Plant Diversity B.Sc. (BCZ) 2023 Past Paper PDF

School of Sciences FFFFFFFFFFFF (Formerly School of Architecture, Science & Technology) Yashwantrao Chavan Maharashtra Open University V100 B.Sc....

School of Sciences FFFFFFFFFFFF (Formerly School of Architecture, Science & Technology) Yashwantrao Chavan Maharashtra Open University V100 B.Sc. [BCZ] Plant Diversity {2023 Semester-I Pattern} BNY101 Email: [email protected] Website: www.ycmou.ac.in Phone: +91-253-2231473 School of Sciences, YCMOU, Nashik – 422 222, MH, India  Yashwantrao Chavan BNY101 Maharashtra Open Plant Diversity University Semester-I Brief Contents Vice Chancellor’s Message................................................ 3 Foreword By The Director................................................ 4 Credit 01................................................................................ 5 Credit 01 -Unit 01: Viruses............................................ 6 Credit 01 -Unit 02: Bacteria........................................ 24 Credit 01-Unit 03: Algae.............................................. 45 Credit 01-Unit 04: Life cycle of algae....................... 65 Credit 02.............................................................................. 86 Credit 02-Unit 01: Fungi.............................................. 87 Credit 02-Unit 02: True Fungi................................. 103 Credit 02-Unit 03: Lichens- Symbiotic Associations 135 Credit 02-Unit 04: Mycorrhiza................................ 150 Credit 03............................................................................ 160 Credit 03-Unit 01: Bryophytes................................. 161 Credit 03-Unit 02: Morphology Anatomy And Reproduction Of Bryophytes..................................................................... 177 Credit 03-Unit 03: Pteridophytes............................ 210 Credit 03-Unit 04: Morphology, Anatomy And Reproduction Of Pteridophytes............................................................... 225 Credit 04............................................................................ 257 Credit 04-Unit 01: Gymnosperm............................. 258 Credit 04-Unit 02: Morphology, Anatomy And Reproduction Of Gymnosperms............................................................... 272 Credit 04-Unit 03: Morphology Of Angiosperms 294 Credit 04-Unit 04: Anatomy Of Angiosperm........ 344 Feedback Sheet for the Student.................................. 372 V100_BNY101: Plant Diversity Page 1  BNY101: PLANT DIVERSITY Yashwantrao Chavan Maharashtra Open University Vice-Chancellor: Prof.Dr. Sanjeev Sonawane School of Sciences Director of the School: Dr. Chetana Kamlaskar Programme Advisory Committee Dr.Chetana Kamlaskar Dr. Sunanda More Director, Associate Professor Former Director, School of Sciences, YCMOU, Nashik School of Sciences , YCMOU, Nashik Dr.Prashant Gawande Dr.Mangala Sonawane Dr.Chetan Jawale Associate Professor, Associate Professor, HOD & Associate Professor of Department of Member of Board of Studies Zoology at RYK College, Botany,SantGadge Baba SPPU, Pune Nashik Amravati University Department of Botany, KTHM College, Nashik Dr. Anil Kurhe Dr. Dhananjay Mane Dr. Ashok Borhade Associate Professor, Professor, Department of Professor, Department of Zoology, ACS Chemistry Shivaji College Department of Chemistry, HPT College, Satral, Tal-Rahuri, Umerga Arts & RYK Science College, Dist-Ahmednagar, MS Nashik Development Team Instructional Course Coordinators Book Writer Book Editor Technology Editor Dr. Sunanda More Dr.Bharat P. More Prof.Rajesh. B.Nagare Dr. Shamrao M.Baraskar Former Director, School of Sciences, HOD Dept. of Botany HOD Dept. Of Botany School of Sciences YCMOU, Nashik Prof. Ramkrishna More Jamkhed Mahavidyalaya , YCMOU, Nashik Arts,Comm.& Science Jamkhed 413201 College, Akurdi, Pune This work by YCMOU is licensed under a Creative Commons Attribution- NonCommercial-ShareAlike 4.0 International License.  Book Publication : 09-Nov-2023 Publication No:  Publisher : Mr. B. P. Patil, Registrar (I/C), YCMOU, Nashik- 422 222, MS  ISBN: V100_BNY101: Plant Diversity Page 2  V ICE C HANCELLOR ’ S M ESSAGE Dear Students, Greetings!!! I offer cordial welcome to all of you for the Bachelor’s degree programme of Yashwantrao Chavan Maharashtra Open University. As a post graduate student, you must have autonomy to learn, have information and knowledge regarding different dimensions in the field of Botany and at the same time intellectual development is necessary for application of knowledge wisely. The process of learning includes appropriate thinking, understanding important points, describing these points on the basis of experience and observation, explaining them to others by speaking or writing about them. The science of Education today accepts the principle that it is possible to achieve excellence and knowledge in this regard. The syllabus of this course has been structured in this book in such a way, to give you autonomy to study easily without stirring from home. During the counseling sessions, scheduled at your respective study centre, all your doubts will be clarified about the course and you will get guidance from some qualified and experienced counsellors/ professors. This guidance will not only be based on lectures, but it will also include various techniques such as question-answers, doubt clarification. We expect your active participation in the contact sessions at the study centre. Our emphasis is on ‘self study’. If a student learns how to study, he will become independent in learning throughout life. This course book has been written with the objective of helping in self-study and giving you autonomy to learn at your convenience. During this academic year, you have to give assignments, complete laboratory activities, field visits and the Project work wherever required. You have to opt for specialization as per programme structure. You will get experience and joy in personally doing above activities. This will enable you to assess your own progress and thereby achieve a larger educational objective. We wish that you will enjoy the courses of Yashwantrao Chavan Maharashtra Open University, emerge successful and very soon become a knowledgeable and honorable Bachelor’sdegree holder of this university. I congratulate “Development Team” for the development of this excellent high quality “Self- Learning Material (SLM)” for the students. I hope and believe that this SLM will be immensely useful for all students of this program. Best Wishes! - Prof. Dr. Sanjeev Sonawane Vice-Chancellor, YCMOU V100_BNY101: Plant Diversity Page 3  F OREWORD B Y T HE D IRECTOR Dear Students, Greetings!!! This book serves the primary goal of acquainting graduate level students, particularly those in the field of Science, with advanced Botany concepts essential for their study. It offers a complete exploration of Botanical principles and their practical applications. Throughout the book, you will find numerous illustrative examples designed to enhance your understanding and skills. We have taken a "learn at your own pace" approach, so each unit of the book is designed to be as user-friendly as possible. To do this, the book is written in a self - instructional format, making sure that each unit follows a carefully structured approach. This not only facilitates comprehension but also keeps the learning process engaging. Eachunit of book commences with clearly defined learning objectives, using action verbs aligned with Bloom's Taxonomyto help you understand what you'll achieve.Additionally, each unit begins with an introduction to stimulate the learner's curiosity and enthusiasm for the upcoming content. As you progress, you'll encounter detailed explanations supported by tables, figures, exhibits, and solved illustrations, all thoughtfully included enhancing the ability to learn. This SLM book is written in simple language with conversational style, concise sentencesand covers the entire syllabus. The topics within each unit are presented in a logical sequence, starting from simple concepts and progressing to more complex one, ensuring that the material is approachable f or learners with varying levels of intellectual capacity. To enrich learning experiences, each unit contains a diverse range of exercises, including multiple-choice questions, conceptual questions, and practical problems. These exercises aim to guide students in understanding every aspect of a particular concept, gradually building their knowledge and skills. We are grateful to the learners, resourceful writers, diligent editors, and the dedicated School faculty and staff who contributed to the development of this Self-Learning Material (SLM) book. Hope this book becomes a valuable companion to support your academic pursuits and enrich your understanding of content covered in this course. Let’s Grow Together…. Best Wishes to all of you!!! - Dr. Chetana Kamlaskar Director, School of Science, YCMOU V100_BNY101: Plant Diversity Page 4  C REDIT 01 V100_BNY101: Plant Diversity Page 5  CREDIT 01 -UNIT 01: VIRUSES LEARNING OBJECTIVES After successful completion of this unit, you will be able to  Describe the structure and shape of viruses.  Discuss the life cycle of viruses.  Identify a virus replicates itself once it attaches to a host cell.  Distingwish types of viruses.  Disease Caused by viruses to crops. INTRODUCTION Virus is a Latin word which means “poison” or “slimy liquid”. Just like its meaning, viruses are small infectious agents that are capable of multiplying in living cells of plants, animals and bacteria. A virus is made of DNA or RNA genome, inside a protein shell known as a capsid. They cannot survive or reproduce outside the body of the host. Viruses are popularly known for being the cause of a contagion. A virus particle is made of genetic material stored inside a protein shell or a capsid. The genetic material present in the virus might have single-stranded or double-stranded DNA or RNA, which might be linear or circular in shape. Usually, viruses measure in width from 20 nanometres (nm) to 400 nm. Reproduction in viruses occurs when they infect their host cells and convert them into virus-making factories. There are many other interesting properties of a virus, based on their size and shape. Now, let’s look at the life cycle of a virus to get a better understanding. 