Arihant Biology Handbook PDF

hand book KEY NOTES TERMS DEFINITIONS FLOW CHARTS Biology Highly Useful for Class XI & XII Students, Medical Entrances and Other Competitions Sanjay Sharma Supported by Kavita Agarwal Navraj Bharadwaj ARIHANT PRAKASHAN, (SERIES) MEERUT  Arihant Prakashan (Series), Meerut...

hand book KEY NOTES TERMS DEFINITIONS FLOW CHARTS Biology Highly Useful for Class XI & XII Students, Medical Entrances and Other Competitions Sanjay Sharma Supported by Kavita Agarwal Navraj Bharadwaj ARIHANT PRAKASHAN, (SERIES) MEERUT  Arihant Prakashan (Series), Meerut All Rights Reserved © Publisher No part of this publication may be re-produced, stored in a retrieval system or distributed in any form or by any means, electronic, mechanical, photocopying, recording, scanning, web or otherwise without the written permission of the publisher. Arihant has obtained all the information in this book from the sources believed to be reliable and true. However, Arihant or its editors or authors or illustrators don’t take any responsibility for the absolute accuracy of any information published and the damages or loss suffered there upon. All disputes subject to Meerut (UP) jurisdiction only. Administrative & Production Offices Regd. Office ‘Ramchhaya’ 4577/15, Agarwal Road, Darya Ganj, New Delhi -110002 Tele: 011- 47630600, 43518550; Fax: 011- 23280316 Head Office Kalindi, TP Nagar, Meerut (UP) - 250002 Tele: 0121-2401479, 2512970, 4004199; Fax: 0121-2401648 Sales & Support Offices Agra, Ahmedabad, Bengaluru, Bareilly, Chennai, Delhi, Guwahati, Hyderabad, Jaipur, Jhansi, Kolkata, Lucknow, Meerut, Nagpur & Pune ISBN : 978-93-13196-51-8 Published by Arihant Publications (India) Ltd. For further information about the books published by Arihant log on to www.arihantbooks.com or email to [email protected] /arihantpub /@arihantpub Arihant Publications /arihantpub PREFACE Handbook means reference book listing brief facts on a subject. So, to facilitate the students in this we have released this Handbook of Biology. This book has been prepared to serve the special purpose of the students, to rectify any query or any concern point of a particular subject. This book will be of highly use whether students are looking for a quick revision before the board exams or just before other Medical Entrances. This handbook can even be used for revision of a subject in the time between two shift of the exams, even this handbook can be used while travelling to Examination Centre or whenever you have time, less sufficient or more. The format of this handbook has been developed particularly so that it can be carried around by the students conveniently. The objectives of publishing this handbook are : — To support students in their revision of a subject just before an examination. — To provide a focus to students to clear up their doubts about particular concepts which were not clear to them earlier. — To give confidence to the students just before they attempt important examinations. However, we have put our best efforts in preparing this book, but if any error or what so ever has been skipped out, we will by heart welcome your suggestions. Apart from all those who helped in the compilation of this book, a special note of thanks goes to Miss Akansha Tomar of Arihant Publications. Authors CONTENTS 1. The Living World 1-6 — Characteristics of Living Beings — Taxonomy — Biodiversity — Taxonomical Aids — Systematics 2. Biological Classification 7-23 — Biology : Nature and Scope — Kingdom–Fungi — Classification of Living Organisms — Kingdom–Plantae — Kingdom–Monera — Kingdom–Animalia — Kingdom–Protista — Viruses and Viroids 3. Plant Kingdom 24-42 — Plants : Producers of Ecosystem — Gymnospermae — Algae — Angiospermae — Bryophyta — Alternation of generations — Pteridophyta 4. Animal Kingdom 43-73 — Basis of Classification — Phylum–Arthropoda — Phylum–Porifera — Phylum–Mollusca — Phylum–Coelenterata (Cnidaria) — Phylum–Echinodermata — Phylum–Platyhelminthes — Phylum–Hemichordata — Phylum–Aschelminthes — Phylum–Chordata — Phylum–Annelida 5. Morphology of Flowering Plants 74-103 — Plant Morphology : An Overview — Flower — Stem — Fruit — Leaf — Seed — Inflorescence 6. Anatomy of Flowering Plants 104-121 — The tissues — Anatomy of Dicot and Monocot — Plant Tissue System Plants — Secondary Growth in Plants  7. Structural Organisation in Animals 122-151 — Tissue — Neural Tissue — Epithelial Tissue(By Ruysch) — Earthworm — Connective Tissue — Cockroach — Muscular Tissue — Frog 8. Cell : The Unit of Life 152-166 — Cell — Structure and Components of — Cell Theory Eukaryotic Cell — Components of a Cell 9. Biomolecules 167-188 — How to Analyse Chemical — Nucleic Acids Composition? — DNA — Biomolecules — RNA — Carbohydrates(Saccharides) — Enzymes — Proteins — Metabolites — Lipids 10. Cell Cycle and Cell Division 189-194 — Cell Cycle — Amitosis — Dividing or M-phase — Significance of Cell Cycle 11. Transport in Plants 195-206 — Process Involved in Passive — Upward Water Movement in a Transport Plant — Plant-Water Relation — Uptake and Transport of Mineral — Long Distance Transport of Water Nutrients — Absorption of Water by Plants — Translocation and Storage of Food in Plants (Phloem Transport) 12. Mineral Nutrition in Plants 207-214 — Classification of Mineral Nutrients — Hydroponics — Deficiency Symptoms of Essential — Metabolism of Nitrogen Mineral Nutrients 13. Photosynthesis in Higher Plants 215-227 — Chemistry and Thermodynamics — Photorespiration of Photosynthesis — Factors Affecting Photosynthesis — Chloroplast : Photosynthetic Organ of Cell 14. Respiration in Plants 228-238 — Cellular Respiration — Anaerobic Cellular Respiration — Aerobic Respiration — Factors Affecting Respiration — Pentose Phosphate Pathway (PPP) 15. Plant Growth and Development 239-248 — Growth — Seed Dormancy — Development — Photoperiodism — Plant Hormones/Phytohormones/ — Abscission of Plant Parts Plant Growth Regulators (PGRs) 16. Digestion and Absorption 249-264 — Human Digestive System — Digestive Enzymes — Alimentary Canal — Digestive Hormones — Digestive Glands — Disorder of Digestive System — Physiology of Digestion 17. Breathing and Exchange of Gases 265-275 — Respiration — Transport of Gases — Human Respiratory System — Regulation of Respiration — Lungs — Disorders of Respiratory System — Exchange of Gases 18. Body Fluids and Circulation 276-296 — Body Fluids — Human Circulatory System — Blood — Blood Vascular System — Lymph — Portal System — Circulatory System 19. Excretory Products and Their Elimination 297-306 — Excretion — Regulation of Kidney Function — Excretory Products — Micturition — Human Excretory System — Role of Other Organs in Excretion — Mechanism of Filtrate Concentration 20. Locomotion and Movement 307-329 — Locomotion — Skeletal System — Movement — Joints — Muscle — Disorders of Muscular and — Specialised Muscle Phenomena Skeletal System 21. Neural Control and Coordination 330-359 — Human Neural System — Nerve Impulse — Central Nervous System — Synapse — Brain — Sense Organs — Brain Ventricles — The Visual Sense-The Eye — Spinal Cord — Human Ear-Organ of Hearing and — Reflex Action Balance — Reflex Arc 22. Chemical Coordination and Integration 360-370 — Glands — Regulation of Hormone Action — Hormones — Major Hormones of Human — Human Endocrine System Endocrine System — Mechanism of Hormone Action 23. Reproduction in Organisms 371-375 — Reproduction in Plants — Events in Sexual Reproduction of — Reproduction in Animals Both Plants and Animals 24. Sexual Reproduction in Flowering Plants 376-390 — Flowers — Fertilisation — Pre-fertilisation : Structures and — Post-fertilisation Events Events — Development of — Pollination Embryo/Embryogenesis 25. Human Reproduction 391-414 — Male Reproductive System — Fertilisation — Female Reproductive System — Implantation — Gametogenesis — Embryonic Development — Spermatogenesis — Foetal Development — Structure of Sperm — Placenta — The Menstrual Cycle — Lactation 26. Reproductive Health 415-425 — Problems Related to Reproductive — Acquired Immuno Deficiency Health Syndrome — Population Explosion — Infertility — Strategies to Improve — Assisted Reproductive Technology Reproductive Health — Detection of Foetal Disorders — Medical Termination of Pregnancy during Early Pregnancy — Sexually Transmitted Diseases 27. Principles of Inheritance and Variation 426-449 — Heredity — Sex-Determination — Variations — Linkage — Gregor Johann Mendel — Mutation — Mendel's Laws of Inheritance — Pedigree Analysis — Chromosomal Theory of Inheritance 28. Molecular Basis of Inheritance 450-468 — DNA as Genetic Material — Wobble Hypothesis — DNA — Regulation of Gene Expression — RNA — Human Genome Project — Gene Expression — DNA Fingerprinting — Genetic Code 29. Evolution 469-499 — Origin of Universe — Mutation Theory — Origin of Life — Mechanism of Evolution — Evidences of Evolution — Evolution of Human — Theories of Evolution — Human and Other Primates — Darwinism 30. Human Health and Diseases 500-521 — Human Health — Acquired Immuno Deficiency — Common Diseases in Humans Syndrome — Immunity and Immune System — Cancer — Complement System — Drugs — Vaccination and Immunisation — Addiction — Allergies — De-addiction — Autoimmunity — Adolescence 31. Strategies for Enhancement in Food Production 522-537 — Animal Husbandry — Apiculture/Bee-Farming — Improvement of Animals through — Sericulture Breeding — Lac Culture — Pisciculture/ Fish Farming/ Culture — Plant Breeding Fishery — Single Cell Protein 32. Microbes in Human Welfare 538-547 — Microbes in Household Products — Bioherbicides — Microbes in Industrial Products — Bioinsecticides — Biopesticides — Microbes in Sewage Treatment 33. Biotechnology : Principles and Processes 548-561 — Principle of Biotechnology — Gel Electrophoresis — Genetic Engineering/Recombinant — Bioreactors DNA Technology — Downstream Processing — Tools of rDNA Technology 34. Biotechnology and Its Applications 562-574 — Types of Biotechnology — Applications of Biotechnology in — Applications of Biotechnology in Industry and Environment Plant Tissue Culture — Applications of Biotechnology in Medicine 35. Organisms and Population 575-585 — Organism and its Environment — Population and Community — Responses to Abiotic Factors — Characteristics of Population — Adaptations 36. Ecosystem 586-603 — Ecosystem — Features of Ecosystem — Components of Ecosystem — Food Chain — Ecosystem: Structure and — Food Web Characteristics — Ecosystem Services 37. Biodiversity and Conservation 604-617 — Levels of Biodiversity — Loss of Biodiversity — Patterns of Biodiversity — IUCN and Red List Categories — Importance of Biodiversity — Biodiversity Conservation 38. Environmental Issues 618-639 — Pollution — Ozone Layer Depletion — Greenhouse Effect — Degradation by Improper — Global Warming Resource Utilisation and — Acid Rain Maintenance Appendix 640-644  1 The Living World Life is a characteristic quality that differentiates inanimate (non-living) objects from the animate (living) forms. Characteristics of Living Beings Catabolism Process of breakdown of complex substances into simpler ones, Growth e.g., respiration. Living organisms Short-term Adaptations Anabolism grow with increase Temporary changes to Process of formation in mass and number respond to changing of complex substances of individuals/cells. environment, from simpler ones, e.g., hibernation and e.g., photosynthesis. Heat Stroke aestivation. Increase in body temperature above the Long-term Adaptations A series of chemical normal level. Permanent changes in processes catalysed by enzymes, occurring Hypothermia response to changing Decrease in body environment, within the body temperature below the e.g., humming birds. of living beings. normal level. Metabolism Adaptation Thermoregulation Genetic mechanism of Process that allows an organism to survive, Characteristics your body to maintains thrive and reproduce by of its core internal constantly enhancing Living Beings temperature itself. Conciousness Cellular Organisation Reproduction Composition and Ability of an Process of producing arrangement of organism to young ones by ·cells in body. sense its living things. environment. Multicellular Organisms Asexual Reproduction Organisms with multiple Irritability Does not involve the cells of various type, Ability of an organism to fusion of gametes or e.g., Hydra. react against external stimuli, sex cells, e.g., Amoeba. Unicellular Organisms e.g., movement of an Organisms having a Sexual Reproduction organism towards the light single cell, Involves the fusion of source. e.g., Amoeba. gametes, e.g., humans. 2 Handbook of Biology Biodiversity It is the degree of variability among living organisms. It includes all the varieties of plants and animals. It encompasses all the ecological complexes (in which the diversity occurs), ecosystem, community diversity, species diversity and genetic diversity. It comprises all the millions of species and the genetic differences between them. Systematics It is the study of the biodiversity. It attempts to classify the diversity of organisms on the basis of following four fields viz, identification, classification, nomenclature. 1. Identification It aims to identify the correct name and position of an organism in the already established classification system. It is done with the help of keys. Key is a list of alternate characters found in organisms. An organism can be identified easily by selecting and eliminating the characters present in the key. 2. Classification It involves the scientific grouping of identified organisms into convenient categories or taxa based on some easily observable and fundamental characters. The various categories which show hierarchical arrangement in decreasing order are Kingdom → Phylum → Class → Order → Family → Genus → Species 3. Nomenclature After classification, organisms are subjected to a format of two-word naming system called binomial nomenclature. It consists of two components, i.e., generic name and specific epithet. For example, in Mangifera indica, ‘Mangifera’ is the generic name and ‘indica’ is the specific name of mango. This system was proposed by C Linnaeus (a Swedish Botanist) in (1753) in his book Species Plantarum. Polynomial system of nomenclature is a type of naming system containing more than two words. Trinomial system is a component of polynomial system and contains three words. Third word represents the sub-species and first two-words remain the same as in binomial system. Codes of Biological Nomenclature There are five codes of nomenclature which help to avoid errors, duplication and ambiguity in scientific names.  The Living World 3 These codes are as follows ICBN International Code of Botanical Nomenclature ICZN International Code of Zoological Nomenclature ICVN International Code of Viral Nomenclature ICNB International Code for Nomenclature of Bacteria ICNCP International Code for Nomenclature for Cultivated Plants Types of Specification in Nomenclature The ICBN recognises following several types are given below Syntype Holotype Any of the two or more Prototype specimen from specimens cited by an which description of a new author when there is species is established. no holotype. Specification Isotype in Paratype It is the same as Nomenclature Specimens described holotype. along with the holotype. Neotype Lectotype New nomenclature type Specimen selected from when the holotype is original material when not available. there is no holotype. Taxonomy It deals with the principles and procedures of identification, nomenclature and classification of organisms. It reflects the natural and phylogenetic relationships among organisms. It also provides the details of external and internal structures, cellular structure and ecological information of organisms. The term taxonomy was coined by AP de Candolle, 1813. Various Branches