Science and Technology Standard Ten Part 2 PDF (Maharashtra 2021)

Permission is granted for enforcing this textbook from the academic year 2018-19 in the meeting, held on the date 29.12.2017, of the co-ordination committee constituted by the Government resolution No: Abhyas-2116/(Pra.kra.43/16) S.D-4 dated 25.4.2016 SCIENCE AND...

Permission is granted for enforcing this textbook from the academic year 2018-19 in the meeting, held on the date 29.12.2017, of the co-ordination committee constituted by the Government resolution No: Abhyas-2116/(Pra.kra.43/16) S.D-4 dated 25.4.2016 SCIENCE AND TECHNOLOGY STANDARD TEN PART – 2 Maharashtra State Bureau of Textbook Production and Curriculum Research, Pune. The digital textbook can be obtained through DIKSHA App on a smartphone by using the Q.R Code given on title page of the textbook and useful audio-visual teaching-learning material of the relevant lesson will be available through the Q.R Code given in each lesson of this textbook. A First Edition : 2018 © Maharashtra State Bureau of Textbook Production and Reprint : 2021 Curriculum Research, Pune - 400 004. The Maharashtra State Bureau of Textbook Production and Curriculum Research reserves all rights relating to the book. No part of this book should be reproduced without the written permission of the Director Maharashtra State Bureau of Textbook Production and Curriculum Research,'Balbharati', Senapati Bapat Marg. Pune 411 004 Science Subject Committee: Science Study Group : Dr. Chandrashekhar Vasantrao Murumkar, Chairman Dr. Prabhakar Nagnath Kshirsagar Dr. Vishnu Vaze Dr. Dilip Sadashiv Joag, Member Dr. Prachi Rahul Choudhary Dr. Sushama Dilip Joag, Member Dr. Shaikh Mahommed Waquioddim H. Dr. Pushpa Khare, Member Dr. Ajay Digambar Mahajan Dr. Gayatri Gorakhnath Choukade Dr. Imtiaz Sirajuddin Mulla, Member Shri. Prashant Panditrao Kolse Dr. Jaydeep Vinayak Sali, Member Shri. Sandip Popatlal Chordiya Shri. Sachin Ashok Bartakke Dr. Abhay Jere, Member Smt. Shweta Dilip Thakur Dr. Sulabha Nitin Vidhate, Member Shri. Rupesh Dinkar Thakur Smt. Mrinalini Desai, Member Shri. Dayashankar Vishnu Vaidya Shri. Sukumar Shrenik Navale Shri. Gajanan Shivajirao Suryawanshi, Member Shri. Gajanan Nagoraoji Mankar Shir. Sudhir Yadavrao Kamble, Member Shri. Mohommed Atique Abdul Shaikh Smt. Dipali Dhananjay Bhale, Member Smt. Anjali Lakshmikant Khadke Smt. Manisha Rajendra Dahivelkar Shir. Rajiv Arun Patole, Member Secretary Smt. Jyoti Medpilwar Smt. Dipti Chandansingh Bisht Cover and Illustrations: Smt. Pushpalata Gawande Shri. Vivekanand Shivshankar Patil Smt. Anita Patil Smt. Kanchan Rajendra Sorate Ashana Advani Shri. Rajesh Vamanrao Roman Typesetting : Shri. Nagesh Bhimsevak Telgote DTP Section, Textbook Bureau, Pune Shri. Shankar Bhikan Rajput Shri. Manoj Rahangdale Shri. Hemant Achyut Lagvankar Coordination: Smt. Jyoti Damodar Karane Rajiv Arun Patole Shri. Vishwas Bhave Special Officer for Science Paper Translation : Dr. Jaydeep Vinayak Sali 70 GSM Creamwove Shri. Sandip Popatlal Chordiya Print Order : Scrutiny : Dr. Chandrashekhar V. Murumkar Printer : Dr. Pushpa Khare Production : Publisher : Shri. Sachchitanand Aphale Shri. Vivek Uttam Gosavi Chief Production Officer Controller Shri. Rajendra Vispute Maharashtra State Textbook Bureau, Production Officer Prabhadevi, Mumbai - 400 025 B C NATIONA ANT D  Preface Dear students Welcome to Std X. We have great pleasure in offering you this Science and Technology textbook based on the new syllabus. From the primary level till today, you have studied science from various textbooks. In this textbook, you will be able to study the fundamental concepts of science and technology from a different point of view through the medium of the different branches of Science. The basic purpose of this textbook Science and Technology Part-2 can be said to be ‘Understand and explain to others’ the Science and Technology that relates to our everyday life. While studying the concepts, principles and theories in science, do make the effort to understand their connection with day to day affairs. While studying from this textbook, use the sections ‘Can you recall?’ and ‘Can you tell?’ for revision. You will learn science through the many activities given under the titles such as ‘Observe and discuss.’ and ‘Try this’ or ‘Let’s try this. Make sure that you perform all these activities. Activities like ‘Use your brain power!’, ‘Research’, ‘Think about it’ will stimulate your power of thinking. Many experiments have been included in the textbook. Carry out these experiments yourself, following the given procedure and making your own observations. Ask your teachers, parents or classmates for help whenever you need it, interesting information, which reveals the science underlying the events we commonly observe and the technology developed on its basis, has been given in details in this textbook through several activities. In this world of rapidly developing technology, you have already become familiar with computers and smartphones. While studying the textbook, make full and proper use of the devices of information communication technology, which will make your studies easier. For more effective studies, you can avail additional audio-visual material for each chapter using the Q.R code through an App. This will definitely help you in your studies. While carrying out the given activities and experiments, take all precautions with regard to handling apparatus, chemicals, etc. and encourage others to take the same precautions. It is expected that while carrying out activities or observation involving plants and animals, you will also make efforts towards conservation of the environment. You must of course take all the care to avoid causing any harm or injury to them. Do tell us about the parts that you like, as well as about the difficulties that you face as you read and study and understand this textbook. Our west wishes for your academic progress. (Dr. Sunil Magar) Pune Director Date: 18 March 2018, Gudhipadva Maharashtra State Bureau of Textbook Indian Solar Year : 27 phalgun 1939 and Curriculum Research, Pune E  For Teachers The real objective of science education is to learn to be able to think about events that are happening around us, logically and with discretion. In view of the age group of Std X students, it would be appropriate now, in the process of science education, to give freedom and scope to students’ own curiosity about the events of the world, their propensity to go looking for the causes behind them and to their own initiative and capacity to take the lead. As experimentation is necessary to learn the skills of observation, logic, estimation, comparison and application of available data, which form a part of science education, deliberate efforts must be made to develop these skills while dealing with laboratory experiments give in the textbook. All observations that the students have noted should be accepted and then they should be helped to achieve that the expected results. These two years in middle school lay the foundation of higher education in Science. Hence, it is our duty and responsibility to enrich and enhance the student’s interest in science. You all will of course always actively pursue the objective of developing their creativity and imbuing them with a scientific temper. You can use ‘Let’s recall’ to review the previous knowledge for a lesson and ‘Can you tell?’ to introduce a topic by eliciting all the knowledge that the students already have about it from their own reading or experience. You may of course use any of your own activities or questions for this purpose. Activities given under ‘Try this’ and ‘Let’s try this’ help to explain the content of the lesson. The former are for students to do themselves and the latter are those that you are expected to demonstrate. ‘Use your brain power!’ is meant for application of previous knowledge as well as the new lesson, and ‘Always remember’ gives important suggestions/information or values. ‘Research’, ‘Find out’, ‘Do you know?’ ‘ Introduction to scientists’ and ‘Institutes at work’ are meant to give some information about the world outside the textbook and to develop the habit of doing independent reference work to obtain additional information. This textbook is not meant for reading and explaining in the classroom but guiding students to learn the methods of gaining knowledge by carrying out the given activities. An informal atmosphere in the classroom is required to achieve the aims of this textbook. All students should be encouraged to participate in discussions, experiments and activities. Special efforts should be made to organize presentations or report-reading in the class based on students activities and projects, besides observing of Science Day and other relevant occasions/days. The science and technology content of the textbook has been complemented with Information Communication Technology. These activities are to be conducted under your guidance along with the learning of various new scientific concepts. Front and back covers : Pictures of various activities, experiments and concepts in the book. DISCLAIMER Note : All attempts have been made to contact copy righters (©) but we have not heard from them. We will be pleased to acknowledge the copy right holder (s) in our next edition if we learn from them. F  Competency Statements Std X The students are expected to achieve the following competency level after studying the text book Science and Technology II The Living World. * To analyze the scientific information about heredity and state opinions about new hybrid species. * To understand evolution theories or living and state there characteristics. * To explain reproductive systems of plants and animals. * To state importance of cell science by collection of information of cell on utility and various medical facilities. * To understand production processes of various biotic factors by experiments and prove them scientifically. * To collect and analyze useful data by observing diversity of animals through different tools. * To describe animals in the surroundings on scientific basis and classify them. * To develop awareness of hobbies like watching the things and their conservation. * To present documentary on animals. * To collect useful and scientific information on human reproductive system and explain effects on society. * To eradicate superstitions and rigid customs prevailing in society. Natural resources and disaster management * To explain role of environmental guard by conservation of environment, various laws and rules. * To adapt scientific life style in the role of environmental guard. * Get attention of society towards negligence towards conservation of environment. * To plan and implement programs about conservation of environment. * To play self-role in disaster management considering international understanding, help and togetherness. Diet and Nutrition * To set up the experiments, projects in our environment in small scale considering advantages and disadvantages of Biotechnology. * To aware farmers and components of society by various graphs of Biotechnology. * To take feedback of comparative study of progress of Biotechnology in India and the other countries. * To find out various problems regarding conservation of ecosystems. * To collect data on conservation of ecosystem and to take a distinct role to awake the society. * To change one’s lifestyle by taking into account the various aspects and effects which endanger social health. * To spread the roles of government and non-government organizations to nurture social health. Energy * By considering the serious consequences of the energy crisis, adopt proper lifestyle and motivating others to decide their lifestyle accordingly. * Explain the steps involved in the process of generation of electrical energy. * To analyze the correlation of electricity generation processes and environment. * Knows the importance of green energy and saves energy in daily life. Information Communication Technology. * Use of Information Communication Technology in daily life. * Exchange of knowledge about science and Technology with the help of internet. * Awareness about the proper use of information communication technology. * Based on the information gathering, with various types of information related to Science and Technology. To predict it. Ability of prediction on the basis of science and technology data collected from internet. * To understand dangers (cybercrimes) while using information communication technology and take precautions against them. * Effective use of various systems developed through information communication technology in daily life. G  CONTENT No. Chapter Page No. 1. Heredity and Evolution 1 2. Life Processes in Living Organisms Part -1 12 3. Life Processes in Living Organisms Part - 2 22 4. Environmental management 36 5. Towards Green Energy 47 6. Animal Classification 61 7. Introduction to Microbiology 77 8. Cell Biology and Biotechnology 88 9. Social health 101 10. Disaster Management 109 Academic Planning Two separate books have been prepared for science and technology. Science and technology part 2 contains ten chapters mainly related to Biology, Environment, Microbiology, Biotechnology. While thinking about science and technology, it is expected that an integrated approach will be taken while teaching and a connection will be made between different components of science and technology. In previous standards, we have studied various topics in science and technology together. For technical ease two separate books of science and technology part 1 and part 2 have been prepared, but it is necessary that an integrated perspective be taken while teaching. Out of the ten chapters included in textbook science and technology part 2, the first five chapters are expected to be taught in the first session while the next five chapters in the second session. At the end of a session, a written examination for 40 marks and a practical examination for ten marks should be conducted. Exercises and projects have been given at the end of every chapter in the text book. In view of evaluation, representative questions similar to those in the activity sheets of language books are given in exercises. You may make similar other questions for your use. The students should be evaluated based on these questions. Detailed information about this will be given in separate evaluation scheme. H  1. Heredity and Evolution Ø Heredity and Hereditary Changes Ø Transcription, Translation & Translocation Ø Evolution Ø Evidences of Evolution Ø Darwin’s Theory of Natural Selection Ø Lamarckism Ø Speciation Ø Human Evolution 1. Which component of the cellular nucleus of living organisms Can you recall? carries hereditary characters? 2. What do we call to the process of transfer of physical and mental characters from parents to the progeny? 3. Which are the components the DNA molecule? Heredity and hereditary changes You know that heredity is the transfer of biological characters from one generation to another via genes. Gregor Johann Mendel is pioneer of the modern genetics. It took a long time to understand the conclusions of his research about heredity. In 1901, the reasons behind the sudden changes were understood due to the mutational theory of Hugo de Vries. Meanwhile in 1902, Walter Sutton observed the paired chromosomes in the cells of grasshopper; until then it was not known to anyone. Research started in the direction of finding the nature of genetic material when it was proved that genes are carried via chromosomes. Through which 1944, trio of scientists Oswald Avery, Mclyn McCarty and Colin McLeod proved that except viruses, all living organisms have DNA as genetic material. In 1961, the French geneticists Francois Jacob and Jack Monod proposed a model for process of protein synthesis with the help of DNA in bacterial cells. It helped to uncover the genetic codes hidden in DNA. Thereby, the technique of recombinant DNA technology emerged which has vast scope in the field of genetic engineering. The science of heredity is useful for diagnosis, treatment and prevention of hereditary disorders, production of hybrid varieties of animals and plants and in industrial processes in which microbes are used. Transcription, Translation and Translocation 1. Sketch and explain the structure of DNA and various types of RNA. Can you tell? 2. Explain the meaning of genetic disorders and give names of some disorders. With the help of RNA, the genes present in the form of DNA participate in the functioning of cell and thereby control the structure and functioning of the body. Information about protein synthesis is stored in the DNA and synthesis of appropriate proteins as per requirement is necessary for body. These proteins are synthesized by DNA through the RNA. This is called as ‘Central Dogma’. mRNA is produced as per the sequence of nucleotides on DNA. Only one of the two strands of DNA is used in this process. The sequence of nucleotides in mRNA being produced is always complementary to the DNA strand used for synthesis. Besides, there is uracil in RNA instead of thymine of DNA. This process of RNA synthesis is called as ‘transcription’. 1  ` The mRNA formed in nucleus comes in RNA Polymerase RNA Nucleotides cytoplasm. It brings in the coded message from DNA. The message contains the codes for amino acids. The code for each amino acid consists of three nucleotides. It is called as ‘triplet codon’. Dr Har Govind Khorana, a scientist of Transcription Indian origin has made an important contribution in discovery of triplet codons for 20 amino acids. For this work, he has 1.1 Transcription been awarded with the Nobel Prize in 1968, along with two other scientists. Nucleus Each mRNA is made up of thousands of triplet codons. As per the message on mRNA, amino acids are supplied by the tRNA. For this purpose, tRNA has ‘anticodon’ having tRNA mRNA complementary sequence to the codon on Amino Acid mRNA. This is called as ‘translation’. The Ribosome amino acids brought in by tRNA are bonded together by peptide bonds with the help of rRNA. During this process, the ribosome mRNA Codon keeps on moving from one end of mRNA to other end by the distance of one triplet codon. 