VIII Science Textbook PDF

Science Class VIII Department of School Education Ministry of Education and Skills Development Thimphu Published by Department of School Education (DSE) Ministry of Education and Skills Development (MoESD) Thimphu Provisional edition 2013 First edition 2017 Second...

Science Class VIII Department of School Education Ministry of Education and Skills Development Thimphu Published by Department of School Education (DSE) Ministry of Education and Skills Development (MoESD) Thimphu Provisional edition 2013 First edition 2017 Second edition 2020 Reprint 2023 Copyright © 2023 DSE, MoESD, Thimphu. Acknowledgments The Royal Education Council would like to thank all the science faculty members of the Colleges of Education, Paro and Samtse and teachers from different schools for their valuable contributions towards the development of this book. Our sincere gratitude goes to Ministry of Education, Royal Society for Protection of Nature, Ministry of Agriculture, Ministry of Health, Ministry of Economic Affairs, and other relevant agencies for their unfailing support, starting from the development of the Science Curriculum Framework to the production of science textbooks and manuals. The curriculum revision was possible with the generous financial and technical support rendered by relevant stake holders. The National Environment Commission in integration of Sustainable Waste Management from ‘Ecology Note: Towards a Clean, Green, and Beautiful Bhutan’. The United Nations Population Fund (UNFPA) through Ministry of Education in inclusion of components of Comprehensive Sexuality Education in strengthening life skill education for children. Our sincere courtesy to all the source of pictures that are used in this book. Advisors Sangay Zam, Secretary, Ministry of Education, Thimphu Tshewang Tandin, Director General, Department of Adult and Higher Education, Ministry of Education, Thimphu Kesang C Dorji, Director, Department of Curriculum and Research Division, Ministry of Education, Paro Kinga Dakpa, Director General, Royal Education Council, Paro Wangpo Tenzin, Dean, Royal Education Council, Paro Coordination Wangchuk, Royal Education Council, Paro Proof Reading Gopilal Acharya, Free Lance Editor, Thimphu Amber Kumar Rai, Curriculum Officer, Royal Education Council, Paro Sharda Rai, Subject Specialist, Bhutan Council for School Examination and Assessment, Thimphu Art Work and Layout Surjay Lepcha, Curriculum Officer, Royal Education Council, Paro Sangay Tshering, Teacher, Drugyel HSS, Paro. No part of this book shall be used without written permission fromDSE, MoESD, other than for educational purposes. ISBN 978-99936-0-417-4  Foreword Today, science is an indispensable discipline of learning that shapes the lives of humankind and their wellbeing. The enduring engagement of people in the scientific world of exploration, inquiry and investigation has culminated in the addition of an ever-growing repository of scientific knowledge and milestones. Through the time, how science works and affects the world has been influencing the way we view and deal with the subject. Unfortunately, many a times, the subject is seen as very complex and difficult, hard to comprehend and demanding to learn, thereby posing challenges in our effort in instilling scientific beliefs and attitudes in young learners. Such generalisation has influenced the learners to shy away from the experiential learning and the scientific endeavour in favour of a discipline that is perceived to be easier. Therefore, it is time that concerted efforts are pursued in making learning of science a way of igniting the fire of curiosity and investigation in the minds of learners. Towards making education meaningful and relevant for students, it is imperative to link the scientific concepts to the real world through rigorous engagement of learners in the scientific processes of observation, inquiry, investigation, experimentation and generalisation. The timely revision of science textbooks is an attempt to align learning outcomes with the emerging global view of science and educational philosophies, accentuate the development of scientific skills of doing science, and foster the scientific temper and literacy in young minds. However, the endeavour in science education in our context emanates from the national, social, cultural and religious belief system imperative to nurturing nationally rooted and globally competent citizens who can productively contribute to the nation building initiatives and development of a dynamic global society. Therefore, it is our sincere hope that the science curriculum provides a limitless avenue for every learner as a young scientist to explore continuously and engage in doing science. The meaningful participation is crucial in the development of transversal competencies of critical thinking, creativity, communication and collaboration along with other essential life skills fundamental to succeed and excel in the 21st century world as productive and socially responsible individuals. I would like to wish all our teachers and students, a fulfilling social and academic engagement and experiential experiences through enduring and enterprising learning and doing science as part of every learner’s life. Tashi Delek Kinga Dakpa Director General  Contents Foreword iii Introduction vii UNIT I : Life Processes 1. Cell 1 2. Human as Organism 16 3. Green Plant 58 4. Living Things and their Environment 76 UNIT II : Materials and their Properties 5. Classifying Material 96 6. Material and Change 124 7. Separating Mixture 142 8. Patterns in Chemistry 154 UNIT III : Physical Processes 9. Force and Motion 176 10. Work, Power and Energy 195 11. Electricity and Magnetism 214 12. Light and Sound 237 13. The Earth and Beyond 273 Annexture Annexture A 282 Annexture B 293 Annexture C 305  Introduction Science as a body of knowledge allows an individual to explore, create, and organize ideas in the form of testable explanations and predictions that ultimately enable the discovery of new knowledge. Science has thus far played an important role in helping humankind to best understand the universe, make the best use of natural resources, and advances accordingly. The importance of Science has been revealed through the way science and scientific knowledge has shaped the lives of human since the time immemorial. The advancement of a human world was possible due to the influence of science as almost all the activities, from sowing a seed to building a rocket involves scientific knowledge. Thus, science has become an indispensable discipline for the survival and advancement of humankind. Being conscious of the role science has played in shaping the lives of humankind and the power it holds for further advancement, catching up with the new and possible discoveries in the field of science are very important and urgent to progress along with the world around us. Nonetheless, the unfounded belief of viewing science as a subject for the elite learner has affected the way we view and deal with the subject. Many times, the subject is seen as very complex and difficult, tough to comprehend, and demanding to make sense out of associated concepts. Such generalization has influenced the learners to shy away from it in favour of a discipline that is perceived to be easier. This trend has challenged the effort of instilling scientific beliefs and attitudes in young learners. It has, therefore, called for a concerted effort to make learning of science a way of igniting the fire of curiosity in the minds of learners. Such a move is possible only when all the players collaborate to provide and use the right tools, forum, opportunities and instructions supported by consistent follow-up and monitoring while teaching and learning science. In essence, dealing with science should foster seeing, using and doing the real things so as to give ‘the feel of real science’ to the learners. It is imperative to link the concept to the real world, for science encompasses the understanding of structure and behaviour of the physical and natural world that can be better understood only through the use of the scientific inquiry process. vii Scientific Process A scientific process is an inquiry approach that involves a systematic understanding of the natural and physical world. It forms the basis of experimentation for scientific knowledge. It is imperative to know the basic scientific process to derive predictions and confirmations from the ideas and information gathered through observation of different phenomena. Thus, it entails asking relevant questions related to observation, testing ideas, and communicating the findings. The scientific process includes: 1. Observation It is the fundamental skill that enables learners to view the world objectively and systematically by using all the senses. It consists of gathering information, evidences, and ideas about different phenomena. This facilitates learners to compare, contrast, and generalise ideas about the world around them. These experiences foster inquisitiveness in them. 2. Questioning The competency that involves creative and critical thinking which attempts to link the known with the unknown ideas. It enhances the ability of the learners to put their observations in the form of a question that is clear, concise, and testable. 