LOWER SECONDARY SCIENCE TEXTBOOK

Review Questions

1 Which of the following is true of an acid?

A It has a pH value of 7.
B It turns red litmus paper blue.
C It turns blue litmus paper red.
D It has a pH value of more than 7.

2 The diagram shows what happens when red and blue litmus papers are
dipped in solution X.

Red litmus paper Blue litmus paper
turns blue remains blue

Which of the following substances could possibly be solution X?

A Vinegar
B Lime juice
C Distilled water
D Sodium hydroxide

Study the table below and answer questions 3 – 4.

Substance S T U

pH 3 8 6

3 Which substance(s) will turn blue litmus paper red?

AS
B S and T
C S and U
D T and U

4 What gas is produced when magnesium is added to substance S?

A Helium
B Oxygen
C Hydrogen
D Carbon dioxide

Acids and Alkalis 125

5 What will happen when sodium hydroxide solution is added gradually
to a conical f lask of dilute nitric acid containing Universal Indicator?

A The pH increases.
B The pH decreases.
C The colour of the indicator will not change.
D The colour of the indicator changes from blue to red.

6 When solutions of P and Q are mixed, neutralisation occurs and a
solution with a pH of 7 is obtained. What could the pH values of P and
Q be?

pH of P pH of Q
A2 5
B3 7
C2 12
D7 12

7 Which of the following word equations does not show neutralisation
between an acid and an alkali?

A sulfuric acid + zinc  zinc sulfate + hydrogen
B nitric acid + sodium hydroxide  sodium nitrate + water
C sulfuric acid + sodium hydroxide  sodium sulfate + water
D hydrochloric acid + calcium hydroxide  calcium chloride + water

8 The colour of a red cabbage indicator is as below:
• Original colour: purple
• Colour in acid: pink
• Colour in alkali: green
a) If a red cabbage has bluish-green leaves, what can you infer about

the soil it is growing in?
b) If a red cabbage has pink leaves, what substance can you add to

the soil to restore the original colour of the plant?

9 State one similarity and one difference between acids and alkalis.

126 Acids and Alkalis

Chapter Reproduction
in Plants
15
The bee in the photo below landed on a flower to collect nectar.
Can you see the specks on the bee? What are these specks and
how do they help the flower in reproduction? Let us learn more
about flowers and how they reproduce.

Firman Allah Subhanahu Wa Ta’ala
Tafsirnya:
Maka hendaklah manusia itu melihat
kepada makanannya (24): Sesungguhnya
kami benar-benar telah mencurahkan air
(hujan dari langit) (25). Kemudian Kami telah
membelah bumi (dengan tumbuh-tumbuhan
yang tumbuh dari dalamnya) dengan sebaik-
baiknya (26). Lalu kami tumbuhkan biji-bijian
di bumi itu (27); Dan buah anggur serta
sayur-sayuran (28); Dan zaitun serta pohon-
pohon tamar (29); Dan kebun-kebun yang
menghijau subur (30); Dan pelbagai buah-
buahan serta bermacam-macam rumput (31)
untuk kegunaan kamu dan binatang-binatang
ternak peliharaan kamu (32).

Then let man look at his food (24): We pour
forth water in abundance (25). And We split
the earth in clefts (26). And We caused
therein the grain to grow (27); And grapes
and clover plants (i.e. green fodder for the
cattle) (28), And olives and date-palms (29),
And gardens dense with many trees (30), And
fruits and herbage (31) (To be) a provision
and benefit for you and your cattle (32).

(Surah Abasa: 24-32)

Let’s Explore

• What are the different parts of a
flower and what are their functions?

• What is pollination and fertilisation in
plants?

• Why and how do plants disperse their
seeds?

• What are the conditions required for a
seed to grow?

127Reproduction in Plants

15.1 Parts of a Flower

You should be able to:
• identify and state the functions of the main parts of an

insect-pollinated fl ower: petal, sepal, stamen (anther and
f ilament) and carpel (stigma, style, ovary and ovules);
• distinguish between the male and female parts of a f lower;
• draw the main parts of an insect-pollinated fl ower.

Flowers in Brunei Darussalam

New plants are produced from seeds. Seeds are found in
fruits. Each f lower becomes a fruit after fertilisation.
The following are f lowers that can be found in Brunei
Darussalam.

