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SBA1A_ans_e

New Senior Secondary Mastering Biology Book 1A Practical workbook answer p.1/31

    Suggested answers to Practical Workbook

    for SBA

Ch 1 Introducing biology

    Practical 1.1 Design an investigation of the effect of fresh

    pineapple on the setting of jelly

    Propose a hypothesis (p. 1-2)

    It is the fresh pineapple that causes the jelly to remain in liquid form.

Design and perform an experiment (p. 1-2)

    1 (Answer varies with Ss. The recommended quantity of jelly powder and water is stated on

    the packet of the jelly powder. Jelly will not set if it is too dilute.)

2 Method II. This makes sure the concentrations of the jelly solutions in different containers

    are the same.

    A Identifying variables

    Independent Controlled Dependent variable Control variable variables (What will you (What is the control (What will you (What will you keep measure?) in this experiment?) change?) constant?) The presence of fresh Whether the jelly set The amount of jelly The jelly without

    pineapple. or not. solution in each fresh pineapple.

    container, the size

    and shape of the

    containers, the

    cooling temperature,

    the time allowed for

    setting, etc.

? Oxford University Press 2009

New Senior Secondary Mastering Biology Book 1A Practical workbook answer p.2/31

    B Designing the set-up

C Collecting data

    1 (Answer varies with Ss.)

    2 Repeat the experiment a few more times.

D Risk assessment and safety precautions

    1 During the preparation of jelly solution, the hot water may burn our body.

     The knife used to cut the pineapple is very sharp and may cut our fingers.

    2 Wear a pair of thick gloves when handling hot water.

     Handle the knife with care.

Write an experimental report (p. 1-4)

    Objective

    To investigate the effect of fresh pineapple on the setting of jelly.

    Hypothesis

    It is the fresh pineapple that causes the jelly to remain in liquid form.

    Apparatus and materials

    1 electronic balance 2 glass rods 1 refrigerator 1 knife

    32 beakers (500 cm) fresh pineapple

    31 measuring cylinder (100 cm) hot water 2 plastic containers jelly powder Procedure

    1 Cut a fresh pineapple into small pieces.

    32 Add 50 g of jelly powder and 200 cm of hot water to a beaker. Stir the mixture with a

    glass rod until all the jelly powders dissolve.

    ? Oxford University Press 2009

New Senior Secondary Mastering Biology Book 1A Practical workbook answer p.3/31

    3 3 Pour 100 cmof jelly solution into two containers respectively. Leave the jelly solutions at

    room temperature for one hour.

    4 Put the small pieces of fresh pineapple into one of the containers. Then, refrigerate two

    containers overnight.

    5 Observe any changes of jelly solutions in the two containers on the next day. Results

    The jelly without fresh pineapple set.

    The jelly with fresh pineapple does not set.

    Analysis and discussion

    1 It is used to confirm that the presence of fresh pineapple is the only factor that prevents the

    jelly from setting.

    2 (Answer varies with the design.)

    Conclusion

    The presence of fresh pineapple prevents the jelly from setting.

? Oxford University Press 2009

New Senior Secondary Mastering Biology Book 1A Practical workbook answer p.4/31

    Ch 2 The cell as the basic unit of life

    Practical 2.1 Observation with a light microscope

    Results (p. 2-4) (Drawings vary with the cells observed. Drawings of human cheek cells and onion epidermal

    cells are given as examples.)

Questions (p. 2-4)

    1 To allow entry of a suitable amount of light. A dim image may result if there is insufficient

    light while a faint image may result if the light is too bright.

    2 The coarse adjustment knob leads to a larger degree of movement of the body tube.

     Any downward movement of the body tube controlled by the coarse adjustment knob may

    damage the objective or the slide because the distance between the objective and the slide

    is very small.

? Oxford University Press 2009

New Senior Secondary Mastering Biology Book 1A Practical workbook answer p.5/31

    3

     Low power High power

    Area of specimen large small observed (small / large) Details of specimen less more (more / less)

    Brightness of image bright dim (bright / dim)

4 Towards the left. An inverted image is formed in the microscope. It moves in a direction

    opposite to the actual movement of the flatworm.

Practical 2.2 Preparation of temporary mounts of animal cells

    and tissues Results (p. 2-7)

    Questions (p. 2-8) 1 To flatten the specimen so that they can be seen easily in one plane of focus for the

    objective lens. To prevent the objective lens from getting dirty by touching the specimen

    or the mounting medium. To prevent the specimen from drying out because of

    evaporation. To protect the specimen from being damaged.

2 Cell membrane, nucleus and cytoplasm.

3 Anywhere inside the cell.

4 No. / Yes, they have small vacuoles.

? Oxford University Press 2009

New Senior Secondary Mastering Biology Book 1A Practical workbook answer p.6/31

    Practical 2.3 Preparation of temporary mounts of plant cells

    and tissues Results (p. 2-12)

    Questions (p. 2-13) 1 Cell wall, cell membrane, nucleus, cytoplasm, chloroplast and granule.

2 Near the side of the cell.

3 No. Not all of them contain chloroplasts or chlorophyll. Only those with chloroplasts are

    green.

