Basic Science English VIII (2016) PDF

BASIC SCIENCE Part - 2 Standard VIII Government of Kerala Department of Educat...

BASIC SCIENCE Part - 2 Standard VIII Government of Kerala Department of Education KT-487-1/Basic.Sci. 8(E) Vol-2 State Council of Educational Research and Training (SCERT), KERALA 2016  The National Anthem Jana-gana-mana adhinayaka, jaya he Bharatha-bhagya-vidhata. Punjab-Sindh-Gujarat-Maratha Dravida-Utkala-Banga Vindhya-Himachala-Yamuna-Ganga Uchchala-Jaladhi-taranga Tava subha name jage, Tava subha asisa mage, Gahe tava jaya gatha. Jana-gana-mangala-dayaka jaya he Bharatha-bhagya-vidhata. Jaya he, jaya he, jaya he, Jaya jaya jaya, jaya he! PLEDGE India is my country. All Indians are my brothers and sisters. I love my country, and I am proud of its rich and varied heritage. I shall always strive to be wor- thy of it. I shall give respect to my parents, teachers and all elders and treat everyone with courtesy. I pledge my devotion to my country and my people. In their well-being and prosperity alone lies my happiness. State Council of Educational Research and Training (SCERT) Poojappura, Thiruvananthapuram 695012, Kerala Website : www.scertkerala.gov.in, e-mail : [email protected] Phone : 0471 - 2341883, Fax : 0471 - 2341869 Typesetting and Layout : SCERT First Edition : 2015, Reprint : 2016 Printed at : KBPS, Kakkanad, Kochi-30 © Department of Education, Government of Kerala Dear students, You were provided with opportunities to observe your surroundings and engage in simple experiments and investigative activities in earlier classes. The classroom experience, undoubtedly, might have helped you to record the information systematically and assimilate ideas through discussion and analysis. While understanding the scientific approach, there should also be the attitude to take forward the skills to apply them in day-to- day life. Moreover, an eco-friendly perspective must be adopted too. All these, through direct experiences, enquiry and understanding preferably. This textbook presents ideas in accordance with this. There are experiments, illustrations and explanatory details that enable the comprehension of these ideas. There are opportunities appropriate to the situation to make learning more enjoyable. Go ahead, thinking, asking questions, approaching ideas critically and quizzing with teachers and friends. Make learning a joyful experience. Regards, Dr. J. Prasad Director, SCERT  TEXTBOOK DEVELOPMENT TEAM Emerson F EXPERTS GGHS, Chavara, Kollam Satheesh. R Prof. Sivasankara Pillai GHSS Anchal West, Kollam Head (Rtd.), Dept. of Physics, Women's College, Trivandrum Shajil. U.K GGHSS, Balussery, Kozhikode Dr. S Mohanan Nisar Ahamed M Reader & Head (Rtd.), Dept. of Physics, GHSS Venjarammood, Trivandrum University College, Trivandrum Rasheed Odakkal Paul P I GVHSS Kondotti, Malappuram Associate Prof., Dept. of Zoology, Mar Ivanios Vineesh T.V College, Trivandrum GHS Chenad, Wayanad Dr Alaudeen M P.D. Baby Principal (Rtd.) Govt. College, Elerithattu St. Antony's HSS, Mutholi, Pala Sebastian Lukose T.J Gopalan N.K Sel. Grade Lecturer (Rtd.), University College, HSA (Retd), KKMGVHSS Vadakara Trivandrum Unnikrishnan T.I Dr. N Ratheesh Headmaster (Retd), AKKRHS for Boys, Asst. Professor, SN College, Kollam Kozhkode Pradeepkumar K.V ENGLISH VERSION Moothedath HSS, Taliparamba, Kannur Dr. Saji Mathew Premachandran K.V Asst. Professor, School of Letters, GHSS Maniyoor, Vadakara, Kozhikode M.G University Sajikumar K.G Famila E R GV & HSS for Girls, Manacaud, Trivandrum HSST, GHSS, Karunagappally Sureshkumar K Anil M R AMHSS, Thirumala, Trivandrum Govt. GHSS, Karamana, Trivandrum Babu Payyath BPO, BRC, Kozhikode Dr Subash Babu K Deputy Director Muhammed Abdul Nazar Collegiate Education, Trivandrum Master Trainer, IT @ School Santhoshkumar V.G ARTISTS BYKVHSS, Valavanoor, Malappuram Musthajib E C Dr. Vishnu V.S MMETHS, Melmuri Asst. Prof., College of Engineering, Trivandrum Noushad Vellalasseri Sadanandan C Ganapath AUPS, Keezhisseri Pantheerankave HSS, Kozhikode Muhammed Shameem Muhammed Rafi C. VAUPS, Kavanoor Govt. Technical HS, Naruvambram, Kannur Shabu Ismail Lohithakshan K PMSAVHSS Chappanangadi, Malappuram Assisi School for the Deaf, Malapparambu K.T. Manoj Viswanathan P CBHSS Vallikkunnu, Malappuram DDE Office, Malappuram Hasan C.C Academic Co-ordinator MMVHSS Parappil, Kozhikode Preethi K.A Dr. Ancey Varughese SHS Mannarkadu, Palakkad Research Officer, SCERT 12. Why Classification?................ 167 13. Diversity for Sustenance......... 181 14. For the Continuity of Generations............................ 197 15. Solutions................................ 213 16. Water...................................... 224 17. Fibres and Plastics.................. 237 18. Reflection of Light in Spherical Mirrors.................... 246 19. Sound..................................... 262 20. Static Electricity..................... 276  Certain icons are used in this textbook for convenience For further reading (Evaluation not required) ICT possibilities for making concepts clear Significant learning outcomes Let us assess Extended activities  Fed up with the search! If these books were arranged in order, it would have been very easy to locate the book suggested by our teacher… Did you notice the opinion of the girl searching for a book? What are the advantages of arranging books in proper order? Haven’t you noticed the arrangement of books in a library? In what all ways books may be arranged? Discuss. $ $ Things need to be classified first in order to arrange them properly. Aren’t the things in your study room and kitchen arranged according to their types? Human beings show a tendency to classify things around them. What are the bases for such classification? Basic Science VIII 167  $ Shape $ Colour $ Size $ Use $ Observe the figures. Fig. 12.1 What criteria can be used for classifying these organisms? $ size $ beauty $ speed $ sharp incisors $ claws that can be withdrawn into the feet $ Which among these criteria is the most suitable one for classification? Why? Discuss. If more specific criteria are adopted, classification becomes more accurate. It will be easy to study organisms if they can be classified according to suitable criteria. 168 Basic Science VIII Let’s classify and learn Observe the illustration given below. Do you know all the peculiarities of the organisms shown in the illustration? Notice the classification of these organisms on the basis of certain observable characteristics. Analyse the criteria used for classification. Those with wings Those without wings Wing A pair of observable Two pairs of observable wings wings Number of wings Legs with equal length Legs with unequal length Peculiarity of legs Transparent wings Non transparent wings Peculiarity of wings Illustration 12.1 Basic Science VIII 169  Why is the classification of these organisms very easy? $ Less number of organisms $ Specific indicators $ Two clear options for each indicator Classification becomes easier with the use of such specific indicators. Analyse with the help of the indicators the note given below and write down the inferences in the science diary. Keys for identification Taxonomic keys are the scientific indicators used for identifying and classifying plants and animals. One of the most important taxonomic keys is the dichotomous key. Each indicator in this key has two possibilities of selection. By choosing the peculiarities of the organism to be identified and by proceeding systematically one can identify and classify the organism. Illustration 12.1 