IS

4.1 cells
➢ Cells are the basic unit of living things.
➢ Living things that are made up of one cell only, such as Amoeba and bacteria,are called
unicellular organisms.
➢ Living things that are made up of more than one cell, such as animals and plants,are called
multicellular organisms.
➢ Human body is made up of about 100 trillion cells.

Animal cells Plant cells

cell membrane, nucleus, cytoplasm(jelly-like) cell membrane, nucleus, cytoplasm, cell wall,
(large)vacuole, chloroplast(some)

➢ Cells are too small to be seen with the naked eye, we can use a microscope to observe cells.
➢ The microscopes commonly used in the school
laboratory are light microscopes (a several hundred
times).
➢ Electron microscopes are more powerful, usually in
research laboratories.
➢ A microscope has different eyepieces and objectives,
each has a magnification.
➢ The longer the eyepiece, the lower the magnification.
The longer the objective, the higher the magnification.
➢ Eyepiece x objective = microscope (magnification)
➢ Using a microscope
1. Place the microscope near a light source (lamp/near a window)
2. Choose a low-power eyepiece and rotate a low-power objective into position.
3. Adjust the mirror to obtain the most suitable brightness.
4. Place the slide on the stage. Hold the slide in place with the clips.
5. Look from the side. Turn the coarse adjustment knob carefully to lower the objective
(or to raise the stage) until the objective is just above the slide.
6. Turn the coarse adjustment knob in the opposite direction slowly. Stop turning when
you can see a clear image of the **.
7. Turn the fine adjustment knob up and down until you can obtain the sharpest image.

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 ➢ The image observed is magnified and inverted under the microscope.

➢ DNA(deoxyribonucleic acid) is the genetic material inside the nucleus which control the
activities of the cell.
➢ “Book of life” because it contains all instructions needed for the cells to carry out activities so
that our bodies can function, grow and reproduce.
➢ DNA determines what features we receive from our parents. 4.5
➢ There are thread-like structures called chromosomes inside the nucleus.
➢ Chromosomes are made up of DNA and proteins. The DNA coils up and wraps around the
proteins.
➢ Chromosomes 4.3

➢ Cells can undergo cell division to form new cells.

➢ Living things grow by increasing the number and size of cells.
➢ When the daughter cells reach a certain size, they may divide
again. As a result of repeated cell divisions and the increase in
size of cells, living things grow bigger.

4.2 How are cells organized in living

things?
➢ Each type of cells carries out a particular job. For example, in our
bodies, there are hundreds of different types of cells.
➢ These different types of specialized cells all come from stem
cells.Stem cells can differentiate into different types of cells. Cells
become specialized to perform a particular function. The process of cells becoming specialized
is called cell differentiation.

➢ The level of organisation of multicellular organisms:

○ cell (heart muscle cell)
○ tissue (heart muscle tissue)
○ organ (heart)
○ system (circulatory system)
○ organism (the human body)
➢ Tissues are group of similar cells working together
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 ○ Human tissues:
■ Muscle tissue(for movement)
■ Nerve tissue(for carrying messages in the body)
■ Bone tissue(for support)
○ Plant tisues:
■ Vascular tissue(for transporting water, nutrients and minerals)
■ Epidermal tissue(for protection)
➢ Individual tissues group together to form an organ.
○ Example: heart is with heart muscle tissue, blood tissue and nerve
tissue, they work together and enable the heart to pump blood around
the body.
○ Example of organs———————————————————————>
○ In plants, the organs include the flower, leaf, stem and root. The
stem is an organ consisting of vascular tissue and epidermal tissue.
➢ A group of organs that work together is called a system.
○ Example, The digestive system is made up of the stomach, intestines, liver and several
other organs.
○ Breathing system, reproductive system, nervous system, circulatory system.

4.3 Human reproduction

➢ Living things produce offspring to ensure the continuity of species.
➢ Humans reproduce by sexual reproduction.This involves the fusion
of a male sex cell(sperm) and a female sex cell(ovum,ova(p)or egg).
○ The sperm has a head and a tail. It looks like a tadpole.
There is a nucleus inside the head. The nucleus carries the
genetic materials of the male parent. The tail enables the
sperm to swim.
○ The ovum has a spherical shape. It is much larger than a
sperm. It is surrounded by a jelly coat. The nucleus of the
ovum carries the genetic materials of the female parent.
The cytoplasm contains food substances. The ovum cannot
move by itself.