1.2 Translation & Translocation This is called as ‘translocation’. Such many chains come together to form complex proteins. These proteins control various Main Sequence functions in the body of living organisms and their appearance too. Living organisms can produce new individuals like themselves due to genes Replacement only and some of those genes are transmitted to the next generation without any changes. Due to this, some of the characters of parents are transmitted to their offsprings. However, sometimes sudden changes occur in those genes. Sometimes, any nucleotide of the 1.3 Mutation gene changes its position that causes a minor change which is nothing but the ‘mutation’. Some mutations may be minor but some may be considerable. Ex. Mutation may cause the genetic disorders like sickle cell anaemia. 2  1. What is the function of the appendix of our digestive system? Can you recall? 2. Are our wisdom teeth really useful for chewing the food? 3. Why did the huge animals like dinosaur become extinct? Evolution 4. Why are many species of animals and birds getting extinct? Evolution is the gradual change occurring in living organisms over a long duration. This is a very slow-going process through which development of organisms is achieved. All the stages in changes occurred in various components ranging from stars and planets in space to the biosphere present on the Earth should be included in the study of evolution. Formation of new species due to changes in specific characters of several generations of living organisms as a response to natural selection, is called as evolution. 3.5 billion years ago, life had been non Internet is my friend existent on the Earth. At the beginning, there may have been only simple elements in the Collect the information from internet ocean on the Earth and simple type of organic about Big-Bang theory related with the and inorganic compounds may have been formation of stars and planets and present it formed from those. Complex compounds like in your class. proteins and nucleic acids may have formed over the long period from those simple A peek into History compounds. First primitive type of cells may Many philosophers and religious scholars have been formed from the mixture of different have written their views about formation of types of organic and inorganic compounds. life. There seems to be a thorough discussion Number of those cells may have increased at over the formation of Universe, in various the cost of surrounding chemicals. There may cultures like Indian, Chinese, Roman, had been some differences among those cells Greek, etc. Various cultures have noted and according to the principle of natural different type of information about planets, selection, some may have shown good growth stars, the ‘panchmahabhuta’, living and some may have perished which could not organisms, etc. in the form of poetry, stories adjust with the surrounding. and religious / sacred books. At present, crores of species of plants and animals with huge diversity regarding shape Theory of Evolution: and complexity are present on the Earth. According to this theory, first living material Animal diversity ranges from the unicellular (protoplasm) has been formed in ocean. In Amoeba and Paramecium to man and giant due course of time, unicellular organism was whale. The plant diversity consists of various formed. Gradually, changes occurred in the species ranging from unicellular Chlorella to unicellular organisms from which larger and the huge banyan tree. The life exists on Earth more complex organisms were formed. All everywhere from equator to both the poles. those changes were slow and gradual. Duration Organisms are present at all the places like of all these changes is at most 300 crore years. air, water, land, rock, etc. Humans have Changes and development in living organisms shown curiosity about origin of life and had been all round and multi-dimensional reasons for such a great diversity in life and this led to evolution of different types present on the Earth since ancient period. of organisms. Hence, this overall process is Different theories about origin and evolution called as evolution which is organizational. of life have been proposed till today of which Progressive development of plants and animals theory of 'Gradual development of living from the ancestors having different structural organisms is accepted. and functional organization is called evolution. 3 Evidences of evolution Collective thinking upon all above mentioned theories implies that evolution is everlasting process of changes. However, it needs proof to prove it. Following are various proofs available in support of the theories mentioned above. 1. Morphological Evidences Observe the following images and note the similarities between given Try this animal images and plant images. Various similarities like structure of mouth, position of eyes, structure of nostrils and ear pinnae and thickly distributed hairs on body are seen in animals whereas similarities in characters like leaf shape, leaf venation, leaf petiole, etc. occur in case of plants. This indicates that there are some similarities in those groups and hence it proves that their origin must be same and 1.4 Morphological evidences must have common ancestors 2. Anatomical Evidences If you carefully observe the pictures, there doesn’t seem any superficial similarity between human hand, foreleg of ox, flipper of whale and patagium of bat. Similarly, use of each of those structures is different in respective animals. However, there is similarity in structure of bones and joints in organs of each of those Human foreleg Patagium Flipper animals. This similarity indicates that hand of ox of Bat of Whale those animals may have common 1.5 Structure of bones ancestor. Can you tell? 1. Which are the different organs in body of organisms? 2. Is each of the organs useful to organism? Use of ICT : Collect the information of geological dating and Present it classroom. 4 3. Vestigial Organs Degenerated or underdeveloped useless organs of organisms are called as vestigial organs. In living organisms, sudden development of new tissues or organs for living in changing environment is not possible. Instead, existing organs undergo gradual changes. Mostly, a specific structure in the body is useful under certain situation. However, same structure under different situation may become useless or even harmful. Such structure begins to degenerate under such situation as per the principle of natural selection. It takes thousands of years for a structure to disappear. Such organs are seen in different phases of disappearance in different animals. Such organ, though non-functional in certain organisms, it may be functional in other organisms i.e. it is not vestigial in other organisms. Appendix, which is useless to human, is useful and Small fully functional organ in ruminants. Similarly, muscles of Intestine ear pinna, which are useless to human, are useful in monkeys for movement of ear pinna. Various vestigial organs like tail-bone (coccyx), wisdom teeth, and body hairs are present in body of human being. Large Intestine Appendix Ear muscles Wisdom teeth Tail bone (Coccyx) 1.6 Vestigial organs Observe and discuss. Observe the following pictures. Use of ICT Find how the vestigial organs in certain animals are functional in others. Present the information in your class and send it to others. 1.7 Some fossils 4. Palaeontological Evidences A question may arise in your mind that which organisms existed millions of years ago? How can we tell this? Now this secret has been hidden in the Earth. Large number of organisms get buried due to disasters like flood, earthquake, volcano, etc. Remnants and impressions of such organisms remain preserved underground. These are called as fossils. Study of fossils is an important aspect of study of evolution. 5  Carbon consumption of animals and plants stops after death and since then, only the decaying process of C-14 occurs continuously. In case of dead bodies of plants and animals, instead of remaining constant, the ratio between C-14 and C-12 changes continuously as C-12 is non-radioactive. The time passed since the death of a plant or animal can be calculated by measuring the radioactivity of C-14 and ratio of C-14 to C-12 present in their body. This is ‘carbon dating’ method. It is used in palaeontology and anthropology for determining the age of human fossils and manuscripts. Once the age of fossil been determined by such technique, it becomes easy to deduce the information about other erstwhile organisms. It seems that vertebrates have been slowly originated from invertebrates. Aves Introduction to Scientists (Birds) Cenozoic Carbon dating method Mammals era is based upon the radioactive decay of Mesozoic naturally occurring C-14 Reptiles and it is developed by era Willard Libby. He has been awarded Amphibia with Nobel Prize (1960) Pisces for this invention. The age Palaeozoic of the materials determined era by this method are published in the journal Invertebrates ‘Radio Carbon’ 1.8 Sedimentary rocks and fossils 5. Connecting Links Observe and discuss. Observe the following pictures and discuss the characters observed. Duckbill Platypus Lungfish Peripatus 1.9 Some animals with special characteristics 6  Some plants and animals show some morphological characters by which they can be related to two different groups; hence they are called as ‘connecting links’. Ex. In Peripatus, characters like segmented body, thin cuticle, and parapodia-like organs are present. Similarly, these animals show tracheal respiration and open circulatory system similar to arthropods. This indicates that Peripatus is connecting link between annelida and arthropoda. Similarly, duck billed platypus lays eggs like reptiles but shows relationship with mammals too due to presence of mammary glands and hairs. Lung fish performs respiration with lungs irrespective of being fish. These examples indicate that mammals are evolved from reptiles and amphibians from fishes. Observe and discuss. I Carefully observe the stages of embryonic development of some animals shown in fig. 1.10 6. Embryological Evidences: II Comparative study of embryonic developmental stages of various vertebrates given in the picture shows that all embryos show extreme III similarities during initial stages and those similarities decrease gradually. Similarities in initial Fish Salamander Tortoise Chicken Pig Cow Rabbit Man stages indicate the common origin of all these animals. 