3. Hypothesis It is an educated guess and possible explanation about the observation and question. Based on the limited evidence as a starting point, learners carry out further investigation. Therefore, the hypothesis is a specific and testable prediction about what may happen in a study. 4. Background information It is the collection of relevant and significant information regarding the topic in order to provide a comprehensive understanding of what has been said on the topic and by whom. Through this step, the learner build-up a story related to the question and hypothesis. 5. Design It is an experimental set-up that allows investigation of the relationship between variables. This allows learners to manipulate the variables and test whether their prediction is accurate. viii  6. Data collection It is the systematic observation, measurement, and recording of information about various phenomena happening in the experimental set-up. It allows learners to gather evidence to answer stated research questions, test hypotheses, and evaluate outcomes. 7. Analysis It is an interpretation of data through the use of analytical and logical reasoning to determine the patterns, relationships, and trends. The learner makes sense out of the information recorded to establish a relationship between variables, based on which results and conclusions are drawn. 8. Conclusion It is the step where the learner makes generalisation of the information based on the data analysis and interpretation. The generalisation may or may not support the hypothesis. This facilitates learners to develop the skills of articulating diverse information to draw a comprehensive conclusion about the phenomena. 9. Sharing This is the final step wherein the learner presents their findings in the form of a final report, display or presentation as asked by the subject teacher. The learners explore and learn to use different forms of communication such as graphic, audio-visual, etc. to share their ideas or findings. Textbook Content The content in this textbook covers topics on Biology, Chemistry, and Physics in equal proportion to promote the learning of concepts in all the three disciplines. The concepts under each topic are made learner-friendly by incorporating various kinds of activities that meaningfully engages both teacher and learners. Essentially, this textbook contains the following learning experience plan. Learning objectives: The list of statements that define what learners are expected to know at the end of each topic or chapter. Activity: This provides information on the aim, the materials required and steps to carry out the activity. It is intended to provide hands-on experience for the learners and test the learned theory or to draw generalization and build concepts. Do you know? This is provided as additional information to add to general knowledge in science. This is not for testing. ix Questions: Where appropriate, the questions are provided to immediately test the concepts learned. This will help learners to test their understanding. Exercise: This is provided to check the understanding of the concepts learned in the chapter. It has different sets of questions to test learning in terms of scientific knowledge, skills, and values and attitudes. Model Question Paper: This is provided at the end of the textbook to help learners familiarize with the type of questions that are expected in the terminal examinations. It provides cues of the range of cognitive level of learnings, skills, the values and attitudes that the science curriculum is expected to achieve. The realization of the curriculum aspirations and intends is determined by the way the curriculum is implemented. So, the use of various strategies that allows learners to explore diverse strategies will help realize the curriculum’s intent besides fostering scientific aptitude and attitude in the learners. The provision of avenues to arouse curiosity will go a long way in fostering intellectual development and enhancement of overall performance. If the right tools and strategies are being used, this science curriculum will provide a limitless avenue for the learners to explore continuously on and beyond the scientific concepts embedded in this book. STEM Unit Royal Education Council x  Chapter 1 Cell You have learnt that living things are made up of cells. The cell is the structural and functional unit of life. It contains special parts called cell organelles, which have definite structures and functions. A group of similar cells form a tissue; a group of tissues form an organ; and then the organs together form an organ system. The study of cell, tissue, organ, and organ system help us to understand the levels of organisation found in the multicellular organism. 1. The Parts of Cell and their Functions Learning Objectives On completion of this topic, you should be able to: identify the cell organelles of plant and animal cell. explain the functions of cell organelles. draw the labelled diagram of plant and animal cell. A cell consists of cytoplasm, nucleus, and other living parts, which are collectively called protoplasm or protoplast. A number of specialised parts, called cell organelles, are present in the cytoplasm. The cell organelles have definite shape, size, and function. Activity 1.1. A journey inside the cell Let us make a journey into the plant cell. http://www.glencoe.com/sites/common_assets/science/virtual_labs/E08/E08. html 1 Reprint 2023  Chapter 1: Cell Table 1.1 The Cell Oganelles and their Functions Sl No Structure Cell Organelle Function Endoplasmic 1............................... reticulum 2............................... Synthesis of protein 3 Chloroplast............................... 4 Golgi bodies............................... 5.............................................................. i. Copy and complete Table 1.1. ii. Name and write the functions of cell organelles that you would come across if it was a journey inside an animal cell. iii. List three cell organelles present in animal cell which are not present in Table 1.1. 2 Reprint 2023  Chapter 1: Cell Questions 1. Relate each cell organelle with one item listed in the box based on their function. Brick wall, torch, generator, kitchen, computer, water tank, sieve, table Example, Cell wall: Brick wall i. Cell membrane: ………………………… ii. Mitochondria:……………………....……. iii. Chloroplast:……………………………..... iv. Nucleus:…………………………………... v. Vacuoles:………………………………….. 2. Find the names of five cell organelles hidden in the word maze. A J F B H E M O S O S Y L A I H V V A C U O L E T Q U N O E C M I T O C H O N D R I A X C S U E L C U N W P L A S T I D 3. Write the function of the following cell organelles. i. Leucoplast ii. Vacuole iii. Cell membrane http://www.biologyjunction.com/cell_functions.htm http://www.carolguze.com/text/102-19-tissuesorgansystems.shtml http://www.innerbody.com/ 3 Reprint 2023  Chapter 1: Cell 2. Levels of Organisation in Multi-cellular Organism Learning Objectives On completion of this topic, you should be able to: define tissue. classify plant tissues and animal tissues with examples. explain the structures of plant tissues and animal tissues. identify plant tissues using a compound microscope. describe organs, organ systems, and organism with examples. Cell is the simplest unit of life. All living things have evolved from single-celled or unicellular forms. Activity 1.2. From simple to complex Using the pictures given in Figure 1.1, create a flowchart to show the levels of organisation in human body. Based on your arrangement, answer the questions. (a) Organ system (b) Tissue (c) Organism (d) Organ (e) Cell Figure 1.1. Levels of organisation in human body. i. Which picture did you place in the beginning of your flowchart? Why? ii. Which picture did you place at the end of your flowchart? Why? a. Tissue What is tissue? In a multicellular organism, a group of similar cells perform specific functions in the body. This group of similar cells that perform particular function is called tissue. Can we find tissue in unicellular organism? 4 Reprint 2023  Chapter 1: Cell Types of Tissue Plants and animals are made up of different types of tissues. Different tissues perform different functions. These tissues can be categorised into many types. Plant Tissue Activity 1.3. Observing a plant tissue Materials required Permanent slide of dicot stem (TS) and a compound microscope. Procedure Step 1. Take a permanent slide of dicot stem Precaution (TS). Do not let the objective Step 2. Observe it under the microscope. lens touch the glass slide. Step 3. Draw what you observe. Are the dicot cells similar in structure? Explain your observation. Plant tissues are basically of two types: meristematic tissue and permanent tissue. Meristematic tissue is found at all growing points of a plant, such as tips of roots, stems and branches. It is also present in between the bark and the wood of trees. It multiplies and brings about the growth of plants. Permanent tissues are made up of either living or dead cells, which have lost their ability to multiply. They have permanent Meristematic shapes and perform particular functions. tissue Permanent tissues are of two types: simple permanent tissue and complex permanent Root cap tissue. Figure 1.2. Longitudinal section (LS) of root tip. 5 Reprint 2023  Chapter 1: Cell i. Simple permanent tissues are of the following types: Parenchyma consists of oval, spherical, or polygonal cells as shown in Figure 1.3. The cell wall is thin, and there are spaces between the cells. TS Thick cell walls Elongated Thin cell dead cells walls LS (a) Parenchyma (b) Collenchyma (c) Sclerenchyma Figure 1.3. Simple permanent tissues. They are found in soft parts of plants such as in the central part of roots and stems. The functions of these tissues are to store food and water, and also provide temporary support to the plant. Collenchyma are living cells with thick Phloem cell walls without spaces between them. Xylem They may be circular, oval or polygonal in shape as shown in Figure 1.3. Collenchyma is mostly found in non-woody plants, leaf stalks, and veins of leaves. It provides support and flexibility to the plant. Sclerenchyma are dead cells with thick cell walls that are closely packed. The cells of this tissue are elongated and have pointed ends or polygonal in shape as shown in Figure 1.3. It is found in stems and veins of leaves. It provides strength and protection to the plant. Figure 1.4. Complex permanent tissues. 