Chromosomes:

Male Female

Body cell Sex cell (sperm) Body cell Sex cell (ovum)

No. of chromosomes 46 (23 pairs) 23 46 (23 pairs) 23

No. of autosomes 44 22 44 22

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Sex chromosomes XY half X, half Y XX X

Male reproductive system

Female reproductive system

Process of human reproduction

1. Fertilization
○ During sexual intercourse, the husband inserts his penis into
the vagina of his wife.
○ Semen with millions of sperms is ejected into the vagina.
○ One sperm may fuse with the ovum to form a zygote
(fertilized ovum), this is called fertilization.
○ If there is no ovum in either of the oviducts, there is certainly no fertilization. All the
sperms will die in two to three days.
○ Sperm(23 chromosomes)+ovum(23 chromosomes)=zygote(46 chromosomes)
2. Implantation
○ After fertilization, the zygote divides many times to
form a ball of cells:embryo.
○ The embryo is moved through the oviduct to the
uterus.
○ It attaches to the uterine lining, the woman is now
pregnant.
3. Development of the embryo
○ After implantation, the embryo begins to
develop in the uterus. It develops inside a bag:
amnion (filled with a watery liquid which acts
as a cushion to protect the embryo against
shock).
○ At the site where the embryo is implanted in
the uterine lining, a placenta begins to form.

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 The placenta is attached to the embryo by an umbilical cord.
○ The embryo needs to get oxygen and nutrients from its mother, and get rid of carbon
dioxide and other wastes. The placenta allows this exchange of materials between the
embryo's blood and the mother's blood.
○ The embryo develops into a foetus about eight weeks after fertilization. The foetus
has all the major organs formed. The foetus then continues to
develop in the uterus.
4. Birth of a baby
○ The baby changes its position and lies with its head downwards.
○ Labour (the birth giving process) begins with a sign of pain in the
abdomen, because the muscles of the uterus contract strongly.
○ The amnion breaks and the watery liquid flows out to lubricate the
vagina, the opening of the uterus becomes wider.
○ The muscles of the uterus contract more strongly and frequently
to push the baby out.
○ The baby cries for the first time and takes its first breath.
○ The doctor clamps and cuts the umbilical cord.
○ The placenta is expelled from the mother's body.

Puberty
➢ Every person is born with a complete set of reproductive organs that will
become mature for reproduction at puberty.
➢ It usually starts at the age of 10 or 11 and ends around 18. It usually occurs earlier in girls
than in boys.
When teenagers enter puberty, their bodies produce more sex hormones, which cause various body
changes, including:
➢ Secondary sexual characteristics begin to show. These are the external features we see in
adult males and adult females.
○ Males:
■ Beards grow.
■ Larynx becomes larger and voice becomes deeper.
■ Shoulders become wider and the body becomes more muscular.
■ Hair grows in pubic area and armpits.
○ Females
■ Breasts develop.
■ Hair grows in pubic area and armpits.
■ Hips become wider.
➢ Signs of sexual maturity appear. These are the signs of the reproductive organs of males and
females starting to become mature. In males, the testes start to produce sperms. In females,
ova start to develop in the ovaries.
○ Wet dreams(nocturnal emission):
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 ■ Boys start to produce semen. The semen may flow out from the penis during
sleep.
○ Menstruation(period):
■ Each month, an ovum becomes mature and is released into the oviduct (i.e.
ovulation).
■ To prepare for the implantation of the embryo, the uterine lining thickens with
increased blood supply. If the ovum is not fertilized, the thickened uterine lining
breaks down. The tissues of the uterine lining, blood and the unfertilized ovum
pass out through the vagina.
■ It usually lasts about five days.
■ Menstruation occurs periodically. This periodic
change is called the menstrual cycle. A menstrual
cycle (the time from the first day of one
menstruation to the next) usually lasts 28 days. The
length of a menstrual cycle may vary from person to
person.

4.4 Being parents

Pregnancy
➢ If a sperm successfully fertilizes an ovum and implantation occurs, the woman becomes
pregnant.
➢ The pregnancy period lasts about 38 weeks.
➢ She should take extra care to manage health.
➢ When a woman is pregnant, her body will show some changes, which include:
○ absence of menstruation
○ swollen breasts
○ nausea
○ frequent urination
○ feeling tired easily
○ constipation
Parenting
➢ Newborn babies cannot take care of themselves.
➢ They need much care and protection from their parents.
➢ Parenting is essential for the healthy growth of babies.
➢ Examples:
○ Provide baby with daily necessities, such as food, clothing and shelter (feed the baby,
change nappies for the baby)
○ Guide the baby and teach the baby different basic skills, like how to walk and talk
(teach the baby to walk, teach the baby to talk)
➢ Other animals: dolphins
○ The length of pregnancy in dolphins is around 12 months.