1.10 Embryos during different stages Darwin’s theory of natural selection Charles Darwin had collected innumerable specimens of plants and animals and depending upon the observations of those specimens; he published the theory of natural selection which preaches the survival of fittest. For this purpose, Darwin had published a book titled ‘Origin of Species’. While explaining the concept, Darwin says that all the organisms reproduce prolifically. All the organisms compete with each other in a life- -threatening manner. In this competition, only those organisms sustain which show the modifications essential for winning the competition. However, besides this, natural selection also plays important role because nature selects only those organisms which are fit to live and the rest perish. Sustaining and selected organisms can perform reproduction and thereby give rise to the new species with their own specific characters. Darwin’s theory of natural selection was widely accepted for long duration. However, some objections were raised against the theory. Some of the main objections are- 1. Natural selection is not the only factor responsible for evolution. 2. Darwin did not mention any explanation about useful and useless modifications. 3. There is no explanation about slow changes and abrupt changes. Irrespective of all these objections, Darwin’s work on evolution has been a milestone. 7  Introduction to Scientists Charles Robert Darwin (1809-1882) This English biologist proposed the theory of evolution. He showed that all the species of living organisms have been gradually evolved over the period of thousands of years from common ancestor. He proposed that principle of natural selection is responsible for this evolution. Lamarckism Jean-Baptiste Lamarck proposed that morphological changes occurring in living organisms are responsible for evolution and the reason behind those morphological changes is activities or laziness of that organism. He called this concept as principle of ‘use or disuse of organs’. Further, he said that the neck of giraffe has become Introduction to Scientists too long due to browsing on leaves of tall plants by extending their neck for several generations; similarly, shoulders of the ironsmith have become very strong due to frequent hammering movements. Wings of birds like ostrich and emu have become weak due to no use. Legs of the birds like swan and duck have become useful for swimming due to living in water and snakes have lost their legs by modifications in their body for burrowing habit. All these examples are types of ‘acquired characters’ and are transferred from one to another generation. This is Jean-Baptiste Lamarck (1744-1829) called as theory of inheritance of acquired characters or Lamarckism. Lamarck proposed that the activities of the organisms are responsible for their evolution. This French naturalist proposed that each animal or plant undergo some changes in its life span and those changes are transferred to the next generation and 1.11 Giraffe such changes occur in next Development of organs due to specific activities or their subsequent generations too. degeneration due to no use at all was widely accepted but transfer of those characters from generation to generation was rejected. Because it had been verified many times Internet is my friend that modifications brought in us are not transferred to next generation and thereby Lamarck’s theory was disproved. Collect the pictures and information of various The living organism can transfer the characters which it species of monkeys from has acquired, to the next generation. This is called ancestry of internet. acquired characters. 8 Speciation Formation of new species of plants and animals is the effect of evolution. Species is the group of organisms that can produce fertile individuals through natural reproduction. Each species grows in specific geographical conditions. Their food, habitat, reproductive ability and period is different. However, genetic variation is responsible for formation of new species from earlier one. Besides, geographical and reproductive changes are also responsible. Similarly, geographical or reproductive isolation also leads to speciation Human Evolution The biodiversity that is known today has been said to be formed from very simple unicellular organism due to evolution. In this evolution, origin of human evolution can be shown as per the picture given below. Last dinosaurs disappeared approximately seven crore years ago. At that time, monkey-like animals are said to be evolved from some ancestors who were more or less similar to the modern lemurs. Tail of these monkey-like animals of Africa is said to be disappeared about 4 crore years ago. They developed due to enlargement in brain their hands were also improved and thus ape-like animals were evolved. Meanwhile, these ape-like animals reached the South and North-East Asia and finally evolved into gibbon and orang-utan. Remaining ape-like animals stayed in Africa and from them, gorilla and chimpanzee evolved about 2.5 crore years ago. Evolution of some of the 2 crore year old species of apes seems to be occurred in different way. They had to use their hands more for eating food and other work. man with erect posture Cro-Magnon man 50,000 Years ago 20,00,000 Years ago 15,00,000 Years ago 1,50,000 Years ago 40,00000 Years ago 1,00,00000Years ago Austrelopithecus Skilled Human Ancient animals like lemurs 2,50,00000 Years ago Neanderthal Rama pithecus 4,00,00000Years ago 7,00,00000Years ago Dryopithecus Egyptopithecus 1.12 Journey of human Those apes started to live on land as the forests started to decline due to dry environment. Their pelvic girdle developed in such a way that they started to stand in erect posture in grasslands and thereby their hands became available for use, anytime. These first human- -like animals with erect posture which were using their hands have evolved about 2 crore years ago. First record of human-like animal is with us in the form of ‘Ramapithecus’ ape from North India and East Africa. Afterwards, this ape grown up in size and became more intelligent and thus the ape of South Africa evolved about 40 lakh years ago. 9  The morphology of these human-like animals started to appear like to be the member of the genus Homo, about 20 lakh years ago and thus skilled human developed. About 15 lakh years ago, human walking with erect posture was evolved. It may have existed in China and Indonesia of Asian continent. 1.13 Development of human brain Evolution of upright man continued in the direction of developing its brain for the period of about 1 lakh years and meanwhile it discovered the fire. Brain of 50 thousand year old man had been sufficiently evolved to the extent that it could be considered as member of the class- wise-man (Homo sapiens). Neanderthal man can be considered as the first example of wise-man. The Cro-Magnon man evolved about 50 thousand years ago and afterwards, this evolution had been faster than the earlier. 1.14 Neanderthal man About 10 thousand years ago, wise-man started to practice the agriculture. It started to rear the cattle-herds and established the cities. Cultural development took place. Art of writing was invented about 5000 years ago and thus the history had been started. Modern sciences emerged about 400 years ago and industrial society was established about 200 years ago and now we have reached at this stage, and still we are searching the details of roots of human ancestry. Exercise 1. Complete the following diagram. 2. Read the following statements and justify the same in your own words Morphological with the help of suitable examples. a. Human evolution began approximately 7 crore years ago. b. Geographical and reproductive Evidences isolation of organisms gradually of leads to speciation. Evolution c. Study of fossils is an important aspect of study of evolution. d. There is evidence of fatal Similarities in bones structure science among chordates. 