Answer to Workbooks
New Biology — a modern approach
11 Food requirements in humans
Class Practice
11.1
Heterotrophic nutrition
11.2
1.
2.
3.
4.
5.
1.
3.
5.
Food and food substances
F
T
F
T
F
Most heterotrophs are animals. (Some saprophytic fungi are also heterotrophs.)
The food we eat every day make up our diet.
As vitamins, minerals and dietary fibres are necessary for keeping us healthy, they are
called protective food substances.
11.3 Carbohydrates
A.
1. T
2. T
3. F
4. F
B.
3.
4.
6.
1.
2.
3.
4.
5. T
6. F
7. T
In disaccharides only sucrose is non-reducing sugar.
Both hydrolysis and condensation require the presence of suitable enzymes.
Polysaccharides do not give a sweet taste.
F
C
D
E
5.
6.
B
A
11.4 Fats
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11.5 Proteins
1. T
2.
4.
6.
2. F
3. T
4. F
5. T
6. F
A molecule of fat is made up of three molecules of fatty acid combined with one
molecule of glycerol.
Essential amino acids cannot be made in human body.
The excess amino acids are broken down in the liver by deamination.
11.6 Vitamins
1. T
2. F
3. F
4. T
5. F
6. T
7. F
2. Plants can make their own vitamins from simple substances.
3.
5.
7.
Fat-soluble vitamins are more heat resistant than water-soluble vitamins.
Lack of vitamin A causes night blindness.
Vitamin D helps the absorption of calcium and phosphorus in the small intestine.
11.7 Mineral salts
11.8 Dietary fibres
11.9 Water
1. C
2.
3.
4.
5.
A
C
B
D
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11.10 Food tests
(a) Clinistix paper
(b)
(c)
(d)
(e)
(f)
(g)
(h)
(i)
(j)
colour changes from pink to blue
Benedict's test
formation of brick-red ppt.
iodine test
colour changes from brown to blue black
Albustix paper
colour changes from yellow to green
spot test
formation of permanent translucent spot
(k) DCPIP test
(l) The blue DCPIP is decolourised
11.11 The need for a balanced diet
11.12 Food and energy
A. Q
S
R
P
B.
1.
2.
C.
1.
2.
3.
P
Q
1. F
2. F
3. F
4. T
5. T
A balanced diet contains the right amount of all the food substances.
A pregnant woman needs extra food because she needs more energy for the growth
of the foetus.
Energy for living comes from carbohydrates, fats and proteins.
11.13 The health problems resulting from an improper diet
1. C
2. D
3. B
4. A
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Exam Practice
A. Multiple Choice Questions
1. D
2. C
3. C
4. B
5. A
6. B
7. B
8. D
B.
Structured Questions
1. (a) 430
370
320
278
252
230
430
370
320
278
215
182
(b)
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(c) 3 years of age.
Children need to maintain a higher metabolic rate in order to support their period of
(d)
2.
(a)
(b)
(c)
(d)
3.
4.
greatest growth / compensate for the higher rate of heat loss.
After the age of 14, boys are more active than girls. Girls have thicker subcutaneous
fat so that the rate of heat loss is lower than that of boys. Girls require less energy
than boys.
The calcium requirements of group II is greater than that of group III, because
group II requires more calcium for the development of bones.
15
(i) Group I: —— = 2
7.5
20
Group II: —— = 1
20
50
Group III: —— = 0.83
60
45
Group IV: —— = 0.9
50
Therefore, group I requires the greatest amount of protein per unit weight.
(ii) Group I grows faster than other groups. Protein is important for growth.
People in group III are more active and they have thinner subcutaneous fat.
Girls lose blood every month / during menstruation. Iron is important for the
formation of red blood cells / haemoglobin.
(a) B contains reducing sugar and vitamin C.
C contains protein and fat.
(b) butter
fruit / orange / kiwi
pork / beef / fish
(c) food sample D
(d) The blue DCPIP becomes colourless.
(e) In cold areas, people lose heat at a faster rate. Food sample A contains fat which can
release much more energy to compensate for the heat loss.
(a) W — fats, X — carbohydrates, Y — water, Z — proteins
(b) Beans also contain mineral salts and vitamins which are not shown in the table.
