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© Pelangi Publishing (Thailand) Co., Ltd. 2019 All rights reserved. No part of this publication may be reproduced, stored in any retrieval system or transmitted in any form or by any means without permission of Pelangi Publishing (Thailand) Co., Ltd. 2019
Title page.indd 1
ISBN 978-616-541-315-2 First Published 2562
11/28/18 9:55
Contents Human Body Systems
1
1.1 Respiratory System 1.2 Excretory System 1.3 Circulatory System 1.4 Nervous System Conceptual Map Basic Recall STEM Activity Mastery Practice
2 9 11 18 23 24 25 27
2
Human Reproduction
28
2.1 Male Reproductive System 2.2 Female Reproductive System 2.3 Puberty 2.4 Menstrual Cycle 2.5 Fertilization and Pregnancy 2.6 Importance of Pre-natal Care 2.7 Importance of Research in Human Reproduction Conceptual Map Basic Recall Mastery Practice
29 31 33 35 37 40 41 46 47 48
3
Mixtures
49
3.1 Separating Mixtures 3.2 Solutions Conceptual Map Basic Recall STEM Activities Mastery Practice
50 54 60 61 62 64
4
Forces
65
4.1 Resultant Force on the Same Plane (Net Force) 4.2 Liquid Pressure and Buoyancy 4.3 Friction 4.4 Moment of Force 4.5 Natural Fields Conceptual Map Basic Recall STEM Activity Mastery Practice
66 73 82 89 94 97 98 99 101
1
Chapter
Chapter
Chapter
Chapter
5
Motion
103
5.1 Scalar and Vector Quantities 5.2 Distance and Displacement 5.3 Speed and Velocity Conceptual Map Basic Recall STEM Activity Mastery Practice
104 108 110 112 113 114 116
6
Work and Energy
117
6.1 Work and Power 6.2 Simple Machines 6.3 Energy Conceptual Map Basic Recall STEM Activity Mastery Practice
118 120 122 127 128 129 131
7
Earth
132
7.1 Layers of the Earth 7.2 Slow Processes that Change the Surface of the Earth 7.3 Sources of Energy Conceptual Map Basic Recall STEM Activity Mastery Practice
133 134 136 142 143 144 146
8
Soil
147
8.1 Soil 8.2 Soil Formation 8.3 Soil Uses and Soil Improvement Conceptual Map Basic Recall STEM Activity Mastery Practice
148 153 154 157 158 159 161
9
Water
162
9.1 Surface Water and Groundwater 9.2 Hazards due to Surface Water and Groundwater Conceptual Map Basic Recall Mastery Practice
163 165 168 169 170
Chapter
Chapter
Chapter
Chapter
Chapter
Special
s Featureok o in This B
Learning Outcomes
Includes the latest development and / or extra information on science and technology.
Evaluates the understanding of the students for every subtopic.
States the learning objectives of each chapter.
Points out the important tips for students to take note.
Provides direct access to useful websites by scanning the QR codes given.
Helps students to recall the concepts and definitions learned in the chapter.
Provides information on the potential developments of science and technology.
Provides extra information and / or statistical information that are relevant to the concept learned.
Explains the scope of career which requires the relevant knowledge of scientific concepts.
Points out the common mistakes that students make and the correct ways of answering questions.
Provides subjective questions covering the entire learning outcomes of each chapter.
Provides direct access to the interactive exercises by scanning the QR codes given.
Explains how scientific concepts are applied in our daily life.
Guides students to test a hypothesis in order to make a discovery.
The 4C’s of the 21st Century Skills are: Communication Sharing thoughts, questions, ideas and solutions.
Assists students in reviewing the entire chapter.
Guides students to find an answer through observations using scientific methods.
Focus Smart + AR Download the free “PelangiThai” app.
Collaboration Working together to reach a goal. Putting talent, expertise and smarts to work. Critical Thinking Looking at problems in a new way and linking learning across subjects and disciplines.
