Form 5 Answers (Homework)

PAPER 1

1. D  2. B  3. C  4. B  5. A  6. D  7. D  8. A  9. C  10. D  11. A  12. B  13. B  14. C  15. A  16. A
17. C  18. D  19. C  20. D  21. B  22. A  23. B  24. D  25. A  26. D 27. C   28. D  29. B  30. B
31. B  32. D   33. C   34. B  35. A  36. D  37. B  38. C  39. B  40. D

PAPER 2

1.  (a) (i) Lymph
           (ii)  Bacteria passing through the lymph nodes are destroyed. / More lymphocytes produced in  
                  lymph after passing through the lymph nodes.
    

     (b) A high hydrostatic pressure in the arteriole end of the capillary network forces small molecules  to diffuse through the capillary walls into the interstitial spaces between cells to form tissue fluid. The pressure is higher in the tissue fluid and causes the tissue fluid to be forced into the lymphatic capillaries and hence forming lymph / fluid X.

(c) The blood contains erythrocytes, leucocytes and platelets but fluid X contains only leucocytes.

(d) Tissue fl uid will not be able to return to the blood circulatory system and will accumulate in the spaces between the organs or tissues.

(e) About 90% of the tissue fl uid is absorbed back into the blood capillaries at the venous end of the capillary. The remaining 10% drains into the lymphatic capillaries forming lymph. Lymph in the right lymphatic duct and the thoracic duct eventually fl ows into the right and left subclavian veins of the blood circulatory system respectively.

Xylem : Transports water and dissolved mineral salts absorbed by the roots to the upper parts

               of the plant

Phloem : Transport organic substances from the leaves to the storage organs and from the

                storage organs to the growing regions..

 (c) The xylem consists of elongated tubes which run continuously from the roots to the

      leaves. The xylem walls are lignified to prevent them from collapsing.

 (d) The part of the branch where the nail is hammered may die because the xylem tissues are

       destroyed and water fl ow in the xylem tissue is blocked.

SECTION B

3 (a) (i) X : Red blood cell / Erythrocyte

             Y : White blood cell / Leucocyte

             Z : Platelet

(ii) • Main function of cell X: carries / transports oxygen to body cells.

      • Cell X (erythrocyte) contains haemoglobin, which is a respiratory pigment that can

         combine with oxygen.

      • Haemoglobin combines with oxygen to from oxyhaemoglobin (HbO8) which is bright

        red in colour.

      • When blood flow through the capillaries in the alveoli / lungs, oxygen diffuse into the

         blood.

·    Oxygenated blood is formed.

      • Oxygen is carried in the blood as oxyhaemoglobin.

      • Oxyhaemoglobin is transported along body and release oxygen when it reaches the body

        cells.

      • Oxygen enters the cells through diffusion from the capillaries.

     (b) • In the blood capillaries, the substances are including erythrocytes, leucocytes,

             platelets, water, dissolved oxygen, amino acids, glucose, fatty acids, glycerol,

             vitamins, minerals salt and blood plasma protein.

           • The high hydrostatic pressure in the capillaries forces the plasma to pass across the

             one-cell thick capillary walls into the spaces between the cells. The substances which

             are forced out into the interstitial spaces consisting of water, leucocytes and dissolved

            substances to form the tissue fluid.

            • The larger molecules like erythrocytes, platelets and plasma proteins cannot pass

              through the capillary walls.

            • The substances like water, leucocytes and dissolved substances in tissue fluid diffuse

              into the lymphatic capillaries.

            • The tissue fl uid now is called lymph once it enters the lymphatic system. The lymph  

              re-enters the blood circulatory system when it fl ows into the subclavian veins in the

             shoulder.

              • The lymphatic system transports the products of digestion to all the cells.

               • The dissolved substances in the blood including the products of digestion like  

                glucose, amino acids, fatty acids and glycerol are forced into the interstitial spaces

                to form tissue fluid.

               • The tissue fl uid transports these substances to the cells.

               • There are 2 ways the interstitial fl uid is returned to the circulatory system. 90% of  

                the tissue fluid returns to the blood circulatory system directly; 10% returns through

                the lymphatic vessels which connects the blood circulatory system at the subclavian

                vein.

               • The lacteals helps to carry fatty acids and glycerol from the small intestines and

                 connects the blood circulatory system at the subclavian vein.

4 (a) • There is a difference in concentration gradient between soil and epidermal cell. Soil

           water is hypotonic to the epidermal cell / The cell sap of the root cells is more

           concentrated than the surrounding soil solution.

        • So water diffuses into the root hair cells and epidermal cells by osmosis.

         • The osmotic pressure of the epidermal cells decrease in which it is hypotonic

          compared to the adjacent cells.

       • Water molecules diffuses / enters into the adjacent cells, and in this way, water moves

          across the root from cell to cell by osmosis.

        • Water in the soil is hypotonic to the concentration of the cell sap in the root hair cells.

        • So, water from the soil diffuses into the root hair cells by osmosis.

      • When water enters the cells of the root, it causes the cell sap to become more diluted

        than the cell sap of the adjacent cortex cell.

       • This causes the water to diffuse from the root hair cell into the adjacent cortex cells by

         osmosis.