01-01: DISCOVERY Viruses were first discovered after the development of a porcelain filter, called the Chamberland-Pasteur filter, which could remove all bacteria visible in the microscope from any liquid sample. In 1886, Adolph Meyer demonstrated that a disease of tobacco plants, tobacco mosaic disease, could be transfer red from a diseased plant to a healthy one via liquid plant extracts. In 1892, Dmitri Ivanowski showed that this disease could be transmitted in this way even after the Chamberland-Pasteur filter had removed all viable bacteria from the extract. Still, it was many years before it was proven that these “filterable” infectious V100_BNY101: Plant Diversity Page 6 agents were not simply very small bacteria, but were a new type of tiny, disease - causing particle. Virions, single virus particles, are very small, about 20–250 nanometers in diameter. These individual virus particles are the infectious form of a virus outside the host cell. Unlike bacteria (which are about 100 times larger), we cannot see viruses with a light microscope, with the exception of some large virions of the poxvirus family. It was not until the development of the electron microscope in the late 1930s that scientists got their first good view of the structure of the tobacco mosaic virus (TMV) and other viruses. The surface structure of virions can be observed by both scanning and transmission electron microscopy, whereas the internal structures of the virus can only be observed in images from a transmission electron microscope. The use of these technologies has enabled the discovery of many viruses of all types of living organis ms. They were initially grouped by shared morphology. Later, groups of viruses were classified by the type of nucleic acid they contained, DNA or RNA, and whether their nucleic acid was single- or double-stranded. More recently, molecular analysis of viral replicative cycles has further refined their classification. Fig. Various types of viruses V100_BNY101: Plant Diversity Page 7 SHORT ANSWER QUESTIONS WITH MODEL ANSWER 01 1) Who is credited with the discovery of the first virus? A) Louis Pasteur B) Robert Koch C) Martinus Beijerinck D) Alexander Fleming 2) Which of the following statements about viruses is true? A) Viruses are considered living organisms. B) Viruses can carry out metabolic processes. C) Viruses are smaller than bacteria. D) Viruses have a cellular structure. 3) What is a characteristic feature of viruses that distinguishes them from other microorganisms? A) Viruses contain both DNA and RNA. B) Viruses can reproduce independently outside of a host cell. C) Viruses lack cellular structure. D) Viruses can be treated with antibiotics. 4) When were the first viruses discovered? A) In the 19th century B) In the early 20th century C) In the 17th century D) In ancient times MODEL ANSWER 01 1) C) Martinus Beijerinck 2) C) Viruses are smaller than bacteria. 3) C) Viruses lack cellular structure. 4) B) In the early 20th century V100_BNY101: Plant Diversity Page 8 01-02: ULTRA STRUCTURE , REPLICATION AND LIFE CYCLE Ultrastructure In the simpler viruses the virion consists of a single molecule of nucleic acid surrounded by a protein coat, the capsid; the capsid and its enclosed nucleic acid together constitute the nucleocapsid. In some of the more complex viruses the capsid surrounds a protein core, and in other viruses the capsid is surrounded by a lipoprotein envelope. The capsid is composed of morphological units called capsomers, which are held together by noncovalent bonds. Individual capsomers, which consist of one or more polypeptide molecules, are usually visible by electron microscopy. In helical nucleocapsids, the viral nucleic acid is folded throughout its length in a specific relationship with the capsomers, but there is no such specific relationship between RNA and protein in the small icosahedral picornaviruses. Fig. Ultrastructure of Virus Replication and life cycle The stages in the life cycle of a virus are 1) Attachment or Absorption Here, the attachment proteins on the surface of the virus align to specific receptors on the surface of the animal cells. Apart from virus binding, cellular receptors usually have glycolipids or glycoprotein. The interaction between these specific attached proteins and cellular receptors determine the host range. V100_BNY101: Plant Diversity Page 9 Host range is crucial in viral attachment, as the attachment of a virus is, specific binding between capsid proteins and specific receptors on the surface of the host cell. If the host range is narrow, the virus can only infect a small number of cell types. Similarly, if the host range is broad, the virus can infect a large number of cell types. 2) Penetration or Entry In this stage, the virus or its genetic material enters the cell. Viruses with envelopes usually enter through fusion with the membrane. Sometimes viruses take the cells in bulk by a bulk transport process known as endocytosis. Some viruses inject their DNA into the cell. 3) Genome Replication and Gene Expression Viral genome either has double or single-stranded molecules of DNA or RNA, but never both together. In this stage, the viral genome is copied and its genes are expressed to make viral proteins. This way, new virus particles can be assembled. The genetic material for this process is from the host; the tools for replication and gene expression are also given by the host. The produced viral proteins are different and vary from one virus to the other. All viruses should encode capsid proteins and all enveloped viruses should encode envelope proteins. Sometimes viruses also encode proteins that hinder the host genome, by blocking the host’s defence techniques, to benefit the virus. Viruses encode proteins that hinder the host genome, aid in viral replication and have a major role in the life cycle of viruses. 4) Assembly Capsomers are the outer covering of proteins that protect the genetic information of a virus. In this stage, newly developed capsid proteins come together to form capsomers. Capsomers interact with other capsomers to form a fully developed capsid protein. Viruses such as the head-tail viruses, first assemble an empty capsid and then store it with a viral genome. But, the rest of the viruses create the capsid around the viral genome. 5) Release This is the last stage in the life cycle of viruses, where they release newly created viruses from the host cell. Different kinds of viruses exit the cell in different methods. Some follow the process called lysis, where the virus bursts the host cell. V100_BNY101: Plant Diversity Page 10  The other viruses follow the process called exocytosis, where the virus exits from the cell’s own pathways. There are some other viruses which bud from the plasma membrane of the cell. When the new virus is released, it has the ability to kill the host cell. But some other viruses do not hinder the host cell, leave it as it is and continue to make more virus particles. Fig. Life Cycle of Virus SHORT ANSWER QUESTIONS WITH MODEL ANSWER 02 1. What are viruses, and how do they differ from other microorganisms? Viruses are infectious agents that are smaller and structurally simpler than bacteria, fungi, and other microorganisms. They consist of genetic material (either DNA or RNA) enclosed in a protein coat called a capsid. Some viruses also have an outer lipid envelope. Unlike bacteria or fungi, viruses lack the cellular machinery required for independent life. They cannot carry out metabolic processes, replicate, or produce energy on their own. Instead, they are obligate intracellular parasites, relying on host cells to replicate and propagate. 2. How do viruses infect host cells? Viruses infect host cells through a multistep process. First, they attach to specific receptors on the surface of the host cell, often with high specificity for certain cel l V100_BNY101: Plant Diversity Page 11 types or species. Once attached, viruses inject their genetic material into the host cell. This genetic material takes control of the host cell's machinery, forcing it to replicate the virus's genetic material and produce viral proteins. These components assemble to form new viral particles, eventually leading to the release of numerous virus particles, often destroying the host cell in the process. 1) How many molecules of nucleic acid consist by virion. 2) What is Capsomers? 3) Name the protein which is surrounded by capsid. 4) Define capsid 01-03: DNA VIRUS A DNA virus is a virus that has a genome made of deoxyribonucleic acid (DNA) that is replicated by a DNA polymerase. They can be divided between those that have two strands of DNA in their genome, called double-stranded DNA (dsDNA) viruses, and those that have one strand of DNA in their genome, called single - stranded DNA (ssDNA) viruses. DNA viruses are ubiquitous worldwide, especially in marine environments where they form an important part of marine ecosystems, and infect both prokaryotes and eukaryotes. Baltimore classification The Baltimore classification system is used to group viruses together based on their manner of messenger RNA (mRNA) synthesis and is often used alongside standard virus taxonomy, which is based on evolutionary history. DNA viruses constitute two Baltimore groups: Group I:double-stranded DNA viruses, and Group II:single-stranded DNA viruses. Double-stranded DNA viruses All dsDNA viruses have their mRNA synthesized in a three -step process. First, a transcription preinitiation complex binds to the DNA upstream of the site where transcription begins, allowing for the recruitment of a host RNA polymerase. Second, once the RNA polymerase is recruited, it uses the negative strand as a template for synthesizing mRNA strands. Third, the RNA polymerase terminates transcription upon reaching a specific signal, such as a polyadenylation site. dsDNA viruses make use of several mechanisms to replicate their genome. Bidirectional replication, in which two replication forks are established at a replication origin site and move in opposite directions of each other, is widely used.Some dsDNA viruses use a strand displacement method whereby one strand is synthesized from a template strand, and a complementary strand is then synthesized from the prior synthesized strand, forming a dsDNA genome.some V100_BNY101: Plant Diversity Page 12  dsDNA viruses are replicated as part of a process called replicative transposition whereby a viral genome in a host cell's DNA is replicated to another part of a host genome. Some example of dsDNA viruses are adenoviruses, herpesviruses, poxviruses Single-stranded DNA viruses ssDNA viruses have the same manner of transcription as dsDNA viruses. However, because the genome is single-stranded, it is first made into a double- stranded form by a DNA polymerase upon entering a host cell. mRNA is then synthesized from the double-stranded form. The double-stranded form of ssDNA viruses may be produced either directly after entry into a cell or as a consequence of replication of the viral genome. Eukaryotic ssDNA viruses are replicated in the nucleus. Most ssDNA viruses contain circular genomes that are replicated via rolling circle replication (RCR). ssDNA RCR is initiated by an endonuclease that bonds to and cleaves the positive strand, allowing a DNA polymerase to use the negative strand as a template for replication. Replication progresses in a loop around the genome by means of extending the 3'-end of the positive strand, displacing the prior positive strand, and the endonuclease cleaves the positive strand again to create a standalone genome that is ligated into a circular loop.The new ssDNA may be packaged into virions or replicated by a DNA polymerase to form a double-stranded form for transcription or continuation of the replication cycle. Some examples of ssDNA viruses are Human enterovirus B (coxsackievirus B3), Hepatitis A virus, and Rhinovirus (type 14). SHORT ANSWER QUESTIONS WITH MODEL ANSWER 03 3. What are the different types of viruses? Viruses exhibit tremendous diversity. They can be classified based on several factors, including their genetic material, structure, and replication strategies. Viruses can be categorized as DNA or RNA viruses, enveloped or non-enveloped viruses, single- stranded or double-stranded viruses, and many other criteria. For example, HIV is a retrovirus with RNA as its genetic material, while the influenza virus is an RNA virus with an envelope. 