of Taxonomy Taxonomic Field Basis Alpha (α) Taxonomy Morphological traits Artificial Taxonomy Habit and habitat of organisms Natural Taxonomy Natural similarities among organisms Chemotaxonomy Presence or absence of chemicals in cells or tissues Cytotaxonomy Cytological studies Numerical or Phenetic Taxonomy Number of shared characters of various organisms Phylogenetic or Omega (ω) Taxonomy Based on phylogenetic relationships 4 Handbook of Biology Classical Taxonomy It is also known as old taxonomy. In classical taxonomy, species is the basic unit and it can be described on the basis of one or few preserved specimens. Organisms are classified on the basis of some limited features. Modern Taxonomy/New Systematics The concept of modern taxonomy was given by Julian Huxley (1940). According to it, species are dynamic and ever-changing entity. Studies of organisms are done on a huge number of variations. It includes cytotaxonomy, numerical taxonomy, chemotaxonomy, etc. Taxonomic Categories Classification is not a single step process. It involves hierarchy of steps in which each step represents a rank or category. Since, the category is a part of overall taxonomic arrangement, it is called the taxonomic category. The taxonomic categories, which are always used in hierarchical classification of organisms are called obligate categories. The sub-categories like sub-species, sub-class, sub-family, etc., which facilitate more sound and scientific placement of various taxa are called intermediate categories. Arrangement of taxonomic categories in a descending order during the classification of an organism is called taxonomic hierarchy. It was first introduced by Linnaeus (1751) and hence, it is also known as Linnaean Hierarchy. Taxonomic Categories For Plants For Animals Kingdom Kingdom Division Phylum Class Class Order Order Family Family Genus Genus Species Species Taxonomic categories showing hierarchical arrangement in ascending order  The Living World 5 Taxon represents the rank of each category and referred to as a unit of classification. The term ‘Taxon’ was first introduced by ICBN during 1956. According to Mayr (1964), taxon is a group of any rank that is sufficiently distinct to be worthy of being assigned a definite category. In simple words, taxon refers to a group of similar, genetically related individuals having certain characters distinct from those of other groups. (i) Kingdom It is the highest category in taxonomy. A kingdom includes all the organisms which share a set of distinguished characters. (ii) Phylum or Division (Cuvier, Eichler) It is a taxonomic category higher than class and lower in rank to kingdom. The term ‘Phylum’ is used for animals, while ‘Division’ is commonly employed for plants. It consists of more than one classes having some similar correlated characters. (iii) Class (Linnaeus) It is a major category, which includes related orders. (iv) Order (Linnaeus) It is a group of one or more related families that possess some similar correlated characters, which are lesser in number as compared to a family or genera. (v) Family (John Ray) It is a group of related genera with less number of similarities as compared to genus and species. All the genera of a family have some common or correlated features. They are separable from genera of a related family by important differences in both vegetative and reproductive features. (vi) Genus (Term given by John Ray) It comprises a group of related species, which has more characters common in comparison to species of other genera. In other words, genera are the aggregates of closely related species. (vii) Species Taxonomic studies consider a group of individual organisms with fundamental similarities as a species (John Ray). It is the lowest or basic taxonomic category, which consists of one or more individuals of a population. 6 Handbook of Biology Taxonomical Aids They include techniques, procedures and stored information that are useful in identification and classification of organisms. Some of the taxonomical aids are as follows Herbarium Manuals and Catalogues Storehouse of collected Provide information for plant specimens that are identification of names dried, pressed and of species found in an area. preserved on sheets. Museums Taxonomical Aids Monographs Place for the collection Contain information of preserved plants and on any one taxon. animal specimens. Keys Botanical and Zoological Parks Used for identification of Contain the living collection of plants and animals based plants and animals in the on their similarities and conditions similar to their dissimilarities. natural habitat. Importance of Taxonomical Aids l These aids help to store and preserve the information as well as the specimens. The collection of actual specimens of plant and animal species is essential and is the prime source of taxonomic studies. l These are also essential for training in systematics which is used for the classification of an organism. Hence, taxonomic aids facilitate identification, naming and classification of organisms using actual specimens collected from the fields and preserved as referrals in the form of herbaria, museums, etc.  2 Biological Classification Biology : Nature and Scope Biology (L. bios – life; logos – knowledge) is the branch of science, which deals with the study of living organisms and their life processes. Aristotle is called the Father of Biology, but the term ‘Biology’ was first coined by Lamarck and Treviranus in 1802. It has two main branches, i.e., Botany (study of plants) and Zoology (study of animals). l Father of Botany Theophrastus l Father of Zoology Aristotle Classification of Living Organisms Classification is an arrangement of living organisms according to their common characteristics and placing the group within taxonomic hierarchy. The branch of science which deals with description, nomenclature, identification and classification of organisms is called taxonomy. Some major branches of taxonomy are (i) Numerical taxonomy It is based on all observable characteristics. Number and codes are assigned to characters and data is processed through computers. (ii) Cytotaxonomy In this taxonomy, the detailed cytological information is used to categorise organisms. (iii) Chemotaxonomy The chemical constituents are taken as the basis for classification of organisms. 8 Handbook of Biology On the basis of reference criteria, the classification of living organisms can be of three types Classification of Living Organisms Artificial Natural Phylogenetic or or or Prior Classification Phenetic Classification Cladistic Classification 1. Artificial or Prior Classification In this system of classification one or very few characters are considered as the key feature of classification. This classification system never throws light on affinities or relationships between the organisms. 2. Natural or Phenetic Classification The classification system in which organisms are classified on the basis of their permanent vegetative characters. In this classification system, the grouping of heterogenous groups (unrelated) of organisms is avoided. 3. Cladistic or Phylogenetic Classification This classification may be monophyletic (i. e. , one ancestry), polyphyletic (i. e. the organism derived from two ancestors) and paraphyletic (i. e. , the organism does not include all the descendents of common ancestor). Cladistics is a method of classification of organisms based upon their genetic and ancestral relationships, which are more scientific and natural. The most accepted, five kingdom system of classification of living organisms was proposed by RH Whittaker. These five kingdoms are Monera, Protista, Fungi, Animalia and Plantae. Other Classification Systems l Two kingdom system–Carolus Linnaeus (Animalia and Plantae). Merits Photosynthetic organisms were included into plant kingdom and non-photosynthetic organisms were included into animal kingdom. Demerits Some organisms do not fall naturally either into plant or animal kingdom or share characteristics of both. l Three kingdom system–Ernst Haeckel (Protista, Animalia and Plantae). Merits Created a third kingdom which includes unicellular eukaryotic microorganisms and some multicellular organisms. Demerits Monerans were not placed correctly.  