is a dichotomous key. The taxonomic keys are continuously revised by including peculiarities of newly identified organisms. Indicators  Taxonomic keys  Peculiarity of dichotomous keys Thus, the method of classification is the act of grouping of organisms based on similarities or differences. Taxonomy Taxonomy is the branch of biology that identifies organisms, classifies them on the basis of similarities and differences and names them scientifically. For the purpose of classification, the characteristic features of organisms, their external and internal features, genetic constitution, evolutionary relationships etc., are to be thoroughly studied. This study reveals the relation between various groups of organisms. It also enables us to acquire a general idea about the plants and animals of various geographical areas. Moreover, taxonomy provides evidences that are helpful to explain the stages of evolution of organisms from the simple to the complex. Based on similarities or differences, all organisms including human beings are placed in different levels of classification. It was a scientist named Carl Linnaeus who fixed taxonomic hierarchy and provided a scientific base for classification. Hence he is known as the Father of Taxonomy. 170 Basic Science VIII Let’s familiarise ourselves with some scientists who have made valuable contributions in the history of taxonomy. Aristotle (Greece) Theophrastus (Greece) The Father of Biology. He The Father of Botany. He classified organisms as classified plants into annuals, those with red blood cells biennials and perennials. and those without red blood cells. (B.C. 384-322) (B.C. 371-287) John Ray (England) Charakan (India) Recorded more than 18000 The Father of Ayurveda. He plants in the book ‘Historia wrote the treatise Charaka Generalis Plantarum’. Samhita by including in it Used the term ‘species’ for around 200 plants and the first time. animals. A.D. 1st century (A.D. 1627-1705) Carl Linnaeus (Sweden) The Father of Modern Taxonomy. Suggested the taxonomic hierarchy. Proposed binomial nomenclature, the scientific naming method for organisms. (AD. 1707-1778) Taxonomic hierarchy proposed by Linnaeus Kingdom Species Phylum Genus Class Family Order Order Family Class Genus Species Phylum Illustration 12.2 Kingdom Basic Science VIII 171  According to biological definition, species is a group of organisms that can produce fertile offsprings through sexual reproduction. Species is the basic level of classification. Organisms of a species share maximum similarity of features. Organisms of similar species constitute the genus. Similar genus constitute the family and families join to form the order. Various orders constitute the class. Related classes join to form phylum. All phyla constitute the kingdom, which is the highest level. Observe the illustration given below and discuss it on the basis of the indicators. Write down your inferences in the science diary. Kingdom Animalia Phylum Chordata Class Mammalia Order Carnivora Includes all animals. Includes vertebrates Includes the vertebrates Mammals that have teeth only. that feed their young ones to tear off flesh. with milk. Family Felidae Genus Felis Species domesticus Those with withdrawable Shows features of the Along with the features of claws along with the family Felidae. Small sized the genus Felis, shows features of the order- body. No roaring sound. unique features of the Carnivora. domestic cat. Illustration 12.3 172 Basic Science VIII Indicators Which are the organisms included in Hortus Malabaricus kingdom Animalia? Hortus Malabaricus (Garden Which organisms are excluded at each of Malabar) is the first book consecutive levels? Why? on Kerala’s plant wealth. This book was published in 12 At what levels of this illustration can volumes from Amsterdam in humans be included? the Netherlands during the Complete the worksheet identifying the levels years 1678 to 1693. The book of classification of cat. was written under the leadership of Admiral Van Rheede, the Cochin Governor of Dutch East India Company. Great Kingdom ˛ native scholars like Kollattu Itti Achuthan Phylum ˛ Vaidyar, Ranga Bhat, Vinayak Pandit and Appu Class ˛ Bhat made remarkable contributions in the Order ˛ writing of the book. Malayalam fonts were used for the first time for this book in which Family ˛ classification of plants, pictures and local names Genus ˛ are recorded. This was one of the books that Species ˛ greatly influenced Carl Linnaeus. Taxonomic hierarchy of plants Linnaeus also classified plants by including them in various levels from species to kingdom. Though revised in course of time, these are still used as the basic levels of classification. Kingdom – Plantae Kingdom – Plantae Phylum – Angiospermophyta Phylum – Angiospermophyta Class – Monocotyledonae Class – Dicotyledonae Series – Calycinae Series – Sapindales Family – Arecaceae Family – Anacardiaceae Genus – Cocos Genus – Mangifera Species – nucifera Species – indica Find out more examples of the classification of plants and write them down in the science diary. Basic Science VIII 173  Diversity in names Notice the organisms given in the picture and their names in diffferent areas. Uppan, Chemboth, Vatta, Podukanni, Chakoram Uputhi Papaya, Kaplanga, Pazhuthara, Karinkanni, Karamusa, Omakka Kalkunnan, Chethumbooram Fig. 12.2 If an organism has so many names in a single language, how much will be the diversity when their names in other languages are also considered! Is the presence of different names a hindrance to their study? Discuss. Binomial nomenclature Binomial nomenclature was proposed to solve the difficulties arising out of an organism being known by various names in different languages and regions. This is a commonly accepted scientific method of naming. Binomial nomenclature is the scientific method of naming by joining two words. It was Carl Linnaeus who proposed binomial nomenclature. The first word of the scientific name indicates the genus and the second word indicates the species. By this method the scientific name of an organism is the same all over the world. According to this, the scientific name of human beings is Homo sapiens. 174 Basic Science VIII Complete the table given below appropriately, finding out the scientific names of various organisms. Expand the table by including the names of more organisms. Organism Scientific name Elephant Peacock Cassia fistula Dog Hibiscus Neem Paddy Corvus splendens Table 12.1 Towards more precision Bos taurus According to the two kingdom classification that was prevalent earlier, organisms were classified under two large categories namely, Kingdom Plantae (plants) and Kingdom Animalia (animals). In the light of the knowledge gained later on the diversity of species, an American botanist Robert H.Whittaker classified Robert H.Whittaker organisms into five kingdoms. (1920-1980) Fig. 12.3 Five kingdom classification Kingdom Some organisms Peculiarities included in the kingdom Monera Bacteria Unicellular organisms without nucleus Protista Amoeba Unicellular organisms with a nucleus Non-motile, heterotrophic unicellular/ Fungi Mushrooms multicellular organisms Autotrophic, multicellular, non-motile Plantae Plants organisms. Heterotrophic multicellular organisms Animalia Animals that have the capacity of locomotion. Table 12.2 Basic Science VIII 175  Modern trends in taxonomy In the past, knowledge of the peculiarities of microorganisms like bacteria was limited. Later, it was found out that the archaebacteria belonging to the Kingdom Monera are different from other bacteria in cell structure and physiological functions. Then kingdom Monera was further divided into two Kingdoms; namely archaea and bacteria. Besides this, one more level of classification named domain was added above the kingdom. It was the American scientist Carl Woese who proposed this six kingdom classification. Analyse the illustration given below with the help of the indicators. Discuss it and write down your inferences in the Fig. 12.4 science diary. Carl Woese (1928-˛2012) Domain Archaea Domain Kingdom – Archaea Eukarya Domain Bacteria Kingdom – Protista Kingdom – Fungi Kingdom-Bacteria Kingdom – Plantae Kingdom – Animalia Illustration 12.4 Indicators  Limitations of two kingdom classification.  