(c) (i) butter
(ii) cabbage
(d) Beans. Beans contain the highest percentage of carbohydrates which can supply
energy. Beans also have a relatively high percentage of proteins for growth.
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Answer to Workbooks
5.
(a) too much carbohydrates
too much fat
}
any three
absence of dietary fibres
absence of vitamin C
(b) Eat less french fries.
Use less sugar for coffee.
Eat fresh fruits or vegetables.
(c) Constipation — absence of dietary fibres
Scurvy — absence of vitamin C
C.
STS Connections
(a) D
B
C
(b) No, it is not a balanced diet. It does not contain any cereals or grains which should be in
the greatest amount in a balanced diet. It has too little fruits and vegetables, and too
much meat.
(c) It supplies inadequate energy for metabolism and daily activities. It contains too little
cellulose and hence would result in constipation.
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Answer to Workbooks
12 The human digestive system
Class Practice
12.1 The processes of nutrition in humans
1. C
2. D
3. E
4. B
5. A
12.2 The human digestive system
(a) oesophagus
(b) stomach
(c) duodenum
(d) ileum
(e) appendix
(f) colon
(g) rectum
12.3 The teeth
A. Functions in humans
B.
biting and cutting
tearing
crushing and grinding
crushing and grinding
1. dental formula
2. enamel
3. dentine
4. crown
5. root
6. periodontal membrane
7.
8.
Number in humans
8
4
8
12
pulp cavity
neck
12.4 Oral health
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12.5 Periodontal disease
1. T
2.
4.
5.
7.
2. F
3. T
4. F
5. F
6. T
7. F
8. T
Bacteria in the plaque break down sugar and starch in the food into acid which dissolves
the enamel, causing tooth decay.
If tooth decay is not serious, the tooth can be repaired by a dentist.
The rate of tooth decay can be reduced by adding fluoride to drinking water.
Calculus can be scraped off by a dentist.
12.6 The functions of different parts of the alimentary canal and its associated glands
A. 1. duodenum
2. ileum
3. mouth cavity
4. salivary glands
5. stomach
B.
6.
7.
8.
9.
10.
11.
12.
(a)
(b)
(c)
pancreas
rectum
anus
colon
liver
gall bladder
oesophagus
mouth cavity
surface area
digestive enzymes
(d)
(e)
(f)
(g)
(h)
(i)
(j)
(k)
salivary glands
pancreas
stomach
pancreas
bile
liver
gall bladder
peristalsis
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Answer to Workbooks
C.
1.
2.
2.
3.
5.
8.
T
F
3. F
4. T
5. F
6. T
7. T
8. F
Food inside the stomach is churned up to form chyme.
Bile does not contain any digestive enzymes. It contains bile salts which emulsify
fats into oil droplets.
Water-soluble vitamins and minerals are absorbed at the ileum.
Most water in the gut is absorbed in the small intestine. Only some of it is
12.7 Assimilation
1. B
2. C
3. A
4. A
Exam Practice
A. Multiple Choice Questions
1. B
2. A
3. C
4. D
5. B
6. D
7. C
8. B
9. C
10. A
11. C
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B.
New Biology — a modern approach
Structured Questions
1. (a) small intestine / ileum
(b) A — capillaries, B — lacteal
(c) (i) diffusion / absorption of food
(ii) There are many villi on the wall of ileum. They increase the surface area for
diffusion.
(d) (i) hepatic portal vein
(ii) liver
(e) (i) active transport
(ii) Mitochondria. Active transport requires energy which is released by respiration
taking place in mitochondria.
2.
(a) enamel
(b) (i) incisor
for biting and cutting
(ii) canine
for tearing
(iii) premolar
for crushing and grinding
(iv) molar
for crushing and grinding
(c) molars
(d) Tooth decay results from a chemical reaction between oral bacteria and food debris
after eating. Sugars and starch are broken down into acid. The acid dissolves the
enamel, causing tooth decay.
(e) Tooth B causes pain. The pulp tissue may be destroyed by bacteria. There are nerves
inside the pulp cavity. When the nerves are stimulated, it is very painful.
3.
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(a) X — stomach
Y — duodenum and ileum / small intestine
Z — colon and rectum / large intestine
4.
5.
(b) X
(c) Fats are emulsified to form smaller oil droplets before they are digested by the
enzyme lipases.