4 Similarities: Both of them have a nucleus, a cell membrane and cytoplasm.

    Differences:

     1 Plant cells are often larger than animal cells.

     2 Plant cells have a definite shape while the animal cells do not.

    3 Plant cells have a thick cell wall and some have chloroplasts. Animal cells do not

    have cell walls or chloroplasts.

     4 Plant cells usually have a large vacuole while animal cells do not.

? Oxford University Press 2009

New Senior Secondary Mastering Biology Book 1A Practical workbook answer p.7/31

Practical 2.4 Examination of prokaryotic and eukaryotic cells

    Results (p. 2-15)

     Prokaryotic cell Eukaryotic cell

    Size Usually smaller Usually larger

     DNA lying free in the Genetic material DNA enclosed in the nucleus cytoplasm

    Nuclear membrane Absent Present

Organelles bounded

    by a double membrane Absent Present (e.g. mitochondria)

    Endoplasmic reticulum Absent Present

Questions (p. 2-16)

    14 cm1 Actual size of E. coli = = 0.00023 cm = 2.3 μm 60 000

    13 cmActual size of Guinea pig bone marrow cell = = 0.00104 cm = 10.4 μm 12 500

    Guinea pig bone marrow cell is larger than E. coli.

2 Cell X is a eukaryotic cell because it has a true nucleus.

? Oxford University Press 2009

New Senior Secondary Mastering Biology Book 1A Practical workbook answer p.8/31

    Ch 3 Movement of substances across cell membrane

    Practical 3.1 Demonstration of osmosis using dialysis tubing

    Results (p. 3-2)

    Set-up Change in liquid level in the capillary tube

    Experimental Rises

    Control Lowers until it reaches the liquid level of water in the beaker

Questions (p. 3-3)

    1 Its small bore gives a more obvious change in liquid level.

2 Sucrose solution on the outside of the tubing will affect the result. Rinsing the tubing

    ensures no such sucrose solution is present.

3 a There is a net water movement from distilled water to sucrose solution.

    b Osmosis.

    c Differential permeability.

4 After a certain period of time, the force produced by the weight of the liquid column

    balances the force developed by the water potential gradient.

5 a The liquid level will rise faster and higher.

    b The liquid level will drop and the tubing will eventually shrink.

Conclusion (p. 3-3)

    When sucrose solution is separated from distilled water by a dialysis tubing, osmosis takes

    place and there is a net movement of water molecules from distilled water to sucrose solution.

Practical 3.2 Demonstration of osmosis using living animal

    tissue

    Results (p. 3-6)

    Set-up Change in liquid level in the thistle funnel A Rises

    B Lowers until it reaches that of water in the beaker

? Oxford University Press 2009

New Senior Secondary Mastering Biology Book 1A Practical workbook answer p.9/31

    Questions (p. 3-6)

    1 Set-up B is a control. It shows that any change in liquid level in set-up A is due to the

    concentrated sucrose solution.

2 Distilled water has a higher water potential than concentrated sucrose solution, so there is

    a net movement of water from the distilled water to concentrated sucrose solution through

    the differentially permeable animal tissues by osmosis. The volume of liquid inside the

    thistle funnel increases and the liquid level rises.

Conclusion (p. 3-7)

    Living animal tissues are differentially permeable. When solutions with different water

    potential are separated by living animal tissues, osmosis takes place.

Practical 3.3 Study of osmosis in red blood cells

    Results (p. 3-9)

    Concentration of Appearance of the red blood cells sodium chloride solution

    0% Many red blood cells swell and burst.

    0.45% Few red blood cells swell and burst.

    0.9% Red blood cells are normal.

    1.35% Few red blood cells shrink and become wrinkled.

    1.8% Many red blood cells shrink and become wrinkled.

Questions (p. 3-9)

    1 0.9% sodium chloride solution is isotonic to the red blood cells. At this concentration, the

    red blood cells appear normal. It shows that there is no net movement of water into or out

    of the cells because there is no difference in water potential between the cells and its

    surrounding.

2 0% and 0.45% sodium chloride solutions are hypotonic to the red blood cells. At these

    concentrations, the red blood cells swell and burst. It shows that the water potential of the

    red blood cells is lower than that of the sodium chloride solution. Water enters the red

    blood cells by osmosis.

    ? Oxford University Press 2009

New Senior Secondary Mastering Biology Book 1A Practical workbook answer p.10/31

3 1.35% and 1.8% sodium chloride solutions are hypertonic to the red blood cells. At these

    concentrations, the red blood cells shrink and become wrinkled. It shows that the water

    potential of the red blood cells is higher than that of the sodium chloride solution. Water

    leaves the red blood cells by osmosis.

    Conclusion (p. 3-10) When red blood cells are put in a hypotonic solution, water enters the cells by osmosis.

    The red blood cells swell and finally burst.

    When red blood cells are put in a hypertonic solution, water leaves the cells by osmosis.

    The red blood cells shrink.

Practical 3.4 Study of osmosis in living plant cells

    Results (p. 3-12) In concentrated sucrose In less concentrated sucrose In very dilute sucrose

    solution solution solution

    Questions (p. 3-13) 1 To prevent the evaporation of sucrose solution, which may change its water potential and

    affect the results. This also provides a flat surface for observation and keeps the objective

    lens of the microscope clean.

2 The cytoplasm swells up gradually until the cell membrane presses tightly against the cell

    wall.

? Oxford University Press 2009

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