The Simpur flower is the national flower Morning glory
of Brunei.

Hibiscus

128 Reproduction in Plants

Bougainvillea Frangipani

Ixora Orchid

Have you seen these f lowers in Brunei Darussalam?

?

Can you name two other f lowers that are commonly found in Brunei?

129Reproduction in Plants

Parts of a flower

Although f lowers come in many different colours and sizes,
they have some common parts.

A f lower may consist of the following parts:
• petals,
• sepals,
• stamen (male part of a f lower which consists of the
anther and filament), and
• carpel (female part of a f lower which consists of an ovary,
a style and one or more stigmas).

Bauhinia

Stigma

Carpel Style Anther Stamen
(female Filament (male part
part of the of the
fl ower) fl ower)

Ovary
Sepal

Petal

Cross-sectional drawing of a Bauhinia flower

130 Reproduction in Plants

The table below lists the functions of the parts found in a
flower.

Parts of a flower Functions

Petal Petals are normally brightly coloured
to attract insects. They may also act as
‘landing pads’ for insects.

Sepal Sepals are leaves that protect the
flower before it opens.

Anther The anther contains and produces
pollen grains. The pollen grains contain
the male sex cells of the flower.

Filament The filament is the stalk that supports
the anther.

Stigma The stigma receives the pollen grains.

Style The style is a tube-like structure that
connects the stigma to the ovary. It
supports the stigma.

Ovary The ovary consists of ovules. Ovules
contain the female sex cells of
the flower.

Parts of a flower and their functions

Quick Check

1. State the functions of the parts of a flower.
2. Draw a flower and label its parts.

131Reproduction in Plants

15.2 Pollination

You should be able to:
• define pollination as the transfer of pollen grains from an

anther to a stigma;
• describe the role of insects and the wind as agents of

pollination;
• compare the differences between an insect-pollinated

flower and a wind-pollinated flower.

Pollination

Pollination is the transfer of pollen grains from an anther
to a stigma of a flower. The pollen grains can be from the
same flower or from a different flower.

Stigma
Pollen grain is transferred from
the anther to the stigma.

Anther containing pollen

The process of pollination

132 Reproduction in Plants

Pollen grains
Each pollen grain contains a male sex cell. Pollen grains
from different f lowers look different. They have different
shapes, sizes and structures, depending on the agents
of pollination.

Pollen grain of the sunflower Pollen grain of the lily Pollen grain of the primrose

Agents of pollination
An agent of pollination helps to transfer pollen grains
from the anther to the stigma. There are two main agents
of pollination — insects and the wind.

Insect pollination Wind pollination

133Reproduction in Plants

Science Bites Insect pollination
When insects feed on the nectar of these f lowers, the anther
Some f lowers have rubs against the body and legs of the insects, sticking pollen
lines or coloured grains onto them. When they f ly to another f lower, the
patches to guide pollen grains rub off from the insect and onto the stigma of
insects to the nectar that f lower.
in them. These lines
or coloured patches
are called nectar
guides.

Bees and butterflies play an important role in pollination.

Insect-pollinated f lowers usually have the following
characteristics:
• large and brightly-coloured petals,
• scented,
• produce nectar,
• stamen and stigma are found inside the f lower, and
• pollen grains are spiky and sticky.

WB Link Activity 15.1 The Flame of the Forest flower is an insect-
134 Reproduction in Plants pollinated flower

Wind pollination
As the wind blows over the f lower, the pollen grains are
carried by the wind and transported to the stigma of
another f lower.

Wind-pollinated f lowers usually have the following
characteristics:
• dull-coloured f lowers,
• small petals or no petals at all,
• not scented,
• do not produce nectar,
• stigma is feathery, and
• pollen grains are very light.

The willow flower is a wind-
pollinated flower.

Comparison between insect-pollinated and
wind-pollinated flowers
The table below summarises the different features of
insect-pollinated and wind-pollinated f lowers.

Insect-pollinated flowers Wind-pollinated flowers

Have large, brightly-coloured May have small, dull petals or
petals no petals at all
Quick Check
Scented Not scented
1. Def ine
Usually produces nectar Do not produce nectar pollination.

