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  • 1. Smart Science 6 Textbook
  • 2. Smart ScienceGRADE 6TEXTBOOKPhilippine Copyright 2009 by DIWA LEARNING SYSTEMS INCAll rights reserved. Printed in the PhilippinesEditorial, design, and layout by University Press of First AsiaNo part of this publication may be reproduced or transmitted in any form or by any meanselectronic or mechanical, including photocopying, recording, or any information storage andretrieval systems, without permission in writing from the copyright owner. Exclusively distributed by DIWA LEARNING SYSTEMS INC 4/F SEDCCO 1 Bldg. 120 Thailand corner Legazpi Streets Legaspi Village, 1229 Makati City, Philippines Tel. No.: (632) 893-8501 * Fax: (632) 817-8700 ISBN: 978–971–46–0095–9REVIEWERMarina Balce was a former assistant dean and associate professor at the College of Education, LaSalle College–Antipolo. She taught biological sciences for Psychology students and thesis writing forgraduating Education students in the same college. She was also a Trainee of the Japan InternationalCooperation Agency (JICA) at the Aichi University in Nagoya, Japan, where she attended a specialtraining on Practical Work in Elementary School Science. Dr. Balce finished her bachelor’s degree inSecondary Education major in Biology at the University of the East–Manila. She has a master’s degreein Biology Education from the De La Salle University–Manila and a doctorate in Science Educationmajor in Biology from the University of the Philippines–Diliman.
  • 3. To the Learner Do you ask yourself questions about the world you live in? Do youwonder about what lies beyond the blue skies or what rests below theseas? Do you ask questions about the blooming trees and colorful flowersyou see, the heat and cold you feel, or the various scents you smell? Doyou wonder about the sun, the moon, and the stars? Your young, activemind has so many questions because you are curious about so manythings. This book will help you discover the answers to the questions youhave about yourself, the world, and everything beyond it. This book willbe your constant companion as you unlock the many mysteries of lifethrough various learning experiences. Moreover, this book will teach youhow to apply the wonders of science to your day-to-day activities. Let this book help you find the answers to the questions you haveabout yourself, your world, and the universe. Let this take you a step closerto understanding life and in discovering the wonders of science!
  • 4. Unit 1 Body SystemsChapter 1 The Circulatory System Lesson 1 Parts of the Circulatory System and Their Functions ....................................2 Lesson 2 Pathway of Blood ......................................................................................11 Lesson 3 Some Diseases Affecting the Circulatory System........................................14 Lesson 4 Caring for Your Circulatory System ...........................................................19 Think Back .................................................................................................................23 Measure Up! .................................................................................................................23Chapter 2 The Nervous System Lesson 1 Nervous System: Control Unit of the Body ................................................25 Lesson 2 Parts of the Nervous System and Their Functions ......................................29 Lesson 3 How Messages Travel ...............................................................................34 Lesson 4 Body Responses to Stimuli ........................................................................38 Lesson 5 Some Disorders and Diseases Affecting the Nervous System .....................42 Lesson 6 Caring for Your Nervous System ...............................................................46 Think Back .................................................................................................................51 Measure Up! .................................................................................................................51Unit 2 The EcosystemChapter 3 Relationships among Organisms Lesson 1 Relationships in the Ecosystem ..................................................................54 Lesson 2 Producers and Consumers.........................................................................59 Lesson 3 Food Chain and Food Web .......................................................................64 Lesson 4 Decomposers ............................................................................................68 Lesson 5 Nutrient Cycles .........................................................................................71 Think Back .................................................................................................................76 Measure Up! .................................................................................................................76Chapter 4 The Environment Lesson 1 Effects of Deforestation .............................................................................79 Lesson 2 Destructive Human Activities ....................................................................85 Lesson 3 Preservation and Conservation of Our Ecosystem ......................................90 Think Back .................................................................................................................93 Measure Up! .................................................................................................................93