Possibilities of five kingdom classification.  Circumstances that led to the formulation of six kingdom classification. 176 Basic Science VIII Find out the various levels of classification of human beings based on the six kingdom classification and complete the table suitably. Domain Eukarya Kingdom Phylum Class Order Primates Family Hominidae Genus Species Table 12.3 Read the newspaper report. Ebola casting death New Delhi : The world under the threat of Ebola! According toWHO reports, a total of 9208 have died of Ebola.The illness is caused by Ebola virus...... Why is it difficult to control diseases like Ebola ? Read the description on virus. Discuss with the help of the indicators and write down the inferences in the science diary. Catch me if you can! Acellular. With only protein coat and the genetic material. I am a pathogen- causative organism of many dreaded diseases. I can’t be destroyed easily. I can only live inside a live cell. I am inactive outside the cell. When I enter the host cell, I multiply using the materials there. I multiply H.I.V rapidly and destroy that cell. Then I enter new cells. Our world is a world full of mysteries. Basic Science VIII 177  Indicators  What are the peculiarities of virus?  Can virus be included in any of the classification methods we have discussed earlier? Why? No attempts at classification can be perfect and complete. The attempts still continue. The fact is that the more acceptable ones gain general approval. New variety of butterfly identified in Western Ghats. Kottayam : With the discovery of a new kind of butterfly, the importance of Western Ghats in matters of biodiversity has been once again emphasised. It is a group of scholars from Delhi University that identified the new variety of butterfly. These butterflies inhabit the dense forests in the Western Ghats. How do we ensure that the organisms mentioned in such reports have never been identified ? Based on the given indicators, discuss and write down the inferences in the science diary.  Observation of peculiarities  Verification of details  Use of taxonomic keys  Scientific naming  Classification There are millions of unidentified organisms on Earth. The scientific world accepts newly identified organisms by classifying them on the basis of their peculiarities and name them scientifically. Researchers all over the world continue their search for new organisms. 178 Basic Science VIII  Significant learning outcomes The learner can  identify and explain the significance and importance of taxonomy.  prepare notes on scientists who have contributed to the field of taxonomy.  list the peculiarities of organisms by identifying the relevance of classification.  explain the relevance of naming organisms according to binomial nomenclature.  identify, list and exhibit the scientific names of familiar organisms.  compare and explain modern trends in taxonomy and various methods of classification.  list the peculiarities of virus. Let us assess 1. Identify the word pair relation and fill in the blanks. a. Five kingdom classification : Robert H.Whittaker Six kingdom classification : b. Charaka : Charaka Samhita John Ray : 2. Hints about some organisms are given below. Name the kingdom to which these organisms belong: a. Multicellular heterotrophic organisms with a nucleus and capacity for locomotion. b. Multicellular, heterotrophic, non-motile organisms with a nucleus. c. Unicellular organisms with a nucleus. d. Multicellular, autotrophic, non-motile organisms with a nucleus. Basic Science VIII 179 3. Write from the table the name of the organism which has more resemblances with tiger. Give explanations for your answer. Common name Scientific name Tiger Panthera tigris Wolf Canis lupus Lion Panthera leo Cat Felis domesticus Dog Canis familiaris Extended activities 1. Prepare and exhibit labels showing the scientific name and local name of plants in your school premises. 2. Prepare a collage including pictures and notes of animals belonging to Class Mammalia. 3. From being correct to precision is the way of scientific method. Organise a discussion on this topic exemplifying taxonomy. 180 Basic Science VIII Diversity of organisms adds charm to nature. Life forms are diverse, but no organism in nature exists in isolation. Observe the illustration and find out examples for the interdependence of organisms.  Biosphere Abiotic factors are also essential for the existence of the living world which comprises of animals, plants and Biosphere is the part of microorganisms. How are abiotic factors useful to biotic earth where life exists. It extends to soil, atmosphere factors? and water. Discuss and complete the illustration given below suitably. Sunlight (Photosynthesis) Soil Abiotic Air (.........................) factors (.........................) Water (.........................) Illustration 13.1 Sun is the primary source of energy in the living world. Green plants convert light energy to chemical energy through photosynthesis. This energy gets transferred to other organisms through Ecology food chain. Plants that perform photosynthesis are called Ecology is the study of producers while organisms that depend on plants directly interaction between or indirectly for food are called consumers. The consumers organisms and also between the organisms and their that directly depend on plants are called primary surroundings. This branch of consumers. Organisms that feed on primary consumers are study inlcudes different called secondary consumers. Organisms that feed on types of ecosystems, secondary consumers are called tertiary consumers. interaction between You are already familiar with the food web that illustrates organisms, environment protection etc. food relations in nature. Observe the illustration of a food web. With the help of the indicators, discuss and write down the inferences. 182 Basic Science VIII  Illustration 13.2 Indicators  How do food chain and food web differ from each other?  Is a single organism involved in more than one food chain?  Is the possibility of an organism becoming food to more than one organism helpful to the existence of the food chain? Why?  How does the variation in the number of a particular organism in the food chain affect the existence of other organisms? Basic Science VIII 183  Did you read the note on trophic level? Complete the illustration by including the organisms of the food web at various trophic levels. Trophic level Tertiary consumers The term indicates the position (Those who feed on of an organism in the food carnivores too)....................................................... chain. Since the food chain Fourth trophic level starts with plants, they represent the first trophic Secondary consumers level. Herbivores that derive (Carnivores) food directly from plants are....................................................... Third trophic level included in the second trophic level. Carnivores that depend on herbivores for food are Primary consumers (Herbivores)....................................................... included in the third trophic Second trophic level level. Predators that prey on carnivores represent the fourth trophic level. As the Producers Paddy, grass food web turns increasingly (Plants)....................................................... complex, the same organism First trophic level may represent different trophic Illustration 13.3 levels. Indicators  Does the same organism occupy more than one trophic level?  