Biological Classification 9 l Four kingdom system–Copeland (Monera, Protista, Animalia and Plantae). Merits Monerans were placed separately along with other kingdoms. Demerits Monerans were not subdivided in Archaebacteria and Eubacteria. l Six kingdom system–Carl Woese (Archaebacteria, Eubacteria, Protista, Fungi, Animalia and Plantae). Merits Archaebacteria and Eubacteria were separately placed. A. Kingdom–Monera (Prokaryotic, Unicellular Organisms) It includes all prokaryotes such as bacteria, archaebacteria, mycoplasma, actinomycetes, cyanobacteria and rickettsia. 1. Bacteria These unicellular, prokaryotic organisms contain cell wall (feature of plant cells only). These are approximately 4000 species of bacteria, with cosmopolitan occurrence. Bacteria can be regarded both friends and foes on the basis of interaction with human beings. An average weight human (~ 70 kg) has about 2.5 kg of bacteria in the form of gut microflora to supplement the proper digestion and other metabolic functions. Details to bacteria can be visualised in a nutshell as Bacteria Archaebacteria Eubacteria (primitive bacteria) (true bacteria) Methanogens Halophiles Thermoacidophiles (methane producing (salty/marine (present in acidic bacteria) bacteria) sulphur springs) On the basis On the basis On the basis of staining behaviour of structure of nutrition Gram-Positive Gram-Negative Autotrophic Bacteria Bacteria Photosynthetic bacteria Purple-sulphur Cocci Bacilli Spirillum Vibrio bacteria (rounded) (capsule) (spiral) (comma-like) Heterotrophic Saprophytic Symbiotic Parasitic Non-motile Motile 10 Handbook of Biology (i) Archaebacteria These are the group of most primitive prokaryotes. They have a cell wall, made up of protein and non-cellulosic polysaccharides. The presence of 16 srRNA, makes them unique and helps in placing in a separate domain called archaea between bacteria and eukarya. Archaebacteria can live under extreme hostile conditions like salt pans, salt marshes and hot sulphur springs. They are also known as living fossils, because they represent the earliest form of life on earth. Archaebacteria can be used for (a) Experimentation for absorption of solar radiation. (b) Production of gobar gas from dung and sewage. (c) Fermentation of cellulose in ruminants. (ii) Eubacteria Eubacteria are ‘true bacteria’ which lack nucleus and membrane bound organalles like mitochondria, chloroplasts, etc. Eubacteria are usually divided into five phylums– Spirochetes, Chlamydias, Gram- positive bacteria, Cyanobacteria and Proteobacteria. The structural detail of a typical eubacterial cell is given as follows Inclusions Capsule These are reserve food It is made up of gelatinous polysaccharide deposits found in prokaryotic and polypeptide. It protects the bacteria, and eukaryotic cells. These from pathogens and desiccation. It helps may be of glycogen, starch, in adherance to any surface. lipid and sulphur granules. Cytoplasm It contains 80% water, protein, carbohydrate, lipid, organic ions, etc. Ribosomes 70 S type of ribosomes, consists of r RNA and proteins. Plasma Membrane Its structure and functions Cell Wall are similar to eukaryotic It is rigid due to the presence of plasma membrane. murein. Cell wall contains Mg2+ It is also the site of some ions which bind to teichoic acid. respiratory enzymes. This binding protects the bacteria Mesosome from thermal injuries. Complex localised infolding of membrane which serves as respiratory organ, Nuclear Area (Nucleoid) i.e., centre of respiration. It is amorphous lobular mass of fibrillar chromatin type material which occupies 10-20% area of Fimbriae cell. These are short, filamentous structures composed of protein, pilin. These are Plasmid evenly distributed and used for Small, circular, self-replicating attachment rather than motility. extrachromosomal DNA, having Flagellum few genes. Long, filamentous appendage consisting of filament, hook and basal body. It is rotatory in function and contains flagellin protein. Detailed structure of a bacterium  Biological Classification 11 Nutrition in Bacteria The process of acquiring energy and nutrients., is called nutrition. On the basis of mode of nutrition, bacteria are of two types– autotrophic and heterotrophic. About 1% bacteria show autotrophic mode of nutrition and the rest are of heterotrophic habit. Chemosynthetic bacteria oxidise various inorganic substances such as nitrates, nitrites and ammonia and use the released energy for their ATP production. Autotrophic (i.e., photosynthetic) bacteria and heterotrophic bacteria with their related details are mentioned in following tables. Some Photosynthetic Bacteria Group Main Habitats Cell Wall Representatives Prochlorobacteria Live in tissues of marine Gram-negative Prochloron invertebrates. Purple or green Generally anaerobic and Gram-negative Rhodospirillum bacteria reside on sediments of and Chlorobium lakes and ponds. Some Heterotrophic Bacteria Group Main Habitats Cell Wall Representatives Spirochetes Aquatic habitats, Gram-negative Spirochaeta and parasites of animals Treponema. Aerobic rods and Soil, aquatic habitats, Gram-negative Pseudomonas, cocci parasites of animals Neisseria, and plants Nitrobacter, Azotobacter and Agrobacterium Facultative Soil, plants, animal gut Gram-negative Salmonella, anaerobic rods Shigella, Proteus, (enterobacteria) Escherichia and Photobacterium Sulphur and Anaerobic muds, Gram-negative Desulfovibrio sulphate reducing sediments bacteria (as in bogs, marshes) Myxobacteria Decaying plant and Gram-negative Myxococcus and animal matter, bark of Chondromyces living trees 12 Handbook of Biology Group Main Habitats Cell Wall Representatives Mycoplasmas Parasites of plants Cell wall absent Mycoplasma and animals Gram-positive Soil, skin and mucous Gram-positive Staphylococcus cocci membranes of animals and Streptococcus Endospore-forming Soil; animal gut Gram-positive Bacillus and rods and cocci Clostridium Non-sporulating Fermenting plant and Gram-positive Lactobacillus and rods animal material, Listeria human oral cavity, gut, vaginal tract Chemoautotrophes Soil, aquatic habitat Gram-negative Halothiobacillus and Acidothiobacillus Respiration in Bacteria Respiration occurs in the plasma membrane of bacteria. Glucose is broken down into carbon dioxide and water using oxygen in aerobic cellular respiration and other molecules such as nitrate (NO3 ) in anaerobic cellular respiration. Reproduction in Bacteria Bacteria reproduce asexually and sexually both. Asexual Methods Asexually, bacteria reproduce by following methods l Fission Bacteria divide both laterally and longitudinally. l Budding Vegetative outgrowths result into new organisms after maturity. l Spore formation Non-motile spores like conidia, oidia and endospores are formed. Sexual Methods Although sexes are not differentiated in bacteria, following methods of genetic recombination are categorised under sexual reproduction in bacteria. l Transformation F Griffith (1928), Genetic material of one bacteria is transferred to other through conjugation tube.  