[2 Mark Question Answer]

Question 12 Marks

Three plants (a), (b) and (c) were placed in beakers containing coloured water. The water in each beaker was covered with a layer of oil. The leaves were removed from plant (b), while plant (c) was exposed to strong light.
(i) In which plant, (a), (b) or (c) would the water move up the fastest?
(ii) In which plant (a), (b) or (c), would the water move up slowly?
(iii) Why was the water covered with a layer of oil?
(iv) What is being investigated by this experiment?

Answer

(i) In (c), the water would move up the fastest.
(ii) In (b), the water would move up slowly.
(iii) To prevent evaporation of water.
(iv) Absorption of water by the roots.

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Question 22 Marks

Give at least three uses of water to green plants.

Answer

(i) Water is one of the raw materials for photosynthesis.
(ii) Water is important for seed germination.
(iii) Water controls the opening and closing of stomata.

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Question 32 Marks

Explain why:
Bacteria and fungi do not grow in pickles, jams, jellies and squashes.

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.

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Question 42 Marks

The diagram given below represents a plant cell after being placed in a strong sugar solution. Guidelines 1 to 5 indicate the following:
1. Strong sugar solution
2. Cell wall
3. Protoplasm
4. Large vacuole
5. Nucleus
Study the diagram and answer the questions that follow:
(i) What is the state of the cell shown in the diagram?
(ii) Name the structure which acts as a selectively permeable membrane.
(iii) If the cell had been placed in distilled water instead of strong sugar solution which feature would not have been present?
(iv) If the cell in the diagram possessed chloroplasts where would these be present?
(v) Name any one feature of this plant cell which is not present in animal cells.

Answer

(i) Plasmolysed cell
(ii) Plasma membrane
(iii) Large vacoule
(iv) The chloroplasts would be present in the shrunken protoplast.
(vi) Cell wall

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Question 52 Marks

Explain briefly whydo not root hairs become flaccid when fertilisers are added to the moist soil around them?

Answer

The root hairs become flaccid when fertilisers are added to the moist soil around them because fertilisers with moist soil become hypertonic which causes plasmolysis in the cells of the root hair. The turgidity is lost and the cell becomes flaccid.

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Question 62 Marks

What is the utility of plasmolysis?

Answer

Plasmolysis helps in the preservation of meat and fish by salting. It is also helpful in the preservation of jellies and jams by adding concentrated sugar solution to them. It helps in plasmolysing the spores of bacteria and fungi.

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Question 72 Marks

Distinguish between the following:
Plasmolysis and deplasmolysis

Answer

Plasmolysis	deplasmolysi
When a cell is placed in hypertonic solution , water begins to pass out of the cell by osmosis with a consequent shrinkage of protoplasm . This phenomenon is called plasmolysis .	When a plasmolysed cell is placed in hypotonic solution or pure water , endosmosis takes place as a result of which water is reabsorbed by the protoplast of the cell and it regains its original position . This phenomenon is called deplasmolysis .

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Question 82 Marks

Distinguish between the following:
Turgor pressure and osmotic pressure

Answer

Turgor pressure	osmotic pressure
In a turgid cell , the pressure of the cell contents on the cell wall is called turgor pressure .	The pressure by which the water molecules tend to cross the semi-permeable membrance is called the osmotic pressure .

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Question 92 Marks

Distinguish between the following:
Filtration and diffusion

Answer

Filtration and diffusion

Filtration	diffusion
Filtration is the mechanical separation of a liquid from the undissolved particles floating on it .	Diffusion is the movement of substances from an area of higher concentration to an area of lower concentration .

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Question 102 Marks

What is the difference between endosmosis and exosmosis?

Answer

Endosmosis	Exosmosis
1. The process of diffusion of water into the cell from outside is called endosmosis.	1. The diffusion of water from inside to outside of a cell is called exosmosis.
2. It occurs when the cell is placed in a hypotonic solution.	2. It occurs when the cell is placed in a hypertonic solution.

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Question 112 Marks

What is the difference between diffusion and osmosis?

Answer

Diffusion	Osmosis
It is the movement of molecules of a substance from a region of higher concerntration to a region of lower concentration.	It is the process in which water molecules moves through a semi-permeable membrance from a region of higher concentration to a region of lower concentration.

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Question 122 Marks

Mention two ways in which root hairs are suited for absorption of water from the soil?

Answer

(i) The epidermis and endodermis of root hairs are permeable to water.
(ii) Root hairs have a very large surface area.

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Question 132 Marks

Give an account of the importance of turgor pressure in a herbaceous plant.

Answer

Turgor pressure keeps the soft organs like flowers, young shoots, leaves, etc. in stretched form. It is also essential for the growth of the cells. Changes in the turgor pressure causes opening and closing of stomata.

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Biology [2 Mark Question Answer]

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