Is there any possibility of a fifth trophic level?  How does the elimination of organisms from the higher trophic levels affect the ecosystem? Examine the food chains taken from the illustration 13.2. 1. Grass Rabbit Eagle 2. Grass Grasshopper Calotes Eagle 3. Grass Grasshopper Frog Snake Eagle Find out the trophic levels represented by the eagle in these food chains. Write them down in the science diary. The number of trophic levels and the position of organisms in the trophic levels of the ecosystem is not constant. It changes in accordance with the complexity and the length of the food chain. 184 Basic Science VIII Ecological interactions Observe the illustration of some ecological interactions. See 'Jeevibandhangal’ in School Resources in IT @ school, Edubuntu. Flower and butterfly Mango tree and vanda Deer and tiger Paddy and weeds Mango tree and loranthus Illustration 13.4 Complete the illustration given below with suitable examples for ecological interactions. Ecological interactions Predation Parasitism Competition Mutualism Commensalism Beneficial to one Beneficial to one and Harmful to both Beneficial to both Beneficial to one but harmful to harmful to the other. in the beginning. the organisms. and is neither the other. Prey The parasite depends Then beneficial to beneficial nor becomes the food on the host for the one who harmful to the of the predator. nutrition. wins. other. eg: eg: eg: eg: eg:.............................. Mango tree and loranthus........................................................... Mango tree and vanda Illustration 13.5 There are many interactions in nature that we do not see or realise. These interactions maintain the balance and stability of the ecosystems. Food relations are visible instances of interaction among organisms. Basic Science VIII 185  The ecosystem becomes more stable as the diversity of ecological interactions and abiotic factors increases. Diverse ecosystems Observe the pictures given below. Forest Ocean Grassland Tundra Wetland Desert Fig. 13.1 Different types of ecosystems Collect information on the peculiarities of these ecosystems and the organisms found there.With the help of the indicators, discuss and write them down in the science diary. Biodiversity Biodiversity includes all the diverse organisms that inhabit the earth along with their ecosystems. Biodiversity includes various levels like ecosystem diversity, species diversity and genetic diversity. This term which denotes the richness of the biosphere was first used by a British environmentalist, Walter. G. Rosen in 1985. Indicators  Are all ecosystems alike in biodiversity? 186 Basic Science VIII  Are all organisms seen in an ecosystem also seen in another ecosystem?  What is the need for protecting natural ecosystems? Importance of biodiversity What are the benefits of conserving biodiversity? In order to understand it, we must identify the services provided by biodiversity. Observe the illustration given below. On the basis of the illustration, prepare a note on the need for conserving biodiversity. See Jaivavaividhyam Availability of essential innale, innu, nale in materials School Resources in  Food IT @ School, Edubuntu.  Medicine  Fuels  Construction materials Cultural Ecological Services Services  Aesthetics $ Soil formation  Recreation $ Prevention of soil erosion  Study Biodiversity – $ O2 - CO2 balance  Rituals and their practice Services $ Availability of fresh water $ Control of flood $ Climate control $ Auxiliary Services $ Nutrient cycling $ Pollination $ Biological control $ Seed dispersal $ Illustration 13.6 Basic Science VIII 187 Biodiversity depletion Biodiversity in Western What is happening to the biodiversity around us? Ghats under threat Keen observation is necessary to understand it. The Western Ghats, rich in Birds are found everywhere. Birds fall easy victims biodiversity and lying parallel to to changes in the ecosystem. the Arabian Sea, is more than 1500 Let us observe the birds around us to understand kilometre long and 1.25 lakhs the present status of biodiversity. square kilometre wide. This Bird watching is also an interestingly scientific region which is also known by hobby. You can refer to books or internet to identify names like Sahya Mountain or Sahyadri is abundantly rich with unfamiliar birds. Remember to note down the ecosystems such as forests, peculiarities of external features and the nature of grasslands, sacred groves, the birds observed. marshes, rivers and ponds. Very Observe the figure. rare species of the world are found here. This region is rapidly deteriorating due to the thoughtless intervention of human beings. The process of deterioration of ecological diversity in the Western Ghats has been accelerated by agriculture, dams which obstruct the flow of rivers, mining, exploitation of forest wealth, tourism and hunting etc. Fig. 13.2 Different types of birds in Kerala. Our surroundings were once rich with a multitude of birds like these. Has there been any change in the diversity of birds in your locality? What is your finding? Discuss with the help of indicators provided. Indicators  Large scale destruction of ecosystems.  Over exploitation of the natural resources. 188 Basic Science VIII  Excessive use of chemicals in agricultural fields.   No Bird Sings Along with the inferences formulated through discussion, collect relevant supplementary materials and prepare a scientific article. Exhibit it on the wall magazine. Lost links Observe the picture of certain extinct species. Dodo, a The book Silent Spring kind of flightless bird, was common in the island of published in 1962 by an Mauritius. Other species which have become extinct American researcher, Rachel include passenger pigeons which flew in lakhs along Carson attracted attention the North American skies and the Quagga, a wild zebra worldwide because it variety from the southern part of Africa. elaborated on the environmental and health hazards caused by pesticides like DDT. Carson pointed out that birds and other organisms died in large numbers when DDT mixed with petroleum products, affectionately called 'insect bomb', was sprayed widely on agricultural fields. She established with the help Dodo Passenger pigeon of study reports that most pesticides caused cancer. This book was responsible for the ban on DDT in America in 1972. In this age when deadly pesticides are widely used, the ideas put forward by Carson's work are very relevant. Quagga Fig. 13.3  What were the circumstances for the extinction of these organisms?  