4. How does the immune system respond to viral infections? The immune system plays a crucial role in defending the body against viral infections. When a virus enters the body, immune cells, such as white blood cells, recognize viral particles as foreign invaders. They mount an immune response by destroying infected cells, neutralizing viruses through antibodies, and developing immunological memory. This memory enables the immune system to respond more effectively if the same virus is encountered in the future. Vaccines work by training the immune system to recognize and respond to specific viruses without causing the disease itself. V100_BNY101: Plant Diversity Page 13 01-04: RNA VIRUS An RNA virus is a virus other than a retrovirus (A retrovirus is a type of virus that inserts a DNA copy of its RNA genome into the DNA of a host cell that it invades, thus changing the genome of that cell) that has ribonucleic acid (RNA) as its genetic material. The International Committee on Taxonomy of Viruses (ICTV) classifies RNA viruses as those that belong to Group III, Group IV or Group V of the Baltimore classification system. This category excludes Group VI, viruses with RNA genetic material but which use DNA intermediates in their life cycle: these are called retroviruses. including HIV-1 and HIV-2 which cause AIDS. Single-stranded RNA viruses ssRNA viruses can be further classified according to the sense or polarity of their RNA into negative-sense and positive-sense, or ambisense RNA viruses. Positive-sense viral RNA is similar to mRNA and thus can be immediately translated by the host cell. Negative-sense viral RNA is complementary to mRNA and thus must be converted to positive-sense RNA by an RNA-dependent RNA polymerase before translation. Purified RNA of a positive-sense virus can directly cause infection though it may be less infectious than the whole virus particle. In contrast, purified RNA of a negative-sense virus is not infectious by itself as it needs to be transcribed into positive-sense RNA; each virion can be transcribed to several positive-sense RNAs. Ambisense RNA viruses resemble negative-sense RNA viruses, except they translate genes from their negative and positive strands.Some examples of ssRNA viruses are severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and Hepatovirus A Double stranded RNA viruses The double-stranded (ds)RNA viruses represent a diverse group of viruses that vary widely in host range (humans, animals, plants, fungi and bacteria.). genome segment number (one to twelve), and virion organization (Triangulation number, capsid layers, spikes, turrets, etc.). Members of this group include the rotaviruses, which are the most common cause of gastroenteritis in young children, and picobirnaviruses, which are the most common virus in fecal samples of both humans and animals with or without signs of V100_BNY101: Plant Diversity Page 14 diarrhea.Bluetongue virus is an economically important pathogen that infects cattle and sheep. 01-05: IMPORTANT VIRAL DISEASES OF CROPS Viruses cause major damage to many vegetable crops. They are immobile and are usually transmitted from one plant to another by a living organism called a vector or carrier. The most significant vectors of plant viruses include aphids, whiteflies, thrips, and leafhoppers, which have piercing sucking mouthparts that allow the insects to access and feed on the contents of the plant cells. Viruses can also be transmitted by other insects, mites, nematodes, fungi, infected pollen or vegetative propagating material, contact between plants, and infected or contaminated seeds. The virus is transmitted by sap-sucking insects in two ways: persistent transmission and non-persistent transmission, which relates to the time taken by an insect to acquire and transmit the virus. Means of transmission: Aphid VIRUS HOST PLANTS PRIMARY DAMAGE Bean common Mottling, curling, and malformation of Beans. mosaic virus leaves and a general stunting of the plant. Mottling and black necrotic spots in Turnip mosaic cabbage, cauliflower, and Brussels sprouts; Brassicas. virus mosaic with leaf distortion and stunting in turnip, radish, and Chinese cabbage. Cucumber Capsicum; mosaic and Chlorosis and blistering mottle of leaves; tomato; potato; potato mosaic plants are stunted. celery. virus Severe root symptoms in carrots including Carrot virus Y Carrot. shortened roots, knobbiness and severe distortion. V100_BNY101: Plant Diversity Page 15  Stunted plants; lower leaves roll upwards at Potato leaf roll Potato. the margins, develop leathery texture and virus die prematurely. Means of transmission: Thrips SPECIFIC VIRUS HOST PLANTS PRIMARY DAMAGE VECTOR Tomato Ringspots, line WFT, tomato Capsicum; tomato; Spotted Wilt patterns, mottling, thrips, and eggplant; lettuce; Virus and chlorotic onion thrips. peas;potatoes. (TSWV) blotches on leaves. Eye-like or diamond-shaped Iris Yellow spots on leaves and Only by onion Onions; garlic; spring Spotted Virus seed-stalk in thrips. onions; herbs. (IYSV) onions; extensive chlorosis or yellowing. In capsicum: yellowing on leaf margins and Capsicum Melon thrips between veins of Capsicum; tomato; Chlorosis and tomato young leaves; In chillies. Virus (CaCV) thrips. tomato: chlorotic spots and blotches on leaves that become mottled. V100_BNY101: Plant Diversity Page 16 Means of transmission: Whitefly VIRUS SPECIFIC VECTOR HOST PLANTS PRIMARY DAMAGE Affected plants stunted' Begamoviruses - interveinal cucurbits; Tomato yellow chlorosis Silverleaf whitefly capsicum; several leaf curl virus develops; leaves weed species. (TYLCV) bent downwards and stiffened; fruit quality reduced. Chlorosis or yellowing between veins in older Beet Lettuce; beet; cucumber leaves, Greenhouse pseudoyellows cucumber; with symptoms whitefly virus (BPYV) common weeds. spreading to younger leaves; severely affected plants stunted. Early symptoms include necrotic or dead spots; Both Greenhouse Capsicum; affected areas may and Silverleaf eggplant; weeds fall out, leaving Tomato torrado whitefly, with the including shot holes in the virus (ToTV) former responsible Amaranthus, and leaflets; necrosis for spread in Chenopodium, and mottling also Australia. extends to the remainder of the leaves. V100_BNY101: Plant Diversity Page 17  Means of transmission: Tobamoviruses PRIMARY VIRUS HOST PLANTS DAMAGE Mosaic; mottling; leaf Tobacco mosaic Crop plants and weeds: eggplant; distortion; and virus tomato. sometimes leaf death and defoliation. Pepper mild A mild mosaic or Capsicum, including chillies. mottle virus mottle. SHORT ANSWER QUESTIONS WITH MODEL ANSWER 04 5. What are the consequences of viral infections for human health? Viral infections can have a wide range of consequences for human health. Some viruses cause mild illnesses like the common cold or flu, while others can lead to severe diseases such as COVID-19, AIDS, or hepatitis. The effects of viral infections can vary widely, from direct damage to host tissues, triggering inflammation, or disrupting normal cellular functions. In severe cases, viral infections can be life - threatening and require intensive medical intervention. 6. How can we prevent and treat viral infections? Preventing viral infections involves a combination of vaccination, good hygiene practices (such as frequent handwashing), and avoiding close contact with infected individuals or contaminated surfaces. Antiviral medications can be used to treat some viral infections, although their effectiveness varies depending on the virus. The development of new antiviral drugs and ongoing research into viral biology and immunology are essential in the fight against viral diseases. Vaccination has played a pivotal role in controlling the spread of numerous viral infections, including the rapid development of COVID-19 vaccines to combat the pandemic. 1) What is the primary genetic material in viruses? A) DNA B) RNA C) Both DNA and RNA D) Proteins V100_BNY101: Plant Diversity Page 18 2) Which of the following is NOT a common method of virus transmission? A) Airborne droplets B) Sexual contact C) Ingesting contaminated food or water D) Touching infected surfaces 3) What is the main function of the viral capsid? A) To facilitate viral attachment to host cells B) To protect the viral genetic material C) To regulate viral replication D) To produce antibodies against the virus 4) Which of the following is an example of a retrovirus? A) Influenza virus B) HIV (Human Immunodeficiency Virus) C) Herpes simplex virus D) Rhinovirus (common cold virus) ANSWER TO CHECK POINT 01-01 1) B) RNA 2) B) Sexual contact 3) B) To protect the viral genetic material 4) B) HIV (Human Immunodeficiency Virus) SUMMARY Viruses are enigmatic microscopic entities that occupy a unique position in the world of biology. They straddle the line between living and non-living, lacking the cellular structure typical of organisms but possessing genetic material and the ability to replicate within host cells. This duality has made them a subject of immense fascination and research. V100_BNY101: Plant Diversity Page 19  Discovery: Viruses were first discovered in the late 19th century, during studies of tobacco mosaic disease, when it was noticed that an infectious agent could pass through filters that trapped bacteria. Their unique nature became clearer with advancements in electron microscopy, revealing their ultra-small size and distinctive shapes. Ultrastructure: Viruses are incredibly simple in structure. They consist of genetic material, either DNA or RNA, surrounded by a protein coat called a capsid. Some viruses also have an outer lipid envelope. This minimalist design reflects their dependency on host cells for replication. Life Cycle: The life cycle of a virus can be summarized in several steps: attachment to host cell, penetration into the cell, uncoating (removing the protein coat), replication of viral genetic material, assembly of new viral particles, and finally, release of these particles to infect more cells. Viruses hijack the cellular machinery to reproduce, and this often damages or kills the host cell in the process. DNA and RNA Viral Diseases of Crops: Viruses can wreak havoc on crops, causing diseases that result in reduced yields and economic losses. Some notable examples include: 1. Tobacco Mosaic Virus (TMV): Affecting tobacco and other solanaceous plants, TMV causes distinctive mottling and mosaic patterns on leaves, stunting growth. 