Smart Science 6Textbook

Smart Science GRADE 6TEXTBOOK

Philippine Copyright 2009 by DIWA LEARNING SYSTEMS INCAll rights reserved. Printed in the Philippines

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ISBN: 978–971–46–0095–9

REVIEWERMarina Balce was a former assistant dean and associate professor at the College of Education, La Salle College–Antipolo. She taught biological sciences for Psychology students and thesis writing for graduating Education students in the same college. She was also a Trainee of the Japan International Cooperation Agency (JICA) at the Aichi University in Nagoya, Japan, where she attended a special training on Practical Work in Elementary School Science. Dr. Balce finished her bachelor’s degree in Secondary Education major in Biology at the University of the East–Manila. She has a master’s degree in Biology Education from the De La Salle University–Manila and a doctorate in Science Education major in Biology from the University of the Philippines–Diliman.

To the LearnerDo you ask yourself questions about the world you live in? Do you

wonder about what lies beyond the blue skies or what rests below the seas? Do you ask questions about the blooming trees and colorful flowers you see, the heat and cold you feel, or the various scents you smell? Do you wonder about the sun, the moon, and the stars? Your young, active mind has so many questions because you are curious about so many things.

This book will help you discover the answers to the questions you have about yourself, the world, and everything beyond it. This book will be your constant companion as you unlock the many mysteries of life through various learning experiences. Moreover, this book will teach you how to apply the wonders of science to your day-to-day activities.

Let this book help you find the answers to the questions you have about yourself, your world, and the universe. Let this take you a step closer to understanding life and in discovering the wonders of science!

Unit 1 Body Systems

Chapter 1 The Circulatory SystemLesson 1 Parts of the Circulatory System and Their Functions ....................................2Lesson 2 Pathway of Blood ......................................................................................11Lesson 3 Some Diseases Affecting the Circulatory System ........................................14Lesson 4 Caring for Your Circulatory System ...........................................................19Think Back .................................................................................................................23Measure Up! .................................................................................................................23

Chapter 2 The Nervous SystemLesson 1 Nervous System: Control Unit of the Body ................................................25Lesson 2 Parts of the Nervous System and Their Functions ......................................29Lesson 3 How Messages Travel ...............................................................................34Lesson 4 Body Responses to Stimuli ........................................................................38Lesson 5 Some Disorders and Diseases Affecting the Nervous System .....................42Lesson 6 Caring for Your Nervous System ...............................................................46Think Back .................................................................................................................51Measure Up! .................................................................................................................51

Unit 2 The Ecosystem

Chapter 3 Relationships among OrganismsLesson 1 Relationships in the Ecosystem ..................................................................54Lesson 2 Producers and Consumers .........................................................................59Lesson 3 Food Chain and Food Web .......................................................................64Lesson 4 Decomposers ............................................................................................68Lesson 5 Nutrient Cycles .........................................................................................71Think Back .................................................................................................................76Measure Up! .................................................................................................................76

Chapter 4 The EnvironmentLesson 1 Effects of Deforestation .............................................................................79Lesson 2 Destructive Human Activities ....................................................................85Lesson 3 Preservation and Conservation of Our Ecosystem ......................................90Think Back .................................................................................................................93Measure Up! .................................................................................................................93

Unit 3 Matter, Energy, and Motion

Chapter 5 Matter EverywhereLesson 1 The Nature of Matter .................................................................................96Lesson 2 Properties of Matter .................................................................................100Lesson 3 Elements .................................................................................................106Lesson 4 Compounds and Mixtures .......................................................................110Lesson 5 Common Household Materials and Their Uses .......................................116Lesson 6 Technology Improves Materials ..............................................................120Lesson 7 Harmful Effects of Materials ....................................................................123Lesson 8 Proper Usage and Storage of Materials ....................................................127Lesson 9 Proper Disposal of Materials ...................................................................130Think Back ...............................................................................................................134Measure Up! ...............................................................................................................135

