Question 12 Marks
Draw a cross-section of root showing association of soil particles with root hairs.
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Question 22 Marks
What is the significance of diffusion?
Answer
View full question & answer→Significance of Diffusion
(i) It helps in the exchange of respiratory gases.
(ii) It helps in the transport of food molecules without the plant body.
(i) It helps in the exchange of respiratory gases.
(ii) It helps in the transport of food molecules without the plant body.
Question 32 Marks
Define the Cohesive and Adhesive forces.
Answer
View full question & answer→Cohesive Force: The force produced by the molecular attraction between water particles.
Adhesive Force: The force of attraction between the molecules of unlike bodies that act to hold them together is called adhesive force.
Adhesive Force: The force of attraction between the molecules of unlike bodies that act to hold them together is called adhesive force.
Question 42 Marks
What do you mean by transpiration pull ?
Answer
View full question & answer→Transpiration Pull: As the water is lost from the leaf surface by transpiration more water molecules are pulled up due to the tendency of water molecules to remain joined (cohesion), and thus- to produce a continuous column of water through the stem. This phenomenon is known as transpiration pull
Question 52 Marks
Root hairs become flaccid, when fertilizers are added to the moist soil around it. Explain.
Answer
View full question & answer→When fertilizers are added to the moist soil around it, it will form hypertonic solution, resulting the protoplasm to shrink and plasma membrane withdraw itself from the cell wall. Hence, the root hairs also become limp or flaccid.
Question 62 Marks
Explain why the grass in your lawn becomes greener if you add a little fertilizer to it, but it dies if you add a lot of it.
Answer
View full question & answer→If a little fertilizer is added, it provides minerals and other nutrients so the leaves synthesize more chlorophyll and appear greener. If a lot of fertilizer is added, it forms a hypertonic solution resulting in plasmolysis and consequently wilting of parts of the plant. Ultimately the plant dies.
Question 72 Marks
A few RBC’s were kept in three test tubes containing isotonic, hypotonic and hypertonic solutions. What will be the expected observations after a few hours? Explain.
Answer
View full question & answer→The shape and size of the cells will remain unchanged in isotonic solution, because the cells will neither loose nor gain water in it.
Cells will swell up in hypotonic solution as water will enter in it due to endosmosis.
Cells will shrink in hypertonic solution as water will move out of the cell due to exosmosis.
Cells will swell up in hypotonic solution as water will enter in it due to endosmosis.
Cells will shrink in hypertonic solution as water will move out of the cell due to exosmosis.
Question 82 Marks
Give Reasons for the following.
A closed can of dried seeds bursts open if some water enters it by accident.
A closed can of dried seeds bursts open if some water enters it by accident.
Answer
View full question & answer→If some water enters in a closed can of dried seeds, the seeds absorb water by imbibition and osmosis and swell up. The swelling up of seeds exerts a force on the walls of the can, and hence the can bursts open.
Question 92 Marks
Give Reasons for the following.
Freshwater fish cannot survive in seawater.
Freshwater fish cannot survive in seawater.
Answer
View full question & answer→The seawater is saline (having more concentration of salts) and acts as a hypertonic solution for the freshwater. So freshwater fish cannot survive in seawater as it causes the plasmolysis of the cells of the fish and ultimately the fish will die.
Question 102 Marks
Explain why:
Bacteria and fungi do not grow in pickles, jams, jellies and squashes.
Answer
View full question & answer→Jam, jellies and pickles are kept in hypertonic solution of sugar or salt in which plasmolysis of bacteria and fungi takes place. This kills the bacteria and fungi and hence, pickles, jam and jellies are preserved properly.
Question 112 Marks
Give Reasons for the following.
We gargle with saline water in case of throat infection.
We gargle with saline water in case of throat infection.
Answer
View full question & answer→The salt solution (saline water) is hypertonic and when we gargle with it, comes in contact of infection causing bacteria in the throat. The water present in the bacterial cell comes out causing plasmolysis and they get killed giving us relief from infection.
Question 122 Marks
Differentiate between the following
Endosmosis and Exosmosis
Endosmosis and Exosmosis
Answer
View full question & answer→| PEndosmosis | Exosmosis |
| It occurs when a cell is placed in a hypotonic solution. | It occurs when a cell is placed in a hypertonic solution. |
| Water moves into the cell. | Water moves out of the cell |
Question 132 Marks
Differentiate between the following
Plasmolysis and Deplasmolysis.
Plasmolysis and Deplasmolysis.
Answer
View full question & answer→| Plasmolysis | Deplasmolysis |
| In this, the protoplasm of the cell shrinks away from the cell wall. It results in the flaccid condition of the cells and the plant. | In this, the protoplasm of the cell swells up and touches the cell wall. It results in the turgid condition of the cells and the plant. |
| Caused due to exosmosis. | Caused due to endosmosis. |
Question 142 Marks
Differentiate between the following
Turgor pressure and Root pressure
Turgor pressure and Root pressure
Answer
View full question & answer→| Turgor Pressure | Root Pressure |
| t is the pressure of the cell. Contents of a turgid cell on its cell wall. | It is the pressure under which water passes from the living cells into the xylem of root. |
| It is caused when a cell becomes turgid. | It is caused due to alternate turgidity and flaccidity of root cells. |
Question 152 Marks
Differentiate between:
Turgid and Flaccid.
Turgid and Flaccid.
