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Smart Science 4 Textbook

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Page 1: Smart Science Grade 4

Smart Science 4Textbook

Page 2: Smart Science Grade 4

Smart Science GRADE 4TEXTBOOK

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

Editorial, design, and layout by University Press of First Asia

No part of this publication may be reproduced or transmitted in any form or by any means electronic or mechanical, including photocopying, recording, or any information storage and retrieval 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 978-971-46-0091-1

REVIEWERMarina E. 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.

Page 3: Smart Science Grade 4

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!

Page 4: Smart Science Grade 4

Unit 1 Human Body Systems: Skeletal, Muscular, and Digestive

Chapter 1 The Skeletal SystemLesson 1 The Parts of the Skeletal System ......................................................... 2Lesson 2 Disorders and Diseases of the Skeletal System ................................. 13Lesson 3 Caring for Your Bones ..................................................................... 19Think Back ....................................................................................................... 23Measure Up! ....................................................................................................... 24

Chapter 2 The Muscular SystemLesson 1 The Muscles and Their Functions .................................................... 27Lesson 2 Types of Muscles ............................................................................. 34Lesson 3 Disorders and Diseases of the Muscular System ............................... 37Lesson 4 Caring for Your Muscles .................................................................. 41Think Back ....................................................................................................... 45Measure Up! ....................................................................................................... 46

Chapter 3 The Digestive SystemLesson 1 Inside the Digestive System ............................................................. 49Lesson 2 Taking in Food through the Mouth .................................................. 54Lesson 3 Down the Esophagus ....................................................................... 57Lesson 4 Digestion in the Stomach ................................................................ 59Lesson 5 Digestion in the Small Intestine ....................................................... 63Lesson 6 Digestion in the Large Intestine ....................................................... 66Lesson 7 Diseases and Disorders of the Digestive System .............................. 70Lesson 8 Caring for Your Digestive System .................................................... 76Think Back ....................................................................................................... 79Measure Up! ....................................................................................................... 80

Unit 2 The World of Animals and Plants

Chapter 4 The World of AnimalsLesson 1 Animal Reproduction ...................................................................... 86Lesson 2 Baby Animals .................................................................................. 91Lesson 3 Life Cycles ....................................................................................... 95Lesson 4 Complete Metamorphosis ................................................................ 99

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Lesson 5 Incomplete Metamorphosis ........................................................... 103Lesson 6 Beneficial and Harmful Animals .................................................... 106Lesson 7 Protection from Harmful Animals .................................................. 112Lesson 8 Endangered Animals ...................................................................... 116Think Back ..................................................................................................... 119Measure Up! ..................................................................................................... 120

Chapter 5 The World of PlantsLesson 1 The Flower and Its Parts ................................................................ 122Lesson 2 How Do Plants Reproduce? ........................................................... 129Lesson 3 Fertilization in Flowers .................................................................. 132Lesson 4 Seed: Parts and Functions .............................................................. 135Lesson 5 Seed Germination ......................................................................... 138Lesson 6 Spreading Seeds ............................................................................ 141Lesson 7 Plants Also Reproduce Asexually ................................................... 144Lesson 8 Conserving Plants .......................................................................... 149Think Back ..................................................................................................... 152Measure Up! ..................................................................................................... 153

Unit 3 Matter, Energy, and Force

Chapter 6 Matter All around UsLesson 1 What Is Matter? ............................................................................. 156Lesson 2 Properties of Matter ....................................................................... 160Lesson 3 What Are Mixtures? ....................................................................... 166Think Back ..................................................................................................... 169Measure Up! ..................................................................................................... 170

Chapter 7 Energy and ForceLesson 1 Heat It Up! .................................................................................... 172Lesson 2 How Heat Is Transferred ................................................................ 177Lesson 3 Safety First ..................................................................................... 183Lesson 4 Friction .......................................................................................... 187Lesson 5 Controlling Friction ....................................................................... 190Think Back ..................................................................................................... 194Measure Up! ..................................................................................................... 194