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 ○ The baby dolphins soon learn to swim. They swim close to their mothers so that their
mothers can protect them.
○ They get milk from their mothers. The milk contains antibodies which help protect
them from diseases. The whole milk-feeding period lasts up to two years.
Family planning
➢ Married couples should decide how many children they want and when to have them. This is
called family planning
➢ Preventing the fusion of a sperm and an ovum is one of the basic principles of birth control.
➢ Birth control methods:

Preventing sperms from reaching the ovum

Birth control How it works

method

Condom Acts as a barrier to ● Male condom

prevent sperms from It is rolled over the erect penis of the
reaching the ovum husband before intercourse so that
semen is trapped.
● Female condom
It is placed inside the vagina of the
wife before intercourse to catch
semen.

Diaphragm It is placed at the opening of the uterus of

the wife so that sperms cannot enter the
uterus.

Rhythm method A natural method This is to avoid having sexual intercourse

without using birth around the days when ovulation occurs, so that
control devices the sperms have no chance of meeting the
ovum.

Sterilisation A surgery is done to ● Male sterilization

permanently prevent The sperm ducts are tied and cut so
pregnancy that sperms cannot be passed out of
the body.
● Female sterilization
The oviducts are tied and cut so as to
prevent the ova from passing down the
oviducts.

Preventing ovulation

Birth control How it works

method

Birth control pills Stop ovulation by These are taken by the wife regularly
using sex hormones according to a doctor's instructions.

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 ➢ Prevention of sexually transmitted diseases:
○ Sexually transmitted diseases (STDs) are infectious diseases that can be passed from
one person to another through sexual contact.
○ Some birth control methods can help prevent the transmission of STDs:
■ Using condoms in sexual intercourse prevents STDs. Condoms act as a barrier to
prevent direct contact between the penis and the vagina.
■ Other methods such as the rhythm method, birth control pills, diaphragms and
sterilization cannot prevent STDs.

4.5 Heredity and variation

Passing of traits to the next generation
➢ The features each generation inherits from their parents are called traits.
➢ The passing of traits from parents to the next generation is called heredity.
➢ Traits are determined by the DNA(carries genetic information in the nucleus of cells).
➢ The zygote formed after fertilization receives half of its genetic information from the father
and half from the mother.
➢ Through the transmission of genetic information, traits can be passed from one generation to
the next.
➢ The passing of a particular trait through
several generations in a family can be shown in
a tree diagram. We can trace the passing of
the trait through each generation. We may also
predict how likely the trait will occur in the
next generation.
Variations
➢ Variations are determined by heredity and the environment.
➢ The differences in features among individuals of a species are called variations.
➢ Continuous variation:
○ Continuous variation shows a continuous range of differences.
○ Features showing continuous variation include height, body mass,
hand span and intelligence quotient (IQ).
○ We can draw a histogram to present the data of a continuous
variation.
➢ Discontinuous variation:
○ Discontinuous variation shows clear-cut differences.
○ For example:
■ people either have ear lobes or no ear lobes
■ some people are tongue rollers while others are not
■ blood group
■ Hairline

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 ○ We can draw a bar chart to present the data of a discontinuous variation. The following
is an example of bar chart showing the discontinuous variation in blood groups.

Causes of variations
➢ Heredity:
○ Variations determined by heredity are called inherited variations (or genetic
variations). These variations cannot be changed.
○ Examples:
■ Natural hair color
■ Natural eye color
■ discontinuous variations
➢ Environment:
○ Variations determined by the environment are called environmental variations.
○ Example:
■ Hydrangea, its color varies depending on the conditions of the soil in which it
grows.
➢ Some variations are determined by both heredity and the environment.
○ Example:
■ Our skin color is determined by heredity, it is also affected by the environment,
the skin will become darker if we expose it to the sunlight for a longer time.
■ continuous variations

Twins
➢ Identical twins
○ Identical twins result from a single zygote.
○ The two babies have the same genetic materials, so
they are of the same sex and they look like each
other.
○ Variations between identical twins are due to the
differences in their living habits and environments.
➢ Non-identical twins
○ Two babies developed from two different sperms
and ova, they have different genetic materials. They
are called non-identical twins.
○ The two babies are just like babies of two separate
pregnancies. They may be of the same sex or
different sex. They may look different from each
other.

