SCIENCE - edupub.gov.lk

1 ISCIENCEPart - IEducational Publications DepartmentGrade 8 iiFirst Print 2016 Second Print 2017 Third Print 2018 Fourth Print 2019 All Rights ReservedISBN 978-955-25-0132-6 Published by Educational Publications DepartmentPrinted by Neo Graphics (Pvt) LtdNo. 44, Udahamulla Station Road, Gangodawila, National Anthem of Sri LankaSri Lanka MathaApa Sri Lanka Namo Namo Namo Namo MathaSundara siri barinee, surendi athi sobamana LankaDhanya dhanaya neka mal palaturu piri jaya bhoomiya ramya Apa hata sepa siri setha sadana jeewanaye mathaPiliganu mena apa bhakthi pooja Namo Namo MathaApa Sri Lanka Namo Namo Namo Namo MathaOba we apa vidya Obamaya apa sathyaOba we apa shakthi Apa hada thula bhakthiOba apa aloke Apage anupraneOba apa jeevana we Apa mukthiya oba weNava jeevana demine, nithina apa pubudukaran mathaGnana veerya vadawamina regena yanu mana jaya bhoomi karaEka mavakage daru kela bevinaYamu yamu vee nopamaPrema vada sema bheda dureradaNamo, Namo MathaApa Sri Lanka Namo Namo Namo Namo Mathaivwms fjuq tl ujlf.

2 Orefjdatl ksjfiys fjfikdtl mdge;s tl re rh f wm lh ;=< jkdtne ks wms fjuq fidhqre fidhq fhdatl f,i tys jefvkd j;a jk wm fuu ksjfiafid k is h hq;= f ieug u fu;a lreKd .=fKkSfj<S o kSrka Ks uq;= fkd j th u h iem;dlsis l, fkdu rkdwdkkao iurfldakaxU jha; kf;fs; ehkhNthk;xd;Nw ehk; thOk; ,y;yk;ed;Nw clypy; XLk;xd;Nw ek; FUjp epwk;mjdhy; rNfhjuu; ehkhNthk;xd;wha; thOk; tsUk; ehk; ed;wha; ,t; ,y;ypdpNyeyNk tho;jy; Ntz;Lkd;NwhahtUk; md;G fUizAld;xw;Wik rpwf;f tho;e;jpLjy;nghd;Dk; kzpAk; Kj;Jky;y - mJNtahd;W kopahr; nry;tkd;Nwh. Mde;j rkuf;Nfhd; ftpijapd; ngau;g; innovative, changing with right knowledge,Be a light to the country as well as to the from the Hon. Minister of Education The past two decades have been significant in the world history due to changes that took place in technology. The present students face a lot of new challenges along with the rapid development of Information Technology, communication and other related fields.

3 The manner of career opportunities are liable to change specifically in the near future. In such an environment, with a new technological and intellectual society, thousands of innovative career opportunities would be created. To win those challenges, it is the responsibility of the Sri Lankan Government and myself, as the Minister of Education, to empower you all. This book is a product of free education. Your aim must be to use this book properly and acquire the necessary knowledge out of it. The government in turn is able to provide free textbooks to you, as a result of the commitment and labour of your parents and elders. Since we have understood that the education is crucial in deciding the future of a country, the government has taken steps to change curriculum to suit the rapid changes of the technological world.

4 Hence, you have to dedicate yourselves to become productive citizens. I believe that the knowledge this book provides will suffice your aim. It is your duty to give a proper value to the money spent by the government on your education. Also you should understand that education determines your future Make sure that you reach the optimum social stratum through education. I congratulate you to enjoy the benefits of free education and bloom as an honoured citizen who takes the name of Sri Lanka to the world. Akila Viraj Kariyawasam Minister of EducationviForeword The educational objectives of the contemporary world are becoming more complex along with the economic, social, cultural and technological development. The learning and teaching process too is changing in relation to human experiences, technological differences, research and new indices.

5 Therefore, it is required to produce the textbook by including subject related information according to the objectives in the syllabus in order to maintain the teaching process by organizing learning experiences that suit to the learner needs. The textbook is not merely a learning tool for the learner. It is a blessing that contributes to obtain a higher education along with a development of conduct and attitudes, to develop values and to obtain learning government in its realization of the concept of free education has offered you all the textbooks from grades 1-11. I would like to remind you that you should make the maximum use of these textbooks and protect them well. I sincerely hope that this textbook would assist you to obtain the expertise to become a virtuous citizen with a complete personality who would be a valuable asset to the would like to bestow my sincere thanks on the members of the editorial and writer boards as well as on the staff of the Educational Publications Department who have strived to offer this textbook to you.