6 Reprint 2023  Chapter 1: Cell ii. Complex permanent tissues consist of two conducting tissues: xylem and phloem, which together form the vascular bundle. Xylem transports water and dissolved minerals from the roots to the other parts of the plant. Phloem transports food from the leaves to different parts of the plant. Animal Tissue Activity 1.4. Observing an animal tissue Materials required Precaution Do not let the objective Permanent slide of muscle and a compound lens touch the glass slide. microscope. Procedure Step 1. Take a permanent slide of muscle. Step 2. Observe it under the microscope. Step 3. Draw what you observe. Are the muscle cells similar or different in structure? Explain your observation? Like plants, animals are also made up of different Figure 1.5. Epithelial tissue. kinds of tissues. Based on the locations and functions, tissues can be classified into four categories: epithelial tissue, connective tissue, muscular tissue and nervous tissue. Epithelial Tissue covers the surface of the body (skin) and lines the internal organs and cavities of the body such as mouth, nose, stomach, lungs, blood vessels, etc. Epithelial cells may be flat, cuboidal, or columnar in shape. The tissue is mainly responsible for protection against injury and germs, and helps in absorption, secretion, and sensation. (a) Areolar tissue (b) Adipose tissue (c) Cartilage Figure 1.6. Connective tissues. 7 Reprint 2023  Chapter 1: Cell Connective Tissue is also known as supportive tissue. It binds one tissue to another, and connects various organs. Examples of connective tissue are blood, bone, cartilage, ligament and tendons. This tissue also provides protection to various parts of the animal body. Some connective tissues are shown in figure 1.6. Muscle Tissue forms the muscles of the body. It consists of a special type of cells, which has the ability to contract and relax. Thus, it helps the body in its movement. Muscle tissues are of three types: cardiac, striated, and non-striated. (a) Striated Muscle (b) Cardiac Muscle (c) Non-striated Muscle Figure 1.7. Muscle tissues. Nervous Tissue is made up of highly specialized cells called neurones. They transmit messages from all parts of the body to the brain and the spinal cord, and vice versa. The part of neuron containing nucleus is called cell body. Many long cytoplasmic projections called dendrites arise from the cell body. One of the dendrites is long and is called axon. The dendrites carry messages towards the cell body, and the axon carries messages away from the cell body. Dendrite Cell body Axon Nucleus Axon terminals Figure 1.8. A Neurone. 8 Reprint 2023  Chapter 1: Cell b. Organ What is organ? An organ is a group of tissues working together to perform a common function. For example, heart is an organ, which has lining of epithelial tissue, muscular tissue, nerve tissue and connective tissue. All these tissues work together to pump the blood. Other examples of organs are lungs, kidneys, skin, etc. c. Organ System An organ system is a group of organs which work together to carry out a specific function. The human body is made up of different organ systems as shown in Figure 1.9. Respiratory Circulatory Nervous System System System Skeletal Muscular system System Excretory System Digestive System Endocrine Integumentary Reproductive System System System Figure 1.9. Human organ system. d. Organism An individual, such as an animal, a plant, or even a microorganism that reproduce, grow, respire, etc. is known as organism.. Unlike unicellular organisms, multicellular organisms have organs and organ systems. Each organ system coordinates with other organ systems to perform life processes such as digestion, respiration, excretion, etc. 9 Reprint 2023  Chapter 1: Cell Questions 1. Differentiate the following pairs: a. Cell and tissue. b. Organ and organ system. c. Xylem and phloem. 2. Classify the following structures into cell, tissue, organ, organ system, and organism. Structures: neuron, blood, egg, leaf, bone, flower, bacteria, mushroom, bear, eye, human skeleton, and parenchyma. 10 Reprint 2023  Chapter 1: Cell Exercise Multiple Choice Question 1. A cell has mitochondria, centrosome, nucleus, and other cell organelles. Based on this information, it could be the cell of A. an apple. B. a yeast. C. a cat. D. a flower. 2. TWhich of the following tissue would be present in the animal tissue shown in Figure 1.10? Figure 1.10. A. Epithelial tissue and nervous tissue. B. Muscle tissue and connective tissue. C. Nervous tissue and muscle tissue. D. Connective tissue and epithelial tissue. 3. Study the Figure 1.11. W X Y Z Figure 1.11 11 Reprint 2023  Chapter 1: Cell The letters that represent the presence of meristimatic tissue in Figure 1.11 are A. w and y B. y and z C. x and y D. x and z 4. Most organelles in the cell are suspended in the A. cell membrane. B. mitochondrion. C. endoplasmic reticulum. D. cytoplasm. 5. The Figure 1.12 shows four living organisms. Figure 1.12. Which statement about the organisms shown in Figure 1.12 is true? A. They are all single celled and have similar organs. B. They are all single celled and have identical organs. C. They are all multicellular and have similar organs. D. They are all multicellular and have identical organs. 6. What would happen to the cell if lysosomes are damaged? A. The cell would produce more proteins than it needs. B. The cell would have chloroplasts that appear yellow rather than green. C. The cell would be less able to break down the dead and injured cell organelles in its cytoplasm. D. The cell would be less able to regulate the amount of fluid in its cytoplasm. 12 Reprint 2023  Chapter 1: Cell 7. The nose, trachea, and lungs function together during respiration. Thus, they form an A. organism. B. organ system. C. organelle. D. organ. 8. A student touches a hot object and then quickly pulls the hand away. Which body tissues are mostly involved in the student’s reaction? A. Epithelial tissue and muscular tissue. B. Nervous tissue and muscular tissue. C. Connective tissue and muscular tissue. D. Muscular tissue and connective tissue. 9. Which diagram in Figure 1.19 represents single type of a human tissue? (1) Neuron (2) Muscle (3) Kidney (4) Digestive System Figure 1.13. A. (1). B. (2). C. (3). D. (4). 10. Identify the figure that depicts a cell capable of making glucose. Ribosomes Mitochondria Nucleus Vacuole Centrioles Nucleus Golgi Lysosomes bodies Endoplasmic Chloroplasts reticulum Cell A Cell B Cell C Cell D Figure 1.14. 13 Reprint 2023  Chapter 1: Cell A. Cell A. B. Cell B. C. Cell C. D. Cell D. Fill in the blanks. 1. Note the relationship between the first two words and write a suitable word(s) in the blanks. i. Xylem: water; phloem:__________. ii. Epithelial tissue: lining of stomach; connective tissue:_________. iii. Cardiac muscle: muscle tissue; ligament:__________. iv. Parenchyma: storage of food; sclerenchyma:__________. v. Man: organism; lungs:______________. Check whether the following statements are True or False. Correct the false statements. 1. A heart is an organ system. 2. Meristematic tissue is only found in growing regions of plants. 3. Hand lens is used to observe cells. 4. Protoplasm includes cytoplasm, cell organelles, and vacuoles. 5. Collenchyma is for strength and support. Match the following. Column A Column B Absorption, secretion, and sensation Centrosome Carries impulse Cell wall Shape and rigidity to the cell Chromoplast Colour of flowers and fruits Neuron Cell division Epithelial tissue 14 Reprint 2023  Chapter 1: Cell Answer the following questions. 1. It is the part of a cell that acts as a check post with fine pores present in it. i. Name the part of a cell. ii. Compare this part with the cell wall. 2. Figure 1.15 shows the classification of plant tissues. Copy and complete the flow chart labelled from 1 to 6. Plant tissue 1 Permanent tissue Simple permanent tissue 2 3 Collenchyma 4 5 6 Figure 1.15. 15 Reprint 2023  Chapter 2 Human as Organism You have learnt in earlier chapter that the human body is made up of different organ systems. Each organ system is specialised to carry out a specific function. For example, the digestive system converts larger molecules of food substances to simpler forms, while reproductive system helps to maintain the continuity of life. Proper functioning of organ systems is essential to lead a healthy life. The health of an individual is generally affected by several factors, such as environment and changing lifestyles. In this chapter, you will learn about some of the important human organ systems. 