Provides an activity that engages in the application of knowledge of scientists, mathematicians and engineers.
Creativity Trying new approaches to get things done equals innovation and invention.
e cognize th e r u o y o D ans? above org hey do? What do t
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Chapter
Human Body Systems By the end of this chapter, you should be able to • identify the organs and describe the functions of the organs involved in the respiratory system. • explain the mechanisms of inhalation and exhalation and the process of gas exchange. • identify the organs and describe the functions of the organs in the excretory system for the elimination of waste products in kidneys. • describe the structures and functions of the heart, blood vessels and blood. • explain the process of circulatory system using a model. • design and conduct an experiment to compare the normal heart rate and the heat rate after doing activities. • identify and describe the functions of organs in and coordinate the human body.
that control
• realize the importance of our systems by suggesting guidelines how to take care of them.
1.1
Respiratory System
The human respiratory system provides an area for gas exchange between the blood and the environment. It allows oxygen acquisition and carbon dioxide elimination. The gas exchange in lungs is called breathing (external respiration). This exchange involves inhalation and exhalation. Inhalation (taking in of air) allows us to take in oxygen to be used by the body cells. Exhalation (letting out of air) allows us to get rid of carbon dioxide from our body.
Structure of the human respiratory system The air enters the respiratory system through the nasal cavity. As the air passes the nasal cavity, it is warmed and moistened. Dust is trapped by the hair on the nasal cavity. After the air leaves the nasal cavity, it enters the trachea. The wall of the trachea contains C-shaped rings of cartilage which give it support and prevent it from collapsing during inhalation. The trachea branches into two bronchi (singular:bronchus) One bronchus enters the right lung, the other enters the left lung. Each bronchus branches into smaller tubes called bronchioles. The bronchioles end in millions of tiny air sacs called alveoli (singular: alveolus).
Bronchus
Nasal cavity
Bronchiole Alveolus Capillaries
Trachea Intercostal muscle
Bronchus Bronchiole
Rib Left lung
The human respiratory system
The lungs are made up of alveoli, bronchioles and blood capillaries. The lungs are located in a space called the thoracic cavity. The lungs are protected by the ribcage which consists of ribs and intercostal muscles. A sheet of muscle called the diaphragm separates the thoracic cavity from the abdomen.
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Adaptation of the alveoli for efficient gas exchange The alveoli are adapted to make gas exchange in th lungs happen easily and efficiently. Here are the features of the alveoli that allow them to do so: Large surface area The lungs have millions of alveoli to provide a large surface area for gas exchange. Visit this website for more information on the human respiratory system.
Very thin walls The wall of each alveolus is one cell thick to provide a very short distance for the diffusion of gases. Moist inner surface The inner surface of each alveolus is moist so that oxygen can dissolve in the moisture before diffusing across the alveolar wall. Surrounded by numerous blood capillaries The blood capillaries help to transport gases to and from the alveoli quickly. Air movement Alveolar wall (one cell thick) Entry of blood
Exit of blood Alveolar cavity
Thin layer of moisture Red blood cell Capillary
Detailed structure of an alveolus
In the alveoli, oxygen diffuses from the air in the alveolar cavity into the blood and carbon dioxide diffuses from the blood into the alveolar cavity.
Do not confuse breathing with respiration. Breathing is the process of getting oxygen into the lungs and carbon dioxide out of the lungs. Respiration is the release of energy from the reaction of glucose.
Mechanism of human breathing The breathing mechanism consists of two phases. The taking in of air is called inhalation. The letting out of air is called exhalation. During breathing, the lungs expand and return to their normal size to pump air into and out of them.
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The movements of the ribs and the diaphragm bring about breathing. Air exits lungs.
Air enters lungs.
Ribs and ster num rise.
Volume of thorax increases.
Ribs and ster num return to original position.