Page 6: Smart Science Grade 4

Unit 4 The Changing Earth, Weather, and Beyond

Chapter 8 The Changing EarthLesson 1 Water as an Agent of Change ........................................................ 198Lesson 2 Temperature and Rocks ................................................................. 202Lesson 3 Wind and Soil Erosion ................................................................... 204Lesson 4 Plants and Animals Break Rocks .................................................... 208Lesson 5 People Can Also Break Rocks ........................................................ 211Lesson 6 Ways to Prevent Soil Erosion ......................................................... 214Think Back ..................................................................................................... 218Measure Up! ..................................................................................................... 219

Chapter 9 Weather ElementsLesson 1 Different Weather Elements ........................................................... 221Lesson 2 Observing Changes in Air Temperature ......................................... 224Lesson 3 Observing Changes in Wind Speed and Direction ......................... 228Lesson 4 Observing Cloud Formations ......................................................... 233Think Back ..................................................................................................... 237Measure Up! ..................................................................................................... 238

Chapter 10 The Sun-Moon-Earth SystemLesson 1 The Moving Earth .......................................................................... 240Lesson 2 Earth Revolves around the Sun ...................................................... 243Lesson 3 The Moon in Motion ..................................................................... 246Lesson 4 Moon Phases ................................................................................. 249Lesson 5 Eclipses ......................................................................................... 252Lesson 6 Tides ............................................................................................. 257Think Back ..................................................................................................... 261Measure Up! ..................................................................................................... 262

Bibliography ............................................................................................................. 265

Page 7: Smart Science Grade 4

Unit 1 Human Body Systems: Skeletal, Muscular,

and Digestive

Your body is composed of parts that work together to keep you alive. These parts perform their specific functions so efficiently that you hardly notice them working at all!

Activities that are as simple as the movement of your finger or as complex as the digestion of the food that you have eaten are results of the important functions of your body systems.

In this unit, learn about three body systems, namely, skeletal, muscular, and digestive. Know which diseases can affect them and how to take good care of them.

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Chapter 1

Lesson 1The Parts of the Skeletal System

The Skeletal System

Have you seen a building undergoing construction? What have you observed?

As you may have noticed, constructing a building starts by putting together a system of beams and girders, or what is called a framework. The framework is held together by special bolts to make it strong. It must be strong because it provides support to the floors and walls of the building. This way, the building does not collapse.

The human body is just like a building. It has a framework called the skeleton which is made up of superbly joined and balanced system of bones held by ligaments, tendons, and joints.

Find Out1. What are the functions of the skeletal system?2. What are the parts of the skeletal system? What are the functions of

each part?3. How are the bones in the human body classified?4. What are cartilage, joint, and ligament?

Your skeleton gives your body support, shape, and protection. It is made up of bones that have different shapes, sizes, and functions.

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3Human Body Systems: Skeletal, Muscular, and Digestive

The Bones As a newborn, you may have as many as 350 bones. Soon after birth,

your bones start to harden and some of them fuse together. This is due to the accumulation of materials such as calcium and phosphorus in the bones. This process is called ossification. As bones fuse together, they form fewer but bigger and stronger bones. The hardening of the bones continues until early adulthood. An adult’s skeletal system consists of 206 bones.

An adult’s skeletal system

skull

clavicle

ribs

radius

ulna

femur

patella

tibia

fibula

bones of the foot

bones of the hand

pelvic girdle

vertebral column

humerus

sternum

The bones of the body are grouped into two: the axial and perpendicular skeletons.

The axial skeleton consists of the skull, the backbone, and the rib cage. The axial skeleton is made up of 80 bones.

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The skull protects the brain. It consists of 22 different bones—eight paired bones and six unpaired bones. The bones of the skull are divided into the cranial bones and the facial bones. The cranial bones hold and protect the brain. The facial bones, which are found below the skull, provide the framework that forms the face.

The backbone

Bones of the skull

Facial Bones

ethmoid bone

lacrimal bone

nasal bone

zygomatic bone

maxilla

mandible

Cranial Bones

frontal bone

parietal bone

sphenoid bone

temporal bone

lacrimal bone

occipital bone

Get a partner and run your fingers down the middle of his or her back. Describe the body part that you feel.

The backbone is a chain of bones that runs down the middle of your back. It is also called the spine or vertebral column. There are 26 vertebrae (or bones of the spine) attached together by joints. The backbone protects the thick cord of nerves called the spinal cord.