1. Human Digestive System Learning Objectives On completion of this topic, you should be able to: name the parts of the human system. explain the function of each part of digestive system. explain the process of digestion. Humans need nutrients to grow and remain healthy. These nutrients are obtained from the food that we eat. Most of the food is in complex insoluble form (starch), which has to be changed into simpler soluble form (glucose). The conversion of food from complex to simpler soluble form is known as digestion. The process of digestion takes place in the digestive system. This system consists alimentary canal and the digestive glands. 16 Reprint 2023  Chapter 2: Human as Organism Parts of digestive system and their functions The alimentary canal is a muscular tube, which consists of mouth, oesophagus (food pipe), stomach, small intestine, large intestine and anus. The digestive glands, which are part of the digestive system secrete specific substances that help in the process of digestion of food. Figure 2.1 explains the process of digestion. Mouth is the opening of the alimentary canal, where the food is chewed and mixed with saliva. The tongue helps in mixing the Mouth food with saliva. Saliva is a watery liquid containing an enzyme called salivary amylase, which is secreted by salivary glands. This enzyme helps to break down starch into simpler form, for Liver example, maltose. Oesophagus Oesophagus is a straight, narrow and thick-walled muscular tube. In esophagus, peristalsis makes the food move towards the stomach. The wave-like contraction and relaxation of muscular walls of the alimentary canal is called peristalsis. Stomach Stomach is a large pouch with muscular wall, which stores, stirs and mixes the swallowed food with gastric juice and hydrochloric Pancreas acid. These juices are secreted by the wall of the stomach containing gastric glands. The gastric juices further break down the large insoluble molecules of food into soluble ones. Small intestine consists of three segments: duodenum, jejunum and ileum. Small intestine continues the process of breaking Small down the food with the help of enzymes from various glands. intestine Liver is the largest gland of the body that secretes bile. Pancreas secretes pancreatic juice. There are other numerous smaller intestinal glands in the walls of the small intestine that secrete intestinal juice. The inner wall of the small intestine has millions of finger shaped folds called villi, which absorb digested food and water. Large intestine absorbs water and stores faeces. The large Large intestine leads to rectum that opens at the anus through which Anus intestine the faeces is removed (defecation). Figure 2.1. Human digestive system. Do You Know? In humans, the total internal surface area of villi is about 30 square metres or slightly larger than the size of a tennis court. 17 Reprint 2023  Chapter 2: Human as Organism Activity 2.1. What happens to the food we eat? Watch the video using the link given below and answer the questions that follows: https://www.youtube.com/watch?v=zr4onA2k_LY The digestion of food begins in ……1…… The …...2…… is partly broken down by chewing and by the action of salivary amylase. The chewed food reaches ……3…... through oesophagus. With the help of hydrochloric acid and ……4……juice, the food is then converted into a semi-solid state called chyme, which passes into the small intestine. In small intestine, the chyme is completely digested by the action of intestinal juice, bile, and …...5…… juice. The soluble food is then absorbed in the small intestine through ……6…. The absorbed food molecules enter the blood stream through the blood capillaries present in the villi. The blood then ……7…… the absorbed food molecules to all the …...8….. of the body, where it is used for producing ……9…... The undigested food in the small intestine passes into the...…10…... intestine. This undigested food is passed out of the body through the …...11…... in a semi-solid form called...…12…... i. Why is energy not released soon after eating food? ii. How is small intestine adapted to absorb digested food? http://www.enchantedlearning.com/subjects/anatomy/digestive/ http://www.innerbody.com/image/digeov.html http://www.britannica.com/EBchecked/topic/1081754/human-digestive-system 18 Reprint 2023  Chapter 2: Human as Organism Exercise Answer the following questions. 1. Why is chewing of food important part of digestive process? 2. Use Figure 2.2 to answer the questions that follows. Figure 2.2. i. Identify the alimentary organ. ii. How does it help in the process of digestion? iii. Name the gland present in this organ. iv. Name the substance secreted by the gland. 2. Muscles, Joints, and Movement Learning Objectives On completion of this topic, you should be able to: identify different types of muscles with examples. describe different types of joints and their functions. explain the working principle of antagonistic muscles. Movement in human being is produced by combined action of the skeleton and muscles. The skeleton is formed by a framework of bones. Bones are living tissues made up of calcium and phosphorus. How many bones are found in the adult human body? The bones are held together by tendons, ligaments, and cartilages. 19 Reprint 2023  Chapter 2: Human as Organism Tendons are tough fibrous connective tissues that connect muscles to the bones, while ligaments are elastic and fibrous connective tissues, which connect two or more bones at the joints. Cartilages are also connective tissues, found between two or more bones. They prevent bones from rubbing against each other. Patella Cartilage Ligament Tendon Bone Figure 2.3. Joint. a. Muscle Muscle is composed of bundles of cells, capable of contracting and relaxing to produce movement. There are three types of muscles in our body. They are: i. striated muscle. ii. non-striated muscle. iii. cardiac muscle. The various kinds of muscle tissues, their locations, and functions are given in the Table 2.1. Table 2.1 Types of Muscles Muscle Tissue Characteristic Function Striated muscle It is long and cylindrical, non-tapering Helps in and unbranched. It is attached to the voluntary skeleton and is voluntary in nature movement (individual can control it). There are of the body. stripes on it; therefore, it is called striated muscle. It is also known as skeletal muscle or voluntary muscle. For example, muscles of arms, anus, legs and shoulder. 20 Reprint 2023  Chapter 2: Human as Organism Non-striated muscle It is spindle shaped and there are no Causes the stripes on it. It is involuntary in nature movement (individual cannot control). It is found of internal in the internal organs such as intestine, organs. stomach, blood vessels, reproductive system and bronchioles. It is also known as smooth muscle or involuntary muscle. Cardiac muscle It is striated, cylindrical and branched, Helps in the present only in the heart. It is continuous involuntary in nature and it works non- pumping of stop. the blood. Antagonistic Muscle Examine Figure 2.4 and its working mechanism. Contracted Relaxed biceps biceps muscle muscle Relaxed triceps Contracted triceps muscle muscle endon Figure 2.4. Working of antagonistic muscle. From the above two diagrams, we can see that for the arm to move up, the bicep muscle has to contract and the tricep muscle has to relax. To lower the arm, the tricep muscle has to contract and bicep muscle has to relax. Therefore, biceps and triceps in the arms are antagonistic pair of skeletal muscles. Antagonistic muscles are those skeletal muscles that oppose the action of another muscle. 21 Reprint 2023  Chapter 2: Human as Organism b. Joint The point where two ends of bones meet in the body is termed as a joint. Activity 2.2. Know your joint Study Figure 2.5 and answer questions that follows. Skull Hip Back bone Figure 2.5. Different types of joint. Identify the part which has: i. immovable joint. ii. slightly movable joint. iii. movable joint. Types of joint On the basis of movements, joints are of three types: i. Immovable joints Immovable joints are those which do not permit any movement of the bones. For example, joints in skull. ii. Slightly movable joint Slightly movable joints are those which allow slight movement of the bones. For example, joints in the vertebral column. iii. Movable joint Movable joints are capable of free movement. In this type of joint, there is a cavity (space) present in between the ends of two bones. This space is called synovial cavity. It is filled with a lubricating fluid called synovial fluid that prevents friction and acts as a lubricant. For example, joints in the knee and elbow. 22 Reprint 2023  Chapter 2: Human as Organism Bone Ligament Synovial fluid Cartilage Synovium Figure 2.6. Synovial joint. There are four major types of movable joints Table 2.2 Types of Movable Joint Movable Joint Characteristic Example Ball and socket joint In this type of joint, one end of the bone is round Clavicle and ball-like, which fits Hip joints and into the hollow cup shaped the shoulder Scapula socket of another bone. joints. Here, the bones can move Humerus in all directions. Hinge joint This type of joint allows movement in one direction. Elbow joints It moves like a hinge of a and knee joints. door. Pivot joint The joint In such type of joint, the between pointed part of one bone the first and fits into the cavity of the second another bone. vertebrae of the backbone. Gliding joint In this type of In this type of joint, one joint, one bone bone slides over the other. slides over the other. 