A or D.


(i) Sugar and Salt increase osmotic concentration, which causes water to flow osmotically through the trough of potatoes’ C and B cells into the cavity.

(ii) Potato A is a control experiment to ensure that water does not move in the potato cavity because it has lower osmotic content than potato tuber cells.

(iii) Potato tuber D doesn’t have living cells. Dead cells do not support osmosis. Even though there is sugar in cavity D, water cannot pass from the trough through the dead potato cells to the cavity of the tuber.

Q7. Differentiate between chromatin and chromosome.



The DNA double-helix in eukaryotes has created chromatin, a type of structure known as chromatin. It is composed of DNA, protein, and RNA. Chromatin’s primary function is to pack DNA into the nucleus of cells. Chromatin regulates gene expression, and it allows DNA replication. This protein also protects DNA from damage. The proteins can bind with DNA strands in histones.


The highest condensed DNA double-helix structure with proteins is called chromosomes. There are 46 independent chromosomes within the human genome. There may be more than one set in some genomes. Homologous chromosome pairs are copies of the exact copy of a chromosome. This includes 22 homologous pairs (autosomes) and two sex chromosomes.

Q8. What would happen to a cell’s life if it didn’t have a Golgi apparatus?

Answer: All aspects of preservation, modification, packaging, and storage of products in particles fall under the purview of the Golgi apparatus. Without the Golgi apparatus, all storage, modification, packaging, and dispatching of materials within and outside the cell would be impossible.

Q9. What organelle is the cell’s powerhouse? Why?

Answer: During respiration, the cell’s Mitochondria synthesise energy in the form of ATP, which is vital for many living processes.

Q10. Where are the proteins and lipids that make up the cell membrane?

Answer. There are two types of the endoplasmic retina: 

(i) The smooth endoplasmic reticulum (SER) is responsible for producing the lipids that make the cell membrane. 

(ii) The rough endoplasmic retina (RER) houses the ribosomes and is responsible for producing the proteins that make up cell membranes.

Q11. How is a prokaryotic cell different from a eukaryotic cell?


Prokaryotic Cells  Eukaryotic Cells 
  • Prokaryotes are organisms that do not possess a nucleus and are membrane-bound organelles. 
  • It belongs to the kingdom monera.
  • Include bacteria and cyanobacteria. 
  • Cells usually are 0.2 to 2 um in diameter. 
  • Unicellular organisms. 
  • Have no true nucleus, no nucleus membranes, or nucleoli. 
  • Have a single, circular DNA molecule in the nucleoid.
  • Lack of membrane-bound organelle. 
  • Cell walls are mostly made up of peptidoglycans. 
  • Carbohydrates and sterols are not found in the plasma membrane. 
  • Contain a primitive cytoskeleton without cytoplasmic streaming. 
  • Cell division occurs through binary fission. 
  • Sexual reproduction occurs by conjugation. 
  • Eukaryotes are organisms that possess membrane-bound organelles, including the nucleus. 
  • Belong to the kingdom Protista, kingdom Plantae, kingdom fungi, and kingdom Animalia. 
  • Include animals, plants, fungi, protozoa, and algae. 
  • Cells usually are 10 to 100 um in diameter. 
  • Multicellular organisms. 
  • It consists of an original nucleus with double nuclear membranes and nucleoli. 
  • Have multiple linear chromosomes in the nucleus. 
  • Contain membrane-bound organelles such as mitochondria, chloroplast, ER and vesicles. 
  • Cell walls are made up of cellulose, chitin, and pectin.
  • Carbohydrates and sterols serve as receptors on the plasma membrane. 
  • Contain a complex cytoskeleton with cytoplasmic streaming. 
  • Cell division takes place through mitosis. 
  • Sexual reproduction occurs through the production of gametes.  

Q12. How is an animal cell different from a plant cell? 