Do human beings have any role in it? Discuss and write down the inferences in the science diary. Basic Science VIII 189  If not protected, these too...! There are many organisms on the verge of extinction due to several reasons. Some examples are given below. Saraca indica (Ashoka tree) Maramanjal (Tree Turmeric) Red Data Book IUCN (International Union for Conservation of Nature) is an organization for environmental protection, Malabar civet cat Nilgiri Tahr operating in different countries. Under the auspices of IUCN, a list of endangered plants and animals is prepared every year. This is known as the Red Data Book. Some Lion-tailed macaque Malabar hornbill countries prepare Red Fig. 13.4 Data Book on their own. Collect more information about these organisms and write The information in the Red them down in the science diary. Data Book is helpful to identify the extent of Let us preserve diversity biodiversity depletion and Sustainable development is possible only with the protection to plan out appropriate conservation activities. of nature. Analyse the illustration showing a wise approach to biodiversity. Write down your inferences in the science diary. Know Biodiversity Use Protect Illustration 13.7 190 Basic Science VIII There are many national and international organisations and legal systems working for the conservation of biodiversity. The government conserves bio-rich areas declaring them as protected areas. Two types of conservation methods are prevalent. They are: 1. in-situ conservation method in which organisms are protected in their natural habitats and 2. ex-situ conservation method in which organisms are protected outside their natural habitats. Let us familiarise ourselves with some examples of such conservation methods. In-situ conservation Wild Life Sanctuary National Parks These are forest areas declared as National Parks are designed to protect protected areas to prevent the wild lives along with the protection extinction of wild lives by protecting of historical monuments, natural the ecosystem. Peppara, Periyar, resources and geographical features Wayanad etc., are examples of wild of an area. Eravikulam, Silent Valley, life sanctuaries in Kerala. Anamudi Shola, Mathikettan Shola and Pambadum Shola are the national parks in Kerala. Community Reserves Community reserves are areas protected with the participation of the public. These are ecologically important places located in populated areas. The Kadalundi Community Reserve spread over the districts of Malappuram and Kozhikode is an example. Basic Science VIII 191  Biosphere reserves These are vast regions designed with an aim to protect world's important ecosystems, biodiversity and genetic resources. Biosphere reserves like the Nilgiris and Agasthyarkoodam include areas belonging to Kerala too. Sacred groves These are small areas of biodiversity protected in regions inhabited by human beings. Due to Ecological hotspots changes in life style many of these which were Ecological hotspots are areas highly bio-rich have been destroyed. Only a few rich in endemic species but are remaining now. Sacred groves play an facing the threat of habitat important role in the conservation of water in the region too. destruction. Each hotspot is ecologically a very important area of biodiversity. Out of the 34 hotspots all over the world, 3 of them are in India. They are the Western Ghats, North-Eastern Himalayas and the Indo-Burma region. Complete the illustration of in–situ conservation suitably. In-situ conservation Wild life sanctuary National parks Community reserve Biosphere reserve $ Protection of $ $ Conservation with ecosystems $ people's participation $ $ $ $ eg: Wayanad eg:........................... eg:........................... eg: Agasthyarkoodam Illustration 13.8 192 Basic Science VIII  Ex-situ conservation Zoological gardens Zoological gardens are conservation centres where different varieties of animals are protected and housed separately and where necessary arrangements are made available for their reproduction. They also function as conservation centres of organisms which have become extinct in wild. There are zoological gardens at Thiruvananthapuram and Thrissur in Kerala. Botanical gardens These are wide research centres where rare and important plants of diverse species are protected. We can identify many plants and get more information about them by visiting a botanical garden. Jawaharlal Nehru Tropical Botanical Garden and Research Institute (JNTBGRI) at Palode in Thiruvananthapuram and Malabar Botanical Garden (MBG) at Olavanna in Kozhikode are examples. Gene Banks These are research centres with facilities to collect seeds and gametes to preserve them for a long time. Organisms can be recreated out of them whenever required. Rajiv Gandhi Centre for Biotechnology at Thiruvananthapuram is an example. KT-487-2/Basic.Sci. 8(E) Vol-2 Indicators  What is the scope of ex-situ conservation?  What is the significance of gene banks? See 'Vanyajeevisamrakshanam' in School Resources in IT @ School, Edubuntu. Basic Science VIII 193  Many government and non-government organisations design and coordinate environment protection activities. Let us familiarise ourselves with some of the organisations and institutions at the national and international levels. IUCN WWF (International Union for (World Wide Fund for Nature) Conservation of Nature) Biodiversity conservation, prevention of IUCN is a Switzerland based exploitation and pollution of natural independent organisation resources are the objectives of WWF. Its working for the protection of headquarters is also in Switzerland. biodiversity. There are organisations and institutions that work for the protection of nature in our place too. Enquire about them and collect information. What can I do for the protection of nature? $ Plant saplings and nurture them. $ As far as possible, try to get information about forests and environment directly. Share the knowledge gathered. $ Keep the surroundings clean. $ Take part in awareness programmes. $ $ 194 Basic Science VIII  It is our duty to conserve and keep Knowing our forests bioresources for future generations. If we Nature camps are conducted in about 30 do not act with this realization, our centres by the Department of Forest and existence itself will be in danger. Wild life in Kerala. One gets an otherwise impossible opportunity to be part of safari trips into forests in these camps of one to three days duration. You can also participate in these camps by applying to the concerned wild life warden under the auspices of the school Nature Club. Make use of such opportunities to learn about forests closely. Significant learning outcomes The learner can  illustrate trophic levels by including organisms in the ecosystem.  explain how the various ecological interactions influence the existence of ecosystem.  explain what biodiversity is.  find out the causes of biodiversity depletion and suggest remedies.  engage in conservation activities realizing the importance of conservation of biodiversity. Let us assess 1. Phytoplankton – zooplankton - fish - seal - shark a) In which trophic level is the secondary consumer of this food chain included? b) Rewrite the food chain in such a way that the organism in the third trophic level figures in the second trophic level. Basic Science VIII 195 2. Find the odd one out from the following. Justify your answer. a) Quagga, Malabar civet cat, Nilgiri Tahr, Lion-tailed macaque. b) Eravikulam, Mathikettan shola, Periyar, Silent Valley 3. Examine the statements given below and rewrite if there are errors. a) Extinct species are included in the Red Data Book. b) WWF is an organisation working with the objective of protection of biodiversity. c) Gene banks are included in in-situ conservation. Extended activities 1. Identify the plants and animals around you and prepare a local Biodiversity Register. 