6 W. M. Jayantha Wickramanayaka,Commissioner General of Educational Publications,Educational Publications Department,Isurupaya, viiMonitoring and Supervision W. M. Jayantha Wickramanayaka - Commissioner General of Educational Publications Educational Publications DepartmentDirection W. A. Nirmala Piyaseeli - Commissioner of Educational Publications (Development) Educational Publications Department Co-ordination K. D. Bandula Kumara - Deputy Commissioner Educational Publications DepartmentW. Suvendra Shyamaleen Jayawardana - Assistant Commissioner Educational Publications DepartmentY. M. Priyangika Kumari Yapa - Assistant Commissioner Educational Publications DepartmentG.

7 M. A. Dinushi N. Muhandiram - Assistant Commissioner Educational Publications DepartmentPanel of Editors 1. Dr. A. A. L. Rathnathilaka - Senior lecturer Department of Chemistry University of Kelaniya2. Dr. P. R. K. A. Vitharana - Senior lecturer Department of Education University of Peradeniya 3. Dr. Nilwala Kottegoda - Senior lecturer Department of Chemistry University of Sri Jayawardanapura4. M. P. Vipulasena - Director ( SCIENCE ) Ministry of Education5. R. S. J. P. Uduporuwa - Senior lecturer National Institute of Education 6. K. V. Nandani Sriyalatha - Commissioner (retired) Educational Publications Department7. V. Rajudevan - Assistant lecturer National Institute of Education8. P. Atchuthan - Assistant lecturer National Institute of Education9.

8 K. D. Bandula Kumara - Assistant Commissioner Educational Publications Department10. W. Suvendra Shyamaleen Jayawardana - Assistant Commissioner Educational Publications Department11. Y. M. Priyangika Kumari Yapa - Assistant Commissioner Educational Publications DepartmentviiiPanel of Writers1. Dr. K. Ariyasinghe - Professional SCIENCE Writer2. P. I. Wijesundara - In-Service Advisor ( SCIENCE ) Zonal Education Office, Udugama3. R. M .P. Bandara - Teacher Service Neluwa National School, Neluwa4. L. Gamini Jayasooriya - In-Service Advisor ( SCIENCE ) Divisional Education Office, Wennappuwa5. S. M. Saluwadana - SCIENCE Co-ordinator Dept. of Provincial Education North Central6. H. T. C. Gamini Jayarathne - In-Service Advisor (retired) 7.

9 K. Indika Jayawardhana Peiris - Teacher Service Methodist High School, Moratuwa8. W. G. A. Ravindra Veragoda - Teacher Service Sri Rahula National School, Alawwa9. A. M. T. Pigera - Assistant Director of Education (retired)10. Suyama Kottegoda - Teacher Service Bandaragama Central College, Bandaragama11. M. A. P. Munasinghe - Project Officer (retired) National Insitute of Education12. T. Balakumaran - Teacher Service (retired) 13. J. Emanuvel - Principal St. Anthoney Boys School, Colombo 1314. M. M. S. Zareena - Teacher Service Budurdeen Mahmood Ladies College, Kandy15. M. M. Hareesa - Teacher Service Fathima Muslim Ladies College, Colombo 12 Language Editing 1.

10 M. R. S. K. Ganegoda - Teacher Service (retired)Cover Page, Illustrations and Page Layout1. Malaka Lalanajeewa - Graphic DesignerTechnical Assistance1. M. D. Tharindu Samarasinghe - Educational Publications Department 2. P. Naveen Tharaka Peiris - Educational Publications DepartmentixContents pageImportance of Microorganisms 01 Microorganisms 01 Effects of microorganisms on food 03 Impact of microorganisms on humans and their activities 0601 Animal Classification 12 Main invertebrate groups 13 Main vertebrate groups 1702 Diversity and Functions of Plant Parts 24 Diversity and functions of plant leaves 25 Diversity and functions of plant stems 30 Diversity and functions of plant roots 3303 Properties of Matter 39 Discontinous nature of matter 39 Utilizing physical properties of matter 4504 Sound 62 Musical instruments that produce