Animal Cells  Plant cells
  • Animal cells are smaller than plant cells 
  • It comes in various sizes and tends to have round or irregular shapes. 
  • Animal cells store energy in the form of the complex carbohydrates’ glycogen. 
  • 20 amino acids need protein production, and animal cells produce only 10 amino acids. 
  • Only stem cells can convert to other cell types. 
  • Animal cells can increase in size by increasing cell numbers. 
  • Animals’ cells don’t have a cell wall but have a cell membrane. 
  • It contains cylindrical structures that organise the assembly of microtubules during cell division. 
  • Cilia is only found in animal cells. 
  • Glyoxysomes are not found in animal cells. 
  • Animals’ cells do not have plastids. 
  • Animal cells do not have plasmodesmata. 
  • Animal cells may have many small vacuoles. 
  • Plant cells are giant. 
  • The cells are more similar in size and are typically rectangular or cube-shaped. 
  • Plant cells store energy as starch. 
  • Plants can synthesise all 20 amino acids. 
  • Plant cell types are capable of differentiation. 
  • Plant cells mainly increase cell size by becoming larger. 
  • They are composed of cellulose as well as a cell membrane. 
  • Plant cells have a cell wall composed of cellulose and cell membrane. 
  • Plant cells do not typically contain centrioles. 
  • Cilia are not found in plant cells. 
  • Glyoxysomes are present in the plant cells. 
  • Plant cells rarely contain lysosomes as the plant vacuole handles molecules’ degradation. 
  • Plant cells have plastids such as chloroplasts. 
  • Plants have plasmodesmata. 
  • The cells have a large central vacuole. 

Q13. How is a bacterial cell different from an onion peel cell? 


Bacterial Cell Onion peel cell 
  • The cell size is generally tiny and ranges between 1 to 10 mm.
  • The nucleus is absent in bacterial cells. 
  • Bacterial cells contain a single chromosome.
  • The nucleolus is absent. 
  • Membrane-bound cell organelles are absent. 
  • Cell division takes place by fusion or budding. 
  • The cell size is generally large, ranging between 5 to 100 mm.
  • The nucleus is present in onion peel cells. 
  • An onion peel cell contains more than one chromosome. 
  • The nucleolus is present. 
  • Membrane-bound cell organelles include mitochondria plastids, endoplasmic reticulum, Golgi apparatus, lysosomes, peroxisomes, etc. 
  • Cell division takes place by mitosis of meiotic cell division. 

Multiple Choice Questions 

Q14. Which one of these can be made into a crystal ?

(a) A Bacterium

(b) An Amoeba

(c) A Virus

(d) Sperm Soln

Answer: The correct option is (c). A Virus

Explanation: Viruses can be considered intermediates between non-living and living because they cannot metabolise or reproduce themselves. For all of its processes, the virus needs a host. Viruses can also be stored as crystal-like chemicals. Virus crystals are a collection of millions of virus cells.

Q15. If you allow a cell to swell, it will become more prominent.

(a) The cell’s water molecules are more concentrated than those in the surrounding medium.

(b) Water molecules are more concentrated in the surrounding medium than in the cell.

(c) The cell’s water molecules are the same as those in the surrounding medium.

(d) Water molecules concentration does not matter

Answer: (b) Water molecules are more concentrated in the surrounding medium than in the cell.

Explanation: Water molecules are more concentrated in the surrounding medium than in the cell. This causes the cell to swell.

Q16. The components of chromosomes are

(a) DNA

(b) protein

(c) DNA, protein

(d) RNA Solution

Answer: (c) DNA, protein

Q17. Which of these options is not a function Ribosomes

(i) It aids in the production of protein molecules

(ii) It aids in the production of enzymes

(iii) It aids in the production of hormones

(iv) It aids in the production of starch molecules

(a) (i), and (ii).

(b) (iii), and (iii).

(c) (iii), and (iv).

(d) (iv), and (i).

Answer: The correct option is (c), (iii), and (iv).

Explanation: The ribosomes are responsible for protein synthesis. Protein is the basis of enzymes. Ribosomes are responsible for the production of enzymes and protein. Therefore, options (iii) and (iv) are incorrect.

Q18. Which one of these is not connected to the endoplasmic-reticulum?

(a) It acts as a transport channel for proteins between the nucleus, cytoplasm and the cell membrane.