(e) Pancreatic juice, bile, intestinal juice
(f) P is dietary fibre. It gives bulk to food and stimulates peristalsis. It prevents
constipation.
(a) by using pH paper
(b) It indicates the number of decaying teeth.
(c) The results show that the number of decaying teeth increases with the decrease in
pH of the saliva.
(d) Toothpaste is alkaline and it neutralises the acid in the mouth. It also contains
abrasive for cleaning the surface / plaque of the teeth.
(e) Mouth bacteria break down sugar in candy into acid which dissolves the enamel,
causing tooth decay.
(a) A — liver, B — gall bladder, C — duodenum, D — caecum
E — pancreas, F — colon, G — ileum, H — rectum / anus
(b) (i) bile
(ii) liver / A
(iii) It emulsifies fat to form smaller oil droplets.
(c) The diet of a carnivore is more nutritive, and the food substances in the diet can be
digested more easily.
(d) It is longer and larger in a rabbit. It can store more cellulose material. Bacteria are
present to digest cellulose.
C.
STS Connections
(a) The government has started to provide school dental care service since 1980s. Children
can have dental check-up regularly and many oral health problems can be prevented.
(b) If the tooth decay has already reached the pulp cavity and infection has spread to the
base of the tooth, the tooth cannot be repaired. If the tooth decay is not too serious in that
the dentine has not been damaged, amalgam can be used to fill the decayed part.
(c) Bacteria of plaque left on teeth release toxins to destroy the fibres which hold the teeth
firmly in jawbone. The teeth become loose afterwards and finally fall out.
(d) Brush the teeth thoroughly at least twice a day to remove plaque. Do not smoke. Use
dental floss daily to remove food debris between teeth. Have a dental check-up at least
once a year to remove calculus. (any 2)
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13 The human breathing system
Class Practice
13.1 Gaseous exchange
1. F
2. T
3. T
4. T
5. F
6. F
1. Gaseous exchange is the exchange of oxygen and carbon dioxide between an organism
5.
6.
and its surroundings.
Gaseous exchange also occurs in plants.
Gaseous exchange also involves other gases such as water vapour.
13.2 The general plan of the human breathing system
A.
1. F
2. T
3. F
4. F
5. T
1.
4.
(a)
(b)
(c)
(d)
(e)
The blood capillaries in the nasal cavity can warm the incoming air before it goes
into the lungs.
Breathing stops during swallowing because the opening of the trachea is closed by
the epiglottis.
When the vocal cords vibrate, sound is produced.
vocal cord
alveoli
trachea
bronchi
larynx
(f)
(g)
(h)
(i)
(j)
epiglottis
pleural membrane
diaphragm
intercostal muscles
rib cage/thoracic basket
3.
B.
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Answer to Workbooks
13.3 The process of gaseous exchange in the alveoli
1. The oxygen dissolves in the moisture of the alveoli. It diffuses across the walls of the
2.
3.
alveoli and the capillaries into the blood. It then diffuses through the cell membrane into
the red blood cell.
1. The walls of the alveoli are very thin which provide a short distance for diffusion of
gases.
2. There are numerous alveoli which provide a large surface area for diffusion of gases.
3. The alveoli are surrounded by a network of capillaries. They provide a rich blood
supply to transport gases to and from the respiratory surface.
4. The walls of the alveoli are moist. Thus the oxygen can dissolve in this fluid and
diffuse across the walls of the alveoli.
(Any three)
The blood in A contains more carbon dioxide and less oxygen than that in B.
13.4 The mechanism of ventilation
1. A, C
2.
Location
Intercostal
muscles
Diaphragm
muscles
State
Function
Contracated
Move ribs and
sternum upwards
and outwards
Contracted
Flatten the
diaphragm
Resulting
thoracic
volume
Resulting
thoracic
pressure
Air
movement
Air flows
Increased
Decreased
From the
atmosphere
into the
lungs
The relation of exercise to energy requirement, rate of cellular respiration and ventilation
1.
Student B
2.
No.
3.
He will have similar breathing depth when doing exercise.
4.
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
(i)
increases
decreases
nerve impulses
respiratory centre
faster
intercostal
diaphragm
deeper
faster
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Exam Practice
A. Multiple Choice Questions
1. C
2. B
3. B
4. D
5. B
6. C
7. A
8. B
9. B
10. B
B.