Have rough and sticky pollen Have small and light pollen 2. Explain how
grains that can stick onto an grains that can be carried by insects and
insect’s body the wind the wind can
pollinate a fl ower.
Stamens and stigmas are Stamens and stigmas are
found within the f lower found outside the f lower 3. How is an insect-
pollinated fl ower
Stigmas are small and sticky Stigmas are large and different from a
feathery to catch pollen grains wind-pollinated
fl ower?
Differences between insect-pollinated flowers and
wind-pollinated flowers 135Reproduction in Plants

15.3 Fertilisation and
Seed Dispersal

You should be able to:
• def ine fertilisation as a process which involves the fusion of

a male sex cell and a female sex cell to form a zygote;
• describe the mechanism and importance of seed dispersal

with reference to a local seed or fruit;
• recognise that seeds are dispersed by wind, water, animals

and self-dispersal.

Fertilisation

Fertilisation is a process where a male sex cell fuses
with a female sex cell to form a zygote. The male sex cell
has to travel from the pollen grain down a pollen tube, to
meet the female sex cell in the ovule. Let us take a look
at this process.

Pollen grain Pollen tube Pollen tube
Style Male sex cell
inside pollen
Ovary tube
Ovule
Female
sex cell
(ovum)

1 2 3
A pollen grain lands A pollen tube The pollen tube enters
on the stigma. grows out of the the ovule. A male sex
Pollination has taken pollen grain. cell fuses with the
place. female sex cell to form
a zygote. Fertilisation
has taken place.

Formation of the pollen tube

136 Reproduction in Plants

Development of the fruit and seeds Fruit
Fertilisation causes the f lower to start developing into a Seeds
fruit. Most parts of the f lower such as the style, stigma and
petals will dry up and drop off.
The fertilised ovule will become the seed and the ovary
becomes the fruit.

Flower petals start
to wither

Ovules develop
and become
the seeds.

Ovary starts Ovary grows
to grow bigger and

becomes the fruit

Development from a flower to a fruit

Fleshy fruit
Seed

Fruits such as longans and mangoes have a seed enclosed
inside the fleshy fruit.

137Reproduction in Plants

Methods of dispersal

After fertilisation, the seeds need to be moved to a suitable
place where they can germinate. The dispersal of seeds is
a process of moving the seeds away from the parent plant.
The seeds need to be dispersed to:
• prevent overcrowding, and
• reduce competition for nutrients, water and sunlight.

The four main methods of seed dispersal are:
• wind dispersal,
• water dispersal,
• animal dispersal, and
• self-dispersal.

Method of Description Example
Dispersal Seeds dispersed by the wind are Wing-like
usually light. Some fruits have structure
Wind thin, wing-like or parachute-like
dispersal structures attached to them to
help them float in air,
e.g. Shorea fruit.

Others have hair-like structures Hair-like
surrounding the seed. These structure
fruits are easily carried away by
the wind, e.g. dandelion.

Water Many plants that live near water
dispersal have fruits and seeds that can
float. These fruits fall into the
water and are washed away from
the parent plant, e.g. coconut.
The coconut has trapped air
inside the husk which allows it to
float on water.

Lotus seeds are contained in a
cone-shaped pod that is able to
float on water. As the pod drifts
away, it releases the seeds in
different places.

138 Reproduction in Plants

Method of Description Example
Dispersal Animals disperse seeds in several Spikes
ways. Fruits such as tomatoes,
Animal papayas, ciku, and guavas are WB Link Activity 15.2
dispersal fleshy and juicy. They attract 139Reproduction in Plants
animals, which then eat the fruits
and discard the seeds. Some
seeds may be eaten but are not
digested. Seeds of fruits like the
watermelon and chilli have tough
seed coats that protect them
from being digested by digestive
juices in the stomach. They are
then passed out with the animal’s
faeces, often far away from the
parent plant.

Some fruits and seeds have
spikes or hooks to cling onto
the fur or feathers of animals,
or onto the clothing of human
beings. As the animals move
from place to place, the seeds
are carried away and dropped off
at different places where they
may grow into new plants.

Self- Some fruits such as peas, saga
dispersal and beans, scatter their seeds by
exploding. The seeds are stored
in pods. When the pod dries,
they split along their lengths and
scatter the seeds in different
directions.