2. Prepare a science journal by including information, pictures and reports of biodiversity. 3. Prepare and exhibit posters that emphasise the importance of conservation of biodiversity. 196 Basic Science VIII Observe the pictures related to the reproduction of plants. Is the sprouting of sapling from a seed the same as the growth of new plants from leaves? Why? Discuss and write down your inferences in the science diary. There are different modes of reproduction in nature to produce new generation. Some examples are given below. Collect more information about different types of reproduction and write them down in your science diary. Bacteria Fungus Hydra Binary fission Spore formation Budding An existing cell divides to Spores are minute cells that can Buds are formed in the form two new cells. Under survive in unfavourable parent body. When it favourable conditions, rapid conditions and develop into grows, it separates itself multiplication of organisms new organisms under from the parent body and like bacteria take place by favourable conditions. This is a develops into a new binary fission. type of asexual reproduction. organism. Fig. 14.1  Flowers are the sex organs in plants. Collect flowers from the surroundings and observe them with the help of a hand lens. Identify the parts that take part in reproduction and complete the illustration given Pollination and floral below. diversity Pollination is an example for mutualism between plants Flower and animals. More than two Male reproductive part Female reproductive part lakhs of animals help in pollination. Majority of them are insects. Fragrance and style ovary filament colours of flowers are means to attract insects. Now you can guess why flowers pollen grain ovule blooming at night are mostly white in colour and possess intense smell. Besides living male gamete things certain plants depend on wind and water for fertilization pollination. The shapes and nature of flowers differ Illustration 14.1 according to the pollinator. After pollination Most plants have more than one pollinator. But certain Pollination is the transfer of pollen grains to the stigma plants depend on particular of the flowers. What is the change that happens to the organisms for pollination. The pollen grain after fertilization? extinction of these organisms Observe the figure. adversely affects the very existence of such plants as Tube nucleus well. Generative nucleus Pollen tube Before pollination After pollination Fig. 14.2 Let us observe through a simple experiment the growth of the pollen tube from the pollen after pollination. Plan the experiment according to the hints given in the illustration. Prepare a note on the experiment and record it in the science diary. 198 Basic Science VIII Stages of the experiment Stage 1 Stage 2 Stage 3 Collect anthers from any of Place the pollen grains on Observe through a the flowers available in the a glass slide. Add 2 or 3 microscope after 3 to locality. eg: lily, Mexican lilac drops of sugar solution to it. 4 hours. (sheemakonna), hibiscus. Then place a cover glass over it. Illustration 14.2 Did you observe the growth of the pollen tube? On the basis of the indicators, discuss the given notes and figure on fertilization in plants. Note down the inferences in your science diary. Fertilization Pollen grain contains two nuclei such as Pollengrain Stigma generative nucleus and tube nucleus. The pollen tube develops from the pollen grain Tube nucleus that falls on the stigma and grows towards the Generative ovary. Along with this the nuclei in the pollen nucleus also enter the pollen tube. The generative Pollen tube nucleus divides in the pollen tube to form two male gametes and the tube nucleus disintegrates. Ovule One of the male gametes that reaches the ovary Ovary through the pollen tube fuses with the egg to form zygote. The second male gamete fuses Polar nuclei with the polar nuclei in the ovary, and Egg endosperm is formed from it. Zygote develops into embryo and endosperm becomes the stored food needed for the embryo’s growth. Fig. 14.3 Basic Science VIII 199  Indicators  Formation of male gametes.  Formation of embryo.  Formation of endosperm and its function. Reproduction in human beings In higher organisms including human beings specific organ system is developed to produce gametes. Analyse the illustration and notes given below and write the inferences in your science diary. Male Reproductive System Vas deferens: The duct that carries sperms from the testes to the ureter. Prostate gland : Produces secretion that contains the factors required for the nutrition and movement of gametes. Penis: Formed of specialised muscles and blood spaces. Urine and semen come out through the duct (ureter) inside the penis. It helps to deposit sperms in the vagina. Testis : Seen inside the scrotal sac. Produces sperms and male hormones. Illustration 14.3 Sperm Sperm is the male gamete. It is motile and microscopic. The sperm has a head, middle piece and a tail. They move with the help Middle piece Head of the tail. Mitochondria, present in the Tail middle piece, provides the energy for movement. Nucleus that contains paternal Nucleus chromosomes is seen in the head. Sperms are formed inside a pair of testes Mitochondria located in the scrotal sac outside the Fig. 14.4 200 Basic Science VIII abdominal cavity. Testis also produces testosterone, the male sex hormone. Temperature less than the body temperature (35-36oC) is favourable for the formation of sperms. The scrotal sac helps to maintain this temperature. Sperms along with the secretion of glands including the prostate gland reaches the penis and is secreted outside. This process is called insemination. Indicators  Characteristics of sperms.  Location of testes and the production of sperms.  Importance of glands. Female Reproductive System Ovary : Produces ovum and female hormones. Fallopian tube/ oviduct : Carries ovum to the uterus. Fertilization takes place in the fallopian tube. Uterus : Foetus completes its growth in uterus. Endometrium : Inner layer of the uterine wall. Foetus grows by adhering to the endometrial wall. Vagina : Part through which uterus Illustration 14.4 opens out. Sperms are deposited here. Cell membrane Ovum Outer membrane Ovum is the female gamete. It is larger than a sperm. Ovum is non motile. Specialised protective layers are seen outside the cell membrane of the ovum. Nucleus Fig. 14.5 Basic Science VIII 201  A pair of ovaries situated in the abdominal cavity produces ova, and the female sex hormones called estrogen and progesterone. Ovulation is the process of releasing mature ovum from the ovary. Normally one ovum matures per month. Indicators Ovulation  Characteristics of ovum. Fig. 14.6  Function of ovary. Menstruation: a natural You must have now understood the structure and process function of gametes in human beings. Menstruation is a natural Compare the characteristics of sperms and ova and biological process that takes place in girls as part of their complete the given table suitably. physical growth. Menstruation starts early or late, in Characteristics Sperm Ovum accordance with one’s heredity, food habits, state of health or hormone variations. Size Prior to menstruation, mild back pain, pain in lower abdomen, nausea etc., may be Motility experienced. The duration of menstrual cycle may not be the same in every individual. Morphology Generally menstrual cycle repeats once in 28 days. For Table 14.1 the first one or two years, menstrual cycle may be If fertilization fails to occur irregular. If the irregularity continues, medical assistance