DNA and heridity

DNA contains all information needed to control the activities within our cells. It also determines the
traits we inherit from our parents.
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➢ Structure of DNA
○ DNA consists of two strands.
○ There are four different kinds of bases: A, T, C and G for short. The bases on the two
strands pair up in a way that makes DNA a double helix(AT, CG).
○ The way the bases pair up is known as complementary base pairing. If the sequence of
bases on one strand is known, the sequence of complementary bases on the other
strand can also be known.
➢ Sequence of bases on DNA and genetic code
○ The sequence of bases on DNA acts as genetic code, which encodes 'messages' that
determine our traits.
○ Every three bases encode one 'message', so it is called a triplet code.

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3.1 Living Things
➢ Living things have some vital functions for sustaining life

Vital function Description ● Example

Nutrition ● Living things need food for ● A giant panda needs to eat 12 to 38 kg
energy and nutrients. of bamboo a day.
● Plants can make their own food by
photosynthesis.

Respiration ● Living things need to ● A seal can hold its breath underwater
breathe. They use the for almost an hour. Then it goes up to
oxygen in the air to break the surface to breathe.
down food to provide ● Mangrove plants can take in oxygen
energy. through aerial roots.

Movement ● Living things can move. ● The cheetah is the fastest runner on
land. It can run 100m in less than 6
seconds.
● The bud of a sunflower turns slowly to
face the Sun during the day.

Growth ● Living things can grow. ● A baby kangaroo is less than 2.5cm long
when it is born. It can grow to 2.6m tall
as an adult.
● Bamboo is one of the fastest growing
plants in the world. It can grow as much
as 90cm each day.

Sensitivity ● Living things can detect ● An eagle can see a fish 3km away and
and react to stimuli in the swoop down to catch it.
environment. ● The shy plant responds to touch by
folding its leaves.

Excretion ● Living things remove waste ● An elephant produces about 18 litres of

from their bodies. urine a day.
● Waste in plants is stored in leaves. The
waste is removed when the leaves fall
off.

Reproduction ● Living things produce the ● A newborn bourse can stand up and run
next generation by within a few hours of birth.
reproduction, they cannot ● A spider plant can produce new spider
live forever. They die from plants without seeds.
disease, old age or are
eaten by other living
things. Reproduction is
necessary to ensure the
continuous survival of living

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 things.
➢ Non-living things may have some functions similar to the living things.
○ Example: a car can move, uses fuel for energy, gives off exhaust gases.
○ A self-driving car even has some sensors and a computer that detect and react to
stimuli on the road. It does not grow or reproduce.

➢ There is a wide variety of living things on Earth.

➢ Scientists have identified more than 1250000 kinds of animals and 320000 kinds of plants.
➢ Scientists estimate that there may be as many as 100 million kinds of living things on Earth.
○ Microorganisms(only be seen with a microscope)
■ Mould is a microorganism that is commonly found growing on food.
○ Animals
■ The blue whale is the largest animal in the world. It can grow up to 30m long.
■ The ostrich is the largest bird in the world(2m tall). It cannot fly but it can run
very fast.
○ Plants
■ Fern is a plant that does not produce flowers.
■ Rafflesia Arnoldi’s flower is the largest in the world. It’s diameter can be over
1m.

3.2 Grouping of living things

➢ Classification help us identify and study living things systematically.
➢ Scientists classify living things into groups based on their key features.
➢ Steps for classifying living things
a. Observe key features in living things.
b. Put living things with similar key features in the same group.
c. Give the group a name.

➢ Scientists make a key based on the key features of living things.

➢ A key can be used to identify living things that are similar.
➢ When making a key for classifying living things, we should choose
features that do not change over time.