Volume of thorax decreases. Diaphragm relaxes and arches upwards.
Diaphragm contacts and flattens out. b Exhalation
a nhalation The breathing mechanism
The table below shows the comparison of the mechanisms of inhalation and exhalation. Inhalation
Exhalation
• Diaphragm muscles contract. • Diaphragm flattens out.
• Diaphragm muscles relax. • Diaphragm arches upwards.
• External intercostal muscles contract. • Internal intercostal muscles relax.
• External intercostal muscles relax. • Internal intercostal muscles contract.
• Ribcage moves upwards and outwards.
• Ribcage moves downwards and inwards.
• Volume of thoracic cavity increases.
• Volume of thoracic cavity decreases.
• Air pressure in the lungs decreases.
• Air pressure in the lungs increases.
• Air flows into the lungs.
• Air is forced out of the lungs.
Comparison of the mechanisms of inhalation and exhalation
Investigating the relationship between the air pressure in the thoracic cavity and the process of inhalation and exhalation Materials/Apparatus: Elastic sheet, balloons, glass jar, Y-tube and cork Procedure: 1. A model is set up as shown in the next page. 2. The elastic sheet is pulled down. Are there any changes to the size of the balloons? 3. The elastic sheet is pushed up. Are there any changes to the size of the balloons?
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Cork Y-tube Balloon Glass jar Elastic sheet
4. All observations are recorded. Observation: 1. The balloons inflated when the rubber sheet is pulled down. 2. The balloons deflated when the rubber sheet is pushed up. Discussion: The table below shows the parts of the human respiratory system which are represented by the material/apparatus in the model. Material/ Apparatus
Glass jar
Y-tube
Balloons
Elastic sheet
Respiratory system
Thoracic cavity
Respiratory tract
Lungs
Diaphragm
Conclusion: 1. When the elastic sheet is pulled down, the pressure inside the glass jar decreases. Air from outside enters the balloons. 2. When the elastic sheet is pushed up, the pressure inside the glass jar increases. Air is forced out of the balloons. The table below shows the composition of inhaled air, exhaled air and alveolar air respectively. Content There is more carbon dioxide than oxygen in exhaled air.
Exhaled air contains 16% oxygen, 4% carbon dioxide and 79% nitrogen.
Inhaled air
Exhaled air
Alveolar air
Oxygen
21%
16%
14%
Carbon dioxide
0.04%
4%
6%
Nitrogen
79%
79%
80%
Water vapor
Variable
Saturated
Saturated
Temperature
Variable
34°C
37°C
Composition of air in respiration
The changes in the contents of air after entering the lungs are due to gas exchange in the alveoli.
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Gas exchange The diffusion of oxygen from the alveoli into the blood capillaries During inhalation, air is taken into the lungs through the nasal cavity, passing through the trachea, bronchi, bronchioles and finally alveoli. Air that reaches the alveoli is called alveolar air. It is rich in oxygen and poor in carbon dioxide. Blood that reaches the capillaries surrounding the alveoli is poor in oxygen and rich in carbon dioxide. Gas exchange takes place in the lungs by diffusion. Oxygen diffuses from the alveoli into the red blood cells in the capillaries. At the same time, the red blood cells in the capillaries release carbon dioxide which diffuses into the alveoli. The transport of oxygen by blood The red blood cells contain the oxygen-carrying pigment called hemoglobin. Oxygen combines with hemoglobin to form oxyhemoglobin. The blood cells are transported around the body.
The diffusion of oxygen from the blood capillaries into the body cells Gas exchange also takes place between the capillaries and the body cells. Oxygen has a higher concentration in the capillaries than in the body cells. Carbon dioxide has a higher concentration in the body cells than in the capillaries. Oxyhemoglobin releases oxygen which diffuses into the body cells. Carbon dioxide diffuses into the blood at the same time. Air flow CO2
O2
Alveolus of lung O2 carried as oxyhemoglobin
Hemoglobin in red blood cells Capillaries
CO2
O2
Oxyhemoglobin releases oxygen.