       • A pushing force called root pressure is generated due to the turgidity of the root cells in

        which the root pressure pushes the water and mineral ions inwards to the xylem vessels

        of the root and stem.

       • There are capillary actions along the xylem vessels.

       • Cohesion and adhesion of water exist in the xylem vessels.

      • The cohesion and adhesion of water  in the xylem vessels provides the force to hold up a

         continuous column of water in xylem vessels of the stem to the top of the plant.

       • Water is also transported from the root to the top of the plant by transpiration pull.

       • Water loss during transpiration creates the transpiration pull in which it draws the water

          from the soil up the xylem vessel in the stem to the leaves to replace the water lost.

4 (b) The rate of transpiration is affected by light intensity, humidity, air movements

         and temperature.

        Light intensity

       • The rate of transpiration increases when light intensity increases.
       • In daylight, the stomata opens and the rate of transpiration increases as more water
         vapour evaporates through the stomata.
      • At night, the stomata closes and the rate of transpiration decreases.

        Air movements

      • When there is no moving air, water vapour that diffuse through the stomata gather
         around the stomata, hence, the air around the stomata is saturated with water vapour and
        causes the rate of transpiration to decrease.
      • In moving air or windy conditions, as the water vapour diffuses through the stomata,
        they are swept away by the fast moving air. This causes the rate of transpiration to
        increase.

       Humidity

      • When the relative humidity in the atmosphere is high, the air is saturated with water
         vapour and this reduces the rate of evaporation of water from the stomata. Hence, the
         rate of transpiration decreases.
     • When the relative humidity is low, the air is dry. Hence the rate of evaporation is higher.
        This causes the rate of transpiration to increase.

        Temperature

     • The rate of transpiration increases when temperature increases.
     • At higher temperature, it will increase the kinetic energy of water molecules, making
        them move out of the leaf more quickly.
     • At lower temperature, it will reduce the kinetic energy of water molecules, making them
       move out slower.

PAPER 3

Aim: To demonstrate root pressure

Problem statement: How can root pressure be demonstrated?

Hypothesis: The faster the movement of wind, the higher is the rate of transpiration.

Variables:

Manipulated variable: The stem of one shoot is cut while other shoots are uncut

Responding variable: The rise in the level of the coloured water

Constant variables: A potted plant and the conditions of the surrounding environment

Materials: A healthy potted plant on a plate filled with coloured water

Apparatus: A glass tube (20 cm long), a rubber tubing, thread and a ruler

Technique: Measuring the height of the coloured water in the glass tube.

1.      A shoot is cut from a healthy potted plant, leaving a portion of the stem about 5 cm above the soil.

2.      1. A shoot is cut from a healthy potted plant, leaving a portion of the stem about 5 cm above the soil.

3.      A part of the glass tube is fi lled with coloured water and a ruler is tied to the glass tube.

4.      A piece of thread is used to mark the initial level of the coloured water in the glass tube.

5.      After three hours, the level of water in the glass tube is recorded.

Presentation of data:

Conclusion: The rise of the coloured water in the capillary tube is caused by root pressure.

2 Aim: To study the effect of the movement of wind/air on the rate of transpiration.

Problem statement: What is the effect of the movement of wind/air on the rate of transpiration?

 Hypothesis: The faster the movement of wind, the higher is the rate of transpiration.

Variables:

 Manipulated variable: Speed of the wind or air movement

 Responding variable: Rate of transpiration

 Constant variables: The size of the plants, average number of leaves between plants, Room temperature, light intensity, type of plant

 Materials: Leafy shoot of hibiscus plant

 Apparatus: Simple potometer, small knife, 250 ml beaker, retort stand, stop-watch, ruler, basin, vaseline, tissue paper and fan.

 Technique: Record the time taken for the air bubble to move through 5.0 cm in the potometer.

 Procedure:

1.      A freshy leafy shoot of a hibiscus is cut in a basin of water.

2.      A simple potometer is placed inside the basin of water.

3.      The shoot is fi tted into the rubber tube of potometer tightly.

4.      The shoot and potometer is holded upright using a retort stand.

5.      The rubber tube and the capillary tube of the potometer should not contain any air bubble.

6.      The leaves and the stem of the plant are dried with a piece of cloth.

7.      Vaseline is applied to all connections to prevent any leakage.

8.      Two points, X and Y are marked on the capillary tube of the potometer. The distance between X and Y is 5 cm.

9.      The open end of the potometer is immersed inside a beaker.

10.  The potometer is put under a fan in the laboratory with the switch on at the lowest speed, that is a speed of 1.

11.  The open end of the potometer is lifted and a drop of water is sucked out using a piece of tissue paper.

12.  As the potometer is placed back in the beaker, a small air bubble is formed inside the capillary tube.

13.  The stop-watch is started when the air bubble reaches the point X. The time taken for the air bubble to move from X to Y is recorded in a table.

14.  Step 10 to 13 are repeated to get an average reading.

15.  Step 10 to 13 are repeated by changing the speed of the fan to 2, 3, 4 and 5, taking the average reading each time.

16.  The readings are recorded in the table and the rate of transpiration is calculated.

 Presentation of data:

 Conclusion: The faster the movement of the air the , the higher the rate of transpiration. The hypothesis is accepted.