Biological Classification 13 l Conjugation Lederberg and Tatum (1946), Transfer of genetic material occurs through sex pili. l Transduction Zinder and Lederberg (1952), Transfer of genetic material occurs by bacteriophage. Economic Importance of Bacteria Economically, some bacteria are useful in producing various useful substances like curd, cheese, antibiotics and vinegar, etc. While other bacteria cause several chronic diseases in humans, plants and other animals, etc. Other Monerans These are as follows 1. Mycoplasma l It was discovered by Nocard and Roux in 1898. These are cell wall less, aerobic and non-motile organisms. Due to the absence of cell wall and pleomorphic nature, they are commonly called as jokers of living world. l The mycoplasmas are also known as Pleuro Pneumonia Like Organisms (PPLO). These are the smallest living cells, yet discovered, can survive without oxygen and are typically about 0.1 µm in diameter. Lipoprotein membrane (3 layers) Ribosomes DNA Soluble RNA Structure of Mycoplasma 2. Actinomycetes l The members of a heterogeneous group of Gram-positive, are generally anaerobic bacteria noted for a filamentous and branching growth pattern. It results in most forms in an extensive colony or mycelium. 14 Handbook of Biology l Morphologically, they resemble fungi because of their elongated cells that branch into filaments or hyphae. During the process of composting, mainly thermophilic and thermotolerent Actinomyces are responsible for the decomposition of the organic matter at elevated temperature. l Generally, Actinomycetes grow on fresh substrates more slowly than other bacteria and fungi. During the composting process, the Actinomycetes degrade natural substances such as chitin or cellulose. l Natural habitats of thermophilic Actinomycetes are silos, corn mills, air conditioning systems and closed stables. Some Actinomycetes are found responsible for allergic symptoms in the respiratory tract, e.g., Extrinsic Allergic Alveolitis (EAA). 3. Cyanobacteria/Blue-Green Algae (BGA) l They are Gram-negative photosynthetic prokaryotes which perform oxygenic photosynthesis. These can live in both freshwater and marine habitats and are responsible for ‘blooms’ in polluted water (eutrophication). l They have photosynthetic pigments, chlorophyll-a, carotenoids and phycobilins and food is stored in the form of cyanophycean starch, lipid globule and protein granules. l Cyanobacteria have cell wall formed of peptidoglycan, naked DNA, 70S ribosomes and the absence of membrane bound organelles like endoplasmic reticulum, mitochondria, Golgi bodies, etc. l The red sea is named after the colouration provided by red coloured cyanobacteria i.e., Trichodesmium erythraeum. l Cyanobacteria can fix atmospheric nitrogen through a specific structure called heterocyst. These are modified cells in which photosystem-II is absent hence, non-cyclic photophosphorylation does not take place. Nitrogen-fixation is performed through enzyme nitrogenase, present in it. 4. Rickettsia l These are small, aerobic and Gram-negative bacteria. They belong to phylum–Proteobacteria, which are capable of growing in low level of nutrients and have long generation time relative to other Gram-negative bacteria. l Rocky Mountain Spotted Fever (RMSF) is a tick borne human disease caused by Rickettsia rickettsii, an obligate, intracellular bacteria.  Biological Classification 15 B. Kingdom–Protista (Eukaryotic, Unicellular Organisms) It includes three broad groups, explained in the following flow chart Kingdom–Protista Plant-like Protists Fungi-like Protists Animal-like Protists (photosynthetic (slime moulds) (protozoans) protists) Subphyla Subphyla Amoeboid Sporozoans Protozoans Flagellated Ciliated Pyrophyta Chrysophyta Euglenophyta Protozoans Protozoans (dinoflagellates) (diatoms) (euglenoids flagellates) Subphyla Myxomycota Acrasiomycota (acellular slime (cellular slime moulds) moulds) In the view of evolution, the kingdom–Protista acts as a connecting link between the prokaryotic kingdom–Monera and multicellular kingdoms like Fungi, Plantae and Animalia. The term ‘Protista’ was given by German biologist, Ernst Haeckel in 1866. The group Protista shows following characteristics in common (i) These are mostly aquatic. (ii) Eukaryotic cell of protists possess well-defined nucleus. (iii) Membrane bound organelles present. (iv) Protists reproduce both asexually and sexually by a process involving cell fusion and zygote formation. (v) They may be autotrophic and heterotrophic (i.e., parasitic). The detailed descriptions of protistan groups are as follows Plant-like Protists (Photosynthetic) These can be 1. Dinoflagellates The group of 1000 species of photosynthetic protists, belongs to the division–Pyrophyta and class–Dinophyceae. They are unicellular, motile and biflagellate, golden-brown coloured protists. They form the important components of phytoplanktons. Their macronuclei possess condensed chromosomes, even in interphase, called as mesokaryon (Dodge; 1966). Sometimes they exhibit the phenomenon of bioluminescence. @unacademyplusdiscounts 16 Handbook of Biology 2. Chrysophytes These include diatoms and desmids. Diatoms are mostly aquatic and sometimes present in moist terrestrial habitat. They are very good pollution indicator. The diatoms do not decay easily as their body is covered by siliceous shell. They pile up at the bottom of water body and form diatomite or diatomaceous earth (can be used as fuel after mining). 3. Euglenoids These are Euglena like unicellular flagellates found mostly in stagnant freshwater. Instead of a cell wall, they have a protein rich layer called pellicle, which makes their body flexible. They have two types of flagella (i) Long Whiplash (ii) Short Tinsel The food is stored in proteinaceous granules called pyrenoids. Photosynthetic euglenoids, behave like heterotrophs in dark, this mode of nutrition is called mixotrophic. The chief member of this group, i.e., Euglena is regarded as connecting link between animals and plants. Fungi-Like Protists (Slime Moulds) They possess the characters of both animals and fungi therefore, combinedly called as fungus-animals. They show saprophytic food habit and consume organic matter. Under suitable conditions, they form Plasmodium. On the basis of occurrence of Plasmodium, these are of two types (i) Acellular/Plasmodial slime moulds, e.g., Physarum, Fuligo septica, etc. (ii) Cellular slime moulds, e.g., Dictyostelium, Polysphondylium, etc. Animal-Like Protists (Protozoans) The most primitive relatives of animals, protozoans are heterotrophic (predator or parasitic) organisms, divided into four major groups (i) Amoeboid protozoans They live in freshwater, moist soil and salt water as parasite. They move with the help of pseudopodia as in Amoeba. Other members of this group are Entamoeba histolytica and E. gingivalis cause various digestive and oral diseases when engulfed through polluted water.  Biological Classification 17 (ii) Flagellated protozoans They are either free-living or parasitic in nature. Chief members are (a) Trypanosoma sp.–carried by tse-tse fly and causes African sleeping sickness. (b) Leishmania sp. carried by sand fly and causes kala-azar or dum-dum fever. (c) Giardia sp. causes giardiasis. (d) Trichomonas vaginalis causes leucorrhoea. (iii) Ciliated protozoans They are aquatic and move actively due to the presence of cilia. They show nuclear dimorphism (macro and micronucleus), e.g., Paramecium, etc. (a) Macronucleus/Vegetative nucleus Controls metabolic activities and growth. (b) Micronucleus/ReproductivenucleusControls reproduction. (iv) Sporozoans They have an infectious, spore-like stage in their life cycle. All are endoparasites. Locomotory organs are cilia, flagella and pseudopodia, e.g., Plasmodium, Monocystis, etc. C. Kingdom–Fungi (Eukaryotic, Heterotrophic Organisms) Fungi are a group of eukaryotic, achlorophyllous, non-photosynthetic and heterotrophic organisms. The basic features of fungi include (i) Fungi lack chlorophyll, hence they are heterotrophic. (ii) They cannot ingest solid food, but absorb it after digestion. The digestive enzymes are secreted on food, then they (fungi) absorb it. (iii) On the basis of food sources, they may be saprophyte or parasites. Cell wall in fungi is made up of nitrogen containing polysaccharides, chitin. Reserved food material is glycogen or oil. Along with certain bacteria, saprotrophic fungi function as the main decomposers of organic remains. With the exception of yeasts (unicellular, fungi and filamentous), fungi bodies consist of long, slender, thread-like structures called hyphae. Mycelium is the network of hyphae. Some are called coenocytic hyphae (continuous tubes filled with multinucleated cytoplasm) and others have cross walls (septae) in their hyphae. Cell walls of fungi are composed of chitin and polysaccharides. 