2. Potato Virus Y (PVY): PVY infects potatoes and other solanaceous crops, leading to reduced tuber quality and yield. 3. Citrus Tristeza Virus (CTV): This virus infects citrus trees, resulting in the decline of tree health and quality of fruit. 4. Rice Yellow Mottle Virus (RYMV): Affecting rice plants, RYMV causes yellow mottling and leads to yield losses in rice-producing regions. 5. Tomato Spotted Wilt Virus (TSWV): TSWV infects a wide range of plants, including tomatoes, and causes symptoms like ringspots, mottling, and wilting. These viral diseases can spread through various means, including insect vectors, contaminated seeds, and plant-to-plant contact. Management strategies involve using disease-resistant crop varieties, practicing good sanitation, and controlling vector populations. In summary, viruses are intriguing and complex entities with a simple structure. They challenge our understanding of life, living, and the very nature of organisms. In agriculture, viruses can lead to devastating crop diseases, posing significant challenges to global food security. Research in virology continues to advance our knowledge of viruses, helping us develop better strategies to combat viral diseases in crops and prevent their impact on the food supply. V100_BNY101: Plant Diversity Page 20  KEY WORDS Ultrastructure, Tobacco Mosaic Virus, Potato Virus Y, Rice Yellow Mottle Virus, Tomato Spotted Wilt Virus. REFERENCES 1. Online Databases and Journals: Access to online databases such as PubMed and journals like "Journal of Virology" and "Virology" can provide up-to-date research articles, reviews, and references on various aspects of virology. When using these references, it's essential to verify their edition and publication date, as the field of virology is continually evolving, and new discoveries are made regularly. Additionally, consulting your institution's library or a university library can help you access a wide range of books and journals on virology for more specialized research and references. MOOCS-- YOUTUBE VIDEOS https://youtu.be/XlLgaHZpZS4?si=lVw-44NUE9ip47tS https://youtu.be/bDzCXvTgAGM?si=SfNwX7mORkl-7hk3 WIKIPEDIA "Wikipedia" defined Virus and important key points and topics related to viruses as follows. Definition: A virus is a small infectious agent that requires a host cell to replicate. It can infect a variety of organisms, including animals, plants, and microorganisms. Key Points: 1. Structure: Viruses are typically composed of genetic material (either DNA or RNA) surrounded by a protein coat called a capsid. Some viruses also have an outer lipid envelope. 2. Replication: Viruses cannot reproduce on their own. They must infect a host cell and hijack the cell's machinery to replicate. This process often damages or destroys the host cell. 3. Classification: Viruses are classified based on their genetic material, replication strategy, and other characteristics. They can be DNA viruses, RNA viruses, or retroviruses, among others. 4. Human Viruses: Some well-known human viruses include HIV (Human Immunodeficiency Virus), Influenza, Herpes, and SARS-CoV-2 (responsible for COVID-19). V100_BNY101: Plant Diversity Page 21 5. Host Range: Viruses are highly specific to their host species or even particular cell types. For example, some viruses only infect bacteria (bacteriophages), while others infect animals or plants. 6. Disease: Many viral infections can cause diseases in their hosts. These diseases can range from mild, such as the common cold, to severe and life-threatening, like Ebola. 7. Vaccination: Vaccines have been developed to prevent several viral infections. They work by stimulating the immune system to recognize and defend against specific viruses. 8. Antiviral Drugs: Some antiviral drugs can inhibit the replication of certain viruses, helping to manage infections. However, viruses can develop resistance to these drugs. 9. Emerging Viruses: New viruses can emerge through mutations, recombination, or zoonotic spillover (transmission from animals to humans). These can pose significant public health challenges. 10. History: The study of viruses dates back to the late 19th century, but our understanding of them has greatly advanced in recent decades with the development of molecular biology techniques. Online Resources: To access comprehensive and up-to-date information on specific viruses, you can visit the following websites: 1. The International Committee on Taxonomy of Viruses (ICTV): ICTV maintains a comprehensive database of virus taxonomy and nomenclature. 2. The CDC's Viral Diseases: The U.S. Centers for Disease Control and Prevention provides information on various viral diseases and vaccines. 3. PubMed: You can search for scientific articles and research papers on specific viruses and their properties. 4. Virology Journal: This open-access journal publishes research on various aspects of virology. Remember that the field of virology is continually evolving, so staying updated with the latest research is important for a comprehensive understanding of viruses. OER-- REFERENCE BOOKS 1.Title: "Fields Virology" Authors: David M. Knipe, Peter M. Howley, et al. Publisher: Wolters Kluwer Edition: 7th Edition (2020). 2. "Principles of Virology" by S. Jane Flint, Vincent R. Racaniello, Glenn F. Rall, and Lynn W. Enquist: This comprehensive textbook covers the fundamentals of virology, including virus structure, replication, pathogenesis, and antiviral strategies. It's an excellent resource for both students and researchers. 3. "Fields Virology" (6th Edition) by David M. Knipe and Peter M. Howley: This multi-volume series is considered a standard reference in the field of virology. It provides detailed information on various aspects of virology, including viral taxonomy, molecular virology, and viral pathogenesis. V100_BNY101: Plant Diversity Page 22 4. "Virology: Principles and Applications" by John Carter and Venetia Saunders: This book offers a comprehensive introduction to virology, with a focus on practical applications. It covers topics such as virus detection, vaccines, and antiviral therapies. 5. "The Dictionary of Virology" by Brian W.J. Mahy and Marc H.V. van Regenmortel: For quick reference, this dictionary provides definitions and explanations of virology-related terms and concepts. It's a handy tool for students and researchers. 6. "Viral Pathogenesis: From Basics to Systems Biology" by Michael G. Katze, Marcus J. Korth, and Gustavo Palacios: This book delves into the molecular and cellular mechanisms of viral pathogenesis, offering insights into how viruses cause disease and interact with host cells. 7. "Principles of Molecular Virology" by Alan J. Cann: This textbook focuses on the molecular aspects of virology, covering topics such as viral genetics, replication, and evolution. It's suitable for those interested in the genetic aspects of viruses. 8. Online Databases and Journals: Access to online databases such as PubMed and journals like "Journal of Virology" and "Virology" can provide up-to-date research articles, reviews, and references on various aspects of virology. V100_BNY101: Plant Diversity Page 23  CREDIT 01 -UNIT 02: BACTERIA LEARNING OBJECTIVES After successful completion of this unit, you will be able to  Define bacteria and explain their classification as prokaryotic microorganisms.  Describe the basic structural features of bacterial cells, including cell wall, cell membrane, and cytoplasm.  Explore bacterial genetics, including the structure of bacterial DNA and plasmids.  State the fundamental characteristics of bacteria, such as their prokaryotic nature, unicellularity, and diverse metabolic strategies.  Analyze the influence of environmental factors, such as temperature, pH, and nutrient availability, on bacterial growth and survival. INTRODUCTION The Earth is home to a wide variety of living beings. It is estimated that about 8.7 million species of living beings are currently on the Earth of which 1.2 million species are known to us. These biotic components have total biomass of about 545.8 gigatons, of which 12.8 % is bacterial biomass, while human accounts for only 0.01%. Bacteria are microscopic, unicellular, prokaryotic organisms. They do not have membrane-bound cell organelles and lack a true nucleus, hence are grouped under the domain “Prokaryota” together with Archae. In a three-domain system, Bacteria is the largest domain. (Living beings are classified into Archae, Bacteria, and Eukaryota domain in the three -domain system.) Bacteria, a singular bacterium, is derived from the Ancient Greek word “backērion” meaning “cane”, as the first bacteria observed were bacilli. The study of ‘Bacteria’ is called ‘Bacteriology’; a branch of ‘Microbiology’. V100_BNY101: Plant Diversity Page 24  Fig. Different Bacterial cell Structure. 02-01: DISCOVERY Bacteria are considered as the first life-form to arise on the Earth about 4 billion years ago. All other life-forms are evolved from the bacteria. Antoni van Leeuwenhoek (1632-1723), a cloth merchant from Belgium, afforded humanity a glimpse into a new world: using microscopes he had built himself, he studied pond and rainwater in 1675, discovering what he described as little animals (“animalcula”) – protozoa and bacteria. Later, he also observed microorganisms in human saliva and dental plaque. It was apparently a life - altering experience: from then on, Leeuwenhoek rubbed his teeth with salt and killed bacteria by gargling with vinegar. Nevertheless, it took roughly 200 years for people to recognize the significance of microorganisms as causes of disease. Scholars in those days instead continued to believe in the theory of miasmas, which held that epidemics were caused by toxic emanations from the ground. Physician Robert Koch (1843-1910) was the first to conduct a systematic search for the microorganisms responsible for diseases. His discovery of the tuberculosis pathogen (Mycobacterium tuberculosis) finally proved the correlation. The research work of Louis Pasteur (1822-1895) revealed the bacteriological roots of fermentation and decay. In addition, he also developed his eponymous pasteurization process, in which food could be disinfected and preserved by briefly heating it. Scottish surgeon Joseph Lister (1827-1912) began successfully using phenol to disinfect wounds prior to operating. V100_BNY101: Plant Diversity Page 25 SHORT ANSWER QUESTIONS WITH MODEL ANSWER 01 1) Who is considered the father of microbiology and is credited with the discovery of bacteria? A) Louis Pasteur B) Anton van Leeuwenhoek C) Robert Koch D) Edward Jenner 2) Which of the following is NOT a characteristic of bacteria? A) Prokaryotic cells B) Lack of a cell wall C) Ability to reproduce by binary fission D) Diverse shapes and arrangements 3) What is the term for the study of bacteria? A) Bacteriology B) Virology C) Mycology D) Protozoology 4) What was the key discovery made by Louis Pasteur in the 19th century that greatly advanced our understanding of bacteria? A) Discovery of antibiotics B) Development of the germ theory of disease C) Invention of the electron microscope V100_BNY101: Plant Diversity Page 26 D) Isolation of the first virus MODEL ANSWER 01 1 )B) Anton van Leeuwenhoek 2)B) Lack of a cell wall 3)A) Bacteriology 4)B) Development of the germ theory of disease 02-02: GENERAL CHARACTERISTIC AND ULTRA-STRUCTURE OF CELL General characters 1) Bacteria are single-celled organisms. They lack organelles such as chloroplasts and mitochondria, and they do not have the true nucleus found in eukaryotic cells. Instead, their DNA, a double strand that is continuous and circular, is located in a nucleoid. 