Answer
View full question & answer→| Turgid | Flaccid |
| (ii) It occurs due to endosmosis. | (i) The cell loses water from the vacuole and cytoplasm under the plasmolytic condition. |
| (ii) It occurs due to endosmosis. | (ii) It occurs due to exosmosis. |
Question 162 Marks
Differentiate between:
Osmosis and Diffusion
Osmosis and Diffusion
Answer
View full question & answer→| Osmosis | Diffusion |
| Osmosis is a special type of diffusion which involves the movement of solvent molecules from a region of their higher concentration to a region of their lower concentration through a semi-permeable membrane. | Diffusion is the movement of solute molecules or ions from a region of their higher concentration to a region of their lower concentration without the influence of a semi-permeable membrane. |
Question 172 Marks
In an experiment, two sets of apparatus were set up as shown below:
In A there is a concentrated sugar solution inside the thistle funnel and red ink in the water outside the funnel. In B there is a concentrated glucose solution with red ink inside the thistle funnel and water outside the thistle funnel.
In both A and B the level of liquid inside the funnels rises up the tubes. In A the sugar solution turns red and in B, the water turns red.
Study the given observations and answer these questions:
Name the process by which red ink moves in A and B.
Which type of pressure forces the water molecules to move towards thistle funnels and cause a rise in the water level?
Where does this process occur in plants and animals?
What material could be used as a semi-permeable membrane?
In A there is a concentrated sugar solution inside the thistle funnel and red ink in the water outside the funnel. In B there is a concentrated glucose solution with red ink inside the thistle funnel and water outside the thistle funnel.
In both A and B the level of liquid inside the funnels rises up the tubes. In A the sugar solution turns red and in B, the water turns red.
Study the given observations and answer these questions:
Name the process by which red ink moves in A and B.
Which type of pressure forces the water molecules to move towards thistle funnels and cause a rise in the water level?
Where does this process occur in plants and animals?
What material could be used as a semi-permeable membrane?
Answer
View full question & answer→(i) Osmosis.
(ii) Osmotic pressure.
(iii) In plants, in the root cells and in animals in the RBC’s.
(iv) Cellophane paper or goat bladder, etc.
(ii) Osmotic pressure.
(iii) In plants, in the root cells and in animals in the RBC’s.
(iv) Cellophane paper or goat bladder, etc.
Question 182 Marks
Given below is an experimental demonstration.
(i) Which phenomenon has been demonstrated in the given figure?
(ii) What is the solute and what is solvent in the above experiment?
(iii) Define the phenomenon in Q. (i) above.
(iv) Give one example from your daily life experiences based on this principle.
(i) Which phenomenon has been demonstrated in the given figure?
(ii) What is the solute and what is solvent in the above experiment?
(iii) Define the phenomenon in Q. (i) above.
(iv) Give one example from your daily life experiences based on this principle.
Answer
View full question & answer→ (i) Diffusion.
(ii) KMnO4 crystals represent the solute and water is solvent.
(iii) The movement of the molecules of a substance from the region of their higher concentration to the region of their lower concentration until a state of equilibrium is achieved in both the regions.
(iv) If a bottle of scent or spirit is opened in one comer of a closed room, its smell can be felt in every part of the room.
(ii) KMnO4 crystals represent the solute and water is solvent.
(iii) The movement of the molecules of a substance from the region of their higher concentration to the region of their lower concentration until a state of equilibrium is achieved in both the regions.
(iv) If a bottle of scent or spirit is opened in one comer of a closed room, its smell can be felt in every part of the room.
Question 192 Marks
A thin strip of epidermal cells from the fleshy scales of an onion bulb was examined in a drop of water, under a microscope. All the epidermal cells looked alike and the figure alongside represents one of them. The thin strip was then transferred to a drop of strong sugar solution and re-examined under the microscope after about five minutes.
(i) Make a sketch of one of the epidermal cells, as it might appear after immersion in a strong sugar solution. Label any two parts which have undergone a change.
(ii) Give the scientific term for the change shown in Q.(i) above.
(iii) What would you do to bring this cell back to its original condition?
(iv) Give the scientific term used for the recovery of the cell as a result of the step taken in Q.(iii) above.
(i) Make a sketch of one of the epidermal cells, as it might appear after immersion in a strong sugar solution. Label any two parts which have undergone a change.
(ii) Give the scientific term for the change shown in Q.(i) above.
(iii) What would you do to bring this cell back to its original condition?
(iv) Give the scientific term used for the recovery of the cell as a result of the step taken in Q.(iii) above.
Answer
View full question & answer→(i) See figure.
(ii) Plasmolysis.
(iii) We would immerse this cell into freshwater, i.e., hypotonic solution.
(iv) Deplasmolysis.
(ii) Plasmolysis.
(iii) We would immerse this cell into freshwater, i.e., hypotonic solution.
(iv) Deplasmolysis.
Question 202 Marks
Given below is the figure of an experimental set up to demonstrate root pressure.
(i) Define root pressure.
(ii) What change would you observe in the water level after some time?
(iii) What role is being played by the root pressure in the given experiment?
(iv) Why the oil has been sprinkled on water?
(i) Define root pressure.
(ii) What change would you observe in the water level after some time?
(iii) What role is being played by the root pressure in the given experiment?
(iv) Why the oil has been sprinkled on water?
Answer
View full question & answer→(i) The collective force exerted by the cortical cells of the root in forcing water upward into the xylem is known as root pressure.
(ii) The water level will rise in the glass tube.
(iii) Root pressure is forcing the water up in the stem.
(iv) To prevent evaporation of water from the tube.
(ii) The water level will rise in the glass tube.
(iii) Root pressure is forcing the water up in the stem.
(iv) To prevent evaporation of water from the tube.