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5Human Body Systems: Skeletal, Muscular, and Digestive

The bones at the sides of your chest form the rib cage. The rib cage protects the heart, lungs, and other internal organs. It also helps you breathe. It consists of 12 pairs of flat, curved bones called ribs. They are connected to each other by muscles. The first upper ribs, called the true ribs, curve around from the spine and join the breast bone in front. The next three pairs are called the false ribs. Each false rib is connected to the rib above it. The lowest two pairs of ribs, called the floating ribs, are attached only to the backbone.

The rib cage

sternum

true ribs

false ribs

floating ribs

Place your hand against your chest. The flat bone that you can feel in front of your chest is the sternum or breast bone. It is connected to the ribs by cartilage.

Breathe deeply three times. Does your chest expand each time you inhale? The cartilage that connects the sternum to the ribs can stretch, allowing you to breathe deeply.

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The pectoral girdle allows you to move your arms and anchors them in your skeleton. The pelvic girdle connects your lower extremities to the axial skeleton and supports your abdominal organs.

The appendicular skeleton is made up of the bones of the girdles and appendages. The appendages include the arms, hands, legs, and feet. There are two girdles in the human body—the pectoral girdle and pelvic girdle. The appendicular skeleton is made up of 126 bones.

Pectoral girdle Pelvic girdle

Your hands are the most nimble parts of your body. You use them to hold heavy objects, but they are also suited to perform delicate tasks like threading a needle.

The bones of your

feet bear the entire weight of your body. When you stand, walk, or jump, your feet give you support and balance.

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7Human Body Systems: Skeletal, Muscular, and Digestive

Have you wondered how your bones are distributed in your body? The table below shows the distribution of bones in the human body.

The Bones of the Body

Types of Skeleton Number of Bones

Axial Skeleton 80 bones

backbone 26

ribs 24 (12 on each side)

skull 22

ears 6 (3 each)

throat 1

sternum 1

Appendicular Skeleton 126 bones

hands 56 (28 each)

feet 52 (26 each)

legs 6 (3 each)

arms 6 (3 each)

shoulders 4

hips 2

Total 206 bones

The Parts of the BoneThe outer layer of

the bone is called the compact bone. This layer is dense and looks smooth. It forms the protective outer part of all bones. The compact bone helps withstand bumps and bangs that your bones may encounter. It also consists of minerals such as phosphorus and calcium.

The bone structure

spongy bone

compact bone

blood vessels and nerve in central canal

spongy bone(spaces contain

red bone marrow)compact bone

yellow boneblood vesselcentral cavity

(contains yellowbone marrow)

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Inside the compact bone is the spongy bone, which is very porous. The spaces in the spongy bone are filled with blood and soft tissue, called red marrow. The red marrow produces red blood cells, some white blood cells, and platelets. It also repairs the compact bone.

Calcium and phosphorus are the minerals needed to build strong bones. What do you think will happen if bones do not have these minerals? The experiment below will help you find out what happens when bones lose their mineral content.

Explore

Removing Minerals from the BonesYou need:three chicken bones (same part/size), three small jars, vinegar, water, gloves

Do the following:1. Clean the chicken bones thoroughly. Try to bend each bone carefully.

Can you bend them? __________________________________________

2. Half-fill one jar with water and the other with vinegar. Leave the third one empty.

3. Put one chicken bone into each jar. Label the setups as follows: “Bone in Water,” “Bone in Vinegar,” and “Bone in Jar.”

4. Leave the jars in a safe place for two days.

5. After two days, remove the chicken bones from the jars and carefully wash them with water. Air dry the bones and then try to bend them. Compare the texture of the three bones.

a. Which bone(s) can be bent? ________________________________

b. Which bone(s) cannot be bent? _____________________________

c. What did the vinegar do to the chicken bone? _________________

Page 15: Smart Science Grade 4

9Human Body Systems: Skeletal, Muscular, and Digestive

If calcium and phosphorus are removed, bones lose their hardness and strength. This is why it is important for you to eat food rich in these minerals to keep your bones strong and healthy. Dairy products such as milk and cheese are rich in calcium. Vitamin D also keeps your bones strong because it helps your body absorb calcium.

Cartilage, Joints, and LigamentsWhen you were born, most of your bones were not yet fully developed.