Dry rubber pods explode and
shoot the seeds into the air. The
seeds then land several feet
away from the parent plant.
Rubber pods can fling their seeds
as far as 15 metres from the
parent plant.

The four methods of seed dispersal in plants.

Quick Check

1. What is fertilisation?
2. Why do seeds need to be dispersed?
3. Describe the ways that seeds can be dispersed.

15.4 Germination

You should be able to:
• describe different stages of seed germination;
• investigate conditions necessary for germination (presence

of water, oxygen and suitable temperature).

Seeds

Seeds have the following main parts:
• an outer covering called the seed coat that protects

the seed,
• the cotyledon which provides food, and
• the embryo which consists of the radicle and plumule.

Seed coat

Position of new root

Seed scar
The structure of a seed

Germination of seeds
The process by which a seed develops into a new plant is
called germination.
During germination, the seed develops:
• a young root (radicle),
• a young shoot (plumule), and
• its first green leaf.

WB Link Activity 15.3

140 Reproduction in Plants

Different stages of seed germination Science Bites
The diagram below shows the various stages in the
germination of a seed. When the seed coat breaks open, Water
it allows the radicle to emerge followed by the plumule. Water softens the
Later in the growth stage, the radicle becomes the roots seed coat so that it
and the plumule becomes the shoot. The plant then uses can split easily. This
the roots to get nutrients and water from the soil and allows the f irst roots
carries out photosynthesis in the leaves to make food. and shoots to grow
During germination, the young plant gets its food from the out. Water also helps
cotyledons (food store). When the young plant has used up dissolve the nutrients
all the food, the cotyledon shrivels and falls off. in the seed leaves
into usable forms.

Air
If the seed is buried
deep into the ground,
it cannot obtain the
oxygen it needs to
germinate.

Temperature
A seed needs suitable
temperature to grow.
If the temperature is
too hot or too cold, it
cannot germinate.

Development of a young green bean plant

Conditions required for germination WB Link Activity 15.4
Germination can only take place under suitable conditions.
Seeds require water, air and suitable temperature Quick Check
to germinate.
1. What is
My seed did not germinate. I‛ve You must have germination?
been waiting for a few days. forgotten to water it
when the soil dried 2. Describe
How could this have happened? the different
up. Seeds need water, stages of seed
air and suitable germination.

temperature to 3. What are the
germinate and grow. conditions
necessary for
germination?

141Reproduction in Plants

Summary

Reproduction in Flowering Plants

Flowers

consist of are
• Sepals Pollinated by:
• Petals • Insects
• Stamen (male part • Wind

of the f lower) may lead to
– anther Fertilisation
– f ilament
• Carpel (female part which
Produces seeds
of the f lower) that are dispersed
– ovary by:
– style • Wind
– stigma • Water
• Animals
• Self-dispersal

142 Reproduction in Plants

Review Questions

1 Which of the following is found in the male part of a f lower?
A Style
B Ovary
C Stigma
D Filament

2 Name the process by which pollen grains from the anther are
transferred to a stigma.

A Dispersal
B Pollination
C Fertilisation
D Germination

3 The diagram below shows a f lower.

Which of the following correctly describes the f lower?
A It has f ive anthers.
B It has f ive stigmas.
C It is wind-pollinated.
D It is insect-pollinated.

4 Which of the following is a characteristic of a wind-pollinated fl ower?
A The petals are large.
B The stigmas are feathery.
C The f lowers produce nectar.
D The petals are brightly-coloured.

143Reproduction in Plants

5 Which of the following shows the correct order of reproduction in a
f lowering plant?

A Fruit → Young plant → Seed → Adult plant
B Seed → Young plant → Adult plant → Fruit
C Adult plant → Young plant → Fruit → Seed
D Seed → Fruit → Young plant → Adult plant

6 The diagram below shows an insect-pollinated f lower.
a) Describe brief ly how fertilisation occurs in the ovary.
b) Label the stigma, anther and f ilament on the diagram.
c) Give two reasons why this f lower is pollinated by insects.

144 Reproduction in Plants

7 State how the fruits and seeds shown below are dispersed.

Dandelion Papaya

Shorea Coconut

8 Some pupils were asked to set up the following experiments to
investigate the conditions necessary for green bean seeds to
germinate.