Classifying animals
➢ Animals can be classified into vertebrates and invertebrates, based on whether or not they
have a backbone.
○ Invertebrates
■ Jellyfish
■ Earthworm
■ Snail
■ Butterfly
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 ➢ Key features of the five groups of vertebrates

Fish ● Live in water ● Angelfish

● Have slimy scales
● Have gills for breathing in water
● Have fins for swimming
● Body temperature changes with the
surrounding
● Lay eggs in water

Amphibians ● Can live in fresh water and on land ● Tree frog

● Have moist skin but no scales ● (A tadpole has gills for
● Young have gills for breathing in water; breathing in water)
adults breathe through lungs and skin
● Body temperature changes with the
surroundings
● Lay eggs in fresh water

Reptiles ● Have hard dry scales ● Pagona lizard

● Have lungs for breathing
● Body temperature changes with the
surroundings
● Lay shelled eggs on land

Birds ● Have feathers ● Macaw parrot

● Have lungs for breathing
● Have beak for feeding
● Have wings
● Body temperature not easily affected by the
surroundings
● Lay shelled eggs on land

Mammals ● Have hair ● Red panda

● Have lungs for breathing ● (A young calf is drinking
● Have mammary glands that produce milk for milk from its mother’s
feeding the young mammary glands)
● Body temperature not easily affected by the
surroundings
● Do not lay eggs but give birth to live young

Classifying plants
● Plants can be classified into vascular plants and non-vascular plants, based on whether or not
they have vascular tissues.
○ Vascular plants: have vascular tissues for transporting water,
nutrients and minerals through their roots, stem and leaves.
Vascular plants can grow taller than non-vascular plants.

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 ○ Non-vascular plants: do not have vascular tissues. They are small plants that usually
grow in damp places. They do not have roots to absorb water, but absorb water directly
through their body surface. (Moss)
● Vascular plants can be further classified into seed plants and seedless plants, based on
whether or not they produce seeds.
○ Seed plants: produce seeds for reproduction. Seeds sure usually protected inside a
fruit.
■ Dandelion(fruit)
■ Peas(pea pod=fruit)
○ Seedless plants: do not produce seeds. Fern is a kind of seedless plant. Fern produce
spores for reproduction. Spores are smaller than seeds.
● Seed plants can be further classified into flowering plants and non-flowering plants, based on
whether or not they produce flowers.
○ Flowering plants: produce flowers and fruits. Most of the fruits and vegetables we eat
come from flowering plants.
■ Cotton tree
■ Bauhinia variegata
■ Orange tree
○ Non-flowering plants: do not produce flowers.
■ Pine(produces pine cones, which contain seeds.)

3.3 Living things and habitats

● A habitat is the natural environment where a living thing lives.
● Living things have special body features that help them survive in their habitats. This is called
adaptation.

Habitat Animal Feature Function

Grassland: Cheetah Long, strong legs run fast to catch prey

Open area with long
grass Sharp claws & teeth to catch prey

Good eyesight find prey easier

Hair colour & spotted pattern to camouflage

Polar region: Polar bear Strong legs & big feet to run on ice
Cold land covered in
ice and snow for most White hair for camourflage
of the year
Thick layer of fat under skin to keep warm

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 Ocean: Shark Fins to swim
Large area of salt
water with waves and Gills to breathe under water
currents
Sharp teeth to catch prey

Wetland: Egret Wings to fly

Area of land flooded
in fresh water or salt Long legs to walk in water
water
Long pointed beak to catch prey

Freshwater pond: Frog Lungs & moist skin to breathe

Small area of calm,
fresh water Skin colour & pattern for camourflage

Long sticky tongue to catch prey

Tropical rainforest: Oranguta Long arms & fingers to climb trees

Warm forest with n
very tall trees, wit Hair colour for camourflage
high rainfalll

Desert: Cactus Long roots to absorb water

Dry areas with little
rainfall, very hot Thick stem to store water
during the day
Needle-like leaves to reduce water loss

3.4 Biodiversity
➢ Scientists have identified more than 1.5 million kinds of living things on Earth.
➢ The existence of many different kinds of living things is called biodiversity.
➢ Biodiversity can be studied at different levels.(of the whole Earth or of a small area, such as a
pond)
➢ Tropical rainforests and coral reefs have the greatest biodiversity on Earth.
➢ Tropical rainforests are home to more than half of all kinds of living things, although they only
cover 6% of the Earth's land surface.
➢ Coral reefs cover less than 1% of the ocean floor, but they are home to more than 25% of
marine living things.

The importance of biodiversity

➢ Keeping the ecosystem sustainable
○ All the living things in an ecosystem are interdependent on each other.
○ The loss of any one kind of living thing will affect the whole ecosystem.
○ A sustainable ecosystem can continue for a long time.
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 Interactions in an ecosystem

Plants Plants provide food for some animals.