(b) It moves materials between different regions of the cytoplasm

(c) It could be used for energy generation

(d) It could be the location for biochemical activities in the cell

Answer: (c) It could be the location of energy generation

Explanation: The function of mitochondria is energy generation. ER is a network that links the nucleus to the cytoplasm and allows for the transport of proteins. It facilitates material transport from one cell to the next.

Q19. Choose the correct one from below. Plasmolysis in the plant cell is defined as the process of?

(a) Plasma membrane in hypotonic media is broken down (lysis).

(b) shrinkage in the cytoplasm within the hypertonic medium

(c)  shrinkage in the nucleoplasm

(d) None of them

Answer (b) shrinkage in the cytoplasm within the hypertonic medium.

Explanation: A cell kept in hypertonic solutions loses most of its fluid. This causes shrinkage in the protoplasm. This happens when the environment is arid.

Q20. Here are some definitions of osmosis. Please read carefully to ensure you choose the correct definition.

(a) Water molecules move from one region with higher concentrations to another through a semipermeable membrane

(b) Movement of solvent molecular from higher to lower concentration

(c) Movement of solvent molecules through permeable membranes from higher to lower concentrations

(d) Movement of the solute molecules from lower to higher concentrations of solution through a semipermeable membrane

Answer: (a) Water molecules move from one region with higher concentrations to another through a semipermeable membrane.

Explanation: Osmosis refers to a special kind of diffusion where water molecules move through semipermeable membranes from one region of higher concentrations to another region of lower concentrations.

Q21. Cells will expand if the concentration of water molecules within the cell is higher  than the concentration of water molecules.

(a) In the surrounding medium

(b) The concentration of water molecules in the surrounding medium is higher  than the concentration in the cell.

(c) The cell’s water molecules are the same as those in the surrounding medium.

(d) The concentration of water molecules is irrelevant

Answer: The correct option is (b)  The concentration of water molecules in the surrounding medium is higher  than the concentration in the cell.


Osmosis refers to a spontaneous process in which solvent molecules move into a region with a higher solute content from a lower solute concentration via a partially porous membrane. This causes the solute concentrations to be equal.

Endosmosis is the movement of solvent from the outside to the inside (inward movement). It is caused by a hypotonic solution. 

Q22. Which of these options is not a function of ribosomes?

  1. It aids in the manufacture of protein molecules.
  2. It is helpful in the manufacture of enzymes.
  3. It aids in the manufacture of hormones
  4. It aids in the manufacture of starch molecules.

(a) I and (II)

(b) II and III

(c) III and IV

(d) IV, I

Answer: the correct answer is (c) 


Ribosomes can be dense, spherical, or granular particles that remain free in the matrix. They also stay attached to the endoplasmic reticulum. They do not have a membrane-bound and can be found in prokaryotic as well as eukaryotic cells. They are essential in the synthesis of proteins. All enzymes and hormones are proteins, but not all hormones.

Q23. Which one of these is not connected to the endoplasmic-reticulum?

(a) It acts as a transport channel for proteins between the nucleus and the cytoplasm

(b) It moves materials between different regions of the cytoplasm

(c) It could be used for energy generation

(d) It could be the location for biochemical activities in the cell

Answer: The correct choice is (c)


Endoplasmic Reticulum is a membranous network that connects to the outer membrane of the nucleus from one end and to the plasma membrane from the other.

It comes in three forms.

(i) Cisternae-closed fluid-filled sac

(ii) Vesicles

(iii) Tubules

It comes in two types: smooth endoplasmic retina, i.e. it has no ribosomes and rough endoplasmic reticulum, which has ribosomes.

Q24. Which of these are covered by one membrane? 

(a) Mitochondria

(b) Vacuole

(c) Lysosome

(d) Plastid


  1. c) Lysosomes, 

Explanation: These are small, spherical, sac-like structures distributed evenly in the cytoplasm and contain powerful enzymes that can digest or break down any organic material. These enzymes are made from the rough endoplasmic retina.

These functions are performed in the body.

  1. They aid in the digestion of large molecules within cells.
  2. They help protect against viruses and bacteria.
  3. Lysosomes use their cell organelles to digest starved cells. Cell death is the result. These lysosomes can also be called suicide bags or cell demolition squads.