18 Handbook of Biology Classification of Fungi (Martin; 1961) Fungi Myxomycetes Eumycetes (body as amoeboid (unicellular, multicellular, naked protoplast) filamentous) Phycomycetes Ascomycetes Deuteromycetes Basidiomycetes (mycelium aseptate and (mycelium septate) (mycelium septate) (septate) multinucleate) l Known as sac fungi, l Known as imperfect l Grow in soil, on logs l Members are found mostly multicellular fungi. and in living plant in aquatic habitats; (Penicillium) or rarely l Deuteromycetes bodies. decaying wood in unicellular (yeast). reproduce only by l Reproduce damp places. l Asexual spores are asexual spores, vegetatively by l Reproduce asexually conidia produced on conidia. fragmentation, sex by zoospores or conidiophores. e.g., Synchytrium, organs are absent. aplanospores. l Sexual spores are Aspergillus, etc. e.g.,Agaricus, etc e.g., Allomyces and ascospores Puccinia, etc. produced on asci. e.g., Albugo, etc. Reproduction in Fungi Three types of reproduction occur in fungi Reproduction Vegetative Asexual Sexual When a vegetative structure During asexual reproduction, In sexual reproduction, the after separation produces several mononucleate and fusion of compatible nuclei new individual, it is called binucleate spores are takes place. It involves three vegetative reproduction. produced which later steps, plasmogamy, It occurs by following germinate into new individuals. karyogamy and meiosis. processes It occurs by following methods It occurs by following methods Fragmentation Zoospore Planogametic copulation Budding Sporangiospore (Phycomycetes) Gametangial contact Fission Chlamydospore Gametangial copulation Sclerotia Oidia Spermatogamy Rhizomorphs Conidia Somatogamy Ascospore (Ascomycetes) Basidiospore (Basidiomycetes) Binucleate spore  Biological Classification 19 Life Cycles of Some Fungi These can be described as follows (i) Life Cycle of Rhizopus The structural representation (sexual and asexual) of life cycle of Rhizopus is as follows Fragmentation Vegetative Reproduction Sporangium Chlamydospore Oidia Asexual Reproduction Rhizopus mycelia Sexual Progametangium(–) Germ spores Reproduction (+ or –) Progametangium (+) Gametangium (–) Germ sporangium Gametangium Haplophase (n) (+) Coenogamete (–) Promycelium Coenogamete + Azygospore Meiosis Fertilisation Diplophase (2n) Zygospore Life cycle of Rhizopus 20 Handbook of Biology (ii) Life Cycle of Yeast The diagrammatic representation of sexual cycle of Saccharomyces cerevisiae is as follows Dwarf strain yeast cells B Budding + C + A Gametangia – Germinate – Plasmogamy L Ascospore D Karyogamy se Ascospores ha op Mature ) pl e (n (2 has Ha ascus Zygote p lo n) E p Di K Young Germination ascus Large strain yeast cell Ascus mother F J cell Meiosis Bud G Budding I H Life cycle of Saccharomyces cerevisiae Heterothallism The phenomenon of having two genetically different and compatible sexual strains in two different thalli is called heterothallism. It was discovered by Blakeslee in Mucor.  Biological Classification 21 Mushroom and Fairy Rings Agaricus compestris is an edible mushroom. It is also called white button mushroom. The fruiting body of Agaricus, arises in concentric rings (called fairy rings or fungal flowers) from the mycelium present in the soil. Lichens They have composite structure and consist of two dissimilar organisms forming a symbiotic relationship between them. Lichens are formed by l Algal Part — Phycobiont — Provide food to fungi l Fungal part — Mycobiont — Provide shelter to algae Lichens are of three types on the basis of their structure (i) Crustose lichens These are point-like, flat lichens, e.g., Caloplaca. (ii) Foliose lichens These lichens have leafy structure, e.g., Hypogymnia physodes. (iii) Fruticose lichens These are branched lichen, form filamentous branching, e.g., Cladonia evansii, Usnea australis, etc. Various forms of lichens are given below Fungal fructification Parmella Graphis Cora (foliose) (crustose) (foliose) Attaching disc Pendent branches Podetia Early foliose part Cladonia Fungal (fruticose) Usnea fructification (fruticose) Forms of lichens Mycorrhiza It is a symbiotic association between a fungus and a plant. Plants prepare organic food and supply them to fungus and in return, fungus supplies water and mineral nutrients to plants. 22 Handbook of Biology D. Kingdom–Plantae (Eukaryotic, Chlorophyllous Organisms) These are chlorophyllous and embryo forming organisms. Mostly non-motile and function as the producers in ecosystem as they can fix solar energy into chemical energy through the process of photosynthesis. The cell wall in plants is cellulosic and stored food material is in the form of starch. A detailed account of plant kingdom is given in chapter 6. E. Kingdom–Animalia (Multicellular, Eukaryotic Organisms) The heterotrophic, eukaryotic organisms which are multicellular and lack cell wall, present in this kingdom. Animals have advanced level of tissue organisation, in which the division of labour is highly specific. The two main groups among animals are Non-chordata and Chordata, divided on the basis of the presence of notochord in them. A detailed account of animal kingdom is given in chapter 7. Viruses and Viroids 1. Viruses The term ‘Virus’ means poisonous fluid. The word was coined by Louis Pasteur. Viruses are very small (0.05-0.2 µm), infective, nucleoprotein particles, which can be called as living because of the presence of nucleic acid as genetic material and ability to produce their own copy-viruses. They show only some properties of living beings, otherwise they behave like non-livings. Hence, these are referred to as the connecting link between living and non-living. On the basis of nature of genetic material, the viruses are of two types (i) Adenovirus DNA containing, e.g., HIV, etc. (ii) Retrovirus RNA containing, e.g., Rous sarcoma virus, etc. On the basis of their host, the viruses can be categorised as (i) Animal virus (Zoophagineae), e.g., HIV, sarcoma, etc. (ii) Plant virus (Phytophagineae), e.g., TMV, etc. (iii) Bacterial viruses (Phagineae), e.g., T4 phage, etc. Characteristics of Viruses Characteristics of viruses are as follows Living l They can replicate. l In host body, they can synthesise protein. l They cause diseases like other living organisms. l Similar gene mutation as living organism.  Biological Classification 23 Non-living l Do not have protoplasm, and do not perform metabolism. l These can be crystallised. l They do not respire. l In vitro culture is not possible. Structure of Viruses (i) Viruses are non-cellular and ultramicroscopic. (ii) Virus has two components (a) A core of nucleic acid called nucleoid. (b) A protein coat called capsid. Envelope, only in Capsomeres, together form some larger viruses. capsid, a protein coat usually highly symmetrical. Genetic material, Core region DNA or RNA inside capsid Structure of a virus (generalised) 2. Viroids (RNA without a Capsid) TO Diener (1917) introduced the term as ‘Subviral pathogens’. Viroids are 100 times smaller than smallest virus. They are known to be infectious for plants only (no animal), e.g., potato spindle tuber caused by viroids. Virion An intact, inert, complete virus particle capable of infecting the host lying outside the host cell in cell free environment is called virion. Virusoids These are like viroids, but located inside the protein coat of a true virus. Virusoid RNA can be circular or linear. These are non-infectious as they are replicated only in their host. Prions/Slow Virus The prions are smallest, proteinaceous infectious particles, i.e., disease causing agents that can be transmitted from one animal to another.  