Uss module 5 chpt 6 Sources of Food

Module 5:
Food Matters
Chapter 6 Sources of Food
1© Copyright Star Publishing Pte Ltd

6.1 Why is food important?
6.2 How is food produced?
6.3 How do fertilisers affect food
production?
6.4 What is the slash-and-burn method
used in
agriculture?
6.5 How can crops be protected?
6.6 How can food production be improved
and
increased? 2© Copyright Star Publishing Pte Ltd

Objectives
 Recognise the importance of food and
food production in our lives

Why is food important?
 Humans need to eat in order to
survive. The food we eat provides the
nutrients we need for us to grow and
the energy to carry out daily
activities.
 Food provides energy for carrying out
processes in the body such as
respiration and breathing.
© Copyright Star Publishing Pte Ltd 4

Different categories of food

Different categories of foods

production?
used in
agriculture?
and

Objectives
 Appreciate the conditions required in
producing food
 State that sunlight, air, water and good
soil (containing nutrients and
appropriate pH) are required for plants
to grow and produce food
 Measure the pH of soil using litmus
paper, universal indicator or a pH
meter

Photosynthesis
 Plants are the primary source of
food for many living things such as
insects and mammals.
 Plants need food to grow. They are
able to make their own food through
the process of photosynthesis.

Photosynthesis
 Plants take in
energy from the
sun to make food
for it to grow. Any
excess food is
stored in the
leaves, stems,
roots and fruits of
the plant.
when animals or humans eat
plants, they absorb the stored
energy from the food

Photosynthesis
 Photosynthesis is the process by which
plants use chlorophyll and light energy
together with carbon dioxide from air and
water from the soil to form sugar and
oxygen.
 Photosynthesis is represented using a word
equation as shown below:

Photosynthesis
 Excess sugar is
changed into
starch to be
stored in the
plant cells. The
presence of
starch is often
used as an
evidence to
show that
photosynthesis
has occurred.
factors needed for photosynthesis
Activity Book Link
Activity 6.1
Testing for Starch

Soil conditions for plants to grow
 Apart from sunlight, air and water, the soil
conditions are important for plants to grow
well.
 The soil must contain the necessary
nutrients for healthy growth of the plants.
 The pH value of the soil also plays an
important
part in determining healthy plant growth. The
pH
can be determined using indicators such as
the
litmus paper, universal indicator or pH

Reactions of different indicators in acidic, neutral and
alkaline soil samples

Reactions of different indicators in acidic, neutral and
alkaline soil samples
Activity Book Link
Activity 6.2
Acidity and Alkalinity of
Soil

production?
used in
agriculture?
and

Objectives
 Understand that fertilisers provide
nutrients for the plant to grow faster
and bigger
 Understand that the use of fertilisers
can be beneficial (increase food
supply) and also cause problems

Fertilisers
 Some soil may not contain sufficient
nutrients or the correct type of
nutrients to help the crops grow well.
 When soils do not contain the required
nutrients, fertilisers can be added to
the soil to help plants grow faster and
bigger.

Fertilisers
 Bag of fertiliser  Fertilisers added to
crops

Fertilisers
 Fertilisers are substances added to
soil to increase the amount of
essential nutrients required by the
plants.
 Adding fertilisers helps to improve
plant growth and crop yield (the
amount of crops produced).

Natural Fertilisers
 Plant and animal
waste products can be
used as natural (non-
chemical) fertilisers.
These fertilisers are
non-toxic and do not
pose a threat to the
environment. One
example is compost,
which consists of
decomposed plant
matter.
compost made from
decomposed plant matter does not
harm the environment

Chemical fertilisers
 Chemical fertilisers are soluble in water. If too much is
added to the soil, the excess fertilisers may be washed
away into the groundwater. These chemicals are toxic
and can damage the environment in the following ways:
(a) Contamination of the main source of drinking water
fertilisers can seep into the ground and
contaminate groundwater

(b) Negative impact on aquatic life
Chemical fertilisers, when washed by the rain
into rivers, lakes or ponds, can pollute these water
bodies. This affects the health of the aquatic plants
and animals as the chemicals are toxic to them.
fishes die as a result of
water pollution
run-off of fertilisers into
water bodies

 Chemical fertilisers are rich
in nutrients such as
nitrogen and phosphorus.
These nutrients cause the
rapid growth of algae on
the water surface called
“algae bloom”.
 The algae form a layer on
the surface of water,
preventing sunlight and
oxygen from reaching the
aquatic plants and
animals living in the water
bodies.
fertiliser-polluted water
promotes rapid
growth of algae
Activity Book Link
Activity 6.3
How Fertilisers Help
Plants Grow

production?
6.4 What is the slash-and-burn
method used in agriculture?
6.6 How can food production be
improved and increased?