Set-up A Beans
Placed in a cupboard Dry soil

Set-up B
Placed near an open window

Beans
Wet soil

Set-up C Set-up D
Placed in a refrigerator Placed in a cupboard

In which set-up(s) will the seeds germinate? Explain why seeds in the
other set-up(s) do not grow into young plants.

145Reproduction in Plants

Chapter Reproduction in
Humans
16
You probably look like your parents. You may have your mother’s
eyes or your father’s nose, for example. How did you get your
parents’ features? Let us find out from this chapter.

Firman Allah Subhanahu Wa Ta’ala
Tafsirnya:
Dan bahawa sesungguhnya Dialah
Yang menciptakan pasangan – lelaki
dan perempuan (45). Daripada (setitis)
air mani ketika dipancarkan (ke dalam
rahim).(46)

And that He (Allah) creates the pairs,
male and female, (45) From Nutfah (drops
of semen – male and female discharges)
when it is emitted. (46).

(Surah An-Najm: 45-46)

Let’s Explore

• What are the structures and
functions of the human male and
female reproductive systems?

• What is puberty?
• How do menstruation and

fertilisation occur?
• What are the harmful

consequences of sexually
transmitted infections like syphilis,
gonorrhoea, chlamydia and AIDS?

146 Reproduction in Humans

16.1 Male and Female Science Bites
Reproductive
Systems Most organs are
found within our
You should be able to: body. However, the
• identify and state the functions of the male and female testes are found on
the outside of the
reproductive organs. male body. This is
because the internal
In order for all species to survive, they must reproduce. This body temperature is
is when a parent produces an offspring. This process requires too high for sperm
the fusing of sex cells from the male and female organisms. cells to survive.
It is known as sexual reproduction.

Male reproductive system

The following organs are part of the male reproductive system.
The male sex cell is called sperm.

Sperm duct Urethra
This transports sperm This is mainly used
from the testes to the to excrete urine.
urethra. However, during
sexual reproduction,
Testis it is used to
(plural: testes) transport sperm.
This organ produces
sperm. Penis
This organ deposits
sperm into the
vagina.

The male reproductive system

147Reproduction in Humans

A human sperm cell is approximately 0.06 mm long.

Each sperm has a head
containing a nucleus that
carries the characteristics
of the male parent.

Sperm cells The sperm has a long tail. The movement
of the tail helps the sperm to swim towards
the egg (female sex cell).

Parts of a sperm

Female reproductive system

The following organs are part of the female reproductive
system. The female sex cell is called the egg or ovum
(plural: ova).

Oviduct (also known Uterus
as the Fallopian This is a muscular
tube) structure where
This is where the egg the foetus develops
is fertilised. during pregnancy.
Ovary (plural: Vagina
ovaries) It is where the sperm
This organ produces are deposited. The
the female sex cells. foetus leaves the
uterus through the
vagina (also known
as birth canal) during
birth.

The female reproductive system

148 Reproduction in Humans

Each ovary produces about 250 mature eggs during the
lifetime of the female. The egg is spherical in shape and has a
diameter of about 0.1 mm.

Cytoplasm Nucleus: An egg cell
Cell membrane It carries the
characteristics Science Bites
of the female
parent. The egg or the ovum
is the largest cell
Parts of an egg cell found in a human
body.
Science Smart

Karl Ernst von Baer (1792 – 1876),
a biologist, laid the foundations
on the study of embryos and
their development. He discovered
that mammals, including humans
develop from fertilised eggs.

Quick Check WB Link Activity 16.1

1. Identify the parts of the male reproductive system and
state their functions.

2. Identify the parts of the female reproductive system and
state their functions.

149Reproduction in Humans

16.2 Sexual
Characteristics

You should be able to:
• show an awareness of the physical changes during puberty;
• briefly describe the menstrual cycle, with reference to

ovulation, menstruation and fertilisation;
• state that ovulation is the release of an egg from the ovary;
• state that menstruation is the shedding of the uterine lining

in the absence of fertilisation;
• state that fertilisation is the fusion of a sperm and an egg

which occurs in the oviduct.

Puberty

As you grow, your body starts to change. You start to mature
physically through a stage called puberty. Puberty usually
takes place in girls when they are about 10 to 12 years old,
and in boys when they are about 12 to 14 years old.