3 Plant Kingdom Plants : Producers of the Ecosystem Plants are multicellular, photoautotrophic and embryo forming (excluding algae) organisms placed in kingdom–Plantae. They have cell wall, which is made up of cellulose and reserve food material in the form of starch (sometimes fat as in seeds). Plants are referred to as producers, because they have unique ability to fix solar energy in the form of chemical energy, through the process of photosynthesis. They supply the energy in ecosystem to other living organisms, hence they are referred to as producers. The plant kingdom is classified as Plant Kingdom Cryptogamae (non-flowering) Phanerogamae (flowering) Thallophyta (plant body is not divided Gymnosperms Angiosperms into root, stem and leaves) (naked seeded plants) (covered seed) Algae Bryophyta Pteridophyta (non-embryophytes, (these are (these are embryo Monocotyledons Dicotyledons lack seeds and embryophytes bearing plants which vascular tissue.) without vascular form seed and contain tissues.) vascular tissue as well.) Ferns Liverworts Hornworts Mosses Algae (L. Alga–sea weeds) These are eukaryotic, autotrophic (holophytic), chlorophyll containing, non-vascular thallophytes. These are characterised by the absence of embryonic stage and presence of non-jacketed gametangia. Mostly, they are of aquatic habitat (both freshwater and marine). The branch of Botany which deals with the study of algae is termed as ‘Algology or Phycology’. FE Fritsch is known as ‘Father of Algology’. (Prof. MOP Iyengar is regarded as Father of Indian Algology).  Plant Kingdom 25 Classification of Algae (FE Fritsch; 1935) Algal Class Colour Reserve Food Examples Chlorophyceae Grass green Starch Chlamydomonas and Spirogyra. Xanthophyceae Yellow-green Fat Microspora and Botrydium. Chrysophyceae Yellow-green and Carbohydrate and Amphipleura and golden-brown leucosin Chrysosphaera. Bacillariophyceae Brown and green Fat and volutin Pinnularia and Melosira. Cryptophyceae Red and Carbohydrate and Cryptomonas. green-blue starch Dinophyceae Dark yellow, Starch and oil Peridinium and brown-red Glenodinium. Chloromonadineae Bright green Fatty compounds Vaucheria and Trentonia. Euglenophyceae Grass green Paramylum Euglena and Phacus. Phaeophyceae Brown coloured Laminarin and Laminaria and Fucus. mannitol Rhodophyceae Red coloured Floridean starch Polysiphonia and Batrachospermum. Myxophyceae Blue-green Protein granules Nostoc and Anabaena. Characteristics of Algae Important characteristics of algae are given below Structure Algae may be unicellular and multicellular. 1. Unicellular It is of two types (i) Motile, e.g., Chlamydomonas, etc. (ii) Non-motile, e.g., Chlorella, etc. 2. Multicellular It is of following types (i) Colonial, e.g., Volvox, Hydrodictyon, etc. (ii) Aggregation, e.g., Tetraspora, Prasinocladus, etc. (iii) Filamentous, e.g., Ulothrix, Cladophora, etc. (iv) Pseudoparenchymatous, e.g., Nemalion, etc. (v) Siphonous, e.g., Vaucheria, etc. (vi) Parenchymatous, e.g., Ulva, Fritschiella, etc. (vii) Well-developed thallus, e.g., Chara, Sargassum, etc. 26 Handbook of Biology Nutrition Mostly algae are autotrophic, due to the presence of chlorophyll. Some are parasitic, e.g., Cephaleuros that causes rust of tea. Reproduction Algae reproduce by (i) Vegetative methods (ii) Asexual methods (iii) Sexual methods Vegetative Reproduction Algae reproduce vegetatively by two methods (i) Fragmentation, e.g., Fucus, Chara, etc. (ii) By hormogones, e.g., Oscillatoria, Nostoc, etc. Asexual Reproduction In this process, some cells form motile or non-motile spores. After release, these spores give rise to new plants. Following spores are involved (i) By zoospore, e.g., Ulothrix, Oedogonium, etc. (ii) By aplanospore, e.g., Chlorella, etc. (iii) By hypnospore, e.g., Vaucheria, etc. (iv) By palmella stage, e.g., Chlamydomonas, Ulothrix, etc. (v) By endospore, e.g., Anabaena, Nostoc, etc. (vi) By akinete, e.g., Chara, Oedogonium, etc. Sexual Reproduction On the basis of shape, size, morphology and behaviour of gametes, the sexual reproduction is of following types Sexual Reproduction Isogamous Anisogamous Oogamous (similar gametes, (gametes are dissimilar (gametes are different morphologically), morphologically), both morphologically and e.g., Spirogyra. e.g., Chlamydomonas sp. physiologically), e.g.,Volvox.  Plant Kingdom 27 Life Cycle of Algae Various algae show different types of life cycles. Life cycles of Spirogyra and Ulothrix are discussed here. Life cycle of Spirogyra It is a green alga of filamentous shape. The detailed life cycle is given below. Aplanospore Azygospore Akinete Asexual reproduction Chloroplast Cytoplasm ds 11 noi Nucleus re 10 Py all1 ll w Ce Vegetative cell Vegetative filament Three degenerating nuclei 2 9 Functional Sexual reproduction nucleus Haploid phase (n) Four haploid nuclei 8 Conjugation Male tube Diploid gamete phase (2n) (n) Female 3 7 gamete at m (n) ug or n io nj rif co cala S is) os ei Zygote (2n) (M 6 5 Zygospore (2n) 4 Life cycle of Spirogyra 28 Handbook of Biology Life cycle of Ulothrix The diagrammatic representation of life cycle of Ulothrix is given below. Palmella stage Akinete Hypnospore Macrozoospores Microzoospore Aplanospore Asexual reproduction 15 Chloroplast 14 Hold Nucleus fast 1 Vacuole Vegetative cell Zoospores 13 Gametangium 2 12 Reduction division Isogametes Resting Vegetative Zygospore (2n) filament 3 Phase (2n) 11 Sexual reproduction Quariflagellate 10 zygospore Haploid phase (n) + 4 my 9 Synga – Vesicle 8 5 Liberations of 7 6 gametes Life cycle of Ulothrix  Plant Kingdom 29 Economic Importance Algae can be both useful and harmful. Several useful algal species with their uses are mentioned here As Food As Medicine Ulva, Sargassum, Laminaria, Chlorella gives chlorellin Porphyra, Nostoc and Laurencia. (antibiotic), Nitella is used as mosquito repellent. In Industries Algae Source of Minerals Diatoms, Chondrus, Laminaria, Polysiphonia and Polysiphonia, Gracilaria Ascophyllum are used in are used in paints, cosmetics, etc. extraction of minerals. In Agriculture In Biological Research Nostoc, Anabaena, help in Chlorella,Scenedesmus and nitrogen-fixation, hence Acetabularia are used as tools used as biofertilisers. for biological research. Ecological Significance Algae like planktons are used as food by others and stabilise the ecosystem. Useful applications of algae Algin, Carrageenan and Agar l Algin, used as artificial fibre to control blood flow in surgery and in production of non-inflammable films, is extracted from marine brown algae. l Carrageenan, extracted from seaweeds is used in cosmetics, boot polish, ice cream, paints, etc. l Agar, extracted from Gelidium and Gracilaria is used in culture medium, biscuits for diabetic patients, etc. – Sargassum is used as food and fodder. – Laminaria, Fucus are used in extraction of iodine, bromine and potash. Harmful Algae Group of algae like Microcystis, Oscillatoria and Anabaena cause water blooms (eutrophication) and death and reduction of aquatic organisms. Bryophyta (L. Bryon–leaf-like; phyton–plant body) It is the simplest and primitive group of land plants. They are also known as amphibians of plant kingdom because of their habitat adaptability in both aquatic and terrestrial environment. They are the connecting link between algae and pteridophytes. Bryophytes 30 Handbook of Biology are autotrophic, non-seeded, cryptogamic plants. The plant body is gametophytic and may be differentiated into stem, leaves and rhizoids. l Bryophytes do not have true vascular tissue (xylem and phloem), but some of them have hydroids (similar to xylem) and leptoids (similar to phloem) which help in the conduction of water and food, respectively. l The sex organs in bryophytes are multicellular, male sex organ is called antheridium and female sex organ is called archegonium. Sexual