Objectives
 State the effect of ‘slash-and-burn’
methods of agriculture on soil fertility
and the environment

Slash-and-Burn
 Slash-and-burn is an agricultural
method where trees are cut down
and burned to clear plots of forest
land. This method is used to make
land available for growing crops,
especially in places where open land
for farming is not available due to thick
vegetation.

Slash-and-Burn

Advantages of slash-and-burn
 Farmers benefit from the slash-and-burn
method of agriculture because:
(a) It is a cheap and fast method of
clearing land for planting new crops.
(b) Ashes from the burnt trees provide
nutrients to the soil.
(c) It reduces the occurrence of pests
and plant diseases.

Disadvantages of slash-and-burn
 The slash-and-burn method of agriculture can
lead to many problems:
(a) Haze, which causes:
(i) Poor visibility
(ii) Breathing difficulties and eye irritation
(iii) Higher air temperature
(b) Soil erosion
(c) Possible spread of forest fires
(d) Loss of natural habitats and extinction of
species
Activity Book Link
Activity 6.4
Clearing Land to Plant
Crops

Haze
 The haze observed in
Singapore is a result of
burning of large areas of
forests in our neighbouring
countries.
 The haze brings with it a
lot of inconvenience
and harm, such as
(i) Poor visibility
The particles in the haze reduce the amount
of sunlight that reaches us. This reduces the
visibility of the surroundings.
fertiliser-polluted water
promotes rapid
growth of algae

Haze
(ii) Breathing difficulties and
eye irritation
The particles in the haze can
cause people
with respiratory problems,
e.g. asthma, to have breathing
difficulties. In serious cases,
this may lead to death.
People with sensitive eyes
may also experience irritation
of the eyes in a hazy
environment.
asthmatic boy using inhaler
the elderly are more prone to
developing
breathing difficulties

Haze
(iii) Higher air temperature
The haze also traps heat in
our surroundings
and prevents heat from
being reflected back into
the atmosphere.
This raises the temperature
around us and contributes
to warming of the
surroundings.
the haze traps heat and
increases surrounding
temperatures

Haze
(b) Soil erosion
When it rains, the tree roots in forested areas keep the top
soil together. This prevents the soil from being washed
away by the rain.
However, when forests are cleared, the top soil is exposed
to wind and rain and can easily be washed away.
Soil erosion can cause landslides and destroy lives and
properties.
landslide caused by soil erosion

Haze
(c) Possible spread of forest fires
Once a forested area is burned, the fire may
become uncontrollable due to strong
winds and spread to surrounding forests.
Instead of a small area of land, the entire
forest may be burnt.
uncontrolled burning can
cause forest fires

Haze
(d) Loss of natural habitats and extinction of
Species
Not only are the forests destroyed as a result of
forest fires, many animals can be injured or
killed because their habitats are lost to the fire.
young orang utan in tree asian elephant in its natural habitat

production?
used in agriculture?

Objectives
 Understand that pesticides and
herbicides can be used to protect crops
against pests and weeds, and their use
has effects on the environment (soil and
water contamination) leading to effects
on the food chain
 Describe and explain the use of
biological control to reduce the use of
pesticides (limited to the control of prey
organisms by their predators)

Why do we need to protect crops?
 We need to protect crops because
they can be damaged by:
(a) Pests
(b) Weeds
rodents feed on crops

Pests
 Crops attract pests such as
insects, rodents and other
animals, e.g. locusts, rats,
mice, squirrels, wild rabbits
and hamsters.
 These pests feed on
crops and destroy them.
 For example, dragon fruit
plantations in Malaysia are
often destroyed by pests
such as monkeys and
squirrels.
dragon fruits are wrapped
and protected from pests

Weeds
 Weeds compete with crops for nutrients.
 This decreases the crop yield as there are less
nutrients available for the crops.
 The plantation with weeds growing among the crops
will have less yield.
weeds such as daisies growing
in a wheat plantation

Chemical Controls to Protect Crops
 The use of pesticides and herbicides are the
two main methods of chemical controls used to
protect crops.
 Pesticides are chemical substances used by
farmers to destroy pests. They can also be
sprayed onto plants or crops to prevent attacks
by pests.
spraying of liquid pesticides over padi field

Herbicides
 Herbicides are chemicals used by farmers to
prevent or destroy weeds which compete with
the crops for nutrients.
 These herbicides are also called weed killers.
They destroy weeds but do not harm the
crops.
farmer spraying weed killer or herbicide
in a soybean field

Effects of Chemical Controls
 The use of pesticides and herbicides
as chemical controls can help protect
the crops from pests and weeds.
However, overuse of these chemicals
can have negative impacts on the
environment.
(a) Soil contamination
(b) Water contamination

Transfer of toxic chemicals in a food chain

Water contamination
(b) Water contamination
Pesticides and herbicides can be carried by
rainwater into rivers, lakes and ponds. These
chemicals can also seep underground and
contaminate the groundwater, which is the main
source of drinking water in many countries.
chemicals can seep into the ground and
contaminate groundwater

Effects of chemical runoff on the
environment and our health
 Aquatic plants and animals living in the rivers,
lakes and ponds will be affected by the
contaminated water. Humans and animals
that drink from the affected water bodies will
also be harmed by the chemicals.