23 Reprint 2023  Chapter 2: Human as Organism Questions 1. Study Table 2.3 and identify the type of joints. Table 2.3 Sl. No Model Type of Joint 1 2 3 4 2. A researcher made an interesting observation about the working condition of thigh muscles during a marathon run. He found out that pairs of thigh muscles helped runners in their leg movement. What type of skeletal muscle did he discover? 3. ‘Muscles of our limbs are voluntary’. Explain in your own words. 4. Name the fluid present in the movable joints. Write down its function. http://kidshealth.org/parent/general/body_basics/bones_muscles_joints.html 24 Reprint 2023  Chapter 2: Human as Organism 3. The Human Respiratory System Learning Objectives On completion of this topic, you should be able to: explain the role of lungs. compare anaerobic respiration in plants with that of animals. explain the effects of smoking on the respiratory system. The digested food after reaching the cells is oxidised to release energy, carbon dioxide, and water. The oxidation of food in cells occurs in presence of oxygen. The oxygen reaches the cells through the process of gaseous exchange in the lungs. a. Gaseous exchange Oxygenated blood Lungs are main organs in the ow t Red blood respiratory process. Lungs ri fl ou contain bronchioles which A nd cells a end in large number of i n alveoli (singular: alveolus). The alveoli are surrounded Deoxygenated by network of capillaries. blood arbon When we breathe in, the inhaled air rich in oxygen dioxide Oxygen reaches the alveoli. The oxygen diffuses into the blood in the capillaries from Red blood alveoli as shown in Figure cells 2.7. B lo o d f ry The oxygenated blood l ow in capilla from the lungs is carried to Figure 2.7. Gaseous exchange in alveolus. the heart and pumped to different parts of the body. The oxygen in the blood then diffuses into the cells. Do You Know? A resting human breathes out about 500 litres of carbon dioxide every 24 hours. 25 Reprint 2023  Chapter 2: Human as Organism The diffused oxygen is used in the cells to oxidise the food (glucose) to release energy, carbon dioxide, and water. The carbon dioxide released during respiration in the cells diffuses into the blood. Next, the heart pumps deoxygenated blood from various parts of the body into the lungs. The carbon dioxide then diffuses into the alveoli and is removed during exhalation. The diffusion of oxygen from alveoli in the blood, and carbon dioxide from the blood in the alveoli takes place at the same time. b. Effect of smoking on lungs Smoking and chewing tobacco have become common habits among people despite their harmful effects on the person’s health, family and economy. Smoking and chewing tobacco severely affect the gaseous exchange in the respiratory system in the individual. The tobacco in the cigarette contains nicotine, tar and many other harmful substances. The tar present in tobacco is one of the main causes of emphysema, a condition in which the alveoli ruptures and cause breathing difficulty. Continued deposits of tar along the lining of the lungs also leads to cell degeneration. Most of the chemicals present in the tar are toxic. The accumulation of toxic chemicals stimulates the body to form a tumour (uncontrolled growth of cells) around the affected area, leading to cancer. Globally, millions of people die every year because of smoking. It is considered as one of the leading causes of human death. Tobacco consumption in our country is increasing among all population groups, especially youth. Activity 2.3 Facts and myths about smoking Work in groups Prepare a presentation slide to advocate on the effects of smoking and tobacco use. Your slides must also help in clarifying myths related to smoking and tobacco use. c. Respiration in human Respiration is important for all organisms for the oxidation of food. There are two types of respiration: i) aerobic respiration ii) anaerobic respiration. 26 Reprint 2023  Chapter 2: Human as Organism Aerobic respiration in animals is similar to that of plants. Aerobic respiration takes place in presence of oxygen. The overall process of aerobic respiration is represented by the following equation: Glucose + Oxygen Carbon dioxide + Water + Energy C6H12O6 + 6O2 6CO2 + 6H2O + 38ATP However, anaerobic respiration in animal is different from plants in some aspects. Anaerobic respiration is a type of respiration that does not use oxygen. The anaerobic respiration in human occurs in the skeletal muscle cells when they work rapidly with insufficient oxygen. The lactic acid produced during anaerobic respiration cause pain in the muscle or muscle fatigue. Anaerobic respiration in animals is represented by: Glucose Lactic acid + energy C6H12O6 2CH3CH(OH)COOH + 2ATP Differences between anaerobic respiration in plant and animal Table 2.4 Comparison of Anerobic Respiration in Plants and Animals Anaerobic Respiration in Plant Anaerobic Respiration in Animal 1. End products are ethanol and 1. End product is lactic acid. carbon dioxide. 2. The energy released is more. 2. The energy released is less. 27 Reprint 2023  Chapter 2: Human as Organism Questions 1. Figure 2.8 contains jumble of sentences related to gaseous exchange. Read the sentences carefully and put them in a proper sequence to build up the concept of gaseous exchange. Air containing oxygen is into the blood and reaches inhaled and taken into the the alveoli in the lungs. alveoli Carbon dioxide and cells. In the cells, oxygen is used for respiration by Gaseous the heart. The heart pumps the mitochondria to release energy, Exchange in blood rich in oxygen to the Human tissues diffuses into lungs and finally carbon dioxide and water. passes out through the mouth or The carbon dioxide diffuses nose. of the lungs. The oxygen diffuses into the blood capillaries and it is taken to Figure 2.8. 28 Reprint 2023  Chapter 2: Human as Organism 2. Our lungs contain billions of alveoli. Figure 2.9 represents gaseous exchange occuring in the alveolus. Copy and complete the figure. Exhaled air contains more _______1________ and less ________2________ Inhaled air contains more _____3______ and less ______4_______ carbon dioxide alveolus _______5_______ capillary Figure 2.9. 3. Which respiration is more efficient in human, aerobic or anaerobic? Why? 4. We often see soccer players suffering from muscle cramp during the game. As a science student, how would you explain this process to your friends? 5. What is wrong with the statement, we breathe in only oxygen and breathe out only carbon dioxide? http://www.excellup.com/InterBiology/plantrespiration.aspx ences/biology/plant-biology/respiration/respiration-energy-for-plant-metabolism http://www.oum.ox.ac.uk/thezone/animals/life/respire.htm http://www.dummies.com/how-to/content/animal-respiration.html 29 Reprint 2023  Chapter 2: Human as Organism 4. Fertilisation and Development of Foetus Learning Objectives On completion of this topic, you should be able to: explain the process of fertilisation. describe the development of foetus. explain the function of placenta. Outline the ways to avoid early sex and teenage pregnancy. Human beings reproduce sexually. It starts with the production of gametes in the reproductive organs followed by fertilisation and the development of foetus in the womb. a. Fertilisation and Implantation Did you know that our life begins from a single cell structure called zygote? The reproduction in human being begins with the production of male gamete (sperm) and the female gamete (ovum). After the puberty, a single ovum is released in female by two ovaries alternatively every month.. Sperms are produced inside the testes of male. During sexual relation, millions of sperms are deposited into the vagina. The sperms travel up the vagina and uterus and reach the fallopian tube where fertilisation occurs. Only one sperm fuses with the ovum. This fusion of sperm and ovum is called fertilisation. It results in the formation of a single-celled structure called zygote. The zygote divides and forms a cluster of cells called blastula. It travels down to the uterus and fixes itself to the wall of the uterus. The fixing of a blastula to the wall of uterus is called implantation. The blastula develops into an embryo. The walls of uterus become thick with increased blood supply to nourish the growing embryo. Within the uterus, the embryo is surrounded by a protective sac called amnion or amniotic sac. The amniotic sac contains a fluid called amniotic fluid. This fluid acts as shock absorber and protects the embryo from damage. After six weeks, the embryo is called a foetus. The foetus is attached to the uterus by an organ called placenta. 30 Reprint 2023  Chapter 2: Human as Organism Embryo fixes into Zygote divides the wall of uterus repeatedly to form (implantation) an embryo Formation of zygote after the fertilisation Fusion of sperm and egg in the fallopian tube (fertilisation) Embryo develops into a foetus with Deposition of sperm human features into the vagina Birth of baby (280 days) Figure 2.10. Stages of foetal development. Activity 2.4. Use Edraw Max or any other drawing tools to create the flowchart that explains the foetus development. 