2) The nucleoid is an irregularly shaped region that does not have a nuclear membrane. 3) Bacteria also have a cell membrane and a cell wall that is often made of peptidoglycan. Together, the cell membrane and cell wall are referred to as the cell envelope. Many bacteria need a cell wall in order to survive. 4) Reproduction occurs through binary fission, which is the splitting of a bacterial cell after it reaches a certain size. 5) Bacteria reproduce asexually, so the two daughter cells that result from binary fission have the same DNA as the parent cell. 6) Some bacteria can also exchange genetic material among one another in a process known as horizontal gene transfer. 7) Bacteria Shapes: Bacteria come in a myriad of shapes. The three main shapes of bacteria are coccus, spiral, and bacillus. V100_BNY101: Plant Diversity Page 27 Ultrastructure of Bacterial Cell The bacterial cell reveals three layers (i) Capsule/Glycocalyx (ii) Cell wall and (iii) Cytoplasm. i) Capsule/Glycocalyx Some bacteria are surrounded by a gelatinous substance which is composed of polysaccharides or polypeptide or both. A thick layer of glycocalyx bound tightly to the cell wall is called capsule. It protects cell from desiccation and antibiotics. The sticky nature helps them to attach to substrates like plant root surfaces, Human teeth and tissues. It helps to retain the nutrients in bacterial cell. Cell wall The bacterial cell wall is granular and is rigid. It provide protection and gives shape to the cell. The chemical composition of cell wall is rather complex and is made up of Peptidoglycan or mucopeptide (N-acetyl glucosamine, N-acetyl muramic acid and peptide chain of 4 or 5 aminoacids). One of the most abundant polypeptides called porin is present and it helps in the diffusion of solutes. Plasma membrane The plasma membrane is made up of lipoprotein. It controls the entry and exit of small molecules and ions. The enzymes involved in the oxidation of metabolites (i.e., the respiratory chain) as well as the photosystems used in photosynthesis are present in the plasma membrane. V100_BNY101: Plant Diversity Page 28 ii) Cytoplasm Cytoplasm is thick and semitransparent. It contains ribosomes and other cell inclusions. Cytoplasmic inclusions like glycogen, poly-β-hydroxybutyrate granules, sulphur granules and gas vesicles are present. Bacterial chromosome The bacterial chromosome is a single circular DNA molecule, tightly coiled and is not enclosed in a membrane as in Eukaryotes. This genetic material is called Nucleoid or Genophore. The DNA is not bound to histone proteins. The single chromosome or the DNA molecule is circular and at one point it is attached to the plasma membrane and it is believed that this attachment may help in the separation of two chromosomes after DNA replication. Plasmid Plasmids are extra chromosomal double stranded, circular, self-replicating, autonomous elements. They contain genes for fertility, antibiotic resistant and heavy metals. It also helps in the production of bacteriocins and toxins which are not found in bacterial chromosome. The size of a plasmid varies from 1 to 500 kb usually plasmids contribute to about 0.5 to 5.0% of the total DNA of bacteria. Plasmids are classified into different types based on the function. Some of them are F (Fertility) factor, R (Resistance) plasmids, Col (Colicin) plasmids, Ri (Root inducing) plasmids and Ti (Tumour inducing) plasmids. Mesosomes These are localized infoldings of plasma membrane produced into the cell in the form of vesicles, tubules and lamellae. They are clumped and folded together to maximize their surface area and helps in respiration and in binary fission. Polysomes / Polyribosomes The ribosomes are the site of protein synthesis. The number of ribosome per cell varies from 10,000 to 15,000. The ribosomes are 70S type and consists of two subunits (50S and 30S). The ribosomes are held together by mRNA and form polyribosomes or polysomes. Flagella Certain motile bacteria have numerous thin hair like processes of variable length emerge from the cell wall called flagella. It is 20–30 μm in diameter and 15 μm in length. The flagella of Eukaryotic cells contain 9+2 microtubles but each flagellum in bacteria is made up of a single fibril. Flagella are used for locomotion. V100_BNY101: Plant Diversity Page 29  Fimbriae or Pili Pili or fimbriae a re hair like appendages found on surface of cell wall of gram - negative bacteria (Example: Enterobacterium). The pili are 0.2 to 20 µm long with a diameter of about 0.025µm. In addition to normal pili there are special type of pili which help in conjugation called sex pili are also found. SHORT ANSWER QUESTIONS WITH MODEL ANSWER 02 1. What are bacteria, and how do they differ from other microorganisms? Bacteria are single-celled microorganisms that are classified as prokaryotes. They are distinct from other microorganisms like viruses and fungi. Unlike viruses, bacteria are complete cells with a cellular structure, including a cell wall, cell membrane, cytoplasm, and genetic material (DNA) organized in a nucleoid region. Bacteria differ from eukaryotic microorganisms, like fungi and protists, in that they lack a true nucleus and membrane-bound organelles. 2. How do bacteria reproduce and multiply? Bacteria primarily reproduce through a process called binary fission. In binary fission, a single bacterial cell divides into two identical daughter cells. This process is rapid and can lead to exponential growth under favorable conditions. Some bacteria can also exchange genetic material through processes like conjugation, transformation, and transduction, allowing for genetic diversity and adaptation to changing environments. 02-03: GROW THE KINETICS AND REPRODUCTIVE STRATEGIES Kinetics of growth refers to the rate at which the number of individual cells (or, more general, of active biomass) changes in a defined system. Studying growth of a microorganism is the basis of biotechnological exploitation of microflora for production of desired product. Optimization of growth of microorganism in a particular media is desirable due to economical and availability of particular growth constituent in a region. Despite this, some microorganisms have specific requirement and they grow in a particular growth media. Modes of Bacterial Cell Division 1. Binary division Binary division is the most common mode of cell division in bacteria in this mode of cell division, a single bacteria cell grows transversely with the synthesis of V100_BNY101: Plant Diversity Page 30 chromosomal DNA. A transverse septum appears in the middle of the cell body that divides the bacterial cell into the two with a distribution of chromosomal DNA, ribosome and other cellular machinery. 2. Budding In this mode of cell division, chromosomal DNA divides to form two copies. Sister chromosomal DNA moves to the one side of the cell and this portion of the cells protrude from main body to form bud. Eventually bud grows in size and get separated from main cell to develop a new cell. V100_BNY101: Plant Diversity Page 31 3.Fragmentation This mode of asexual division is more common in filamentous bacteria. In this mode, filament of the growing cell gets fragmented into small bacillary or coccoid cells, these cellular fragments eventually develop into new cell. Measuring Bacterial growth A number of method’s have been developed to measure bacterial growth in liquid media and in solid support media. A few are discussed below: Microbial count method Microscopic count-bacterial cells can be counted easily on a “petroff-hausser counting chamber” The chamber has a ruling to make square (1/400 mm2) of equivalent volume. A glass slide is placed (~1/50mm height) to make a chamber filled with bacterial cell suspension. Volume of each chamber is 1/20,000 mm3. This chamber can be used to observe bacteria with phase contrast microscope. For example, if each chamber has 8 bacteria then there are 8x20,000,000 or 1.6x108 bacteria/ml. A very high or low concentration of bacterial sample cannot be counted accurately. Plate count method In this method, a defined amount of bacterial culture suspension is introduced onto solid support media to grow and give colonies. If number of colonies on solid media is too high, then serial dilution of original stock can be plated on solid media and number of colony can be counted with a colony counter. A manual colony counter has lamp at the bottom, a grid to divide the bacterial culture plate and a magnifying glass to visualize and count single colony. A plate with colony count of 30-300 can be used V100_BNY101: Plant Diversity Page 32 to determine the number of bacteria present in original stock. Number of bacteria per ml= Number of colonies counted on plate X dilution of sample. Turbidimetric methods This method is based on light scattering principles of particulate matter such as bacteria. A bacteria cell suspension is placed in test cuvette and corresponding media in reference cuvette. The optical density or absorbance of the bacterial suspension is used to measure the number of bacteria number. This method cannot distinguish between live or dead bacteria as both form contribute to the turbidity. Nitrogen content and Dry weight A bacterial cell mass can be measured by direct measurement of dry weight of culture or nitrogen content. Growth cycle of bacteria As discussed earlier, the most common method of bacteria division is binary fission and by this method, one bacteria cell gives two daughter cells. The time a bacteria takes to complete one division is called as generation time and it depends on bacteria species and media properties. Bacterial growth in a liquid media 1. Lag Phase The single cell inoculation into the liquid media doesn’t start dividing as per its generation time. During these phase bacteria gets adjusted to the new media and grow in size instead of dividing into daughter cells. In this phase, bacteria synthesize the most crucial enzymes or co-enzyme present in traces and required for optimal growth and multiplication. In addition, cell is metabolically active and be busy in synthesizing large amount of protoplasm. At the end of this phase, each bacterial cell divides and enter into the next phase of active multiplication. 