  • 5. Unit 3 Matter, Energy, and MotionChapter 5 Matter Everywhere Lesson 1 The Nature of Matter .................................................................................96 Lesson 2 Properties of Matter.................................................................................100 Lesson 3 Elements .................................................................................................106 Lesson 4 Compounds and Mixtures .......................................................................110 Lesson 5 Common Household Materials and Their Uses .......................................116 Lesson 6 Technology Improves Materials ..............................................................120 Lesson 7 Harmful Effects of Materials ....................................................................123 Lesson 8 Proper Usage and Storage of Materials ....................................................127 Lesson 9 Proper Disposal of Materials ...................................................................130 Think Back ...............................................................................................................134 Measure Up! ...............................................................................................................135Chapter 6 Energy around Us Lesson 1 Mechanical Energy..................................................................................137 Lesson 2 Electrical Energy .....................................................................................141 Lesson 3 Chemical Energy .....................................................................................145 Lesson 4 Radiant Energy ........................................................................................148 Lesson 5 Sound Energy ..........................................................................................152 Lesson 6 Energy Transformation and Transfer ........................................................155 Think Back ...............................................................................................................157 Measure Up! ...............................................................................................................158Chapter 7 Force and Motion Lesson 1 Forces in Motion………………………………………………….. ......................160 Lesson 2 Speed……………………………………………………………… .........................164 Lesson 3 Velocity…………………………………………………………… ........................169 Think Back ……………………………………………………………………. ...........................171 Measure Up! ……………………………………………………………………. ...........................172Unit 4 Earth, Our HomeChapter 8 Solid Earth Lesson 1 Layers of Earth ........................................................................................174 Lesson 2 Movement on Earth’s Crust .....................................................................178 Lesson 3 Earthquakes ............................................................................................184
  • 6. Lesson 4 In Case of an Earthquake .........................................................................189 Lesson 5 Volcanoes and Volcanic Eruptions ..........................................................193 Lesson 6 Effects of Volcanic Eruptions ...................................................................198 Lesson 7 Awareness of Volcanic Eruptions ............................................................202 Think Back ...............................................................................................................206 Measure Up! ...............................................................................................................207Chapter 9 Weather and Climate Lesson 1 Factors Affecting Weather and Climate ...................................................209 Lesson 2 Seasons on Earth .....................................................................................216 Lesson 3 Seasons in the Philippines .......................................................................223 Lesson 4 Effects of Weather and Climate ...............................................................227 Think Back ...............................................................................................................231 Measure Up! ...............................................................................................................231Unit 5 Beyond the Solar SystemChapter 10 All about Stars Lesson 1 Stars and Their Characteristics .................................................................234 Lesson 2 Life Stages of a Star .................................................................................241 Lesson 3 Constellations .........................................................................................245 Lesson 4 Using Telescopes to Learn More about Stars ...........................................249 Lesson 5 Our Sun, a Star .......................................................................................255 Think Back ...............................................................................................................259 Measure Up! ...............................................................................................................260Chapter 11 Galaxies and the Universe Lesson 1 Galaxies ..................................................................................................261 Lesson 2 Studying the Universe .............................................................................265 Lesson 3 Space Exploration ...................................................................................271 Think Back ...............................................................................................................275 Measure Up! ...............................................................................................................276 Glossary ...............................................................................................................277 Bibliography ...............................................................................................................280 Index ...............................................................................................................281
  • 7. Unit 1 Body Systems Did you know that the human body is similar to a machine? In fact, the humanbody is often considered as a complex machine as it is composed of several machines.For example, the heart is a “pump,” the eye is a “camera,” the stomach is a “foodprocessor,” and the brain is a “computer.” Each of these machines is composed of parts.These parts differ in size and in shape, but all of them work together to accomplish theirmain goal. And just like machine parts, several of the body parts can now be changed ifthey get defective—thanks to modern technology.
