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iv Science Mathayom 3
Chapter 1 Our Genes 11.1 Traits and Heredity Unit 21.2 Chromosomes 31.3 DNA and Genes 61.4 Inheritance of Traits 71.5 Genetic Disorders 111.6 Applications of the Knowledge of Heredity 13Mastery Practice 19
Chapter 2 Interdependence among Living Organisms and the Environment 22
2.1 Interdependence among Living Organisms 232.2 Interactions between Living Organisms 272.3 Food Web 332.4 Nutrient Cycles 372.5 Limiting Factors of Population Size 402.6 Biodiversity 42Mastery Practice 45
Chapter 3 Natural Resources and the Environment 503.1 Environmental Issues 513.2 Natural Resources 553.3 Ecosystem and Balance 58Mastery Practice 63
Chapter 4 Forces and Motion 674.1 Acceleration 684.2 Action and Reaction Forces 734.3 Buoyant Forces and Liquid 764.4 Static Friction and Kinetic Friction 824.5 Moment of Force 864.6 Motions of Objects 91Mastery Practice 93
2.3 Food Web 332.4 Nutrient Cycles 372.5 Limiting Factors of Population Size 402.6 Biodiversity 42Mastery Practice 45
Butterflies depend on flowers for
food. What else do butterflies depend
on to survive?
4.6 Motions of Objects 91Mastery Practice 93This car is picking up its speed. How
do we calculate its acceleration?
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Contents v
Chapter 5 Energy Changes 965.1 Forms of Energy 975.2 Energy Changes 102Mastery Practice 107
Chapter 6 Electricity 1116.1 Electricity 1126.2 Measuring Electricity 1156.3 Current, Voltage and Resistance 1186.4 Concept of Parallel and Series Circuits 1236.5 Current, Voltage and Resistance in a Series Circuit 1286.6 Current, Voltage and Resistance in a Parallel Circuit 1316.7 Electronic Circuit 1356.8 Cost of Electrical Energy 1366.9 Importance of Safety Precautions in the Use of Electricity 141Mastery Practice 147
Chapter 7 Solar System, Stars and Galaxies 1527.1 Planets 1537.2 Asteroids, Comets and Meteoroids 1567.3 Sun 1577.4 Stars and Galaxies 1617.5 Existence of the Universe 1657.6 Sun-Earth-Moon 166Mastery Practice 175
Chapter 8 Space Expolation 1798.1 Astronomy and Space Exploration 180Mastery Practice 186
6.8 Cost of Electrical Energy 136
in the Use of Electricity 141Mastery Practice 147
6.8 Cost of Electrical Energy 136
Mastery Practice 147Mastery Practice 147
Where does our electricity come from?
What are out there in the space?
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50 Science Mathayom 3
By the end of this chapter, you should be able to• analyze the state of problems concerning
the environment and natural resources in the local area, and propose guidelines
for problem-solving. • explain guidelines for preserving
the equilibrium of the ecosystem.• discuss sustainable utilization
of natural resources. • analyze and explain
utilization of natural resources in terms of the Sufficiency Economy Philosophy.
• discuss environmental problems and propose relevant guidelines for problem-solving.
• discuss and participate in providing care and preserve
the local environment on a sustainable basis.
Natural Resources and the
Environment3
Factories give out harmful gases.How will this affect our lives?
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Chapter 3 Natural Resources and the Environment 51
Air pollution
3.1 Environmental Issues
Humans are the dominant species on the Earth. We have the knowledge and capability to change the environment to suit our needs. However, along the way, some of our activities bring negative effects on the environment.
Some of these activities may not have the immediate effect on the environment, but they may have long-term and irreversible consequences later. These will not only harm the physical environment, but other living things including ourselves.
Air pollution occurs when the air contains pollutants such as smoke, dirt, dust and poisonous gases in harmful amounts, endangering living things. Air pollution is a global problem as air pollutants can flow free. For example, a forest fire in a neighboring country can cause haze to occur in our place.
Acid rain, ozone depletion and global warming are caused by air pollution.
Asbestos, formaldehyde, cigarette smoke and other substances found in our home can cause indoor air pollution.
Acid rain affects water only.
Acid rain affects air, water and land too.
+
+
Combustion offossil fuels
Factory
Nitrogenmonoxide
Nitrogendioxide
Sulfurdioxide
Watervapor
Sulfuric acid
Nitric acid
Acid rain
Destroysforests Makes lakes and
rivers acidicCauses aquaticorganisms to die
Causes respiratoryproblems
Watervapor
Corrodesbuilding
Formation of acid rain and its effects
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52 Science Mathayom 3
Sun
StratosphereUV radiation
Ozone layerabsorbs UVradiation
Troposphere
Earth
MountEverest
Absorption of UV radiation by ozone layer
This ozone layer shields the Earth from the harmful effects of ultraviolet (UV) radiation from the Sun. With the depletion of the ozone layer, more UV radiation can reach the Earth’s surface. Long term effects of UV exposure will cause skin cancer and cataract in humans. Plants and animals will be harmed too.
Therefore, we should replace CFCs with other substances that are not harmful. With the signing of Montreal Protocol, the production and use of CFCs will be phased out in stages.
Greenhouse gases such as carbon dioxide, methane, nitrous oxide and CFCs trap heat from the Sun and prevent the heat from radiating back into space. As the amount of these gases increase, more heat is trapped in the atmosphere. This results in the increase of the Earth’s average temperature. This phenomenon is known as global warming.
Forests absorb about 87 tons of carbon dioxide per hectare through photosynthesis every year. They release the same amount of oxygen into the atmosphere.
