Answers to Hands-on Pg 10-16

1. C 2. C 3. D 4. D 5. B 6. C 7. A 8. B 9. D 10. C

11. D 12. C 13. B 14. A 15. A 16. D 17. D 18. C 19. D

1. (a) P : Erythrocyte

Q : Leucocyte

(b) (i) To transport oxygen from the lungs to the body tissue

(ii) Haemoglobin

(c) Cell P, erythrocyte, is filled with haemoglobin. Oxygen from the lungs diffuses into the red blood cells and combines with the haemoglobin to form oxyhaemoglobin.

Oxygen is carried to the body tissues in the form of oxyhaemoglobin. Upon reaching the tissues, oxygen readily detaches itself and diffuses into the body cells.

(d) Draw the 2 processes of phagocytosis from the Biology text book

(ii)Phagocytosis

(iii) Phagocytosis is carried out by neutrophil, a type of leucocyte.

The neutrophil will move towards a bacterium in an amoebic movement.

Upon coming into contact with the bacterium, a cup-shaped indentation is formed and the bacterium is taken into a vacuole where it is digested by lysosomes.

2. (a) To colour the xylem tissues

(b)

(c) (i) Xylem

(ii) Elongated tube which runs continuously from the roots to the leaves.

(d) When water vapour evaporates from the leaves, a transpirational pull is exerted to draw up water along the xylem vessels.

Cohesive forces between the water molecules prevent the water column in the xylem vessels from breaking.

Adhesive forces between the water molecules and the xylem vessel wall prevent the water molecules from falling back.

As a result of these forces, water molecules are pulled towards the leaves.

(e) Water molecules from the soil are drawn into the root hairs through osmosis. A force exists to ‘pull’ the water from the roots to the xylem vessels. This force is called root pressure, which is responsible for pushing the water from the roots to the stem.

This explains the increase in water level in the tube after one day.

Answers to Hands-on Pg 8-10

Aim : To study the effect of light intensity on the rate of transpiration.

Hypothesis : The higher the light intensity, the higher the rate of transpiration.

MV : Light intensity

RV : Distance traveled by air bubble in 10 minutes

FV : Air movement/temperature/air humidity/type and size of plant

Method :

1. Setup the apparatus as shown in diagram above.

2. Choose a leafy shoot and cut the shoot end in a basin of water.

3. Insert cut stem in the potometer (capillary tube fitted with rubber tubing).

4. Lift the capillary tube to insert an air bubble.

5. Adjust and mark the initial position of the air bubble with a thread.

6. Dry the surface of the leaves before the start of the experiment.

7. Make sure the apparatus is airtight by smearing the joints with vaseline.

8. The air movement / temperature /humidity of the surrounding/type and size of plant must be maintained throughout the experiment.

9. A table lamp was placed 50cm away from the potometer.

10. Measure and record the distance traveled by the air bubble in 10 minutes using a stopwatch.

11. Repeat the experiment by placing the lamp at different distances of 40cm, 30cm and 20 cm from the potometer.

12. Calculate the rate of transpiration using the formula : Distance traveled by air bubble/time.

13. Tabulate the results in a table.

Distance of light bulb (cm)	50	40	30	20
Distance traveled by air bubble in 10 min (cm)	4	8	11	15
Rate of transpiration (cm/s)	4/10 = 0.4	8/10 = 0.8	11/10 = 1.1	15/10 = 1.5

Discussion :

1. When the distance between the light source and the leafy shoot decreases, the light intensity increases.

2. Rate of transpiration is highest when the light source is 20cm from the leafy shoot.

3. Rate of transpiration is lowest when the light source is 50cm from the leafy shoot.

4. When light intensity increases, the stomata open more as photosynthesis increases. Therefore more water vapour is lost through the stomata. Hence the rate of transpiration increases.

Conclusion : The hypothesis is accepted. When light intensity increases, the rate of transpiration increases.