Structured Questions
1. (a) A nasal cavity
B pharynx
C epiglottis
D trachea
E rib
F bronchus
G intercostal muscle
(b)
(c)
(d)
(e)
(c)
2.
(a)
(b)
(c)
(d)
H pleura
I
diaphragm
J
alveolus
In nostrils there are hairs for trapping dirt particles. The lining of the nasal cavity
secretes mucus which traps bacteria and dust, and moistens the incoming air.
H secretes pleural fluid which acts as a lubricant to reduce friction during breathing.
Both structures contract.
The inner lining of D produces mucus and is covered with cilia. The dirt particles
are trapped by the mucus. The cilia then waft the mucus upwards.
No, it is because the opening of the trachea is closed by the epiglottis during
swallowing and breathing stops temporarily.
Inside the normal lung the bronchioles are wider and the alveoli are more deeply
folded than the affected lung.
The narrow bronchioles in the affected lung will slower the airflow into the lung.
Besides, the foldings in the alveoli are less deep and this will decrease the surface
area for gaseous exchange.
The breathing rate increases.
The soot particles increases the thickness of the barrier for diffusion of gases and
also they reduce the surface area for gaseous exchange.
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Answer to Workbooks
3.
4.
(a) (i) [(50 – 42) ÷ 50] × 100% = 16%
(ii) [(42 – 40) ÷ 50] × 100% = 4%
(b) The composition does not change.
(a) He breathes faster and deeper.
(b) Carbon dioxide accumulates in the body. It stimulates the respiratory centre to send
more nerve impulses to diaphragm muscles and intercostal muscles to make them
contract more frequently and more powerfully.
(c) No. A portion of oxygen was taken up by the body during each breath. Since he kept
breathing in and out of the plastic bag, and his body kept taking up oxygen, the
oxygen level in his exhaled air decreased. The oxygen level in the expired air under
normal condition is always about 16%.
Volume of air in the lungs
(d)
Time
5.
6.
(a) The decrease in thoracic pressure causes the lungs to inflate. The lung pressure is
lower than the atmospheric pressure and hence air rushes into the lungs.
(b) (i) Type B.
(ii) Exhaled air still contains 16% oxygen and artificial respiration forces this air
into the lungs of the person.
(a) (i) Graph B
(ii) Graph C
(iii) Graph A
(b) (i) The baby breathes faster but not as deep.
(ii) Since the gas volume of each breath in the baby is too small to get enough
oxygen or expel carbon dioxide, the baby has to breathe faster to offset this
disadvantage.
(c) (i) The adult on a very high mountain breathes faster and deeper.
(ii) Since the oxygen level at a very high mountain is lower than that at sea level,
less oxygen is obtained in a single breath compared with that at sea level.
Therefore, the adult has to breathe faster and deeper in order to get sufficient
oxygen.
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(d) (i) to allow deeper breathing and hence more oxygen enters the lungs
(ii) as a signal of tiredness
(e) graph A
C.
STS Connections
(a) nicotine, tar and carbon monoxide
(b) The irritant substances in the cigarette smoke stimulate the lining of the trachea and
bronchi to secret more mucus. They stop the movement of the cilia. As a result, dirt
particles, germs and mucus cannot be propelled along and cause difficulty in breathing.
In addition, dirt particles in the cigarette smoke settle in the alveoli, reducing the surface
area available for gaseous exchange. Thus George cannot get enough oxygen during the
basketball matches.
To quit smoking does him good because smoking can cause a lot of diseases.
(c) lung cancer, chronic bronchitis, emphysema (肺氣腫) and heart disease (any three)
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Answer to Workbooks
14 The human circulatory system
Class Practice
14.1
Why do we need a circulatory system?
14.2
A.
1.
2.
3.
4.
5.
1.
2.
B.
C.
3.
1.
2.
3.
4.
5.
Blood Vessels
F
F
F
T
T
Small organisms have a large surface area to volume ratio. They do not need a
circulatory system.
The walls of arteries contain thick layers of muscles and elastic fibres. The walls of
veins also contain muscles and elastic fibres but they are much thinner.
The walls of the capillaries are very thin. They are only one-cell-thick.