Chapter 6 Energy around UsLesson 1 Mechanical Energy ..................................................................................137Lesson 2 Electrical Energy .....................................................................................141Lesson 3 Chemical Energy .....................................................................................145Lesson 4 Radiant Energy ........................................................................................148Lesson 5 Sound Energy ..........................................................................................152Lesson 6 Energy Transformation and Transfer ........................................................155Think Back ...............................................................................................................157Measure Up! ...............................................................................................................158

Chapter 7 Force and Motion Lesson 1 Forces in Motion………………………………………………….. ......................160Lesson 2 Speed……………………………………………………………… .........................164Lesson 3 Velocity…………………………………………………………… ........................169Think Back ……………………………………………………………………. ...........................171Measure Up! ……………………………………………………………………. ...........................172

Unit 4 Earth, Our Home

Chapter 8 Solid EarthLesson 1 Layers of Earth ........................................................................................174Lesson 2 Movement on Earth’s Crust .....................................................................178Lesson 3 Earthquakes ............................................................................................184

Lesson 4 In Case of an Earthquake .........................................................................189 Lesson 5 Volcanoes and Volcanic Eruptions ..........................................................193Lesson 6 Effects of Volcanic Eruptions ...................................................................198Lesson 7 Awareness of Volcanic Eruptions ............................................................202Think Back ...............................................................................................................206Measure Up! ...............................................................................................................207

Chapter 9 Weather and ClimateLesson 1 Factors Affecting Weather and Climate ...................................................209Lesson 2 Seasons on Earth .....................................................................................216Lesson 3 Seasons in the Philippines .......................................................................223Lesson 4 Effects of Weather and Climate ...............................................................227Think Back ...............................................................................................................231Measure Up! ...............................................................................................................231

Unit 5 Beyond the Solar System

Chapter 10 All about StarsLesson 1 Stars and Their Characteristics .................................................................234Lesson 2 Life Stages of a Star .................................................................................241Lesson 3 Constellations .........................................................................................245Lesson 4 Using Telescopes to Learn More about Stars ...........................................249Lesson 5 Our Sun, a Star .......................................................................................255Think Back ...............................................................................................................259Measure Up! ...............................................................................................................260

Chapter 11 Galaxies and the UniverseLesson 1 Galaxies ..................................................................................................261Lesson 2 Studying the Universe .............................................................................265Lesson 3 Space Exploration ...................................................................................271Think Back ...............................................................................................................275Measure Up! ...............................................................................................................276

Glossary ...............................................................................................................277Bibliography ...............................................................................................................280Index ...............................................................................................................281

Unit 1 Body Systems

Did you know that the human body is similar to a machine? In fact, the human body 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 “food processor,” 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 their main goal. And just like machine parts, several of the body parts can now be changed if they get defective—thanks to modern technology.

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Chapter 1

Lesson 1Parts of the Circulatory System

and Their Functions

The Circulatory SystemYou have already learned the parts and functions of the reproductive system, the

urinary system, and the respiratory system. These body systems play vital roles for our survival. This chapter will introduce you to the circulatory system, which is responsible for transporting nutrients and oxygen, and collecting wastes in your body.

Find Out

1. 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 simpler materials, these are absorbed by the tiny blood vessels of the small intestine. These simple materials are then used by the cells of the body. But how do the materials reach all the cells throughout the body?

The activity on the next page will help illustrate the similarity of a train system to the circulatory system.

3Body Systems

Analyzing a Train System

Look at the diagram of a train system. Answer the following questions on a separate sheet of paper.

1. 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 system

4. What happens if a train system fails?

Routes of LRT Line 1 and LRT Line 2

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.

Language

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-7

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A train system is like the circulatory system.

A train transports people to different places. People are picked up at certain points and brought to other points in the train system. Blood circulates in the body in a similar manner.

The circulatory system is made up of the heart, blood vessels, and blood. The circulatory system takes care of the distribution of nutrients and oxygen picked up by the blood to the different parts of the body. It transports and delivers nutrients to all cells. It also collects waste materials produced by the cells and brings them to the organs in charge of eliminating wastes from the body.

HeartThe human heart is a muscular organ about the size of a clenched fist. The heart

is inside a protective sac called the pericardium. Made up of strong muscles, the heart receives and pumps blood. The heart is the “blood pump” of the body. It sustains the flow of blood throughout the body.