Along with ovulation, the preparations for the growth should be sought. It is also very of foetus take place in the uterus every month. important to maintain Endometrium, the inner layer of uterus thickens and menstrual hygiene. Menstrual more blood capillaries and glands begin to develop. cycle stops around 45 – 50 But when fertilization does not take place, all these years of age. preparations become futile. The newly formed tissues get destroyed and they peel off from the uterine wall. These tissues get eliminated through the vagina along with blood and mucus. This process is called menstruation. It may last for 3 – 7 days. 202 Basic Science VIII  If fertilization occurs Hormones The ovum released from the ovary reaches the oviduct. Hormones are chemical There it fuses with the sperm and forms the zygote. substances produced in the This process is called fertilization. Though many endocrine glands of the body. sperms reach the oviduct only one sperm fuses with Hormones control and co- the ovum. The single celled zygote undergoes division ordinate various life processes. to become a multicellular embryo. Embryo develops Therefore any variation in the by attaching itself to the endometrium, the inner layer secretion of hormones affects of uterus. the life processes considerably. Continuous cell division Zygote is formed. Ovum fuses with the sperm in the oviduct. Embryo develops by adhering to the uterus Ovulation Illustration 14.5 Illustrate through a flow chart the various stages from ovulation to the beginning of embryonic development in the uterus. Placenta Placenta Uterus Umbilical cord Amnion Amniotic fluid Illustration 14.6 Basic Science VIII 203  Placenta is the part by which the embryo attaches itself to the endometrium and develops. Placenta is composed of foetal tissues and uterine tissues. Oxygen and nutrients reach the foetus through the umbilical cord developed from placenta. Waste materials are also eliminated through the placenta. Placenta helps in the exchange of materials between the mother and the foetus without mixing their blood. The growth of the foetus completes within the amnion, the membraneous covering formed from the embryonic cells during the initial stages of growth. The amniotic fluid within this covering prevents dehydration of the foetus and protects it from shocks. Parturition The gestation period of human beings is about 270 – 280 days. During this period , the foetus completes its growth through gradual changes and the fully grown baby comes out through the vagina. This process is called parturition. The growth of foetus and the birth of the baby are complex processes. Only a woman with physical and mental maturity can accept these changes and give birth to a healthy baby. Fig. 14.7 Complete the given table suitably. -Part Function Endometrium Uterus Placenta Umbilical cord Amnion Table 14.2 Observe the illustration showing the different stages of growth in human beings. Infancy Childhood Adolescence Adulthood Old age Illustration 14.7 Of these, what stage do you belong to? Read the description given below and identify the characteristics of your stage of growth. 204 Basic Science VIII Adolescence – a special phase in life Adolescence is a period of biological significance. This is a period of rapid changes from childhood to adulthood. According to the statistics of World Health Organisation (WHO), the adolescence period is from 11 to 19 years. This is a period from the onset of puberty to the completion of physical growth. Puberty relates to the physical changes that occur in individuals, thereby making them capable of reproduction. In each individual, the adolescence begins with physical changes. Development of brain, rapid increase in height and weight and increased efficiency of glands are the significant features of this period. Changes related to adolescence are more rapid in girls than in boys. This is because the parts of brain that control physical and mental changes develop rapidly in girls. Along with the rapid physical changes, intense mental and emotional changes make adolescence a significant period in one's life. Analyse on the basis of indicators the major physical changes given below. Write down your inferences in the science diary. Physical changes in adolescence In boys In girls Fast growth. Fast growth. Growth of sex organs Growth of sex organs gains momentum. gains momentum. Hair grows in various Hair grows in the pubic region and parts of the body. the armpits. (pubic region, armpits, face, chest) Pitch of the voice deepens. Pitch of the voice becomes sharp. Glands in the skin become more Glands in the skin become more active, active. breast develops. Shoulder bones expand. Hip bones widen. Ejaculation starts. Menstruation starts. Basic Science VIII 205  Indicators  What is adolescence?  How does adolescence influence the physical and mental development of an individual?  Why is the rate of adolescence growth higher in girls Anaemia-causes and than in boys? remedies  Is there any need to be anxious about the physical Anaemia is a condition changes during adolescence? Why? caused either by reduction in Adolescence and food the number of red blood corpuscles in blood or by the Proper nutrition is necessary for rapid growth. Do you deficiency of haemoglobin, follow food habits that ensure the availability of nutrients? the pigment in red blood Read the newspaper report given below. corpuscles. When anaemic, blood loses its capacity to New Delhi: In India 56% of adolescent girls and 30% carry oxygen, and the person of adolescent boys suffer from chronic anaemia due feels weak and exhausted. It to the deficiency of iron. To prevent this the Ministry also causes loss of memory of Health has launched a project to supply iron and concentration as tablets to 13 crores of students coming under the anaemia affects brain’s efficiency. age group of 10 – 19 years. Deficiency of iron in the body Source: http://unicef.in/Whatwedo/33/Adolescents-Nutrition is one of the causes of anaemia. It can be remedied  What is the circumstance that led to the supply of iron- by including iron rich food folic acid tablets to students? items in the diet. Though iron  What is the role of food habits to overcome this tablets may be used as an situation? immediate solution, it is  How should the food habits be regularised so as to advisable to ensure the availability of nutrients ensure the availability of nutrients for the rapid growth through regularisation of of body in adolescence? food habits. Discuss. Food – Certain tips to follow  Breakfast is very important. Do not skip it during busy schedule.  Have right quantity of food at the right time.  Choose a diet that includes fruits, vegetables and pulses.  Reduce the intake of fried food items. 206 Basic Science VIII  Use sugar and salt in limited quantities.  Do not be habituated to bottled drinks, packet food and fast foods.  Remember that chocolate, sweets and ice creams are not good for health.  Keep in mind that excessive likes and dislikes of food items will adversely affect health.  