2.Log Phase In this phase, bacterial cell population is involved in active division and whole cell population is more or less homogenous in terms of chemical composition, physiology and metabolic activity. A plot of number of cell (in log scale) against time gives straight line. The growth of bacterial cell population is increasing at a constant rate and continues until substrate concentration is not limiting. V100_BNY101: Plant Diversity Page 33 3.Stationary Phase Once substrate is limiting, the logarithmic phase of growth begins to decline gradually with a constant number of cells to give a straight line. The population remains constant because numbers of divisions are equal to the number of death events. As substrate is limiting, death of old cell provides enough nutrient for remaining cells to grow and multiply to maintain the constant number. V100_BNY101: Plant Diversity Page 34  4. Death Phase When substrate is not sufficient from dying cells, death rate of bacteria supersede rate of growth and as a result number of bacteria declines sharply. SHORT ANSWER QUESTIONS WITH MODEL ANSWER 02 3. What are the different shapes and arrangements of bacteria? Bacteria exhibit various shapes, including cocci (spherical), bacilli (rod-shaped), and spirilla (spiral-shaped). These shapes can further vary in size and arrangement. Bacteria may occur singly, in pairs (diplo-), in chains (strepto-), in clusters (staphylo- ), or in various other arrangements. The shape and arrangement of bacteria can be helpful in their identification. 4. How do bacteria contribute to the environment and human health? Bacteria play essential roles in the environment and human health. They are involved in nutrient cycling, decomposing organic matter, and fixing nitrogen in the soil. Beneficial bacteria in the human gut aid in digestion and produce vitamins. Some bacteria are used in biotechnology for processes like fermentation and bioremediation. However, some bacteria can also cause diseases and infections in humans and other organisms V100_BNY101: Plant Diversity Page 35 02-03: MECHANISM OF HORIZONTAL GENE TRANSFER Horizontal gene transfer (HGT)is also known as lateral gene transfer refers to the transfer of genetic material from one organism to another without reproduction.Horizontal gene transfer (HGT) between bacteria is driven by three major processes transformation (the uptake of free DNA), transduction (gene transfer mediated by bacteriophages) and conjugation (gene transfer by means of plasmids or conjugative and integrated elements). 1. Transformation Transformation is one of the most common mechanisms of horizontal gene transfer among bacteria. Transformation happens when a recipient competent cell takes up the extracellular naked DNA from the environment or DNA from a dead donor bacterium. Transformation involves homologous recombination, the exchange of genetic material between single-stranded or double-stranded nucleic acids that have extensive regions of similar base sequences. Donor and recipient cells are usually of the same bacterial species. 2. Conjugation Another mechanism of horizontal gene transfer in bacteria is conjugation. Conjugation is the most common mechanism of horizontal gene transfer from a donor bacterial species to a different recipient species. Bacterial conjugation was first discovered in E. coli, and it relies on cell-to-cell contact. The direct contact of cells with each other is important for bacterial conjugation and distinguishes it from other mechanisms of horizontal gene transfer. In bacterial conjugation, the donor cell would pull the recipient cell using a structure called a sex pilus. Sex pilus is a tube-like appendage that allows cell-to-cell contact, and it protects the transfer of DNA plasmid from the donor to the recipient cell. Once they are in contact with each other, DNA is pushed out of the donor cell and transported to the recipient cell. 3. Transduction Transduction involves the transfer of DNA fragments through a viral vector called a bacteriophage. A bacteriophage is a virus that can infect bacteria. Bacteriophage, the transducing particle, would infect a bacterium and then inject its DNA into the V100_BNY101: Plant Diversity Page 36  bacteria. After injection, the DNA from the virus can hijack the bacterium and use it as a host to make more of the DNA. Unlike conjugation, transduction does not require physical contact between the donor cell and the receiver cell. Transduction can happen by a lytic or lysogenic cycle. In the lytic cycle, the bacteriophage takes over the bacterial cell's replication, transcription, and translation machinery to direct it to make new viral particles. Once there are viral particles, it is released into the environment via the lysis of the host. On the other hand, in a lysogenic cycle, the bacteriophage chromosome is inserted as a prophage into the bacterial chromosome. This prophage can remain dormant in the bacteria, but the prophage can be excised from the bacterial chromosome and initiates the lytic cycle if the bacteria are induced. Fig.Mechanism of horizontal gene transfer 02-04: IMPORTANT BACTERIAL DISEASES OF CROPS SHORT ANSWER QUESTIONS WITH MODEL ANSWER 02 5. What is antibiotic resistance, and why is it a concern with bacteria? Antibiotic resistance occurs when bacteria evolve mechanisms to survive exposure to antibiotics, rendering these drugs ineffective. This is a significant concern because it V100_BNY101: Plant Diversity Page 37  limits our ability to treat bacterial infections, leading to longer illnesses and i ncreased mortality. Antibiotic resistance develops through natural selection when bacteria with resistance genes survive and reproduce in the presence of antibiotics. Misuse and overuse of antibiotics in healthcare and agriculture have accelerated the emergence of resistant strains. 6. How do bacteria contribute to scientific research and biotechnology? Bacteria are invaluable in scientific research and biotechnology. They are used as model organisms in labs to study fundamental biological processes. Bacteria are also used in biotechnology for the production of various products, including antibiotics, vaccines, and enzymes. Genetic engineering techniques allow scientists to modify bacterial DNA for applications like producing recombinant proteins and developing genetically modified organisms with beneficial traits. Additionally, bacteria are essential in environmental biotechnology for cleaning up pollutants through bioremediation processes. CHECK POINT 01-02 1. What is the defining characteristic of bacteria? a. Eukaryotic cells b. Multicellularity c. Prokaryotic cells d. Photosynthetic autotrophy. Answer: c. Prokaryotic cells 2. Which of the following bacterial shapes is spherical? a. Bacillus b. Spirillum c. Coccus d. Vibrio Answer: c. Coccus 3. Bacteria are classified based on their cell wall composition. Which of the following groups of bacteria has a thick layer of peptidoglycan in their cell wall? a. Gram-negative bacteria b. Acid-fast bacteria c. Gram-positive bacteria d. Cyanobacteria Answer: c. Gram-positive bacteria 4. Which bacterial metabolic process converts atmospheric nitrogen (N2) into ammonia (NH3), making it available for plants? a. Denitrification b. Nitrate reduction c. Ammonification d. Nitrogen fixation Answer: d. Nitrogen fixation 5. Which bacterial structure is involved in motility and often used for bacterial identification? a. Plasmid b. Flagellum c. Pili d. Capsule V100_BNY101: Plant Diversity Page 38 Answer: b. Flagellum 6. Which bacterial division process results in two genetically identical daughter cells? a. Binary fission b. Conjugation c. Transduction d. Transformation Answer: a. Binary fission 7. What type of bacteria can thrive in extreme environments, such as high - temperature geothermal springs and acidic mine drainage? a. Pathogenic bacteria b. Extremophiles c. Cyanobacteria d. Enteric bacteria Answer: b. Extremophiles 8. Which group of bacteria is responsible for the majority of photosynthesis on Earth and produces oxygen as a byproduct? a. Proteobacteria b. Spirochetes c. Cyanobacteria d. Archaea Answer: c. Cyanobacteria 9. Which bacterial group includes species that cause diseases such as tuberculosis and leprosy? a. Firmicutes b. Actinobacteria c. Chlamydiae d. Bacteroidetes Answer: b. Actinobacteria 10. Which bacterial staining method is used to differentiate bacteria based on differences in their cell wall structure? a. Acid-fast stain b. Gram stain c. Simple stain d. Negative stain Answer: b. Gram stain SUMMARY Discovery of Bacteria: Bacteria were first discovered by Antonie van Leeuwenhoek in the 17th century when he observed them through a simple microscope. However, the field of microbiology significantly expanded in the 19th century with the work of scientists like Louis Pasteur and Robert Koch, who developed techniques for studying and culturing bacteria. This led to the identification of specific bacterial species and their roles in various diseases and processes. General Character and Ultrastructure of Bacterial Cells: Bacterial cells exhibit a wide range of characteristics, but in general, they are prokaryotic and much smaller than eukaryotic cells. Key features include a cell wall, plasma membrane, cytoplasm, ribosomes, and genetic material (DNA). Bacteria can be classified into Gram-positive or Gram-negative based on differences in their cell wall structure. Some bacteria have additional structures like flagella for motility, pili for adherence, and capsules for protection. V100_BNY101: Plant Diversity Page 39  Growth Kinetics of Bacteria: Bacterial growth kinetics typically involve four phases: lag phase (adaptation to the environment), exponential phase (rapid growth), stationary phase (growth rate equals death rate), and death phase (more cells dying than dividing). Bacterial growth is influenced by factors such as nutrient availability, temperature, pH, and oxygen levels. Reproductive Strategies: Bacteria reproduce primarily through a process called binary fission, where a single cell divides into two daughter cells. This is a rapid and efficient means of population increase. Some bacteria can also engage in various forms of genetic recombination, such as conjugation (direct transfer of DNA between bacterial cells), transformation (uptake of external DNA), and transduction (DNA transfer by viruses or phages). Mechanisms of Horizontal Gene Transfer: Horizontal gene transfer (HGT) in bacteria allows for the exchange of genetic material between individuals of the same generation. HGT mechanisms include conjugation (bacterial "mating" through a conjugative pilus), transformation (uptake of free DNA from the environment), and transduction (transfer of DNA by viruses or bacteriophages). These processes play a crucial role in bacterial evolution and adaptation to changing environments. Important Bacterial Diseases of Crops: Bacterial diseases in crops are a significant concern for agriculture. Some important bacterial diseases of crops include:  Fire Blight: Caused by Erwinia amylovora, it affects fruit trees, especially apple and pear.  