Q25. Find the correct sentence.

(a) Lysosomes contain enzymes. They are processed through RER (Rough Endoplasmic Reticulum).

(b) Both rough and smooth endoplasmic reticulum produce lipids and proteins

(c) Endoplasmic Reticulum is associated with the destruction of the plasma membrane

(d) Nucleoids can be found in the nucleoplasm of the eukaryotic nuclear nucleus


(a) Lysosomes contain enzymes. They are processed through RER (Rough Endoplasmic Reticulum).


Prokaryotic cells are composed of one chromosome. This is the explicit content of the cell’s cytoplasm.

The nucleoplasm is enclosed within the nuclear envelope, containing many pores known as the nuclear pores. Two nuclear structures can be found within nucleoplasm: the nucleolus or chromatin material.

One or more nucleolus can be present, and any membrane does not bind it. It is rich in protein (Ribonucleic acid) and RNA molecules. The nucleolus acts as the site of ribosome formation and hence, is known as the factory of ribosomes.

Q25. The proteins and lipids, essential for building the cell membrane, are manufactured by? Choose one from the following:

(a) Endoplasmic Reticulum

(b) Golgi apparatus

(c) plasma membrane

(d) mitochondria


(a) Endoplasmic Reticulum


(i) It increases the surface area of the cells for different metabolic activities.

(ii) It provides internal support for the colloidal matrix, cytoplasm.

(iii) It’s associated with storing, transporting and synthesising metabolic products.

(iv) It aids in forming the cell plate and the nuclear membrane during cell division.

(v) Rough Endoplasmic Reticulum (RER) is involved in the synthesis and maintenance of proteins.

(vi) Smooth endoplasmic reticulum (SER) secretes lipids that, together with proteins, form cell membranes through a process known as membrane biogenesis.

Q26. Choose the odd one out.

(a) Water’s movement across semipermeable membranes is affected by the concentration of substances within it.

(b) Membranes are organic molecules such as proteins and lipids. 

(c) Molecules that dissolve in organic solvents can pass easily through the membrane.

(d) The plasma membranes are rich in chitin sugar found in  plants

Soln: The answer is (d). Plasma membranes contain chitin sugar found in plants.

Explanation: The statement that the plasma membrane contains sugar is false, while the rest of the statements are proper. Plasma membrane from plants contains cellulose.

Short Answer Questions 

Q27. What happens to substances such as CO2 or water when they move in  and out of the cells freely? Discuss.

Answer: Diffusion is the mechanism by which CO2 moves – Cellular waste accumulates at high cell levels, while the outside environment has a relatively lower concentration. The difference in CO2 concentrations inside and outside the cell causes CO2 to diffuse from an area of higher concentration (within the cell) to a region with a lower concentration. The cell membrane allows H2O to diffuse by osmosis. H2O moves through the cell membrane from a higher to a lower concentration region until equilibrium is achieved.

Q29. Why are lysosomes, also known as suicide bags?

Answer: Lysosomes can burst if there is cell damage, and when it is impossible to revive the cell, the enzymes will begin to digest the cell. Lysosomes are  also known as  suicide bags.

Q30. What are the locations of proteins synthesised in cells?

Answer: The ribosomes are responsible for protein synthesis within cells. Ribosomes can also be called protein factories. Ribosomes can be found attached to the rough endoplasmic retina.

Q31. What happens if the plasma membrane breaks down or ruptures?

Answer: The plasma membrane regulates the movement of substances in and out of cells by diffusion or osmosis. If there is a rupture in the plasma membrane, the cell could lead to exposure of the cell component to the external environment and would ultimately result in the death of the cell.

Q32. What would happen if the Golgi apparatus was not there?

Answer: The Golgi apparatus packaging or structural protein arrangement would not occur inside a cell. Without proteins being transported, cell metabolism will cease and eventually die.

Q33. Which organelle can be described as the powerhouse of a cell? Why? 

Answer: Mitochondria is the powerhouse of cells. ATP molecules are the energy that mitochondria release to enable various chemical activities necessary for life. ATP is used by the body to make new chemical compounds and perform mechanical work. The powerhouse of cells, mitochondria, is because they are the source of energy.