Science Bites Physical changes in a boy Physical changes in a girl
Starts to develop facial and Hair starts to grow in the
During puberty, your body hair armpits
reproductive organs Voice ‘breaks’ and deepens Breasts grow bigger
produce chemical Shoulders widen and height Hips widen and become
substances called increases rounder
hormones. Hormones Male reproductive organs Female reproductive organs
cause your body to (testes) mature and produce (ovaries) mature and release
change. Physical sperm eggs
changes during Body becomes more muscular Menstruation starts
puberty are the Pubic hair starts to grow Pubic hair starts to grow
effects of hormones. Penis enlarges

Changes in a boy and a girl during puberty

The menstrual cycle

The menstrual cycle has four main stages:
• menstruation
• repair of uterus lining
• ovulation
• thickening of uterus lining

150 Reproduction in Humans

On average, the whole menstrual cycle usually lasts for about
28 days. Day One of the cycle begins on the fi rst day of
menstruation and it ends on the 28th day, just before the next
menstruation begins.
This cycle may vary for different people. Stress, medication,
diet and vigorous exercise may affect the cycle.

1
1st – 5th day: Menstruation
The uterus is lined with many blood vessels. Every
month, the uterine lining thickens to prepare for a
fertilised egg to grow. If the egg is not fertilised,
the lining breaks down and menstruation occurs.

2
6th – 10th day:
Repair of uterus
lining
The uterus lining
repairs itself and
starts to thicken
again.

4 3

18th – 28th day: 11th – 17th day:
Thickening of Ovulation
uterus lining Ovulation usually occurs
The uterus lining on the 14th day. A mature
continues to thicken. egg is released from the
ovary. If the egg is not
fertilised by a sperm, it
breaks down.

Ovulation
The menstrual cycle

151Reproduction in Humans

Science Bites Fertilisation

Out of the millions During sexual activity, sperm from the male reproductive organ
of sperm that race are deposited in the vagina. The sperm then swim towards
towards the egg, the uterus and oviducts. When a sperm fuses with the egg, it
only one gets to forms a fertilised cell (also known as a zygote). This process is
fertilise the egg. This known as fertilisation.
is because once a
sperm penetrates Oviducts
the egg, the egg’s
surface changes to Egg
prevent the entry Ovary
of other sperm.
Meanwhile, the sperm Sperm Uterine lining
that penetrates the Cervix to receive
egg leaves its tail
behind, as it is no fertilised egg
longer needed. The
nucleus of the sperm
then fuses with the
nucleus of the egg.

Vagina
Sperm travelling towards the egg

Sperm entering an egg cell
Nucleus of both the
egg and sperm fuse
to form the nucleus
of the zygote.

Sperm
Nucleus
Egg cells

Only one zygote
sperm cell
enters the egg

Formation of a zygote

152 Reproduction in Humans

Implantation

After fertilisation, the zygote divides to form a ball of cells
called the embryo. The embryo travels along the oviduct
into the uterus. In the uterus, the embryo is implanted in the
uterus lining. This is called implantation. Implantation is the
early stage of pregnancy.

Embryo

Uterus

Ovary

Cervix Thicker uterus lining

Vagina
Implantation

Development of the foetus Science Bites

The embryo develops into a foetus. In humans, pregnancy The umbilical cord,
lasts about nine months. which, contains blood
vessels, supplies the
Uterus wall foetus with oxygen
and nutrients from
the mother.

Umbilical Oviduct
cord Foetus

Cervix
Foetus (after three months in the uterus)

153Reproduction in Humans

The following summarises the development of the foetus over
the nine-month period.
At the end of this period, the muscles of the uterus contract
to push out the fully developed baby. This process is known
as birth.

Umbilical After 7 weeks
cord

After 6 weeks

The embryo now looks
like a foetus. From this
stage until birth, it is
called a foetus.

After 12 weeks

At this stage, the
heartbeat can be heard
with a highly sensitive
instrument called the
Doppler fetal monitor.

Quick Check After 17 weeks

1. What is puberty? Liquid Umbilical cord
2. Describe the physical Placenta Wall of uterus
Vagina
changes that occur Cervix
during puberty in:
a) boys, and After 38 weeks (9 months)
b) girls.
3. What is ovulation?
4. What is fertilisation?
5. What happens if
fertilisation does not
occur?