5Body Systems

The heart is hollow and divided down the middle into a left side and a right side by a wall of muscle called the septum. Each side of the heart is further divided into the upper and the lower chambers. The upper chamber is called the atrium (also called the auricle); the lower chamber is called the ventricle. Both the left and the right sides of the heart pump blood through the chambers at the same time. The right side pumps blood to the lungs. The left side pumps blood into the different parts of the body.

Connected to the heart are arteries and veins where blood going to and coming from 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 branch out into smaller blood vessels. From the heart, oxygenated blood passes through the aorta 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 the head, the arms, and the rest of the upper trunk to the heart. The inferior vena cava, on the other hand, carries blood from the lower part of the body to the heart. From the different body parts, the two vena cavae pass the blood to the right atrium. Pulmonary veins 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 devised medical procedures and inventions to help people with heart problems. The artificial heart, artificial pacemaker, and artificial valves are some of the inventions that help people suffering from heart ailments and/or valve malfunctions. When a person’s veins and 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 circulates

throughout the body carrying nutrients needed for the growth and normal function of the body cells. Have you seen blood? Do the activity in Explore and observe a prepared blood smear under the microscope.

The parts of the heart. The arrows indicate the direction of the blood flow.

superior vena cavaaorta

pulmonary veins

right atrium

right ventricle

inferior vena cava

pulmonary artery

valve

left atrium

left ventricle

septum

6 Smart Science 6

A Look at a Human Blood Sample

You will need a compound microscope and a prepared slide with a drop of human 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. Blood is actually made up of plasma, red blood cells, white blood cells, and platelets. You will learn more about these components in Table 1.1 below.

Table 1.1 The Components of BloodComponent Description Image

Red blood cells (RBC)

• These are constantly 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 color. Red blood cells

7Body Systems

Sphygmomanometer

Component Description Image

White blood cells (WBC)

• These are mostly formed in 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 diseases and infections.

White blood cells

Platelets • These are minute discs (smaller than red blood cells) that produce substances needed for blood to clot. Clotting prevents blood loss.

Platelets

Plasma • This is the yellowish liquid portion of the blood.

• This is composed of 90% water and 10% dissolved nutrients, proteins, minerals, salts, and waste products.

• This transports nutrients to the cells and carries waste materials.

Plasma

As blood flows, it exerts pressure on the walls of the arteries. The exertion of pressure on the walls of the arteries by the blood is known as blood pressure. Blood pressure is determined by factors such as the strength of the heart muscles, amount of blood in the cardiovascular system, and condition of the arteries. Human blood pressure is measured by an instrument called sphygmomanometer. The normal blood pressure among adults is 120/80 (read as “120 over 80”). The first number (120) is called systolic pressure, while

Plasma cell

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the second number (80) is called diastolic pressure. Systolic pressure refers to blood pressure while the heart contracts. Diastolic pressure, on the other hand, refers to blood pressure while the heart relaxes. You will learn more about the effects of high blood pressure and other circulatory diseases in Lesson 3 of this chapter.

Blood VesselsWhere does blood pass through? Blood flows through a network of tubes in the

body 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.

9Body Systems

Thick-walled and elastic, the arteries carry blood that contains nutrients and oxygen away from the heart. Their thick walls enable them to withstand the pressure of blood 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 the veins.

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 as that in the arteries. Pulmonary veins transport oxygenated blood from the lungs to the heart. 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 blood pass through the walls of the capillaries into the cells, while cellular wastes pass from the cells through the capillary walls then into the blood, making the exchange of nutrients and waste materials possible.

To summarize, blood coming from the heart flows through the blood vessels in this 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 the body.

An electrocardiograph

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.

Check IT out!

The blood vessels

membrane

capillary

connective tissue

artery

arteriole venule

connective tissue

valve

vein

muscle

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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 Yourself

Answer the following briefly.

1. List two major functions of the circulatory system. a. _________________________________________________________________ _________________________________________________________________

b. _________________________________________________________________ _________________________________________________________________

2. Explain how blood flows through the blood vessels. ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________ ______________________________________________________________________