Q34. Each student was given five raisins of equal mass. The raisins were then soaked in distilled water at room temperature. The raisins were soaked in distilled water at room temperature for 10 minutes, overnight for B, and 60 minutes for C. They determined the amount of water that raisins absorb. Answer the following question: 

(a) Name the student whose raisins have the highest percentage of water absorption.

(b) Name the student who will absorb the least amount of water from the raisins.


(a) Maximum percentage of water absorption. Raisins for a ‘B” student.

(b) Minimum Water Absorption. Raisins for ‘A’ students.

Q35. In beaker A, a teacher soaked 10 grams of raisins in 35ml of distilled alcohol and the same amount in a beaker B. The temperature in beaker A was 20°C, and that of beaker B was 40°C. Compare the water absorption of raisins in beakers B and A after an hour. 


Beaker B, heated to 40 degrees Celsius, absorbed more water. The cell membrane’s permeability increases from 0 to 40 degrees Celsius, beyond which denaturation can occur.

Q36. The experiment “To determine how much water raisins can absorb” shows that raisins absorb water after being kept in water for between 5 and 6 hours. What is the reason for the water absorption to occur? What is this phenomenon called?


Water moves into raisins due to endosmosis. Endosmosis refers to water entry into a system, cell, or organ because of hypertonic solutions. In addition, it separates pure water from a dilute solution or pure water by a semipermeable membrane. Further, the skin of raisins forms semipermeable membranes. They contain a high level of sugar. Shallow water can enter raisins and cause swelling.

Q37. A student made these observations as part of an experiment to determine how raisins absorb water. 

(i) Water is taken in a beaker – 50g

(iii) 20 g mass of dried raisins before soaking water

(iii) Mass of raisins after soaking in water – 30g

(iv) Remaining water in the beaker after the experiment – 40 g

Calculate the percent of the water that raisins absorb.

The percentage of water that is absorbed by the raisins = (the initial weight of water) – (final weight of water / initial weight of the water)*100

= (50-40) g / 50 g * 100 = 20%

So as per the above experiment 20% of water is absorbed by the raisins.

Miscellaneous Questions 

Q38. To heat an iron-sulphur mixture for iron sulphide, you should: 

(1) Heat the powder mixture at the base of the test tube with a blue flame.

(2) Heat the iron filings and sulphur mixture in the test tube middle with a yellow flame.

(3) Heat the powder mixture in the test tube at the top with an orange flame.

(4) Heat the iron-sulphur mixture in a test tube at 3/4 of its length using a red flame.

Answer: Option 1 is the correct answer.

Explanation: The Fe and S mixture is prepared by heating them under blue flames in a test tube. They are then heated until they turn grey-black.

Q39. These precautions are required for the experiment to determine the melting point of ice. The wrong precaution is:

(1) Keep the bulb of your thermometer surrounded by crushed ice.

(2) Ice should be stirred frequently to maintain a consistent temperature.

(3) Keep your eyes aligned with the mercury level to determine the final temperature.

(4) Only the tip of the bulb of the thermometer should touch the crushed ice.

Answer: Option 4 is the correct answer.

Explanation: The bulb of a thermometer determines the temperature of any substance/material. The thermometer bulb must be adequately enclosed with crushed ice for accurate temperature measurement.

Q40. This is the correct way to prepare a colloidal solution in water of egg albumin.

(1) To break the eggshell, only the white part should be taken, and then it must be added to water.

(2) To break the eggshell, only take the yellow portion. Then add it to boiling water and stir constantly.

(3) To boil the egg first, crack the eggshell and add the white part to ice water. Mix.

(4) To boil the egg first, crack the eggshell and add the yellow part to the water. Mix thoroughly.

Answer: Option 1 is the correct answer.

Explanation: To prepare a colloidal solution containing egg albumin and water, you must first break the eggshell. Then, only a tiny amount of the eggshell should be removed. After that, the water should be carefully mixed with the egg. For proper mixing of egg with water, constant stirring is required.

Q41. The evaporation and temperature of water were observed by four students (A, B, C and D) under various conditions. They then recorded their observations at regular intervals.