Bacterial Leaf Spot: Caused by Xanthomonas species, it affects a wide range of plants, including tomatoes and peppers.  Bacterial Soft Rot: Often caused by Pectobacterium and Dickeya species, it affects various vegetables, including potatoes.  Crown Gall: Caused by Agrobacterium tumefaciens, it leads to the formation of tumors on the stems and roots of many plants. Management of these diseases involves various strategies, including crop rotation, resistant plant varieties, and the use of antibiotics or biocontrol agents. Bacteria are microorganisms found in diverse environments, displaying remarkable adaptability and significance in various fields. These single-celled prokaryotes exhibit diverse shapes and sizes, and their ultrastructure includes cell walls, plasma membranes, ribosomes, and genetic material. Bacteria can reproduce rapidly through binary fission and engage in horizontal gene transfer mechanisms such as conjugation, transformation, and transduction. Their roles encompass both beneficial functions, such as nutrient recycling and symbiosis, as well as harmful effects, causing diseases in humans, animals, and plants. Understanding bacteria is crucial in fields like medicine, agriculture, biotechnology, and environmental science, where they play pivotal roles. V100_BNY101: Plant Diversity Page 40 KEY WORDS cell wall, plasma membrane, cytoplasm, ribosomes, and genetic material REFERENCES  "Brock Biology of Microorganisms" by Michael T. Madigan, John M. Martinko, and Kelly S. Bender: This is a widely used textbook that provides comprehensive coverage of microbiology, including bacteria, their biology, and their roles in various processes and diseases.  "Prescott's Microbiology" by Joanne Willey, Linda Sherwood, and Christopher J. Woolverton: This textbook covers various aspects of microbiology, including bacteriology, with a focus on microbial diversity, structure, function, and pathogenicity.  "Mims' Medical Microbiology" by Richard V. Goering, Hazel Dockrell, Mark Zuckerman, and Peter L. Chiodini: This book emphasizes the medical aspects of microbiology, including bacterial infections and their clinical relevance.  "Bergey's Manual of Systematics of Archaea and Bacteria" (Online Resource): Bergey's Manual is a comprehensive resource for bacterial taxonomy and systematics. The online version is continually updated to re flect the latest research.  "Microbe" Magazine (Published by the American Society for Microbiology): Microbe is a reputable source for articles and research on a wide range of topics in microbiology, including bacteria. It provides insights into the latest discoveries and developments in the field.  "Nature Reviews Microbiology" (Published by Nature Research): This journal provides authoritative reviews and research on microbiology, including bacterial biology, ecology, and pathogenesis.  "Annual Review of Microbiology" (Published by Annual Reviews): V100_BNY101: Plant Diversity Page 41  This journal features comprehensive reviews of research in the field of microbiology, covering bacteria and other microorganisms.  "Antonie van Leeuwenhoek Journal of Microbiology" (Published by Springer): Named after the pioneering microbiologist Antonie van Leeuwenhoek, this journal covers a wide range of topics in microbiology, including bacteria.  "The Prokaryotes" (4-Volume Set) edited by Eugene Rosenberg, Edward F. DeLong, Stephen Lory, Erko Stackebrandt, and Fabiano Thompson: This extensive reference work provides an in-depth examination of prokaryotes, which includes bacteria. It's an excellent resource for those seeking detailed information on bacterial biology and taxonomy.  "ASM Microbe Library" (Published by the American Society for Microbiology): - The ASM Microbe Library offers a variety of resources, including educational materials, case studies, and research articles on various aspects of microbiology, including bacteria  MOOCS YOUTUBE VIDEOS https://youtu.be/OBej7rFyN7U?si=-SeMCT6O6dLNwsAZ https://youtu.be/H0xmxeh6qoo?si=DinwzFyiUfH57nxr https://youtu.be/ZebbwJ6H_DI?si=OprLvaWhnQjFFb7E https://youtu.be/7tLV20dk-FM?si=oOCpGT8reerT83jm WIKIPEDIA "Wikipedia" defined Bacteria and important key points and topics related to Bacteria as follows. Definition: Bacteria are single-celled microorganisms that are among the most abundant and diverse life forms on Earth. They are prokaryotic, meaning they lack a cell nucleus and other membrane-bound organelles. Key Points: V100_BNY101: Plant Diversity Page 42 1. Cell Structure: Bacterial cells are structurally simpler than eukaryotic cells. They typically consist of a cell wall, cell membrane, cytoplasm, and genetic material in the form of a single, circular DNA molecule. 2. Classification: Bacteria are classified based on various characteristics, including cell shape (cocci, bacilli, spirilla), staining properties (Gram-positive or Gram-negative), and metabolic features (aerobic, anaerobic, autotrophic, heterotrophic, etc.). 3. Diversity: Bacteria exhibit incredible diversity in terms of habitat, metabolism, and morphology. They can be found in various environments, including soil, water, extreme environments like hot springs and deep-sea vents, and even inside the human body. 4. Beneficial Bacteria: Many bacteria play essential roles in various ecosystems and have numerous beneficial applications, such as nitrogen-fixing bacteria in soil, probiotic bacteria in the human gut, and bacteria used in the production of food and medicines. 5. Pathogenic Bacteria: Some bacteria are responsible for causing diseases in humans and other organisms. Examples include Escherichia coli, Staphylococcus aureus, and Mycobacterium tuberculosis. 6. Antibiotics: Antibiotics are drugs used to treat bacterial infections. They work by targeting specific aspects of bacterial biology and killing or inhibiting the growth of bacteria. The overuse and misuse of antibiotics have led to the development of antibiotic-resistant strains of bacteria. 7. Biotechnology: Bacteria are used in biotechnology for various purposes, such as producing recombinant proteins, fermenting foods, and breaking down organic waste in sewage treatment. 8. Evolution: Bacteria are ancient organisms and have played a crucial role in the history of life on Earth. They are thought to be among the earliest life forms, and their evolution has shaped the planet's biology and geochemistry. 9. Genomics: Advances in genomics have allowed scientists to sequence the DNA of numerous bacterial species, contributing to our understanding of their biology and evolution. Online Resources: To access comprehensive and up-to-date information on specific bacterial species and related topics, you can visit the following resources: V100_BNY101: Plant Diversity Page 43 1. MicrobeWiki: A resource that provides information on various aspects of microbiology, including bacteria. 2. National Center for Biotechnology Information (NCBI): This database contains vast amounts of genetic and scientific information about bacteria, including genomic data. 3. Bergey's Manual of Systematics of Archaea and Bacteria: A reference work that provides in-depth information on bacterial taxonomy and classification. 4. The American Society for Microbiology: An organization that offers resources, publications, and conferences related to microbiology, including bacteria. Remember that the field of bacteriology is continuously evolving, and scientific research continues to uncover new insights into the world of bacteria. OER REFERENCE BOOKS 1) "Brock Biology of Microorganisms" by Michael T. Madigan, Kelly S. Bender, Daniel H. Buckley, and W. Matthew Sattley 2) "Microbiology: An Introduction" by Gerard J. Tortora, Berdell R. Funke, and Christine L. Case 3) "Prescott's Microbiology" by Joanne Willey, Linda Sherwood, and Christopher J. Woolverton V100_BNY101: Plant Diversity Page 44  CREDIT 01-UNIT 03: ALGAE LEARNING OBJECTIVES After successful completion of this unit, you will be able to  State that algae are diverse photosynthetic organisms that can be found in various aquatic and terrestrial environments.  Definitions for essential terms related to algae, such as "photosynthesis," "thallus," "chlorophyll," or "phytoplankton.  Identify algal structures and components when presented with images or specimens, such as recognizing different algal groups and their characteristic features.  Describe the diverse forms and functions of algae, including t heir morphological diversity.  Classify algae into different categories based on their pigmentation, habitat, INTRODUCTION Algae are group of plants which are known since ancient civilizations. The term algae were first introduced by Linnaeus in 1753 and it was A. L. de Jussieu(1789) who classified the plants and delimited the algae from rest of the plant world to its present status.They vary in size from micrometers to giant kelps (brown algae) that may attain a length of 60-65 meters. They occur in most habitats, ranging from aquatic to desert land and from hot water springs to snow or ice. Algae are very important producers of organic matter. They contribute food, medicines and other useful industrial and domestic products but at the same time they may be a cause to a mass mortality in the form of water or algal blooms. 03-01: GENERAL CHARACTERISTICS 1. Algae are eukaryotic organisms that have no roots, stems, or leaves but do have chlorophyll and other pigments for carrying out photosynthesis. 2. Algae can be multicellular or unicellular. 3. Unicellularalgae occurmost frequently in water, especially inplankton. Phytoplankton is the population of free‐floating microorganisms composed primarily of unicellular algae. In addition, V100_BNY101: Plant Diversity Page 45  algae may occur in moist soil or on the surface of moist rocks and wood. Algae live with fungi in lichens. 