They were made up mostly of cartilage. Cartilage is a tough, semi transparent, elastic tissue. Almost all bones develop from cartilages. Cartilage has several functions. It covers the surface of joints, allowing bones to slide over one another, reducing friction and preventing damage. The cartilage also acts as a shock absorber.

Cross-section of a joint

bone

cartilage

bone

Feel your elbow and your knee. You can flex and extend your arm because of your elbow. You can perform the same movements with your legs. This is all because of your joints. A joint is a point where two bones meet. Joints allow your body to move in many ways.

Joints are classified by their range of movement. Immovable joints, called fibrous joints, do not move. The dome of the skull, for example, is made of bony plates, which must be immovable to protect the brain. Between the edges of these plates are links or joints of fibrous tissue. Fibrous joints also hold the teeth in the jawbone.

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Partially movable joints or cartilaginous joints move a little. They are linked by a cartilage. Examples of cartilaginous joints are those in the windpipe or trachea, bridge of the nose, and ears.

Freely movable joints or synovial joints move in many directions. The main joints of the body—found at

the hips, shoulders, elbows, knees, wrists, and ankles—are freely movable. They are filled with synovial fluid, which acts as a lubricant to help the joints move easily.

According to their movements, synovial joints may be classified as the

following:

1. Gliding joints – These joints permit side-to-side and back-and-forth movements. An example is the wrist joint.

2. Hinge joints – These joints allow only back-and-forth movements such as bending and straightening. Examples are elbow joints and knee joints.

3. Pivot joints – These joints allow rotational movement only. An example is the joint between the bones in the forearms.

4. Ball-and-socket joints – These joints permit side-to-side, back-and-forth, and rotational movements. Examples are shoulder and hip joints.

nasal bone

cartilage

Bone cartilage of the nose

The synovial joints

hinge joint

gliding joint

ball-and-socket joint

pivot joint

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11Human Body Systems: Skeletal, Muscular, and Digestive

The bones in synovial joints are held together by ligaments. A ligament is a tough band of white, slightly elastic tissue. It binds the bones together to prevent dislocation. Ligaments also support some internal organs like the bladder and liver.

Knowing the parts of your skeletal system will make you understand better how to take good care of it.

ligamentum flavum

intertransverse ligament

posterior longitudinal ligament

anterior longitudinal ligament

supraspinous ligament

interspinous ligament

facet capsulary ligament

Ligament

Home EconomicsBulalo, a Filipino dish that originated from Batangas, is a very tasty soup whose

main ingredient is the kneecap of a cow. Contrary to popular belief that one eats the brain of the cow in bulalo, what you actually find inside the kneecap is the marrow—a kind of soft tissue that is responsible for the storage of fats.

Keep in Mind

• The skeletal system is the framework of the human body. It is made up of bones that give support, shape, and protection to the body.

• The skeletal system is divided into two groups: axial and appendicular skeletons.

• The axial skeleton consists of the skull, the backbone, and the rib cage. The appendicular skeleton consists of the bones of the appendages (arms, hands, legs, feet) and the girdles (pectoral and pelvic).

• The outer layer of the bone is called the compact bone. It forms the protective outer part of all bones.

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• The inner layer of the bone is called the spongy bone. The spaces between the spongy bone are filled with blood and red marrow.

• Cartilage is a tough, semi transparent, elastic tissue that covers the surface of joints. A joint is a point where two bones meet.

• Joints allow your body to move in many ways. Joints can be freely movable, partially movable, or immovable.

• A ligament is a tough band of white, slightly elastic tissue that binds the bone together to prevent dislocation.

Challenge Yourself

Write T on the blank space if the statement is true. If it is false, change the underlined word or phrase to make the statement true.

__________ 1. The skeleton is the framework that supports and protects the body.

__________ 2. The bones of the legs are part of the axial skeleton.

__________ 3. The bones of the feet support the weight of the entire body.

__________ 4. An adult person has 206 bones. Of these, 22 bones form the rib cage.

__________ 5. The rib cage protects the heart and the lungs.

__________ 6. The yellow marrow repairs the hard layer of the bone.

__________ 7. Vitamin C helps the bone absorb calcium.

__________ 8. Hinge joints permit side-to-side, back-and-forth, and rotational movements.

__________ 9. Like the immovable joint, the knee joint can be bent or straightened.

__________10. Pivot joints allow rotational movement only.