Plants provide shelter for some animals.

Plants give out oxygen for all living things to breathe.

Plant roots help to hold the soil in place.

Animals Animal waste helps keep the soil fertile.

Some animals provide food for other animals.

Some insects such as bees feed on nectar in flowers. In return, they help
flowering plants reproduce by spreading polllen.

Some animals such as earthworms live in the soil. Their movement helps to
keep the soil loose and moist.

Microorganisms Some microorganisms live on the soil. They break down dead plants and
animals, and turn their remains into nutrients. Plants absorb these
nutrients for growth.

Some microorganisms remove harmful substances from water, thus

purifying the water for other living things.

➢ Providing resources for humans

○ Living things on Earth depend on each other for survival.
○ Humans also depend on other living things for many of our needs.
○ Humans depend on plants and animals for resources such as food, raw materials and
medicines.

3.5 Reduction in biodiversity

➢ Living things may become extinct because of natural causes such as diseases, climate change
or natural disasters. (Dodo, mammoth)
➢ In the past 50 years, the rate of extinction has been much faster than the rate caused by
natural events.
➢ The rapid reduction in biodiversity is mainly caused by human activities.
○ Destruction of habitats
■ As human population increases, more land is needed to build houses, roads and
farms.
■ We also need more resources such as wood for making paper, building houses and
making furniture.
■ Many forests and other habitats have been destroyed.
■ The living things in these habitats cannot survive.

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 ○ Overexploitation
■ Overexploitation refers to the use of natural resources (including animals and
plants) faster than they can replenish.
■ Humans hunt and kill wild animals for food, medicine, clothing and for other
purposes.
■ Because of overhunting, many wild animals are decreasing rapidly in number and
may soon become extinct.

Elephant Their teeth are used for making crafts.

Tiger Their skin is used for making carpets, and their bones are used
as Chinese medicines.

Shark Their fins are used for making soup.

Rhinoceros Their horns are used as medicines.

Crocodile Their skin is used for making handbags or shoes.

Bluefin Their meat is. Used for making sushi.

tuna
■ As the human population increases, the demand for fish also increases.
■ Modern fishing methods let us catch fish in large numbers.
■ Therefore, fish are being caught faster than they can reproduce.
■ Scientists warn that if overfishing continues, soon there may be no more edible
fish.
■ Some plants are also overexploited. Aquilaria sinensis is one example. It is
overexploited for making incense and medicine.
○ Pollution
■ Human activities produce many different kinds of pollutants.
■ These include exhaust gases, sewage, chemical waste, excess fertilizers,
pesticides, and oil spills from oil tankers.
■ These pollutants damage habitats and are harmful to living things.
■ Pollution causes the death of millions of animals and plants around the world
each year.
■ Examples: Oil spills from oil tankers are harmful to seabirds and other marine
living things\A dolphin ate plastic waste and was suffocated.
➢ Endangered species are the kinds of living things that are in danger of becoming extinct.
○ Black-faced spoonbill
○ Orangutan
○ Green pitcher plant
○ Green turtle
○ Romer’s tree frog
○ Tiger

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3.6 Conservation
➢ We need to protect the environment and the biodiversity of the Earth. This is called
conservation.
➢ We can take some actions to reduce the hunting and killing of wildlife and to protect their
habitats.

For animals Do not buy products such as craft or clothing made from endangered animals.

Do not keep endangered animals as pets.

Do not eat food made from endangered animals.

For plants Do not pick plants when you visit country parks.

Do not buy endangered plants.

For habitats Do not leave any rubbish in country parks or marine parks.
➢ We can support organizations that work on conservation.
➢ We can also take part in conservation programmes such as tree planting and beach clean-up
events.
➢ The 3Rs principle of conservation:
○ Reduce
■ Reduce the use of resources
■ E.g. print on both sides of the paper to reduce paper use.
○ Reuse
■ Reuse items or give them to others in need
■ E.g. donate used clothes to charity groups.
○ Recycle
■ Recycle old materials into new products
■ E.g. put used paper, aluminum cans and plastic bottles into recycling bins. These
can be made into new products.
➢ We must use the Earth’s resources in a sustainable way, so that they are not used up.
○ Sustainable fishing methods
■ Catch only what we need.
■ Catch only adult fish bigger than a certain size, to avoid catching fish before
they can reproduce.
■ Set up a fishing ban period each year, so that the fish can reproduce during this
period.

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