154 Reproduction in Humans

16.3 Sexually
Transmitted
Infections (STIs)

You should be able to:
• recognise the causes and effects of Sexually Transmitted

Infections (syphilis, gonorrhoea, chlamydia, AIDS);
• describe ways on how to prevent Sexually Transmitted

Infections.

Sexually Transmitted Infections (STIs) are infections that
can be transferred from one person to another through any
type of sexual contact. Other ways of transmission may include
contact with contaminated blood and from a mother to her
baby during pregnancy. Some examples of STIs are syphilis,
gonorrhoea, chlamydia, and Acquired Immune Defi ciency
Syndrome (AIDS).

Syphilis Bacteria that cause
syphilis
Syphilis is caused by a bacterium.
The signs and symptoms caused by this infection include
painless sores and ulcers on the mouth and external genitals
(penis or vagina). If left untreated, it can cause insanity or
death. One can never fully recover from syphilis even with
treatment.

Sores are one of the symptoms Syphilis can cause lesions on Science Smart
of syphilis. the skin.
People infected with
This disease is transmitted through sexual activity. It can also syphilis may show
be passed on from mother to baby during pregnancy. symptoms in three
stages. In the fi rst
stage, the infection
starts with sores on
the various body
parts. Two to sixth
months later, the
infected person will
develop body rashes.
This is the second
stage. If the infection
is not treated, it will
progress to the third
stage where the
bacteria start to attack
the brain, paralysing
the infected person or
causing blindness.

155Reproduction in Humans

Gonorrhoea

Gonorrhoea is caused by a bacterium.

Bacteria that cause gonorrhoea

Signs and symptoms usually appear a few days after a person
contracts the disease. These include the following:
• Yellow pus is discharged from the end of the urethra.
• A burning sensation is experienced when urinating.
• In women, pus from the vagina may spread to the uterus

and oviducts.

Gonorrhoea may cause blindness in
newborn babies.

Gonorrhoea can be passed on from the infected mother to the
baby when the bacteria enter the baby’s eyes during birth.
This may cause the newborn baby to become blind.

156 Reproduction in Humans

Chlamydia

Chlamydia is another example of an STI caused by a bacterium.

Bacteria that cause Chlamydia

Chlamydia is also known as a ‘silent’ disease. This is because
almost 75% of infected women and 50% of infected men do
not show any symptoms. If symptoms do occur, they most
often appear within 1 to 3 weeks of exposure. The following
table summarizes the symptoms experienced by infected
women and men.

Infected women Infected men

An unusual vaginal discharge White or cloudy discharge

Pain or a burning sensation Pain or a burning sensation
when passing urine when passing urine

Lower abdominal pain Pain in the testes
sometimes with nausea

Symptoms of chlamydia infection

Without treatment, the infection can spread to other
parts of the body causing damage and long-term health
problems, including infertility. In pregnant women, chlamydia
infections may cause the babies to be born with conjunctivitis
and pneumonia.

157Reproduction in Humans

Acquired Immune Deficiency Syndrome
(AIDS)

Acquired Immune Defi ciency Syndrome (AIDS) is a disease
that is caused by a virus called the Human Immunodefi ciency
Virus (HIV). Our bodies have a natural defence called the
immune system that helps to fi ght infections within. HIV
destroys the immune system, and exposes the body to many
harmful infections.

HIV virus that causes AIDS

The symptoms of HIV infection may appear only after a few
months or even years. At fi rst, an HIV-infected person may
just fall sick more easily compared to before. Then, the person
may begin to lose weight, and start having diarrhoea and fever.
AIDS is the fi nal stage of the HIV infection. At this stage,
the virus has completely destroyed the body’s resistance to
disease. The following symptoms may appear:
• severe weight loss,
• chronic diarrhoea and fever,
• lung infections (e.g. pneumonia and tuberculosis),
• cancer of the blood vessels, and
• brain infection.

Lesions caused by cancer of the blood vessels

158 Reproduction in Humans

Spread of HIV
Although an HIV-infected person may not show any signs
or symptoms for months or even years, the virus remains
in the body.