Some applications have replaced CFCs with HCFCs which have shorter life spans when exposed to the atmosphere.
Gaseous pollutants from vehicles and factories when dissolved in rainwater form acid rain. Acid rain corrodes metals, marble and stonework. It also increases the acidity of rivers and ponds, killing small living things in them. Plant tissues and roots are destroyed too. It causes respiratory problems too.
We should reduce the emission of the gaseous pollutants by using scrubbers in industrial plants. Catalytic converters should be used to convert harmful emissions from our vehicles.
Chlorofluorocarbons or CFCs from coolants in air conditioners and refrigerators, propellants in aerosol cans and solvents in electronic industries are destroying the ozone layer in our atmosphere.
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Chapter 3 Natural Resources and the Environment 53
Land pollution
When the heat is intense, ice at the poles will melt. This will cause flooding in low-lying areas. The weather and wind pattern will change, causing some areas to experience severe droughts and floods. This will definitely cause the decline in the yield of crops. Spread of pests and disease-carrying vectors will increase outbreak of diseases.
We should reduce the combustion of fossil fuels and deforestation. We should plant more trees and develop other cleaner sources of energy such as solar, wind and geothermal energy.
Melting of polar ice Drought Flood
Carbon dioxide causes the depletion of the ozone layer.
Carbon dioxide does not contribute to the depletion of the ozone layer. However, the increasing quantity of carbon dioxide in the air will lead to global warming.
As our population grows, our solid waste materials increase too. We are running out of land space for burying solid waste. Many of these materials are not biodegradable. Some need tens or even hundreds of years before they break down. Objects made of materials such as glass and plastic take even longer period of time to break down.
Solid waste left in open dumps
http://www.buzzle.com/articles/land-pollution.htmlMore information on land pollu-tion can be found in this web-site.
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Chapter 3 Natural Resources and the Environment 55
All wastewater should be treated before being released into the environment. If not, all our water sources including the underground water will be contaminated and the cost to purify them will be very great for us to bear.
3.2 Natural Resources
What do timber, water, air, coal and cotton have in common? They are natural resources. Natural resources are useful materials that are found in nature. We need food, water and air to survive, and other materials and energy to make everything.
Renewable resources are natural resources that are replaceable by ongoing natural processes. Forests, air, water and animals are some examples of renewable resources.
3.1Q1. List three ways how air pollution affects our atmosphere.Q2. What causes ozone depletion? Q3. How can hazardous chemicals from landfills affect groundwater?
Examples of renewable resources
Non-renewable resources are natural resources that are available in limited amount and are not quickly replaced by natural processes. For example, coal, petroleum, metals and minerals are non-renewable resources. These resources are formed in special conditions and take millions of years to form.
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62 Science Mathayom 3
Environment
Renewable resources
Non-renewable resources
3Rs
Replant
Philosophy of sufficiency
economy
Measures can be taken
Acid rain
Depletion of ozone layer
Global warming
Air pollution Water pollution Land pollution
Balanced ecosystem
Sustainable wayNatural Resources
Fill in the blanks with the given words.
land pollution balance sufficiency economy reduce global warmingwater pollution reuse air pollution recycle acid raindepletion of ozone layer renewable non-renewable treated
1. happens when the air has pollutants in amounts that are harmful to living things.
2. is formed when acidic gaseous pollutants dissolve in rainwater.
3. happens when CFCs destroy the ozone layers.
4. Greenhouse gases trap and prevent heat from radiating back to space. It will cause .
5. happens when waste on land is not disposed properly. Leaching may happen at landfills.
6. Untreated wastewater when released into our water bodies will cause
. Oil spills at oceans cause serious harm to aquatic lives.
7. All wastewater should be before being
released into rivers.
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62 Science Mathayom 3 Chapter 3 Natural Resources and the Environment 63
Objective Questions
1. What is the effect of an increase of carbon dioxide in the atmosphere?A Depletion of the ozone layerB Global warmingC Land slidesD Water pollution
2. What is the importance of the ozone layer?A Absorbs infrared radiationB Absorbs ultraviolet radiationC Traps greenhouse gasesD Absorbs chlorofluorocarbons
3. Chemical P is used as coolants in air conditioners and as solvents in electronic industries. What is the effect of P on the environment?A Water pollutionB Greenhouse effectC Land pollutionD Depletion of the ozone layer
4. Ultraviolet radiation canI cause an increase in the temperature on
EarthII lead to severe climate changesIII damage chlorophyll in plantsA I onlyB III onlyC I and II onlyD I, II and III
5. What contribute to the increase of carbon dioxide in the atmosphere?I The combustion of fossil fuelsII WildfiresIII DeforestationIV Open burningA I and III only B II and IV onlyC I, III and IV onlyD I, II, III and IV
6. What contributes to the formation of acid rain?A Sulfur dioxideB Solid wasteC Excessive use of fertilizersD Oxygen
7. Which of the following is not true about water pollution?A Bacteria in untreated sewage may harm
humans.B Pesticides and fertilizers are often
washed off into rivers, causing water pollution.
C Fish are killed when they swallow oil from oil spills in the ocean.
D Melting of ice at the poles causes water pollution.
8. recources are resources that are replaceable by ongoing natural processes. resources are resources that are limited and not quickly replaced by natural processes.
9. We should , and
our things to reduce the demands for natural
resources.
10. The philosophy of emphasizes on moderation, reasonableness and self-awareness.
11. in ecosystem is the equilibrium that exists when the needs of living things are being met and the conditions remain for a long period.
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