31 Reprint 2023  Chapter 2: Human as Organism Placenta Placenta is an organ attached to the wall of the uterus. A cord containing blood vessels connects the placenta with the foetus. This cord is called umbilical cord. Nutrients, oxygen and other substances pass from the mother’s blood into the foetus through the placenta. It also carries carbon dioxide and waste materials from the foetus to the mother’s blood. Gestation period and birth The period between the formation of zygote and the birth of baby is called gestation period. It is about 280 days in humans. The state of carrying foetus in the uterus of a woman is called pregnancy. The emergence of a baby from the body of mother is called birth. At the time of birth, the muscles of uterus contract to push the baby out through the vagina. Questions 1. Study Figure 2.11 and fill up the missing terms in the boxes numbered 1 to 4 in your note book. Ovum 1........ Fertilisation Leads to the formation of a structure called 2........ Divides to form 3........ Forms brain, body parts, and becomes 4........ Ready for birth and born as Baby Figure 2.11. 32 Reprint 2023  Chapter 2: Human as Organism Work in groups: Read the following passage and answer the questions that follow: The Woes of Yongmin Yongmin was an only child born in a broken family. Her parents divorced when she was 5 years old and she lived with her maternal grandparents. Her mother owned an entertainment center in a town and hardly spent time with Yongmin. She never saw her father after her parents got divorced. However, her grandparents never let Yongmin miss her parents. She was blessed with their love and care. Yongmin completed her class ten with distinction and enrolled in a Higher Secondary School. Her grandparents were proud of her and gifted a smartphone on her achievement. She was found using her phone till late at night. Complaints started to come from the school regarding her academic performance.However, grandparents did not take it into account as they feared losing Yongmin. One late evening, Yongmin’s grandmother found her with a boy below the house exchanging unhealthy touches. She became suspicious and asked Yongmin about the incident in which she replied rudely. Her grandmother was shocked and slapped her for acting rude. She packed her things, called the boy and asked him to take her with him. Her grandmother pleaded her to rethink but in vain. She was resolved to marry him when she was just 16. She turned deaf ear to her grandparents and walked out with that boy. After six months, her grandfather found Yongmin in the street carrying a child and begging for food. As soon as she saw her grandfather, she broke into tears. She apologized for failing to obey her elders. The grandfather lodged a complaint to the police against that boy. It was found that the boy had such relations with a lot of teenage girls and had played with them. He was punished with accordance to the law of the country. 1. Why didn’t Youngmin listen to the requests of her grandparents? 2. State the problems she encountered after leaving her house. 3. Although, at the age of 16, Youngmin’s body is ready to reproduce; is she ready to start a family? Support your answer with a brief explanation. 33 Reprint 2023  Chapter 2: Human as Organism 4. Assume that you are Yongmin in the story and answer the following questions; i. How would you have resolved the problem of “family instability” appropriately and differently? ii. List down as many alternatives as possible that would have helped you to make informed decision on getting married. iii. Write down all the disadvantages of early marriage. Do You Know? Identical twins: These twins are identical in looks and of the same sex. They develop from a single zygote. Fraternal twins: These twins look different and may be of same sex or different sexes. They develop from two separate zygotes. http://www.s-cool.co.uk/a-level/biology/reproduction/revise-it/sexual-reproduction-in- humans-the-first-stages 34 Reprint 2023  Chapter 2: Human as Organism 5. Sense Organs Learning Objectives On completion of this topic, you should be able to: describe the structure of an eye and their functions. describe the structure of an ear and their functions. identify the types of taste receptors and their functions. explain nose as a sense organ for smell. describe the structure of a skin and their functions. All living organisms respond to physical and chemical occurring after changes in the environment. Our body has specialised cells called receptors, which receive stimuli from the environment. Any change in the environment (external or internal) that affects the organism or excites the receptors is called stimulus. Some of the receptors are present in the sense organs. Eyes, ears, tongue, skin, and nose allow us to enjoy the world around us, the beauty of a sunrise; the sound of music; the taste of food; the softness of a fur; the fragrance of a rose, etc. Each of these sense organs is connected to the brain by nerves. Activity 2.4. Discover your senses Your teacher will take you for a short nature walk. List down all the things that you see, hear, smell, taste, and feel during the walk. Stop at various points along the way, and ask your friends to share what they sense. Draw attention on some of the interesting sights, smells, and sounds during the walk. At the end of the walk, form pairs and share what you have experienced during the walk. a. The eye and its structure The eyes are located within the eye sockets. Each eye is in the form of a ball called eyeball, which measures about 2.5 cm in diameter. They are protected by eyebrows and eyelids. The eyebrows protect the eyeballs from perspiration and rain drops getting into them. Eyelids protect the outer surface of the eyes and also shut out light. Each eyelid carries eyelashes, which prevent falling of dust 35 Reprint 2023  Chapter 2: Human as Organism particles into the eye. Tear glands or lacrimal glands are situated at the upper side of each eyelid. They produce tears which help to flush out foreign particles and prevent infection. Eyebrow Upper eyelid Eye lash Pupil Iris Conjunctiva ower eyelid Figure 2.12. External structure of an eye. 36 Reprint 2023  Chapter 2: Human as Organism Structure of Eyeball Showing Its Parts and Function Figure 2.13. Structure of an eye. 37 Reprint 2023  Chapter 2: Human as Organism Activity 2.5 Observing the contraction and dilation of pupil Work in pairs Precaution Procedure Do not look at the Sun or very bright objects directly. Case-I 1. Look into your friend’s pupil and observe its size. This must happen inside the class. 2. Let your friend do the same. 3. Draw the size of the pupil in your exercise book. Case-II 1. Go outside the class. 2. Look at the bright objects for a while. 3. Observe your friend’s pupil again. 4. Let your friend do the same. 5. Draw the size of the pupil in your exercise book. i. Compare the size of the pupil in case-i and case-ii. ii. Name the muscle responsible in changing the size of the pupil. iii. Why does the size of the pupil change? Activity 2.6. How do we see ? Copy and complete the following text. Light enters your eye through a clear portion of the sclera called the …1… It is curved, so the light rays slightly bend as they pass through it. Light then passes through …2… humour and then through the pupil. The…3… adjusts the size of the pupil. It is the coloured part of the eye. In dim light, the iris …4… and the pupil gets bigger; in bright light, the iris expands and the pupil gets smaller. …5… is located behind the iris. It is the structure that can change shape in order to focus light onto the retina, so that we can see the objects clearly. The ciliary muscles, around the lens control the shape of the lens. Behind the lens is a clear gel-like substance called the …6… humour. The light passes through this and strikes the …7… which is the inner most layer of the eye. It contains two types of cells: rods and cones. Rods are sensitive to …8… light, while the cones are sensitive to bright light and colour. The rods and cones send messages through the …9… nerve, which carries the information to the …10… The brain interprets the image of the object. 38 Reprint 2023  Chapter 2: Human as Organism b. The ear and its structure The ear consists of three parts namely external ear, middle ear, and the inner ear. The external ear consists of pinna, auditory canal, and the eardrum. The middle ear is a small chamber with three small bones called ear ossicles. These bones are malleus, incus, and stapes that fits on the oval window. Stapes is the smallest bone in the human body. The middle ear is connected to throat by eustachian tube which balances air pressure on either side of the ear drum. Ear ossicles Semicircular canals Incus Stapes Malleus Auditory nerve Auditory canal Tympanic membrane Cochlea Pinna Eustachian tube Figure 2.14. Human ear. The inner ear has two main parts, the cochlea and the semi-circular canal. The cochlea looks like a snail’s shell and is filled with fluid and sensory cells. There are three semi-circular canals arranged in right angles to each other, which are filled with fluids and sensory hairs. When the body is losing its equilibrium, the fluid in the semi-circular canals washes over the sensory hairs and stimulates them. The impulse is sent to brain. The brain perceives that the body is losing its equilibrium, and will signal some muscles to contract and others to relax until balance is maintained. Thus, the ear helps in hearing and body balance. 