Answers to Hands-on Pg 6-8

Beginning of activity - Apparatus with a porous pot

End of activity - Apparatus with a porous pot

Beginning of activity - Apparatus with a leafy shoot

End of activity - Apparatus with a leafy shoot

Discussion:

1. Water evaporates from the surface of the porous pot, causing the water in the capillary tube to rise. This draws the mercury level up. Adhesive forces and cohesive forces enable the water column to be held together.
2. As the water evaporates from the leaf surface, the water in the xylem vessel rises, drawing the mercury up the capillary tube. Adhesive forces between water molecules and the capillary tube wall prevent the water molecules from falling back. Cohesive forces between the water molecules prevent the water column from breaking.

Conclusion :

Adhesive and cohesive forces cause the movement of water in plants.

Answers to Hands-on Pg 4-5

Aim : To study the role of root pressure in the movement of water

Set	Initial water level (cm)	Final water level (cm)	Increase in water level (cm)
Treatment	2	23.5	21.5
Control	2	2.0	0.0

Discussion :

1. The treatment set shows an increase of 21.5cm of water column in the capillary tube whereas there is no increase in water column of the control set.
2. The rise in the water column is caused by a force pushing the water up the stem from the roots. This force is called root pressure.
3. Osmosis

Conclusion :

Water is pushed from the roots up the stem by a force called root pressure

Answers to Hands-on Pg 2-3

Aim : To carry out bark ringing

Discussion :

1. The stem above the ring swells because organic substances synthesized by the leaves are collected there when they cannot be transported to the stem below the ring. This is because the phloem tissues have been removed from the ring.

2. The leaves are fresh and green because the leaves can still receive water and minerals, which are transported by the xylem tissues from the roots.

3. a) The plant will die.

4. b) Organic substances synthesized by the leaves are not transported to the parts below the ring eg the roots

Conclusion :

The phloem tissue is a continuous tube system from the leaves to the roots of a plant and plays an important role in transporting organic substances synthesized during photosynthesis.

To investigate the effect of TSA/V ratio on the rate of diffusion of substances.

Students preparing cubes of different sizes

Answers to Hands-on Pg 16

Section B
3a)– Blood flows from arteries to capillaries. There is higher hydrostatic pressure at the arterial end of the cappilaries due to heart’s pumping pressure. The high hydrostatic pressure forces small amounts of water, nutrients, oxygen gas, carbon dioxide gas, hormones (except erythrocytes, platelets and plasma protein) to diffuse out of the blood capillaries into the spaces around the cells. This fluid is called the interstitial fluid.

(b) – Lymphatic system is a one way system consisting of lymphatic capillaries, lymphatic vessels and lymph nodes. Lymph nodes produce lymphocytes. Lymphocytes produce antibodies. Third line of defence occurs when phagocytosis of pathogens by phagocytes fails. Antibodies produced adhere to the surface of the antigens, making them clump together or agglutinate. Some antibodies cause antigens to disintegrate (lysis).
– Some antibodies produce antitoxins to neutralise the toxins produced.

(c) Similarities: Humans, fish and amphibians have closed circulations in which the blood is confined to blood vessels.
Differences:
- Fish has one chambered heart, amphibian has three and human has four chambers.
- Fish has only one atrium but amphibian and human have 2 atria.
- Fish and amphibian have one ventricle but human has 2 ventricles.
– Humans and amphibians have double circulations.
– The fish has a single circulation.
- In the double circulation, blood is pumped from the heart to the lungs and returns from the lungs to the heart which is then re-pumped to the body.
– In the single circulation, deoxygenated blood from the body is pumped to the gills where gaseous exchange takes place.
– Oxygenated blood from the gills flows to the body and returns to the heart.
– Humans have a completely divided heart where oxygenated blood and deoxygenated blood do not mix.
- Lastly, amphibian has incomplete closed circulation but human has complete closed circulation.