It can be spread to others in any of the following ways:
• through sexual activity with an infected partner,
• through blood transfusion – if the donated blood comes from

an infected donor,
• through sharing of injection needles with an infected person,

and
• the virus may be transmitted from an infected mother to her

baby during pregnancy or childbirth.

Sharing infected needles can spread AIDS Science Bites

HIV cannot be spread by sharing the same utensils such as HIV is dangerous
drinking cups and spoons or through skin contact, such as because of its effects.
shaking hands with an infected person. It can remain in the
body for many years
Prevention of sexually transmitted without the person
infections feeling ill. This means
the person may
Prevention is better than cure. Here are some ways to prevent spread the infection
from getting infected with STIs and to control its spread: without knowing that
• Do not have any sexual relationships other than with your he/she is already
infected.
own spouse. This follows the teachings of Islam.
• Do not abuse drugs or share injection needles. Hospitals in

Brunei Darussalam use disposable needles for injections.
• Do not share instruments that may break the skin and be

contaminated with blood (e.g. razors and toothbrushes).
• Make sure that skin-piercing instruments are sterilised (free

from bacteria and viruses) before they are used on you.

159Reproduction in Humans

Science Smart Educating the public on STIs
The Ministry of Health, Brunei Darussalam and non-
World AIDS Day government organisations (NGOs), such as the Brunei
is observed on 1 Darussalam AIDS Council (BDAC), play an important role in
December every educating the public about the dangers of STIs, how they
year. It is dedicated can be prevented and where to go for assistance. This
to raising awareness information is made available through campaigns, exhibitions,
of HIV and AIDS. posters and pamphlets. BDAC conducts awareness
The Red Ribbon programmes, such as the HAPPY Programme for students.
Foundation organises
many activities and
events to raise the
awareness of HIV
and AIDS. The Red
Ribbon is the universal
symbol of awareness
and support for those
living with HIV.

Health Promotion Board Brunei AIDS council Brunei AIDS council making the
Red Ribbon Human Chain

Don‛t be a victim. Protect WB Link Activity 16.2 and 16.3
yourself by abstaining from sex
until after marriage. You are at Quick Check
risk of developing STIs if you
have multiple sexual partners. 1. What are the signs and symptoms of syphilis?
2. State two ways by which sexually transmitted

infections (STIs) can be spread.
3. List three ways to prevent the spread of HIV.

160 Reproduction in Humans

Summary

Human Reproduction
System

made up of

Female Undergoes Male
consist of physical consists of

Oviducts changes during Urethra
puberty
Uterus
Penis
Vagina
Ovaries produce Eggs Sperm ducts

Sperm produce Testes
through sexual
activity

Fertilisation

Zygote

Foetus
Birth

Baby

Sexually Transmitted Infections

caused by bacteria caused by virus

Syphilis Gonorrhoea Chlamydia AIDS

161Reproduction in Humans

Review Questions

1 What is the human male sex cell known as?
A Ovum
B Sperm
C Zygote
D Epidermis

2 What is the human female sex cell known as?
A Ovum
B Uterus
C Vagina
D Ovaries

3 Where does the implantation of a human embryo usually occur?
A Ovary
B Uterus
C Vagina
D Oviduct

4 In which part of the female reproductive system does fertilisation
usually take place in?

A Ovary
B Uterus
C Vagina
D Oviduct

5 Which one of the following causes gonorrhoea?
A Virus
B Bacteria
C Mosquitoes
D Poor hygiene

6 Which of the following increases the chances of a person getting
infected with AIDS?

A Swimming in a public pool
B Having sexual contact with a person with AIDS
C Breathing in the air breathed out by a person with AIDS
D Touching a door knob that was touched by a person with AIDS

162 Reproduction in Humans

7 The diagram below shows the female reproductive system.

A
B
C
D

a) Identify parts A to D.
b) State the function(s) of parts A to D.

8 The diagram below shows the male reproductive system.

A
B

D
C

a) Identify parts A to D.
b) State how parts A, B, C and D are involved in sexual reproduction.

9 Name the male reproductive structure through which both sperm and
urine pass.

10 What does AIDS stand for? Name the organism that causes the
disease.

11 State three ways by which HIV may be transmitted.

163Reproduction in Humans