39 Reprint 2023  Chapter 2: Human as Organism How do we hear sound? The sound waves from air are collected by Pinna pass through the interprets the type of sound Auditory canal Brain sound waves cause vibration of the impulses are carried by auditory nerves to Tympanic membrane (ear drum) Cochlea vibrations are amplified by are amplified by amplified vibrations are converted into impulses by the Ear ossicles i. malleus ii. incus, and vibrate the iii. stapes fluid in cochlea Round window Figure 2.15. Process of hearing. 40 Reprint 2023  Chapter 2: Human as Organism c. The tongue Tongue is a muscular organ in our mouth. It is used for tasting food substances. The taste of food is detected by the taste buds in the papillae of the tongue. The taste buds are oval bodies consisting of sensory cells. These sensory cells end in hair-like processes, which project out of the taste pores. When substances in solution enter the pores, the sensory hairs are stimulated. The nerve fibres extending from the bases of sensory cells carry the impulses to the brain where the taste is identified. There are mainly four taste sensations located on specific areas of the tongue. The posterior part of the tongue is sensitive to bitter taste; the tip Bitter is sensitive to sweet and salty; Papillae Tasting and the sides are sensitive to Sour region sour taste. Besides tasting the Salty food, the tongue is also used for licking, swallowing, and Sweet articulating speech. Figure 2.16. Taste receptors. d. Nose Nose is used for breathing and smell- Olfactory ing. The nose contains two nostrils Brain nerve that lead to the nasal cavity. This Olfactory cavity contains sensory cells called cells olfactory cells. These cells contain Nasal cavity hair-like fine projections that help to receive the stimuli of the odour. The Air flow impulse generated by the stimuli is transmitted to the brain through the olfactory nerves. The brain then in- terprets the nature of the smell. Figure 2.17. Internal structure of a nose. e. Skin The outermost part of our body is called skin. It is composed of two layers, the epidermis and dermis. The skin contains a variety of specialized structures, 41 Reprint 2023  Chapter 2: Human as Organism including hair, nail, sweat gland, and oil gland. It is supplied with nerves and blood vessels. It is the largest sense organ containing receptors that are sensitive to pain, temperature, and pressure. It removes metabolic waste and regulates body temperature through sweating, protects from germs and injuries, and synthesises vitamin D. Hair Epidermis Dermis Sensory nerve Blood vessel Hair follicle Sweat gland Fat Sebaceous gland Figure 2.18. Structure of skin. Activity 2.7. Care for sense organs Sense organs in our body are important because they perform vital functions. First column in Table 2.6 shows the ways of taking care of our sense organs. Tick ( ) the correct sense organ in relation to the statement given, and give reason in the column provided. Table 2.6 Caring sense organ Ways of taking Eye Ear Nose Tongue Skin Reason care Do not write or read It will stress and strain the eyes under dim light and affect the vision in long run Do not watch television for long duration Take bath regularly 42 Reprint 2023  Chapter 2: Human as Organism Avoid listening to loud music Avoid too much of sunlight Rinse your mouth after every meal Avoid using tongue scraper Use handkerchief to avoid dust particles Do not scream close to your friends Avoid plucking hairs in the nostrils Do not sneeze with your mouth closed Do not wear other’s clothes Do not use earphones for prolonged duration Questions 6. Why is ‘yellow spot’ called the area of best vision? 7. What would happen if eardrum is damaged? 8. Why is it advisable to breathe through nose than mouth? 9. A researcher asked ten students to taste mango pickle. Seven students found the pickle taste sour, while three students found it tasteless. i. What could be the possible hypothesis of the study? ii. What can you conclude from the above study? 5. A person standing in the sun feels hot. Name the sense organ involved in the detection of heat 43 Reprint 2023  Chapter 2: Human as Organism 6. Environment, Lifestyle, and Health Activity 2.8. Identifying sources of pollution Learning Objectives On completion of this topic, you should be able to: explain how various environmental factors affect our health. explain the importance of healthy lifestyle in maintaining a good health. mention the importance of maintaining good eating habits. Our health is affected by many factors such as personal, environmental, and hereditary factors. For a healthy life, we must include balanced diet, regular exercise, clean personal habits, and sufficient rest. Environmental factors such as pollution, urbanization, and climate change affects our health. Some of us may also inherit diseases from our parents. This type of disease is called hereditary disease. In this topic, you will study how environmental factors, unhealthy habits, and lifestyles affect our health. a. Environmental Factors and Health All the natural and man-made conditions around us are called environment. The condition of the environment constantly changes and affects our health and well-being. Some environmental factors include air, food and water supply, climate change, urbanisation, chemicals, and genetically modified organisms (GMOs). Air pollution The contamination of air with dust, smoke, and harmful gases is called air pollution. It is mainly caused by the smoke emitted from industries, vehicles, and domestic use of fuels such as wood and kerosene. This smoke generally contains harmful gases such as carbon monoxide, carbon dioxide, nitrogen dioxide, sulphur dioxide, and other harmful chemicals. Polluted air causes dizziness, headache, eye irritation, lung cancer, sore throat, chest pain, and allergies. Gas like carbon monoxide reduces the oxygen carrying 44 Reprint 2023  Chapter 2: Human as Organism capacity of the blood. It causes suffocation and may even cause death. Sulphur dioxide, carbon dioxide, and nitrogen dioxide gases cause acid rain, which affects the entire ecosystem including our health. Water pollution Any chemical, physical or biological change in the quality of water which has a harmful effect on any living thing is called water pollution. The main causes of water pollution are industrial, agricultural and domestic wastes. The polluted water contains large numbers of pathogens, which cause diseases such as cholera, dysentery, typhoid, and other skin diseases. The toxic or poisonous chemicals like mercury and lead from industrial wastes can enter our body through food and water and affect our health. Water polluted with nitrates from fertilisers may cause cancer, birth defects and genetic disorder. Land pollution Land gets polluted due to contamination from agriculture, industrial waste, mining activities, and solid waste dumping. Excessive use of chemicals in agriculture leads to soil pollution. Industries produce huge amount of chemical wastes, that cause land pollution. Mining is another source of land pollution which spreads metals in the soil. These metals get accumulated in plants, which makes it unsafe for consumptions by human and animal. Another major pollutant is garbage. In urban areas most of the pollution is caused by human sewage and household garbage. Activity 2.8. Identifying sources of pollution Work in groups Pollution is a pressing issue nowadays. It is important to examine the different sources that can pollute our environment. i. Identify the potential sources of land, water, and air pollution in your locality. ii. As a responsible citizen, frame a policy to reduce pollution. b. Life styles and health Your lifestyle plays an important role in your health. Lifestyle includes the behaviour and activities that make up your daily life. This includes the work you do, your leisure activities, the food you eat, your interaction with family, friends, and others. 45 Reprint 2023  Chapter 2: Human as Organism People develop different lifestyles according to their beliefs, attitudes, and values. Our life experiences and interactions with others also shape our thoughts and actions. Personal behaviour is affected by the information you learn at home and school, and from the internet, mobile, radio, newspapers, television, etc.. Activity 2.9. Know your lifestyle Copy and complete Table 2.7 and answer the questions that follows. Table 2.7. Knowing Your Lifestyle Lifestyle Activity 1…………………………………………. How do you spend your leisure 2…………………………………………. time? 3………………………………………….. 1…………………………………………. What are your favourite dishes? 2…………………………………………. 