B
D
A
C
E
(a) 1. muscles and elastic fibres
2. lining of wall
X: artery
Y: vein
Z: capillary
(b) to withstand the high pressure of blood
(c) Valves can be found in Y but not in X.
14.3 The heart
1. (a) A.
superior vena cava
B. coronary artery
C. aorta
D. pulmonary artery
(b) It carries blood to the heart muscles to supply oxygen and nutrients.
(c) C carries oxygenated blood while D carries deoxygenated blood.
(d) left atrium
right atrium
left ventricle
right ventricle
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Answer to Workbooks
(e) (i) bicuspid valve
(ii) tricuspid valve
(iii) heart tendon
It prevents the valves from being turned inside out.
2.
(a)
(b) P: aorta
Q: ventricle
R: atrium
14.4 Blood circulation in man
1. F
2. T
3. F
4. F
1. In man, the blood flows through the heart twice in one complete circulation. This is
called double circulation.
3. Deoxygenated blood from the body tissues returns to the right atrium.
4.
After gaseous exchange, the oxygenated blood flows through the pulmonary vein back to
the left atrium.
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14.5 What is blood?
1. A, B, C, D
2.
3.
4.
5.
6.
7.
8.
9.
10.
C, D
B
B
D
E
A
A
C
C
11. C
14.6 The functions of mammalian blood
14.7 What is the lymphatic system?
1. C
2. C
3. A
Exam Practice
A. Multiple Choice Questions
1. C
2. A
3. C
4. A
5. D
6. C
7. B
8. C
9. A
10. A
B.
Structured Questions
1. (a) Person Y. He has the least red blood cells. Iron is necessary for the formation of red
blood cells.
(b) The person easily becomes tired or he/she may faint easily.
(c) Person Y. He does not have enough platelets which are important for blood clotting.
(d) Person X. There is a shortage of oxygen at high altitude. The person produces more
red blood cells in order to get enough oxygen from the air.
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Answer to Workbooks
2.
3.
(a) Red blood cells:
without nucleus
biconcave disc-shaped
irregular shape
filled with haemoglobin
no haemoglobin
(b) Red blood cells are biconcave disc-shaped. This increases the surface area for
diffusion of oxygen. Red blood cells contain haemoglobin which has an affinity for
oxygen.
(c) (i) lymphocyte and phagocyte
(ii) Lymphocyte produces antibodies which kill germs. Phagocyte can engulf germs.
(a) The highest blood pressure is recorded in the arteries and the blood pressure
fluctuates in arteries.
(b)
(c)
4.
(d)
(a)
(b)
5.
White blood cells:
with nucleus
The blood pressure drops in the capillaries.
The blood pressure is lowest in the veins.
The blood pressure fluctuates as a result of alternate contractions and relaxations of
the heart.
High blood pressure at the arterial end forces the fluid out through the capillary
walls to body tissues.
glucose, amino acids, oxygen (any 2)
A - aorta, C - pulmonary veins, E - bicuspid valves, F - heart tendon, H - semilunar valves
K - (inferior) vena cava
(i) E, H, L
(ii) B
(iii) C
(iv) K
(c) The blood in X has to be pumped to all parts of the body. Thicker muscular wall can
create a higher pressure for pumping blood.
(d) To prevent the valves from turning inside out during ventricular contraction
(a) (i) X
(ii) Z
(iii) Y
(iv) X
(v) W
(b) D - hepatic portal vein
D has capillaries at both ends while E has capillaries at one end.
(c) The blood in vessel A contains a higher concentration of CO2 and food but a lower
concentration of O2 than that in vessel B.
(d) The blood in the renal artery contains more glucose, urea, water and oxygen than
that in the renal vein.
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C.
New Biology — a modern approach
STS Connections
(a) The blood pressure in the veins is too low to prevent backflow of blood because
• the blood in the veins is far away from the effect of the pumping action of the heart
• the blood in the veins has experienced great friction after travelling over a long way
(capillary network)
• some fluid is lost from the blood during the formation of tissue fluid
(b) The flow of blood in the veins relies on the contraction of skeletal muscles. Loosened
muscles do not provide enough power to squeeze blood upward.
(c) 1. Do regular exercise.
2. Control your body weight.
3. Avoid long periods of standing (any other reasonable answers).
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