10 3. Complete the statements by choosing 6. Define vestigial organs. Write names correct options from bracket. of some vestigial organs in human (Gene, Mutation, Translocation, body and write the names of those Transcription, Gradual development, animals in whom same organs are Appendix) functional. a. The causality behind the sudden changes was understood due to -- -- 7. Answer the following questions. principle of Hugo de Vries. a. How are the hereditary changes b. The proof for the fact that protein responsible for evolution? synthesis occurs through -- --- was b. Explain the process of formation of given by George Beadle and complex proteins. Edward Tatum. c. Explain the theory of evolution and c. Transfer of information from mention the proof supporting it. molecule of DNA to mRNA is d. Explain with suitable examples called as -- -- -- process. importance of anatomical d. Evolution means -- -- -- --. evidences in evolution. e. Vestigial organ -- -- -- present in e. Define fossil. Explain importance of fossils as proof of evolution. human body is proof of evolution. f. Write evolutionary history of modern man. 4. Write short notes based upon the information known to you. Project : a. Lamarckism 1. Make a presentation on human b. Darwin’s theory of natural selection. evolution using various computer c. Embryology. softwares and arrange a group d. Evolution. discussion over it in the class e. Connecting link. room. 2. Read the book – ‘Pruthvivar 5. Define heredity. Explain the Manus Uparach’ written by Late mechanism of hereditary changes. Dr. Sureshchandra Nadkarni and note your opinion on evolution. 11  2. Life Processes in Living Organisms Part -1 Ø Living Organisms & Life Processes Ø Living Organisms & Energy Production Ø Some Nutrients & Energy Efficiency Ø Cell Division- A Life Process 1. How are the food stuffs and their nutrient contents useful Can you recall? for body? 2. What is the importance of balanced diet for body? 3. Which different functions are performed by muscles in body? 4. What is the importance of digestive juices in digestive system? 5. Which system is in action for removal of waste materials produced in human body? 6. What is the role of circulatory system in energy production? 7. How are the various processes occurring in human body controlled? In how many ways ? Living Organisms and Life Processes Various organ-systems are continuously performing their functions in human body. Along with the various systems like digestive, respiratory, circulatory, excretory and control systems, different external and internal organs are performing their functions independently but through a complete co-ordination. This overall system is in action in more or less same way in all the organisms. Those are in need of continuous source of energy for this purpose. Carbohydrates, fats and lipids are the main sources of this energy and it is harvested by the mitochondria present in each cell. It is not like that only foodstuff is sufficient for energy production but oxygen is also necessary. All these i.e. food stuffs and oxygen are transported up to the cell via circulatory system. Besides, it is coordinated by the control system of the body. i.e. each life process contributes in its own way in the process of energy production. Functioning of all these life processes also requires the energy. Human and other animals consume the fruits and vegetables. Plants are autotrophs. They prepare their own food. They utilize some of the food for themselves whereas remaining is stored in various parts like fruits, leaves, stem, roots, etc. We consume all these various plant materials and obtain different nutrients like carbohydrates, fats, proteins, vitamins, minerals, etc. Which food materials do we consume to obtain these nutrients? We obtain the carbohydrates from milk, fruits, jaggary, cane sugar, vegetables, potatoes, sweet potatoes, sweetmeats and cereals like wheat, maize, ragi, jowar, millet, rice, etc. We get 4Kcal energy per gram of carbohydrates. Let us study the way by which this energy is obtained. Many players are seen consuming some food stuffs during breaks of the game. Why may be the players consuming these food stuffs? Use your brain power Can you recall? 1. What is respiration? How does it occur? 12 Living organism and Energy production Observe Observe and Label the diagram given beside. In living organisms, respiration occurs at two levels as body and cellular level. Oxygen and carbon dioxide are exchanged between body and surrounding in case of respiration occurring at body level. In case of respiration at cellular level, foodstuffs are oxidized either with or without help of oxygen. Can you tell? 1. How many atoms of C, H and O are respectively present in a molecule of glucose? 2. Which types of chemical bonds are present between all these atoms? 2.1 Human respiratory system 3. In terms of Chemistry what happens actually when a molecule is oxidized? Carbohydrates of the food that we consume everyday are mainly utilized for production of energy required for daily need. This energy is obtained in the form of ATP. For this purpose, glucose, a type of carbohydrates is oxidized step by step in the cells. This is called as cellular respiration. Cellular respiration occurs among the living organisms by two methods. Those two methods are aerobic respiration (oxygen is involved) and anaerobic respiration (oxygen is not involved). In aerobic respiration, glucose is oxidized in three steps. 1. Glycolysis Process of glycolysis occurs in cytoplasm. A molecule of glucose is oxidized step by step in this process and two molecules of each i.e. pyruvic acid, ATP, NADH2 and water are formed. Molecules of pyruvic acid formed in this process are converted into molecules of Acetyl-Coenzyme-A. Two molecules of NADH2 and two molecules of CO2 are released during this process. 2. Tricarboxylic acid cycle (Krebs cycle) Both molecules of acetyl-CoA enter the mitochondria. Cyclic chain of reactions called as tricarboxylic acid cycle is operated on it in the mitochondria. Acetyl part of acetyl-CoA is completely oxidized through this cyclical process and molecules CO2, H2O, NADH2, FADH2 are derived. 13 3. Electron transfer chain Pyruvic acid Fatty acids reaction Molecules of NADH2 and Acetyl Co A FADH2 formed during all above processes participate in electron TCA transfer chain reaction. Due to Cycle this, 3 molecules of ATP are obtained from each NADH2 molecule and 2 molecules of ATP Outer Mitochondrial from each FADH2 molecule. Membrane Inner Matrix Besides ATP, water molecules Membrane are also formed in this reaction. 2.2 Mitochondria and Tri-carboxylic acid cycle Electron transfer chain reaction is operated in mitochondria only. Thus, a molecule of glucose ATP: Adenosine triphosphate is is completely oxidized in aerobic energy-rich molecule and energy is respiration and molecules of CO2 stored in the bonds by which phosphate and H2O are produced along with groups are attached to each other. energy. These molecules are stored in the cells as per need. Chemically, ATP is triphosphate molecule formed from Always Remember. adenosine ribonucleoside. It contains a nitrogenous compound-adenine, NAD - Nicotinamide Adenine pentose sugar- ribose and three dinucleotide phosphate groups. As per the need, FAD - Flavin adenine dinucleotide energy is derived by breaking the phosphate bond of ATP; hence ATP is Both coenzymes are formed in the cells called as ‘energy currency’ of the cell. and used in cellular respiration. ATP ADP Adenine Adenine Phosphate bonds with more energy Inorganic Phosphate Ribose Ribose 3.3 ATP: Energy Currency Energy released If there is insufficient amount of carbohydrates in body due to exceptional conditions like fasting and hunger, then lipids and proteins are used for energy production. In case of lipids, they are converted into fatty acids whereas proteins into amino acids. Fatty acids and amino acids are converted into acetyl-CoA and energy is obtained through complete oxidation of acetyl-CoA by the process of Krebs cycle in mitochondria. 