3………………………………………….. i. How would you describe your lifestyle? ii. Compare your lifestyle with lifestyle of your friend. i. Work and leisure activities The kind of work that we do affects our health. Some work requires prolonged exposure to dust, sound, heat, radiations, and toxic chemicals, and continuous use of computer. These may lead to cancer, respiratory problems, deafness, blindness, and other health issues. Leisure activities such as watching television, playing video games and mobiles for extended period of time may lead to obesity, muscular or skeletal problems, strained vision, and other health problems. ii. Unhealthy habits Certain unhealthy habits can lead to poor health. Habits like drinking alcohol, smoking, chewing tobacco and abusing drugs are harmful to health. All these substances lead to addiction, which means it becomes very difficult to stop as the body becomes dependent on them. Some common substances and their health effects are given below. Tobacco contains an addictive chemical substance called nicotine. Smoking cigarettes and chewing tobacco can cause heart attack, chronic lung diseases 46 Reprint 2023  Chapter 2: Human as Organism and cancers of mouth, throat, lungs and oesophagus. It can harm the development of foetus in a pregnant woman. ‘Doma’ chewing is a common habit among the Bhutanese. ‘Doma’ is a combination of betel nut (Areca nut), betel pepper (‘pani’) and lime. The raw betel nut contains arecholic acid, which is an irritant. It acts on the nervous system causing stimulation of the body and dilation of blood vessels, that is why, when people eat ‘doma’ they feel warm. Continuous chewing and swallowing of ‘doma’ increases the risk of mouth, throat and stomach ulcer. It also damages the enamel of the teeth due to rubbing and grinding. Alcoholism refers to uncontrolled consumption of alcoholic beverages like beer, locally brewed alcohol, whisky, etc. Alcohol can damage liver, heart, brain, and also greatly increases the risk of other diseases. Excessive drinking of alcohol over an extended time can cause liver cirrhosis. Cirrhosis is the scaring of the liver tissue that changes the structure of the liver and blocks blood flow, affecting normal liver functions. This may gradually lead to liver cancer. Large amounts of alcohol in the body can turn to fat, causing weight gain and clogged arteries. Therefore, alcoholics are at high risk of stroke, or developing congestive heart failure. Alcohol can cause brain damage, and affect memory, speech, body balance and other brain functions. For women who are pregnant, their baby may develop mental and physical defects. A drug is a substance, which alters the functioning of mind and body of a person. Drugs can cure diseases when taken in right quantities under the supervision of a physician. However, some drugs are consumed by people for pleasure. Such use of drug is called drug abuse. Drug abuse can cause serious damage to the nervous system. Once a person becomes addicted to drugs, it becomes very difficult to stop. Activity 2.10. Carry out research in your community Work in groups Carry out the research using the steps featured below.. Seek help from your teacher and work in collaboration with your friends. Step 1. Identification of problem: Identify the types of substances abused in your community (like unhealthy substances- ‘doma’, alcohol, tobacco, etc.). 47 Reprint 2023  Chapter 2: Human as Organism Step 2. Framing research question: “What unhealthy substances (‘doma’, alcohol and tobacco) are consumed the most in my community?” Step 3. Making a hypothesis: Guess the answer for your research question. Step 4. Data collection: You can collect data by randomly interviewing minimum of 15 people using the survey questionnaire provided. Be polite while interviewing people. Step 5. Data analysis: Record your data using Table 2.8. Plot a suitable bar graph(s) to represent the number of people consuming different unhealthy substances. Look for patterns and relationships. Write your findings. Step 6. Drawing conclusion: Compare your findings with your hypothesis. What is your conclusion? Step 7. Report writing : Share your research works in the class, or during parent teacher meeting. Survey Questionnaire Gender: Male Female Put tick, if ‘Yes’ and cross if “ No’ 1. Do you eat Doma? 3. Do you chew tobacco? If yes, why do you take? If yes, why do you take? a) Peer pressure a) Peer pressure b) Culture and tradition b) Culture and tradition c) Availability c) Availability d) Others d) Others 2. Do you drink alcohol? 4. Do you smoke? If yes, why do you take? If yes, why do you take? a) Peer pressure a) Peer pressure b) Culture and tradition b) Culture and tradition c) Availability c) Availability d) Others d) Others Thank You. 48 Reprint 2023  Chapter 2: Human as Organism Table 2.8 Data Tabulation Doma Alcohol Tobacco Smoke Item Reason Reason Reason Reason Yes No Yes No Yes No Yes No a. a. a. a. b. b. b. b. c. c. c. c. d. d. d. d. Total iii. Food habits The foods that we eat also affect our health. Many studies show that poor nutrition increases the risk of many diseases. Addiction to fast foods such as pizza, burgers, potato chips, and noodles can lead to digestive problems, obesity and malnutrition. iv. Personal habits Good personal habits such as bathing, brushing teeth, washing hands before and after meals, wearing clean clothes, doing regular physical exercise, meditating, etc. are important for healthy living. Activity 2.11. Understanding about food (Go-Slow-Whoa). Materials required: Food cards Go-Slow-Whoa chart Use the food cards provided by your teacher (a card with the names of food) in group. Your teacher will paste the Go-Slow-Whoa chart on the board/ wall. Discuss about the food cards in your group. Take turns to place the food cards on the Go-Slow-Whoa chart and justify the reason for their choice. 49 Reprint 2023  Chapter 2: Human as Organism What are the good eating habits? GO SLOW WHOA Foods that need Foods that need to be consumed Foods that need to be consumed in to be consumed more quantity in less quantity occasionally. regularly Figure 2.19. Quantity of food consumed. Questions 1. Identify the environmental factor in Figure 2.19, and explain its health effects. Figure 2.20. 2. Geyphel likes to eat biscuits for his breakfast, noodles for his lunch, and cakes for his dinner. Most of the time he plays games on his computer or his mobile phone. He hardly goes for outdoor activities. What are the diseases that you foresee in his life? 3. List some of the unhealthy habits that you see in your community. 50 Reprint 2023  Chapter 2: Human as Organism Exercise Multiple Choice Questions 1. Which of the following organ is involved in the absorption of digested food ? A. Mouth. B. Stomach. C. Small intestine. D. Large intestine. 2. Food in the alimentary canal travels through A. mouth- oesophagus-stomach-large intestine-small intestine- rectum. B. mouth- oesophagus-stomach-small intestine-large intestine- rectum. C. mouth- stomach -oesophagus- large intestine-small intestine- rectum. D. rectum-large intestine-small intestine-stomach-oesophagus- mouth. 3. Which is NOT true about smoking? A. It affects most of the organs of our body. B. It is a leading cause of cancer. C. It affects only the smoker. D. It affects the growing foetus in the pregnant mother. 4. Which of the following tissue connects muscle to bone? A. Tendon. B. Ligament. C. Cartilage. D. Nerve. 51 Reprint 2023  Chapter 2: Human as Organism 5. When do organs and organ systems begin to develop in humans? A. In the sperm cell before fertilisation. B. Before fertilisation and after birth. C. In the egg cell after fertilisation. D. After fertilisation and before birth. 6. All are the effects of alcohol EXCEPT A. bleeding gums. B. brain and liver damage. C. loss of speech and memory. D. obesity. 7. Use of vehicles, rise in industries, and burning fossil fuel contribute to A. soil pollution. B. noise pollution. C. water pollution. D. air pollution. 8. While drinking tea, the least likely sense organ used is A. eye. B. nose. C. tongue. D. ear. 9. The knee and elbow are examples of A. pivot joint. B. ball and socket joint. C. gliding joint. D. hinge joint. 10. Which of the following processes happen in the female reproductive system? A. Fertilisation and reproduction. 52 Reprint 2023  Chapter 2: Human as Organism B. Fertilisation and implantation. C. Digestion and gestation. D. Reproduction and digestion. Fill in the blanks. 1. Rods and cones are found in the............ of the eye. 2. The posterior part of the tongue is receptive to............ taste. 3. The muscle that pumps blood throughout the life is............... muscle. 4. Digested food is absorbed by............ of the small intestine. 5. One of the end products of anaerobic respiration in animal is............ acid. 6. The foetus and mother’s womb are connected by....................... 7. Gaseous exchange takes place in alveoli by the process of............ 8............. is the part of female reproductive system where implantation of the embryo takes place. 9. The addictive substance present in the tobacco is..................... 10. Substances which are harmful to our environment are called............ Check whether the following statements are True or False. Correct the false statement. 1. Digested food is ultimately used by the cells. 2. The liver secretes gastric juice. 3. The skull has no joint. 4. The space between two bones at a joint is called synovial cavity. 5. The semicircular canal is responsible for hearing. 6. Fertilisation in human occurs in the uterus. 7. There are a few alveoli in our lungs. 8. Pivot joint is present in our neck. 9. Energy released by aerobic and anaerobic respiration in animal is same. 10. Main cause of pollution is due to human activities. 53 Reprint 2023  Chapter 2: Human as Organism Match the following Column A Column B 1. Cones a. Peristalsis 2. Placenta b. Smell 3. Oesophagus c. Heart disease 4. Obesity d. Colour 5. Olfactory cells e. Nutrition f. Taste Answer the following