Develop the habit of using seasonal leafy vegetables and fruits available in the locality. Adolescence and the concept of beauty The heroic images created by the media with commercial interests influence the Adolescence – A period of challenges adolescent minds very Rapid changes in the development of the brain and in the quickly. Adolescents are very production of hormones during adolescence cause mental conscious about their body. They mistake external and emotional disturbances. The adolescent loses the appearances for personality. consideration and freedom of a child which he/she used to This makes them use enjoy. At the same time, he/she does not get recognition as synthetic cosmetics, change an adult either. It causes identity crisis. A lack of awareness their food habits and follow about one’s own personality during this period leads to unscientific exercises. It may immature decision making. As a result an adolescent may cause severe health fall prey to evil influences such as imitation tendency, bad problems.The eating disorder friendship and bad habits, misuse of mobile phones and known as anorexia, is an internet etc. It is essential to overcome these challenges example. Regular skipping of and keep away from exploitations and temptations.In short, food with an intention to your ability to say ‘No’ to whoever approaches you with make the body slim may cause an aversion to food wrong intentions will protect you from dangers. which is called anorexia. Basic Science VIII 207  Addictive habits 3.3 million lives are lost due to alcoholism every year. Smoking kills nearly 6 million people every year all over the world. ath of causes the de Use of drugs every year. 2 lakhs Path to destruction Did you observe the headlines? Tobacco contains more than These are bad habits we become addicted to. Used seven thousand chemicals such initially out of curiosity or under the influence of as nicotine, benzene etc. About friends, they subdue us psychologically and we 70 of these chemicals are cannot escape even if we desire to do so. carcinogens. Smoking reduces the diameter of blood capillaries Organise an awareness programme against such bad and prevents the diffusion of habits, under the auspices of the School Health Club. oxygen into the tissues. Smoking and the use of tobacco products are the main causes of cancer in the mouth, lungs, throat, In front of the oesophagus etc. Collect computer Everybody says that information regarding the health I forget everything. recklessness is dangerous. and social issues caused by I am not able to But I like being smoking, alcoholism, drug concentrate on my adventurous. addiction etc. Record them in studies. your science diary. Illustration 14.8 Did you notice the illustration? Extreme rashness and misuse of mobile phones and computers are dangerous bad habits, aren’t they? Which are the other similar problems faced by adolescents? How can we overcome such problems? Discuss. 208 Basic Science VIII Need for assertiveness If we can say an emphatic 'No' at the right time, we can avoid many dangers.  What is your response towards this statement?  Can you cite such instances?  How will you respond if such instances occur in your life? Discuss. Helping Hands Service of a nurse Health Club Medical Camp Service of a counsellor Illustration 14.9 Are such facilities available in schools? How can we make use of these facilities? Discuss. Basic Science VIII 209  HEALTH CLUB Health Awareness Class Personality development Adolescent Health Issues. Programmes Paper Presentation: Dr. Priyamvada We have around us a lot of possibilities for personality development. Participate in Venue: School Auditorium collective efforts in and outside the All are welcome school that help us nurture our talents and also develop and promote service Such programmes can be conducted in your school mentality, leadership and discipline. too. Develop and grow as impressive What all topics may be discussed in such a personalities. programme? List out your suggestions. $ $ Put your doubts in the question box and give it to the resource person who leads the class. It will make the class more effective. Write a report of the programme in your science diary. Adolescence – A period of possibilities Self esteem Idealism Decisions Friendship Hopes We have around us many possibilities to develop as good individuals by overcoming challenges. We can create a better tomorrow if we judiciously make use of today’s possibilities. 210 Basic Science VIII  Significant learning outcomes The learner can  identify and explain different stages of sexual reproduction in plants.  identify the parts of human reproductive system and explain their functions.  explain the reasons for the changes in adolescence and interact with one another without anxiety.  follow good food habits by realising the importance of nutritious food.  explain the consequence of bad habits and follow good habits.  make use of the various possibilities to overcome health and mental issues of adolescence. Let us assess 1. Which of the following activities takes place after fertilization in plants? A. Pollen tube grows B. Egg is formed in the ovary C. Ovule becomes the seed D. Male gametes are formed 2. Which part helps in the transportation of materials without mixing maternal and foetal blood? A. Endometrium B. Uterus C. Placenta D. Amnion 3. Sequentially arrange the process that takes place after pollination in plants.  Embryo is formed  Pollen tube grows  Fertilization takes place  Male gametes are formed  Zygote is formed  Generative nucleus divides. Basic Science VIII 211 4. Substantiate the statement: “Excessive likes and dislikes of food materials adversely affects the health”. 5. Home hygiene and social hygiene are as important as personal hygiene for health. Do you agree with this opinion of the doctor who led an awareness class on health? Why? 6. “Adolescence is full of challenges and possibilities”. a. What are the challenges faced by adolescents? b. What are your suggestions to overcome these challenges? 7. It is easy to be addicted to drugs. But to escape from it, is not that easy. a. What should be our approach towards drugs? b. What are the harmful effects of drugs? Extended activities 1. Organise an awareness programme about the existing legal aids to protect children from exploitations. 2. Biological sexual differences is a necessity for the continuity of generations. But should there be boy-girl discrimination in society? Conduct a debate on gender discrimination. 212 Basic Science VIII  The figure shows different types of solutions. There are many instances where solutions are made use of. Some solutions are given in the table below. Identify the states of the solute and the solvent in each of them and complete the table. Solution - State of State of State of the Constituents the solute the solvent solution Brass Solid Solid.......... (Zinc + Copper) Salt Solution.................... Liquid (Salt + water) Soda water (Carbon dioxide + water) Gaseous.................... Mixture of alcohol and water Liquid.................... Table 15.1 Basic Science VIII 213  Is there any relation between the state of the solution and that of the solvent? In most of the cases, the physical states of the solvent and the solution are the same. How do we decide the solvent and the solute in a solution? Normally, the constituent present in smaller amount is considered as the solute and the constituent present in larger amount is considered the solvent. In aqueous solutions, water is always the solvent irrespective of its amount. Let us examine some properties of solutions. Concentration of solution Take equal amounts of water in two glass tumblers. Add one or two crystals of potassium permanganate in the first tumbler and four or five crystals in the second and stir. Expressing Concentration Observe the difference in the colour of the Concentration of solutions can be solutions in the two tumblers. expressed in different ways. What is the reason for the difference in the Mass percentage