Effects of chemical runoff on the
environment and our health
 Some of these chemicals cannot be broken down
and will remain inside plants, animals and our
bodies. This results in the transfer of chemicals
along the food chain. Human beings at the last stage
of the food chain will suffer from the accumulation of
toxic chemicals in the body.

Biological Controls to Protect Crops
 Natural enemies of pests can be used to
control them. This method is called biological
control.
 These natural enemies can be bought or
specially reared by farmers.
 The advantages of biological pest controls are
(a) No chemicals are used, hence there is no
contamination of the soil and water.
(b) Crops are also not contaminated by
chemicals.

Common crop pests and their natural enemies

Disadvantage of Biological control
 Biological control may be a good way
to remove pests; however, introducing
too many of their natural enemies
may disrupt the food chain when
population numbers become too
high to control.

Disadvantage of Biological control
 One such example is the introduction of ferrets
in New Zealand as natural enemies to prevent
rabbits from destroying the crops. At that time,
there were no natural enemies of ferrets, so
the population of ferrets grew at an alarming
rate. This played a role in the decline of native
birds such as the kiwi, weka and blue duck.
the increasing population of ferrets
meant that more kiwis are eaten up

production?
used in agriculture?

Objectives
 Understand that there is a need to
improve the methods of food production:
(i) as the world population increases
(ii) with limitations in space to grow food
 Describe how food production can be
improved by
(i) improving plant and animal varieties
(ii) intensive production methods for
crops, fish and farm animals
 Understand that plant hormones are
used as weed killers and in regulating
growth and ripening fruits

Why do we need to increase our ability to
produce food?
 The increase in world population and limitations in
space to grow food are the two most important reasons
to increase our ability to produce food.
 In addition, harsh weather conditions and climate
changes have led to farmers and scientists looking for
methods to improve food production.
sowing rice seedlings

Different food sources
banana plantation
mechanised irrigation
harvesting grapes
tomato plants

Improving plant and animal varieties
 One way of increasing food production is to improve
the plant and animal varieties.
 Farmers can increase their crop yield by planting
good seedlings which will grow into bigger and better
crops with higher nutritional values and are able to
survive harsh weather conditions.
high-yielding rice grains versus low-yielding rice grains

Improving plant and animal varieties
 Farmers can increase their crop yield by
planting good seedlings which are disease-
resistant.
disease-resistant tomatoes versus tomatoes of poor quality

Increasing food production
 Farmers can also increase food production by
improving the animal varieties such as
(a) good meat and milk producing cattle
(b) chickens that lay bigger and more eggs
(c) animals that grow to larger sizes and at faster
rates (e.g. sheep for wool)
improving animal
varieties can yield better
produce such as bigger eggs
Belgian Blue cattle are bred
specifically for their 'double muscling'
characteristics, which results in leaner
meat lower in fat

Increasing food production
 Food production can also be improved
by intensive production methods for
crops, fish and farm animals. This can
be made possible by advancements
in technology.

Animals reared with intensive production
methods for food and their meat
products

Aeroponics and hydroponics
 In vegetable and fruit farms, farmers use
high technology farming methods such as
hydroponics and aeroponics to increase
food production.
(a) Hydroponics is a method of growing
plants in a special nutrient solution
rows of vegetables grown by hydroponics

Aeroponics
(b) Aeroponics is a method of growing plants in
a mist of nutrient solution regularly sprayed
onto the roots of the plants.
These farms use automation to control the
temperature, water and nutrient supplies to
ensure optimal plant growth.
rice plants sprayed with nutrient solution

Intensive farming methods
 In traditional farming, farmers have
to manually milk the cows, collect
the eggs from chickens while
fishermen go out to sea to fish.
 With the use of intensive farming
methods, the food production of
these farms has been increased.

automated chicken pen to collect the
eggs the hens lay
eggs on production line to be
packaged and sold

Comparing traditional methods of farming with
advanced technology

Use of plant hormones
 Plant hormones
can affect root,
seed, stem,
flower, fruit, and
leaf
development.
Farmers can use
plant hormones as
weed killers, to
regulate growth
and ripen fruits.
spraying of hormones

Plant hormones
 Some plant hormones can kill weeds without
harming the crops. For example, the addition of
plant hormones to rice and wheat, results in weeds
being destroyed without affecting the crops.
 Plant hormones can be used to regulate growth
of fruits. For example, hormones are added to the
tomato plants to promote root formation on the
stems to increase the number of tomato fruits on
the plant.
 Plant hormones can also be used to regulate the
ripening of fruits. For example, the addition of
hormones to fruits prevents them from dropping off
trees before ripening.

Uss module 5 chpt 6 Sources of Food

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