Student Placing of the experimental set-up in/under Temperature recording for 15 minutes
Sun  Increased gradually 
Open-air Decreased gradually 
      (C)   A fan  Initially increased , then became constant. 
      (D)  A corner of the room  Initially increased, then gradually decreased

(1) (A)

(2) (B)

(3) (C)

(4) (D)

Answer: Option 2 is the correct answer.

Explanation: Temperature and pressure in the open air will not change. The temperature will rise first; then, slowly, it will drop. After 15 minutes, temperature observation will gradually decrease.

Q42. The student heats water over a flame to determine its boiling point. He continues to take its temperature readings. He would notice that the water temperature was:

(1) continues to increase regularly

(2) continues to increase irregularly

(3) First, it increases slowly, gradually decreases and finally becomes constant.

(4) increases slowly and then becomes constant.

Answer: Option 4 is the correct answer.

Explanation: Water boils slowly, but then it rises steadily over time. The water temperature during phase transformation is constant because the heat used to raise the temperature will change the state of the water by breaking the force of attraction between particles.

Benefits of Solving Class 9 Science Chapter 5 Important Questions

Many different topics and sub-topics are provided in the critical questions Class 9 Science chapter 5. Students can ensure they get some additional help for scoring better in the exam. Subject experts  have created several pointwise notes that help students conveniently recall the crucial points in the exam and use these important questions for last-minute revisions.In addition, some of the  most important questions will help them to understand every concept and answer any question easily and   get excellent  grades in their exams. . Students get to familiarise themselves with complex concepts such as plasma or cell membranes and more. 

Some of the benefits of solving fundamental unit of life class 9 important questions: 

  • All these questions are based on key concepts. Therefore, the concepts are essential for quick revision before the exam.
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  • Class 9 science chapter 5 important questions are based on  NCERT books aligned with the latest CBSE syllabus. . 
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  • Practising science class 9 chapter 5 important questions will prepare students more effectively for their upcoming exams. 
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Q.1 Complete the boxes with appropriate natural resources and define the zone that comprises of all the three forms of life.


The biosphere is the life supporting zone of earth where all 3 forms of life – air, land and water co-exists.

Q.2 What is humus? Explain the role of earthworms in the formation of humus.


Humus is the decomposed plant and animal material which makes the soil fertile. Earthworms play a major role in converting large pieces of organic matter into rich humus, improving soil fertility.

Q.3 Smog is a serious problem in many countries and continues to harm human health. Justify.


Smog is a visible indication of air pollution. It is a combination of various suspended particles with water vapour and dust. These suspended particles are unburnt carbon particles called hydrocarbons, produced due to combustion of fossil fuels. Ground-level ozone, sulphur dioxide, nitrogen dioxide and carbon monoxide are harmful for senior citizens, children and people with heart and lung problems such as asthma. Smog hampers the visibility and harms the environment.

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FAQs (Frequently Asked Questions)

1. Which are the essential topics explained in chapter 5?

Chapter 5 of Class 9 Science is ‘Fundamental Unit of Life’ . This chapter is important because it explains the fundamental concept of human existence. This chapter deals with essential topics like what living organisms are made from, how they function, the structure of cells, cell membranes or cell walls, nucleus, cell organelles (endoplasmic retina, Golgi apparatus and lysosomes), cell division (mitosis, meiosis) and plastids.

2. Is solving important questions in class 9 Science chapter 5 enough for the exam preparation?

Students will get to revise everything and cover the entire syllabus. These questions are created by the subject experts exclusively for the exams. In addition, there are high chances that some of these questions will be asked in the exam. Students will get a good practice of different types of questions and will be well prepared for the science paper. Therefore, solving important questions in class 9 Science chapter 5 is enough for the exam preparation. However, the students can also refer to other study material available on the website

3. Where can I access the list of important questions for class 9 Science chapter 5?

Students can access the complete list of important questions on our Extramarks website. Furthermore, students can also refer to past  years’ questions papers. It covers the entire syllabus, and each concept is explained thoroughly. Students will get to clear their doubts and improve their scores.