  • 8. Chapter 1 The Circulatory System You have already learned the parts and functions of the reproductive system, theurinary system, and the respiratory system. These body systems play vital roles for oursurvival. This chapter will introduce you to the circulatory system, which is responsiblefor transporting nutrients and oxygen, and collecting wastes in your body. Lesson 1 Parts of the Circulatory System and Their Functions Find Out1. How do you compare the circulatory system with a train system?2. How does the circulatory system function?3. What are the parts of the circulatory system?4. What is the function of each part? Each day, about 2 000 gallons of blood travel many times in your blood vessels.Blood is sent throughout your body with each heartbeat. The circulatory system or cardiovascular system is often described as the “lifeline”of the human body. When the food you have eaten is digested and turned into simplermaterials, these are absorbed by the tiny blood vessels of the small intestine. Thesesimple materials are then used by the cells of the body. But how do the materials reachall the cells throughout the body? The activity on the next page will help illustrate the similarity of a train system tothe circulatory system.2 Smart Science 6
  • 9. Analyzing a Train System Look at the diagram of a train system. Answer the following questions on aseparate sheet of paper. Routes of LRT Line 1 and LRT Line 21. What do the circles represent? How do they function?2. How are people transported by the train system?3. Compare the train system with the circulatory system in terms of being a a. pick up system b. delivery system4. What happens if a train system fails? Body Systems 3
  • 10. A train system is like the circulatory system. A train transports people to different places. People are picked up at certain pointsand brought to other points in the train system. Blood circulates in the body in a similarmanner. The circulatory system is made up of the heart, blood vessels, and blood. Thecirculatory system takes care of the distribution of nutrients and oxygen picked upby the blood to the different parts of the body. It transports and delivers nutrients toall cells. It also collects waste materials produced by the cells and brings them to theorgans in charge of eliminating wastes from the body.Heart The human heart is a muscular organ about the size of a clenched fist. The heartis inside a protective sac called the pericardium. Made up of strong muscles, the heartreceives and pumps blood. The heart is the “blood pump” of the body. It sustains theflow of blood throughout the body. Language Many scientific terms form their plural irregularly. For instance, some words ending in -ium or -um are made plural by changing this ending to -ia. For example, atrium – atria; septum – septa; pericardium – pericardia; and bacterium – bacteria. Note that not all words ending in -ium can be made plural this way. Exceptions include elements such as sodium, calcium, and barium. Research other scientific words that form their plural irregularly and familiarize yourself with them. Check IT out! The Jarvik-7 artificial heart is named after its American physician designer, Robert K. Jarvik. The Jarvik-7 has two pumps, each with a disk- shaped mechanism that pushes the blood from the inlet valve to the outlet valve. Visit the following Web sites for more information on the artificial heart: http://inventors.about.com/library/inventors/ blartificialheart.htm http://sln.fi.edu/biosci/healthy/fake.html Jarvik-74 Smart Science 6
  • 11. The heart is hollow anddivided down the middle into superior vena cava aortaa left side and a right side bya wall of muscle called the pulmonaryseptum. Each side of the heart arteryis further divided into the pulmonary valveupper and the lower chambers. veinsThe upper chamber is called left atriumthe atrium (also called theauricle); the lower chamber is right atriumcalled the ventricle. Both the left ventricle right ventricleleft and the right sides of the septumheart pump blood through the inferior venachambers at the same time. cavaThe right side pumps blood tothe lungs. The left side pumps The parts of the heart. The arrows indicate the direction ofblood into the different parts of the blood flow.the body. Connected to the heart are arteries and veins where blood going to and comingfrom various parts of the body passes through. The aorta, the largest artery in the body,is directly connected to the heart. It branches into smaller arteries which further branchout into smaller blood vessels. From the heart, oxygenated blood passes through theaorta to the different parts of the body. There are also two large veins called vena cavae(singular: vena cava). One of them is the superior vena cava. It carries blood from thehead, the arms, and the rest of the upper trunk to the heart. The inferior vena cava, onthe other hand, carries blood from the lower part of the body to the heart. From thedifferent body parts, the two vena cavae pass the blood to the right atrium. Pulmonaryveins and arteries are also connected to the heart. They connect the heart to the lungs. The heart has two doorlike valves which direct the flow of blood in one direction.The valves prevent oxygenated blood from mixing with deoxygenated blood. What can be done when parts of the heart malfunction? Scientists have devisedmedical procedures and inventions to help people with heart problems. The artificialheart, artificial pacemaker, and artificial valves are some of the inventions that helppeople suffering from heart ailments and/or valve malfunctions. When a person’s veinsand arteries get clogged, he or she is advised to undergo a heart bypass operation.Blood Blood is the liquid component of the circulatory system. Blood circulatesthroughout the body carrying nutrients needed for the growth and normal function ofthe body cells. Have you seen blood? Do the activity in Explore and observe a preparedblood smear under the microscope. Body Systems 5