Body cells Gas exchanges at the lungs and body cells
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Taking care of our respiratory system Our respiratory system is responsible for obtaining oxygen and getting rid of carbon dioxide and aiding in speech production and in sensing odors. There are some factors that can affect the health of our respiratory system and cause respiratory problems. (a) Harmful substances The air we breathe in may contain substances that are harmful to our respiratory system. These substances may come from air pollutants such as cigarette smoke, gases from factories, exhaust fumes from vehicles and haze. The table below shows the types of harmful substances and their effects on our respiratory system. Harmful substances
Sources
Effects
Nicotine
Cigarette smoke
• Causes addiction • Constricts blood vessels, increases blood pressure and stimulates the heart, and raises the blood fat levels
Tar
Cigarette smoke
• Contains several cancer-causing chemicals (carcinogen) • Irritates the respiratory tract, causing ‘smoker’s cough’
Sulphur dioxide
Cigarette smoke Gases from factories
• Irritates the respiratory tract • Causes temporary and permanent damages to the lungs
Carbon monoxide
Cigarette smoke Gases from factories Fumes from vehicles
• Reduces the ability of the blood to carry oxygen as it combines with the hemoglobin in the red blood cells faster than oxygen • Can be fatal in high concentration
Dust
Haze
• Irritates the respiratory tract • Causes difficult breathing in old and sick patients
(b) Diseases of the respiratory system Asthma is a chronic disorder of the lungs in which the airways are prone to constrict. This may due to the patient’s sensitivity to air pollutants. The patient may suffer wheezing, chest tightness, coughing, and breathlessness that range in severity from mild to life-threatening. Bronchitis is the inflammation of the bronchi. This may due to the infection by bacteria or viruses, or chemicals such as those in the cigarette smoke. Someone with chronic bronchitis has a chronic cough and most of the symptoms of acute bronchitis, such as shortness of breath and chest tightness almost every day for months or years.
We should consult a doctor if we have a cough that persists for a week or more.
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Emphysema is a condition due to the loss of air sacs within the lungs. This reduces the surface area for gas exchange, leaving the person constantly short of breath. Smoking is the leading cause of this disease. Lung cancer is caused by uncontrolled growth of cells in the lungs. Cigarette smoking is the leading cause of lung cancer. There is usually no clear symptom at the early stages, but once detected the cancer cells may have spread from the lungs to other organs. We must keep our respiratory system healthy in order for it to function properly. We must practice good habits that help improve the quality of air we breathe in. We can (a) avoid smoking (b) avoid being a second-hand smoker (c) minimize the use of air conditioners (d) keep floor and carpet dust-free (e) make sure a supply of fresh air (f) avoid open burning (g) turn off our vehicle if we are waiting for more than a minute (h) practice the 3Rs (i) implement laws and regulations to control air pollution
Q1. (a) Name the muscles that are used for breathing. (b) Explain how the muscles mentioned in (a) are involved in inhalation. Q2. If there is a hole in the chest wall, a person may not be able to breathe even though his lungs are not damaged. Explain.
1.1
Q3. By what physical process does oxygen enter the blood capillaries from the alveoli? Q4. How does blood supply the body tissues with oxygen? Q5. How do we keep our respiratory system healthy?
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1.2 Secretion is a form of excretion.
Secretion is not a form of excretion because secretion produces useful substances from cells. The addition of digestive juices to food materials is an example of secretion.
Excretory System
Metabolism refers to all the chemical processes that take place in the body. Metabolism may result in the production of waste products which are often toxic. The elimination of the metabolic waste products from the body is called excretion. This is done by the excretory organs. Defecation is not excretion because feces contain undigested food which has not been absorbed into the cells or taken part in metabolism. The importance of excretion (a) Disposal of toxic or poisonous wastes. For examples, urea and carbon dioxide. (b) Disposal of excess substances. For examples, salts and water. The main excretory organs in humans are the skin, lungs and kidney.