14  Introduction To Scientists Process of glycolysis was discovered by three scientists Gustav Embden, Otto Meyerhof, and Jacob Parnas along with their colleagues. For this purpose, they performed experiments on muscles. Hence, glycolysis is also called as Embden-Meyerhof- Parnas pathway (EMP pathway). The cyclical reactions of tricarboxylic acid cycle were discovered by Sir Hans Krebs. Hence, this cyclical process is also Sir Hans Krebs called as Krebs cycle. He has been awarded the Nobel Prize in (1900-1981) 1953 for this discovery. Process of energy production through Anaerobic respiration in living aerobic respiration of carbohydrates, organisms/ cells proteins and fats. Glucose Lipids Carbohydrates Proteins Glycolysis Pyruvic Pyruvic Fatty acids Glycolysis Amino acids acid acid Fermentation Pyruvic acid Fermentation Pyruvic acid Fermentation Acetyl-CoA Alcohol Lactic acid Different Products Krebs Cycle Ex: Vinegar, Yeast Vitamins, etc. Erythrocytes, Muscle cells, CO2 + H2O + Energy Various Microbes Energy Production in Microorganisms through Anaerobic Respiration Some organisms cannot live in presence of oxygen. Ex. Many bacteria. Such living organisms have to perform anaerobic respiration for energy production. Glycolysis and fermentation are two steps of anaerobic respiration. Glucose is incompletely oxidized and less amount of energy is obtained in this type of respiration. Pyruvic acid produced through glycolysis is converted into other organic acids or alcohol with the help of some enzymes in this process. This is called as fermentation. Some higher plants, animals and aerobic microorganisms also perform anaerobic respiration instead of aerobic respiration if there is depletion in oxygen level in the surrounding. Ex. Seeds perform anaerobic respiration if the soil is submerged under water during germination. Similarly, our muscle cells also perform anaerobic respiration while performing the exercise. Due to this, less amount of energy is produced in our body and lactic acid accumulates due to which we feel tired. 15  1. Which type of cellular respiration performs complete Can you tell? oxidation of glucose? 2. Which cell organelle is necessary for complete oxidation of glucose? Energy from different food components Excess of the carbohydrates are stored in liver and muscles in the form of glycogen. What is the source of proteins? What are they made up of? Proteins are the macromolecules formed by bonding together many amino acids. Proteins of animal origin are called as ‘first class’ proteins. We get 4 Kcal of energy per gram of proteins. Amino acids are obtained after digestion of proteins. Those amino acids are absorbed in the body and transported up to each organ and cell via blood. From these amino acids, organs and cells produce various proteins necessary for themselves and the whole body. Those examples are given in the following diagram. Skin: Melanin , Always remember Blood: keratin Excess of amino acids Haemoglobin, obtained from proteins are not Antibodies Bones: Ossein stored in the body. They are broken down and the ammonia Amino formed is eliminated out of the Muscles: Acids Cells : body. If necessary, excess of Actin and various proteins of proteins are converted into other Myosin flexible cell membrane, useful substances like glucose proteins various enzymes through the process of Pancreas: gluconeogenesis. Pituitary Gland : Insulin, Plants produce the necessary Various Trypsin amino acids from minerals denovo hormones and thereby produce different proteins. An enzyme RUBISCO 2.4 Proteins and different amino acids obtained present in the plant chloroplasts is most abundant protein found in Can you recall? nature. From where do we obtain the lipids? The substances formed by specific chemical bond between fatty acids and alcohol are called as lipids. Digestion of lipids consumed by us is nothing but their conversion into fatty acids and alcohol. Fatty acids are absorbed up and distributed everywhere within the body. From those fatty acids, different cells produce various substances necessary to themselves. Ex. the molecules called as phospholipids which are essential for producing plasma membrane are formed from fatty acids. Besides, fatty acids are used for producing hormones like progesterone, estrogen, testosterone, aldosterone, etc. and the covering around the axons of nerve cells. We get 9 KCal of energy per gram of lipids. Excess of lipids are stored in adipose connective tissue in the body. 16  1. Many times, you cannot eat hot food due to inflammation / Think: ulceration in mouth. 2. Some persons experience difficulty in night vision since their childhood or adolescence. Vitamins are a group of heterogeneous compounds of which, each is essential for proper operation of various processes in the body. There are main six types of vitamins, e.g. A, B, C, D, E and K. Out of these, A, D, E and K are fat-soluble whereas B and C are water-soluble. We have seen that, FADH2 and NADH2 are produced in the processes like glycolysis and Krebs cycle. Vitamins like riboflavin (Vitamin B2) and nicotinamide (Vitamin B3) respectively are necessary for their production. 1. Many times, we experience dryness in mouth. Use your brain power 2. Oral rehydration solution (Salt-sugar-water) is frequently given to persons experiencing loose motions. 3. We sweat during summer and heavy exercise. There is about 65 – 70% water in our body. Internet is my friend Each cell contains 70% water weight by weight. Blood-plasma also contains 90% of water. Collect information Functioning of cells and thereby whole body 1. What are symptoms of diseases disturbs even if there is a little loss of water from like night blindness, rickets, the body. Hence, water is an essential nutrient. beriberi, neuritis, pellagra, Along with all above mentioned nutrients, fibers anaemia, scurvy? are also essential nutrients. In fact, we cannot 2. What do you mean by digest the fibers. However, they help in the coenzymes? digestion of other substances and egestion of 3. Find the full forms of FAD, undigested substances. We obtain the fibers from FMN, NAD, NADP. leafy vegetables, fruits, cereals, etc. 4. How much quantity of each vitamin is required every day? Cell Division: An Essential Life Process 1. What happens to the cells of injured tissue? Can you tell? 2. Whether new cells are formed during healing of wound? 3. Do the plants get injured when do we pluck the flowers? How are those wounds healed? 4. How does the growth of any living organism occur? Does the number of cells in their body increase? If yes, how? 5. How the new individual of a species is formed from existing one of same species? Cell division is one of the very important properties of cells and living organisms. Due to this property only, a new organism is formed from existing one, a multicellular organism grows up and emaciated body can be restored. There are two types of cell division as mitosis and meiosis. Mitosis occurs in somatic cells and stem cells of the body whereas meiosis occurs in germ cells. Before study of cell division, we should know the structural organization of cell that we have studied earlier. Each cell has a nucleus. Besides, other cell organelles are also present. Let us study the cell division with the help of this information. 17  Before any type of cell division, the cell doubles up its chromosome number present in its nucleus i.e. if chromosome number is 2n, it is doubled up to 4n. Can you recall? What is the shape of chromosome? Give its names in the figure. A pair of each type of chromosome is present in 2n condition whereas single chromosome of each type is present in n condition and their structure is like the one shown in figure given beside. Mitosis Somatic cells and stem cells divide by mitosis. Mitosis is completed through two main steps. Those two steps are karyokinesis (nuclear division) and 2.5 Chromosome cytokinesis (cytoplasmic division). Karyokinesis is completed through four steps. A. Prophase : In prophase, condensation of basically thin thread-like chromosomes starts. Due to this, they become short and thick and they start to appear along with their pairs of sister chromatids. Chromosomes Genetic Material Centrioles duplicate and each centriole moves to opposite poles of the cells. Nuclear membrane and nucleolus start to disappear. B. Metaphase : Nuclear membrane completely disappears in metaphase. Chromosomes complete their condensation and become clearly visible 4n along with their sister chromatids. All chromosomes are arranged parallel to equatorial plane (central plane) of the cell. Special type of flexible protein fibers (spindle fibers) are formed between centromere of each chromosome and both centrioles. Metaphase C. Anaphase : In anaphase, centromeres split and Prophase thereby sister chromatids of each chromosome separate and they are pulled apart in opposite directions with the help of spindle fibers. Separated sister chromatids are called as daughter Anaphase chromosomes. Chromosomes being pulled appear like bunch of bananas. In this way, each set of chromosomes reach at two opposite poles of the 2n cell. 2n Telophase 2n 2n 2.6 Mitosis 18 D. Telophase : The chromosomes which have reached at opposite poles of the cell now start to decondense due to which they again become thread-like thin and invisible. Nuclear membrane is formed around each set of chromosomes reached at poles. Thus, two daughter nuclei are formed in a cell. Nucleolus also appears in each daughter nucleus. Spindle fibers completely disappear. In this way, karyokinesis completes and cytokinesis begins. The cytoplasm divides by cytokinesis and two new cells are formed which are called as daughter cells. In this process, a notch is formed at the equatorial plane of the cell which deepens gradually and thereby two new cells are formed. However, in case of plant cells, instead of the notch, a cell plate is formed exactly along midline of the cell and thus cytokinesis is 2.7 Cytokinesis completed. Mitosis is essential for growth of the body. Besides, it is necessary for restoration of emaciated body, wound healing, formation of blood cells, etc. Meiosis: 1 2 3 4 5 Prophase- I (1-5) Metaphase I Anaphase I Telophase I 2.8 Meiosis Part-I Meiosis is completed through two stages. Those two stages are meiosis-I and meiosis- II. In meiosis-I, recombination / crossing over occur between homologous chromosomes and thereafter those homologous chromosomes (Not sister chromatids) are divided into two groups and thus two haploid cells are formed. Prophase II Metaphase II Anaphase II Telophase II 2.9 Meiosis Part -II 19  Meiosis-II is just like mitosis. In this stage, the two haploid daughter cells formed in meiosis-I undergo division by separation of recombined sister chromatids and four haploid daughter cells are formed. Process of gamete production and spore formation occurs by meiosis. In this type of cell division, four haploid (n) daughter cells are formed from one diploid (2n) cell. During this cell division, crossing over occurs between the homologous chromosomes and thereby genetic recombination occurs. Due to this, all the four daughter cells are genetically different from parent cell and from each other too. Apparatus : Conical flask, glass slides, cover slips, forceps, compound Try this microscope, watch glass, etc. Materials : a medium sized onion , iodine solution, etc. Procedure : Take a medium sized onion. Keep it in a conical flask filled with water in such a way that the roots of onion will be in contact with water. Observe the roots of onion after 4 – 5 days. Cut the tips of some of the roots and put them in a watch glass. Pour some drops of iodine in watch glass. Take one of the root tip on glass slide press it with the help of forceps. Add 1 – 2 drops of water and carefully place cover slip over it in such a way that air will not be trapped between. Observe the prepared glass slide under the compound microscope. Which phase of cell division did you observe? Sketch its figure. Various phases of cell division occurring in root tips of onion are shown in the following figure. Which one of those could you see in the slide? Use your brain power 1. What do you mean by diploid (2n) cell? 2. What do you mean by haploid (n) cell? 3. What do you mean by homologous chromosomes? 4. Whether the gametes are diploid or haploid? Why? 5. How are the haploid cells formed? 6. What is the importance of haploid cells? 2.10 Phases of mitosis in onion root tip Use of ICT Books are my friend Collect videos and photographs of Read different Encyclopaedias of different life processes in living technical terms in biology and organisms. Prepare a presentation and anatomy and other reference books. present it on the occasion of science exhibition 20  Exercise 1. Fill in the blanks and explain the c. With the help of suitable diagrams, statements. explain the five stages of prophase-I a. After complete oxidation of a glucose of meiosis. molecules, ---- --- --- number of d. How all the life processes contribute to ATP molecules are formed. the growth and development of the b. At the end of glycolysis, ---- --- -- body? molecules are obtained. e. Explain the Krebs cycle with reaction. c. Genetic recombination occurs in -- 5. How energy is formed from oxidation -- -- phase of prophase of meiosis-I. of carbohydrates, fats and proteins? d. All chromosomes are arranged Correct the diagram given below. parallel to equatorial plane of cell in -- -- -- phase of mitosis. Pyruvic Acid e. For formation of plasma membrane, --- --- --- molecules are necessary. f. Our muscle cells perform -- -- -- type of respiration during exercise. Acetyl Co-Enzyme A 2. Write definitions. a. Nutrition. b. Nutrients c. Proteins. d. Cellular respiration e. Aerobic respiration. f. Glycolysis. Lipid Glycolysis Amino acids 3. Distinguish between a. Glycolysis and TCA cycle. b. Mitosis and meiosis. Proteins krebs cycle Fats c. Aerobic and anaerobic respiration. 4. Give scientific reasons. Project : a. Oxygen is necessary for complete With the help of information oxidation of glucose. collected from internet, prepare the b. Fibers are one of the important slides of various stages of mitosis nutrients. and observe under the compound c. Cell division is one of the important microscope. properties of cells and organisms. d. Sometimes, higher plants and animals too perform anaerobic respiration. e. Krebs cycle is also known as citric acid cycle. 5. Answer in detail. a. Explain the glycolysis in detail. b. With the help of suitable diagrams, explain the mitosis in detail. 21  3. Life Processes in Living Organisms Part - 2 Ø Reproduction: Asexual and Sexual reproduction. Ø Reproduction and modern technology Ø Reproductive health Ø Population Explosion 1. Which are the important life processes in living organisms? Can you recall? 2. Which life processes are essential for production of energy required by body? 3. Which are main types of cell-division? What are the differences? 4. What is the role of chromosomes in cell-division? We have studied various life processes in previous classes. All those life processes i.e. nutrition, respiration, excretion, sensation & response (control & co-ordination), etc. are essential to each living organism to remain alive. Besides these life processes, one more life process occurs in living organisms; it is reproduction. However, reproduction does not help the organism to remain alive but it helps to maintain the continuity of the species of that organism. a. Observe Observe the pictures and tell the life process which you b. identified. d. Can you tell? c. 3.1 Some Life processes 1. What do we mean by maintenance of species? 2. Whether the new organism is genetically exactly similar to earlier one that has produced it? 3. Who determines whether the two organism of a species will be exactly similar or not? 4. What is the relationship between the cell division and formation of new organism of same species by earlier existing organism? Formation of new organism of same species by earlier existing organism is called as reproduction. Reproduction is one of the various important characters of living organisms. It is also one of the various reasons responsible for evolution of each species. In living organisms, reproduction occurs mainly by two methods. Those two methods are- asexual and sexual reproduction. Asexual reproduction Process of formation of new organism by an organism of same species without involvement of gametes is called as asexual reproduction. As this reproduction does not involve union of two different gametes, the new organism has exact genetic similarity with the reproducing organism. This is uniparental reproduction and it occurs by mitotic cell division. Absence of genetic recombination is a drawback whereas fast process is advantage of this reproductive method. 22 A. Asexual reproduction in unicellular organisms 1. Binary Fission Daughter Amoeba Parent Amoeba Try this Activity 1 : Take a conical flask and collect the water in it from a pond having stagnant water and aquatic plants. Add some wheat grains and aquatic plants to it. Keep it for 3 – 4 days so that wheat grains & plants will decompose. 3.2 Simple binary fission: Amoeba Early in the morning on fourth day, take a glass slide and put a drop of that water over it. Carefully, put a cover-slip on that drop and observe under compound microscope. You will be able to see many paramecia performing the binary fission. Prokaryotes (Bacteria), Protists (Amoeba, Paramecium, Euglena, etc.) and eukaryotic Parent Paramecium Daughter cell-organelle like mitochondria and Paramecium chloroplasts perform asexual reproduction by binary fission. In this process, the parent cell 3.3 Transverse binary fission : Paramecium divides to form two similar daughter cells. Binary fission occurs either by mitosis or amitosis. Axis of fission / division is different in different protists. Ex.: Amoeba divides in any plane due to lack of specific shape; hence it is called as ‘simple binary fission’. Paramecium divides by ‘transverse binary fission’ whereas Euglena by ‘longitudinal binary fission’. Binary fission is usually performed by living organisms during favourable conditions i.e. availability of abundant food material. 3.4 Longitudinal binary fission: Euglena 2. Multiple Fission Asexual reproduction by multiple fission is performed by Amoeba and other similar protists. Amoeba stops the formation of pseudopodia and thereby movements whenever there is lack of food or any other type of adverse condition. It becomes rounded and forms protective covering around plasma membrane. Such encysted Amoeba or any other protist is called as ‘Cyst’. Many nuclei are formed by repeated nuclear divisions in the cyst. It is followed by cytoplasmic division and thus, many amoebulae are formed. They remain encysted till there are adverse conditions. Cyst breaks open on arrival of favourable conditions and many amoebulae are released. 23  Division of nucleus and Daughter Parent Amoeba cytoplasm amoeba Use your brain power Does the parent cell exist after asexual Cyst reproduction- fission? 