  • 12. A Look at a Human Blood Sample You will need a compound microscope and a prepared slide with a drop ofhuman blood.1. Put the microscope on a sturdy, flat table. Make sure that the microscope receives enough light. Mount the prepared slide with a drop of human blood on the microscope’s stage. Use the stage clips to hold the slide.2. Focus the objectives properly to get a clear view of the sample. Use the low- power objective (LPO) first and then the high-power objective (HPO).3. Observe what you see under the LPO and the HPO.4. Describe how blood looks under both the LPO and the HPO.5. Draw the blood as seen under the LPO and the HPO on a sheet of paper. From the activity, you have observed that blood has different components. Bloodis actually made up of plasma, red blood cells, white blood cells, and platelets. Youwill learn more about these components in Table 1.1 below.Table 1.1 The Components of Blood Component Description ImageRed blood cells • These are constantly(RBC) produced by the bone marrow. • These contain hemoglobin— the iron and oxygen carrier of the blood. Iron is a mineral needed by the body. Hemoglobin that combines with oxygen gives blood its Red blood cells red color.6 Smart Science 6
  • 13. Component Description ImageWhite blood cells • These are mostly formed in(WBC) the bone marrow. • These are bigger than red blood cells. • These are called the “soldiers of the body” for they fight foreign bodies that cause White blood cells diseases and infections.Platelets • These are minute discs (smaller than red blood cells) that produce substances needed for blood to clot. Clotting prevents blood loss. PlateletsPlasma • This is the yellowish liquid portion of the blood. • This is composed of 90% water and 10% dissolved nutrients, proteins, minerals, Plasma cell salts, and waste products. • This transports nutrients to the cells and carries waste Plasma materials. As blood flows, it exerts pressure on the walls of the arteries.The exertion of pressure on the walls of the arteries by theblood is known as blood pressure. Blood pressureis determined by factors such as the strengthof the heart muscles, amount of blood inthe cardiovascular system, and conditionof the arteries. Human blood pressureis measured by an instrument calledsphygmomanometer. The normal bloodpressure among adults is 120/80 (readas “120 over 80”). The first number(120) is called systolic pressure, while Sphygmomanometer Body Systems 7
  • 14. the second number (80) is called diastolic pressure. Systolic pressure refers to bloodpressure while the heart contracts. Diastolic pressure, on the other hand, refers toblood pressure while the heart relaxes. You will learn more about the effects of highblood pressure and other circulatory diseases in Lesson 3 of this chapter.Blood Vessels Where does blood pass through? Blood flows through a network of tubes in thebody called blood vessels. Do the following activity to know more about them.A Look at Blood Vessels You will need a handy face mirror.1. Look closely at the mirror. Observe the white portion of your eye. What do you see?2. Look at the underside of your tongue. Describe what you see.3. Why are certain blood vessels reddish while others are bluish?4. Make a tight fist with your left hand. Then, using your right hand, grasp your left wrist tightly. After a minute, stretch your left palm. Caution: This step should not be done if you bruise easily. You can observe your classmate’s palm instead. a. Did the color of the your palm’s skin change? What could have caused this? b. What are the functions of blood vessels in our body? The bluish and reddish lines you see beneath your skin are blood vessels.Arteries, veins, and capillaries are all blood vessels.8 Smart Science 6
  • 15. Thick-walled and elastic, the arteries carry blood that contains nutrients andoxygen away from the heart. Their thick walls enable them to withstand the pressure ofblood flow. Arteries branch out into arterioles and then into much smaller capillaries.Other capillaries are connected to the venules, which in turn, are connected to theveins. membrane valve connective capillary muscle tissue connective vein tissue artery venule arteriole The blood vessels Veins are elastic and are larger in diameter compared to the arteries; however,they have thinner walls. The pressure of the blood flow along the veins is not as great asthat in the arteries. Pulmonary veins transport oxygenated blood from the lungs to theheart. All other veins carry deoxygenated blood from the organs back to the heart. The smallest blood vessels are the capillaries. Oxygen and nutrients in the bloodpass through the walls of the capillaries into the cells, while cellular wastes pass fromthe cells through the capillary walls then into the blood, making the exchange ofnutrients and waste materials possible. To summarize, blood coming from the heart flows through the blood vessels inthis order: from the arteries, arterioles, capillaries, venules, veins, and back to the heart.These blood vessels form a network that allows the blood to circulate throughout thebody. Check IT out! Vital signs are checked and monitored using the electrocardiograph. It is a machine used to monitor the heartbeat by attaching electrodes to a person’s body. Abnormalities in the hearbeat could be an indication of a heart problem. An electrocardiograph Body Systems 9
  • 16. Keep in Mind• The human circulatory system is a transport system. It is responsible for distributing nutrients to cells, collecting waste materials produced by the cells, and depositing them to specific excretory organs.• The circulatory system has three main components: heart, blood, and blood vessels.• The right side of the heart pumps blood to the lungs while the left side pumps blood to the different parts of the body.• Blood is the liquid component of the circulatory system. It has four components: plasma, red blood cells, white blood cells, and platelets.• Blood flows through a network of tubes called blood vessels. Veins, arteries, and capillaries are blood vessels. Challenge YourselfAnswer the following briefly.1. List two major functions of the circulatory system. a. _________________________________________________________________ _________________________________________________________________ b. _________________________________________________________________ _________________________________________________________________2. Explain how blood flows through the blood vessels. ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________10 Smart Science 6