uss module 5 chpt 6 sources of food

Module 5:Food MattersChapter 6 Sources of Food

© Copyright Star Publishing Pte Ltd

Chapter 6 Sources of Food6.1 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?


ObjectivesRecognise 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.


Different categories of food


Different categories of foods




and increased?


ObjectivesAppreciate the conditions required

in producing foodState 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


PhotosynthesisPlants 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.


PhotosynthesisPlants 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

PhotosynthesisPhotosynthesis 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:


PhotosynthesisExcess 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 LinkActivity 6.1Testing for Starch

Soil conditions for plants to growApart 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 importantpart in determining healthy plant growth. The pHcan be determined using indicators such as thelitmus paper, universal indicator or pH meter.


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


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


Activity Book LinkActivity 6.2Acidity and Alkalinity of Soil



and increased?


ObjectivesUnderstand 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


FertilisersSome 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.


FertilisersBag of fertiliser Fertilisers added

to crops


FertilisersFertilisers 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 fromdecomposed plant matter does

notharm 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

Chemical fertilisers (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 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 rapidgrowth of algae

Activity Book LinkActivity 6.3How Fertilisers Help Plants Grow

Chapter 6 Sources of Food

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?© Copyright Star Publishing Pte Ltd

ObjectivesState the effect of ‘slash-and-

burn’ methods of agriculture on soil fertility and the environment


Slash-and-BurnSlash-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-burnFarmers 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 ofspecies


Activity Book LinkActivity 6.4Clearing Land to PlantCrops

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 alot of inconvenienceand harm, such as

(i) Poor visibility

The particles in the haze reduce the amountof sunlight that reaches us. This reduces thevisibility of the surroundings.

fertiliser-polluted water promotes rapidgrowth of algae

Haze(ii) Breathing difficulties and

eye irritation

The particles in the haze can cause peoplewith 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 surroundingsand 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 cancause 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? 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?© Copyright Star Publishing Pte Ltd

ObjectivesUnderstand 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 effectson 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

PestsCrops 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 wrappedand 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 CropsThe 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 ControlsThe 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 andcontaminate groundwater

Effects of chemical runoff on the environment and our healthAquatic 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 CropsNatural 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? 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?


ObjectivesUnderstand 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 irrigationharvesting 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 varietiesFarmers 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 animalvarieties can yield better

produce such as bigger eggs

Belgian Blue cattle are bredspecifically for their 'double muscling'characteristics, which results in leaner

meat lower in fat

Increasing food productionFood 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 hydroponicsIn 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 methodsIn 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.


Intensive farming methods


automated chicken pen to collect theeggs the hens lay

eggs on production line to bepackaged and sold

Intensive farming methods


Comparing traditional methods of farming with advanced technology


Use of plant hormonesPlant 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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