3.5 Multiple fission 3. Budding: Activity 2 : Bring the active dry yeast powder from market. Take 50 ml Bulge New Bud Daughter Parent yeast lukewarm water in a conical flask. Add yeast cell 5 gm of active dry yeast powder and 10 gm table sugar to that water and mix well the mixture. Keep the flask in warm place and after an hour take a drop of that mixture on a clean glass slide. Put a cover-glass on that drop and observe it 3.6 Budding under the compound microscope. You will see the yeast cells performing budding i.e. a small bud coming out of many parent cells. Asexual reproduction occurs by budding in yeast- a unicellular fungus. Yeast cell produces two daughter nuclei by mitotic division, so as to reproduce by budding. This yeast cell is called as parent cell. A small bulge appears on the surface of parent cell. This bulge is actually a bud. One of the two daughter nuclei enters this bud. After sufficient growth, bud separates from the parent cell and starts to live independently as a daughter yeast cell. B. Asexual reproduction in Multicellular organisms 1. Fragmentation: Spirogyra This type of asexual reproduction occurs in multicellular organisms. In this type of reproduction, the body of parent organism breaks up into many fragments and each fragment starts to live as an independent new organism. This type of reproduction occurs in algae like Spirogyra, and sponges like Sycon. Whenever there is plenty of water and nutrients are available to Spirogyra, its filaments grow up very fast and break up into many small fragments. Each fragment starts to live independently as a new Spirogyra fiber.If the body 3.7 Fragmentation of Sycon breaks up accidentally into many fragments, each fragment develops into new Sycon. 2. Regeneration You may know that the wall lizard breaks up and discards some part of its tail in emergency. Discarded part is regenerated after a period. This is an example of limited regeneration. However, under certain situations, an animal- Planaria breaks up its body into two parts and thereafter each part regenerates remaining part of the body and thus two new Planaria are formed. This is called as regeneration. 3.8 Regeneration 24 3. Budding In case of Hydra, under favourable conditions, at specific part of its body, an outgrowth is formed by repeated divisions of regenerative cells of body wall. This outgrowth is called as bud. Bud grows up progressively and finally forms a small hydra. Dermal layers and digestive cavity of the budding hydra are Hydra Bud in continuity with those of parent hydra. Parent hydra supplies nutrition to the budding hydra. Nascent Hydra Budding hydra separates from parent hydra and starts to lead an independent life when it grows up and becomes able to lead an independent life. 3.9 Budding 4. Vegetative Propagation Reproduction in plants with the help of vegetative parts like root, stem, leaf and bud is called as vegetative reproduction. Vegetative propagation in potatoes is performed with the help of ‘eyes’ present on tuber whereas in Bryophyllum it is performed with the help of buds Bryophyllum present on leaf margin. In case of plants like sugarcane & grasses, vegetative propagation occurs with the help of buds present on nodes. Sweet Potato Try this 3.10 Vegetative reproduction Potato 5. Spore Formation Take a piece of wet bread or ‘bhakari’ and Sporangium keep it in humid place. Fungus will grow on it Greenish Layer within 2 – 3 days. Observe the fungus under compound microscope and draw its diagram. Spores Fungi like Mucor have filamentous body. They have sporangia. Once the spores are formed, Hyphae sporangia burst and spores are released. Spores germinate in moist and warm place and new fungal colony is formed. Rhizoid Piece of bread 3.11 Spore formation Sexual Reproduction Sexual reproduction always occurs with the help of two germ cells. Female gamete and male gamete are those two germ cells. Two main processes occur in the sexual reproduction. 1. Gamete formation: Gametes are formed by the meiosis. In meiosis, chromosome number is reduced to half; hence haploid gametes are formed. 25 2. Fertilization: A diploid zygote is formed in this process by union of haploid male and female gametes. The zygote divides by mitosis and embryo is formed. The embryo develops to form new individual. Two parents i.e. male parent and female parent are involved in this type of reproduction. Fusion of male gamete of male parent and female gamete of female parent occurs. Due to this, new individual always has the recombined genes of both the parents. Hence, the new individual shows similarities with the parents for some characters and has some characters different than both parents. Diversity in living organisms occurs due to genetic variation. Genetic variation helps the organisms to adjust with the changing environment and thereby to maintain their existence. Due to this, plants and animals can save themselves from being extinct. 1. What would have been happened if the male and female gametes Let’s Think had been diploid? 2. What would have been happened if any of the cells in nature had not been divided by meiosis? A. Sexual reproduction in plants Flower is structural unit of sexual reproduction in plants. It consists of four floral whorls as calyx, corolla, androecium and gynaecium; arranged in sequence from outside to inside. Androecium and gynoecium are called ‘essential whorls’ because they perform the function of reproduction whereas calyx and corolla are called as ‘accessory whorls’ because they are responsible for protection of inner whorls. Members of calyx are called as ‘sepals’ and they are green coloured. Members of corolla are called as ‘petals’ and they are variously colored. Corolla (Petals) Stigma Gynoecium Style Female flower Ovary Anther Androecium Filament Male Calyx flower (Sepals) Pedicel 3.13 Papaya Flower 3.12 Parts of flower A flower is called as ‘bisexual’ if both whorls i.e. androecium and gynoecium are present in the same flower. Ex. Hibiscus. A flower is called as ‘unisexual’ if any one of the abovementioned two whorls is present in the flower. If only androecium is present, it is ‘male flower’ and if only gynoecium is present, flower is ‘female flower’. Ex. Papaya. 26  Many flowers have the stalk for support, called as ‘pedicel’ and such flowers are called as ‘pedicellate’ whereas flower without stalk is called as ‘sessile’. Androecium is male whorl and its members are called as stamens. Gynaecium is female whorl and its members are called as carpels. These may be separate or united. Ovary is present at the basal end of each carpel. A hollow ‘style’ comes up from the ovary. Stigma is present at the tip of style. Ovary contains one or many ovules. Embryo sac is formed in each ovule by meiosis. Each embryo sac consists of a haploid egg cell and two haploid polar nuclei. Pollen grains from anther are transferred to the stigma. This is called as pollination. Pollination occurs with the help of abiotic agents (wind, water) and biotic agents (insects and other animals). Stigma becomes sticky during pollination Pollens germinate when they fall upon such sticky stigma i.e. a long pollen tube and two male gametes are formed. The pollen tube carries male gametes. Pollen tube reaches the embryo sac via style. Tip of the pollen tube bursts and two male gametes are released in embryo sac. One male gamete unites with the egg cell to form zygote. This is fertilization. Second male gamete unites with two polar nuclei and endosperm is formed. As two male nuclei participate in this process, it is called as double fertilization. Pollen grain Stigma Egg cell Male Pollen tube Polar Style Gametes Synergids Nuclei Embryo sac Ovules Male Ovary gametes Antipodals 3.14 Double fertilization in angiosperms Do you know? When pollination involves only one flower or two flowers borne on same plant, it is called as self-pollination whereas if it involves two flowers borne on two plants of same species, it is cross-pollination. While discovering the new high yielding and resistant varieties of plants, scientists bring about the pollination with the help of brush. Use of ICT Make an video album of pollination and show it in the class. 27  3.15 Seed germination Try this Take a suitable glass vessel like conical flask or beaker. Add some garden soil in it and sow some pulse grains in it in such a way that you can observe them through glass. Water it every day and record the changes. Ovule develops into seed and ovary into fruit after fertilization. Seeds fall upon the ground when fruits break up and they germinate in the soil under favourable conditions. Zygote develops at the cost of food stored in endosperm of seed and thus a new plantlet is formed. This is called as seed germination. B. Sexual reproduction in human being 1. Which different hormones control the functions of human Can you recall? reproductive system through chemical coordination? 2. Which hormones are responsible for changes in human body occurring during on set of sexual maturity? 3. Why has the Government of India enacted the law to fix the minimum age of marriage as 18 in girls and 21 in boys? We have studied in the chapter of heredity and variation that men have XY sex- chromosomes and women have XX sex-chromosomes. Reproductive system with specific organs develops in the body of men and women due to these sex-chromosomes only. X-chromosome is present in men and