4. The cell of an alga has eukaryotic properties, and some species have flagella with the “9‐plus‐2” pattern of microtubules. 5. A nucleus is present, and multiple chromosomes are observed in mitosis. 6. The chlorophyll and other pigments occur in chloroplasts, which contain membranes known as thylakoids. 7. Most algae are photoautotrophic and carry on photosynthesis. Some forms, however, are chemoheterotrophic and obtain energy from chemical reactions and nutrients from preformed organic matter. Most species are saprobes, and some are parasites. 8. Reproduction in algae occurs in both asexual and sexual forms. 9. Asexual reproduction occurs through the fragmentation of colonial and filamentous algae or by spore formation (as in fungi). Spore formation takes place by mitosis. Binary fission also takes place (as in bacteria). 10. During sexual reproduction, algae form differentiated sex cells that fuse to produce a diploid zygote with two sets of chromosomes. 11. The zygote develops into a sexual spore, which germinates when conditions are favorable to reproduce and reform the haploid organism having a single set of chromosomes. This pattern of reproduction is called alternation of generations. SHORT ANSWER QUESTIONS WITH MODEL ANSWER 01 1. What are algae, and how do they differ from plants? Algae are a diverse group of photosynthetic organisms that can be found in various aquatic environments, including freshwater and marine ecosystems. They are similar to plants in that they perform photosynthesis to produce their own food using chlorophyll and other pigments. However, algae lack the specialized structures found in higher plants, such as roots, stems, and leaves. Unlike plants, many algae are unicellular or have simple multicellular structures, and they do not have true vascular tissues. V100_BNY101: Plant Diversity Page 46 03-02: RANGE OF HABITAT AND THALLUS ORGANIZATION Habitat Algae are a group of ubiquitous organisms which are present in diverse habitats such as water (aquatic algae), land (terrestrial algae), they also grow as an epiphyte, endophyte, and as well as in extreme conditions, in other words it can be said that algae are of universal occurrence Thallus organization The thalli of algae exhibit a great range of variation in structure and organization. It rangesfrom microscopic unicellular forms to giant seaweeds like Macrocystis which measures up to100meters long. Some of them form colonies,orfilaments. The unicellular form may be motileas in Chlamydomonas or non-motileas in Chlorella. Mostalgae have filamentous thallus.eg. Spirogyra. The filaments may be branched.On the basis of thallus organization, algae are dividedinto following types: 1. Unicellular forms 2. Multicellular colonial forms 3. Multicellular filamentous forms 4. Siphonaceous forms 5. Multicellular Parenchymatous forms V100_BNY101: Plant Diversity Page 47  Fig. Range of thallus organization in Algae SHORT ANSWER QUESTIONS WITH MODEL ANSWER 02 2. What is the ecological significance of algae? Algae play a critical role in aquatic ecosystems and the global environment. They are primary producers that form the base of the food web, providing food and oxygen for a wide range of aquatic organisms. Algae also contribute to the carbon cycle by absorbing carbon dioxide during photosynthesis, helping to mitigate climate change. Some types of algae, like diatoms, are important indicators of water quality and can be used to assess the health of aquatic ecosystems. 3. What are the main types of algae, and how are they classified? Algae are classified into several groups based on their pigments, cell structure, and reproductive methods. The primary groups of algae include green algae (Chlorophyta), brown algae (Phaeophyta), and red algae (Rhodophyta). These groups V100_BNY101: Plant Diversity Page 48 vary in color due to the presence of different pigments. Additionally, there are other groups of algae like diatoms (Bacillariophyta) and dinoflagellates (Dinophyta). Each group has distinct characteristics and adaptations to different environmental conditions. 03-03: REPRODUCTION AND ALTERNATION OF GENERATION Reproduction in algae takes place by vegetative, asexual and sexual methods. Vegetative mode of reproduction is encountered by primitive algae whereas in higher forms both asexual and sexual reproductions are common. 1-Vegetative Reproduction- The vegetative reproduction in algae takes place by following methods (i) Fragmentation- Fragmentation is common in filamentous forms. In this process, filament breaks into fragments and each fragment give rise to a new filamentous thallus. The common examples are Ulothrix, Spirogyra, Oedogonium, Zygnema, Oscillatoria,Nostoc etc. (ii) Fission- This process is common in desmids, diatoms, and other unicellular algae.The cell divides into two by mitotic division and then separation occurs through septum formation. (iii) Adventitious branches- Protonema develops in certain algae like Chara and give rise to new thalli when detached from parent thallus. These adventitious branches develop mainly on the rhizoids. Other examples include Dictyota and Fucus. (iv)Tubers- Tubers are spherical or globular bodies which are found on lower nodes or rhizoids of Chara. These tubers when detach from parent plant can give rise to new thalli. (v)Amylum stars- In Chara, star shaped bodies filled with amylum stars are formed that give rise to new individual after detaching from the parent plant. (vi) Budding- In some algae like Protosiphon, budding takes place which results in new individuals. (vii) Hormogonia- In some cyanobacteria like Nostoc, Cylindrospermum V100_BNY101: Plant Diversity Page 49 hormogonia develop that may give rise to new thalli. These hormogonia are of varying lenths and may develop at the place of heterocysts in the thallus. These hormogones are produced by breakage of filament into two or more cells. (viii) Hormospores or hormocysts-Hormospores are thick walled hormogones which are produced in drier conditions. 2-Asexual Reproduction- In a large number of algae asexual reproductions takes place with the help of different kind of spores and other structures. Basically, spores are meant for asexual reproduction and each spore can grow into a newthallus. Spores are one celled structure and are produced internally in the case ofalgae. They are produced within the vegetative cell (Chlamydomonas) or in aspecialized structure called sporangia. They may be motile or non -motile. Motilespores are called zoospores and non-motile as aplanospores. Different types of asexual spores and structures are as follows - (i)Akinetes- In filamentous forms, certain vegetative cells become thick -walled elongated structures called as akinetes. Akinetes are perennating bodies that can survive under unfavorable conditions and can give rise to new individual on occurrence of favorable conditions. e.g., Anabaena (ii) Hypnospores-Hypnospores are thick walled, non-flagellated spores with plentyof food reserves. They are perennating structures. Hypnospores are produced under unfavorable conditions by some green algae. They germinate into new plants with return of favorable environmental conditions. e.g., Chlamydomonas, Protosiphon. In Chlamydomonas nivalis the walls of hypnospores become red due to the presence of pigment Haematochrome due to which snow becomes red. (iii) Zoospores- These are flagellated asexual spores which are formed inzoosporangium or directly from the vegetative cells. The zoospores may be biquadric or multiflagellate. The multiflagellate zoospores are of again two typesflagella arranged on entire length of body or arranged in a ring surrounding a beak like projection. e.g., Chlamydomonas (biflagellate), Ulothrix, Cladophora (quadriflagellate), Vaucheria, Oedogonium (multiflagellate). In Pedias trum, the zoospores do not germinate or divide but orientate themselves in a single plane and become opposed to form a colony just like the parent cell. This feature is not met in any other algae. V100_BNY101: Plant Diversity Page 50 (iv) Aplanospores- These are non-flagellated thin-walled asexual spores that areformed in majority of aquatic algae by the failure of flagella formation due to someunfavorable conditions. 3-Sexual Reproduction- Sexual reproduction is found in advanced algae as compared to less advanced forms where vegetative and asexual methods are main modes of reproduction. Sexual reproduction takes place by fusion of gametes of different sexuality. There is a wide range of variation in the nature of gametes and the mode of sexual reproduction. Any vegetative cell of thallus may produce gametes and thus behave as gametangium or a specialized gametangium may be developed. The gametangia may be morphologically similar (isogametangia) or dissimilar (heterogametangia). The gametes are produced in the gametangia by simple mitotic division or by reduction division. The haploid gametes fuse to make diploid zygote that give rise to the thallus. Depending upon the morphological and physiological characteristics of gametes, sexual reproduction can be of the following types- i) Isogamous- When fusing gametes are morphologically similar and physiologically different (+ and -) then the sexual reproduction is called as isogamous. E.g., Chlamydomonas, Ulothrix, Zygnema, Spirogyra. ii) Anisogamous- In anisogamous sexual reproduction fusing gametes are morphologically as well as physiologically different. The gametes are produced in different gametangia. The microgametes are male gametes while macrogametes are female gametes. e.g., Chlamydomonas. (iii) Oogamous- Oogamy is the most advanced type of sexual reproduction in which microgamete or male gamete fuses with a large female gamete or egg. Male gametes are produced in antheridium while female gamete or egg is produced within a structure called as oogonium. During fertilization male gamete reaches the oogonium to fertilize the egg and a diploid zygote is formed. e.g., Chlamydomonas. (iv)Hologamy- In certain unicellular algae whole thallus behaves like gamete and in this process, fusion takes place between opposite strained gametes or thalli that after fusion make diploid zygote. e.g., Chlamydomonas. (v) Autogamy- In autogamy fusion between two gametes of opposite strains from same mother cell takes place. Since both the fusion gametes comes from same mother cell there is no genetic recombination e.g., Diatoms. V100_BNY101: Plant Diversity Page 51 Alternation of generation Sexual reproduction involves alternation between haploid and diploid generation which we call alternation of generation. In algae, there are five main types of life cycles or alternation of generation. 1)Haplontic Life Cycle- In this type of life cycle the main plant body is gametophytic (haploid) that produces Mito spore during growing season that develops into gametophytic plant. Towards the end of the growing season gametophyte produces gametes (haploid). Zygote/zydospore (di