Skin
Not all mammals sweat. Dogs, for example, have sweat glands only on the pads of their paws and they cool themselves mainly by panting. When a dog pants, water evaporates from the mouth and tongue.
The skin not only protects our body, but also acts as an excretory organ. The skin has many sweat glands which produce sweat when the body is hot. Each sweat gland is a long coiled tube. The sweat gland leads to a sweat duct which opens on the skin surface as a sweat pore. Sweat is extracted from the blood capillaries surrounding the sweat glands. Sweat contains water, mineral salts and urea weat pore
air
Epidermis weat duct
ermis
weat gland
lood vessels atty layer Structure of human skin
Lungs Visit this website to know more about human excretory system.
During cellular respiration, the cells produce carbon dioxide and water as waste products. Carbon dioxide diffuses out of the blood capillaries into the alveoli. Carbon dioxide and water vapor are expelled from the lungs by exhalation.
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Kidneys Kidneys are the main organs in the excretory system. Humans have two kidneys found in the abdomen just above the waist. The main function of the kidneys is to filter waste products and excess water from the blood and excrete them from the body as urine. Urine is a yellowish liquid that contains water, mineral salts and urea. The urine from the kidney enters the ureters to the urinary bladder. The bladder stores urine. When the bladder is full, the urine flows through the urethra to the exterior. Kidneys
Ureters
Urinary bladder
Urethra
The pathway from the formation of urine to the excretion of urine is shown below: Kidney
Ureter
Bladder
Urethra
We should take good care of our kidneys as they help to filter the blood. They remove toxic waste materials from our body and regulate the balance of fluid and mineral salts in our body. Humans can still lead a healthy life with only one healthy kidney. However, if both kidneys fail, the patient may die if he does not go for treatment. We must drink plenty of plain water to help flush out the waste materials. We should avoid salty food. We should exercise more and eat more fruits and vegetables.
Q1. Define the term excretion and explain its importance to the body. Q2. Complete the table below. Excretory organ
Waste products
Skin Lungs
1.2
Kidneys Q3. (a) Where are our kidneys in our body? (b) State the function of each of these organs: (i) Urethra (ii) Urinary bladder (iii) Ureter Q4. How do we keep our excretory system healthy?
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1.3
Circulatory System
All the cells in our body need nutrients, oxygen and water. Meanwhile, carbon dioxide and other waste materials produced by the cells must be removed. An internal transport system is needed to deliver useful materials to the body cells and remove the waste materials from them. The internal transport system is called the circulatory system because useful materials as well as waste materials circulate the body. A circulatory system has four basic characteristics: (a) i tin i The circulating fluid is called blood. Blood transports useful and waste materials. (b) Pumping device The pumping device is the heart. Blood is moved through the body by muscular contractions of the heart. (c) Blood vessels A complex network of blood vessels carries materials to the tissues and back to the heart. There are three main types of blood vessels, namely arteries, veins and capillaries. (d) Valves Valves are present in some blood vessels to prevent backflow and ensure that blood flows in one direction only.
Blood supply to the brain Arteries and veins in the arm
Heart Blood supply to the lungs
Large arteries supply blood to the legs.
The heart and some major blood vessels
The human circulatory system is a double circulatory system. This means that in each complete circuit of the body, the blood must flow through the heart twice. The human double circulatory system consists of (a) the pulmonary circulation which transports blood between the heart and the lungs, and (b) the systemic circulation which transports blood between the heart and all other parts of the body. Chapter 1
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BCB032048
B C B 0 3 2 0 4 8
9 7 8 -6 1 6 -5 4 1 -3 1 5 -2
,!7IG1G5-ebdbfc! Cover M2 Sc TB 2019.indd 1
11/12/2018 14:47