reproduction in bryophytes is mainly oogamous type. Classification of Bryophyta Bryophyta (sub-division) Classes Hepaticopsida Anthocerotopsida Bryopsida (Liverworts) (Hornworts) (Mosses) l Plant body is thalloid l Plant body is thalloid l Primary gametophyte or foliose. and dorsiventrally consists of prostate l Cells have chloroplast flattened. or thalloid without pyrenoids. l Sex organs protonema. l Sporophyte simple or embedded in the l Adult gametophyte differentiated into thallus tissue. consists of stem, foot, seta and l Cells bear large spirally arranged capsule. chloroplast with a leaves. conspicuous l Sex organs develop pyrenoid. from superficial cells. Order Orders Anthocerotales e.g., Anthoceros Orders Bryales Sphagnales e.g., Funaria and e.g.,Sphagnum. Sphaerocarpales Jungermaniales Polytrichum. e.g.,Sphaerocarpus. e.g., Porella Marchantiales Calobryales e.g., Marchantia and e.g., Calobryum. Riccia. Reproduction in Bryophytes Bryophytes reproduce by both vegetative and sexual methods of reproduction. Vegetative Reproduction Following methods of vegetative reproduction are reported in bryophytes (i) By fragmentation The two fragments resulted by progressive death and decay of thallus, produce new thallus, e.g., Riccia.  Plant Kingdom 31 (ii) By adventitious branches Special adventitious branches arise from the mid-ventral surface of the thallus, e.g., Riccia fluitans. (iii) By tubers Some species form perennating tubers at the apices of thallus, e.g., Riccia, Marchantia, etc. (iv) By persistent apices The underground part of thallus in soil remains living and grows into plant, e.g., Riccia, Pellia, etc. Sexual Reproduction The sex organs are highly differentiated and well-developed in bryophytes. The antherozoids or sperms (minute, slender, curved body, having two whiplash flagella) are released from antheridium and reach to archegonium through neck canal cells. The antherozoid fuses with egg cell to produce sporophytic generation. Life Cycle of Bryophytes A typical bryophyte shows following type of life cycle Vegetative reproduction (n) Bryophyte (n) Protonema (n) Male (n) Female Spores (n) Sexual (n) Reproduction Antheridium (n) Meiosis (R/D) Archegonium (n) Ga me Sp t op Spore hyt Antherozoid (n) mother cell (2n) oro e( ph n) Egg (n) yte (2n ) Sporogonium (2n) Fertilisation (syngamy) Embryo (2n) Zygote (2n) Graphic representation of the life cycle of bryophyte (R/D refers to reductional division) 32 Handbook of Biology Economic Importance Bryophytes have limited economic importance, they can be used in following ways (i) They help in soil formation (pedogenesis) and act as agent for biological succession. (ii) Peat from Sphagnum can be used as fuel and in preparation of ethyl alcohol. (iii) They help in protecting soil from erosion. (iv) Some bryophytes are used as fodder for cattle. (v) Due to high water retention capacity, Sphagnum can be used in preserving living materials and used in grafting of plants. Pteridophyta ( L. pteron–feather; phyton–plant) Pteridophytes are seedless, vascular cryptogams. They reproduce by means of spores and can reach to the tree-like heights (30-40 feets). General Characteristics (i) The plant body is differentiated into root, stem and leaves. (ii) The stem may be aerial or underground and is generally herbaceous, rarely solid and stout. (iii) Vascular tissues consist of xylem (without vessels) and phloem (without companion cells). (iv) Alternation of generations is found here, gametophyte is autotrophic and independent. (v) Sporangia containing leaves are called sporophylls. (vi) Antherozoids (flagellated male gametes) are formed in antheridia. (vii) Reproduction is of both vegetative and sexual types. (viii) On the basis of development of sporangia, they are of two types (a) Eusporangiate From a group of superficial initial cells. (b) Leptosporangiate From a single superficial initial cell.  Plant Kingdom 33 Stelar System in Pteridophytes Stele is central vascular tissue surrounded by cortex. It is of two types Protostele Siphonostele Pericycle Endodermis Xylem Phloem Phloem Endodermis Xylem Leaf trace Leaf trace Pith Xylem in centre is surrounded Xylem surrounds the central pith. by phlem e.g., Selaginella. Phloem is outside to xylem, e.g., Pteridium. Endodermis Leaf trace Endodermis Pericycle Pericycle Phloem Phloem Pith Xylem Xylem Leaf gap Haplostele Ectophloic Solenostele Central xylem core Xylem is like hollow cylinder surrounded surrounded by phloem by phloem e.g., Equisetum e.g., Rhynia Outer endodermis Endodermis Outer pericycle Pericycle Outer phloem Phloem Leaf trace Xylem Xylem Inner pericycle Leaf gap Inner endodermis Actinostele Central xylem core is star-shaped Amphiphloic Solenostele phloem is patchy outer Hollow xylem cylinder has phloem on both to xylem, e.g., Lycopodium. outer and inner side of xylem, e.g., Marsilea Classification of Pteridophyta (Smith; 1955, Bold; 1955-57, Benson; 1957) Division–Pteridophyta Sub-division Psilophyta Lycophyta or Sphenophyta or Filicophyta or (rootless Lepidophyta Arthrophyta Pterophyta sporophytes). (differentiated (foliage leaves (sporophyll sporophytes are borne in contains sori contain strobili). transverse e.g., ferns). whorls, e.g., horse tails). 34 Handbook of Biology Reproduction Pteridophytes reproduce by vegetative, asexual and sexual methods. Vegetative Reproduction It takes place by two methods (i) Death and decay of older tissues lead to separation of new branches, which can grow into new plants. (ii) Adventitious buds develop from petiole and later on rooting takes place and get separated. Asexual Reproduction It occurs by meiospores When pteridophytic plants get mature, the special spore bearing structures develop under the surface of pinnules. These structures are (i) Sporangium These are differentiated into capsule and the stalk. Capsule has a single layer of thick wall, which consists of specialised cell along with the normal wall cells. (ii) Spores These are minute, bilateral bodies of brown colour. The spore coat is two layered, i.e., thick exine and thin intine. Sexual Reproduction It is of advanced type, in which the multicellular sex organs (i.e., antheridia and archegonia) are borne on the underside of prothallus. The mucilaginous substance oozes out from archegonia, which contains malic acid. After diffusing into water, it attracts antherozoids through chemotaxis. The male nucleus fuses with the egg nucleus and forms zygote.  Plant Kingdom 35 Life Cycle of Pteridophytes Most pteridophytic plants show similar type of life cycle. Which is diagrammatically represented below. Mesophyll Upper epidermis Circinate Lower epidermis leaf Sporangia (stalked) Placenta Covering by Sori Strobilus indusium Stalk Part of sporophyll Leaflet Rhizome with with sori mesarch xylem Stomium Sporophytic Roots with diarch plant condition of xylem Spores Sporangium First leaf Prothallus with autotrophic Rhizoids nutrition Apicol Notch Sporophytic Rhizoids phase y tic Germinating 2n ph Cushion to spore n me e a G has Apical notch p Antheridia Archegonium Antheridia Antherozoids Cilia Rhizoids Prothallus with Egg archegonia and A single Neck antheridia antherozoids Archegonium Life cycle of Dryopteris Heterospory in Pteridophytes In heterosporous plants, a sporophyte produces two types of sporangia–micro and megasporangia. Microsporangia contain Microspore Mother Cell (MMC) each of which undergoes meiosis and produces microspores. Megasporangia contain megaspore mother cell, which after going through meiosis, produces megaspores. germinate Microspore → Microgametophyte (possess antheridia) germinate Megaspore → Megagametophyte (possess archegonia) 36 Handbook of Biology The differentiation between male and female gametophytes ensures cross fertilisation. This set of conditions occurs in Marsiliaceae and Salviniaceae. Economic Importance Pteridophytes are economically important group of plants. Some of them are (i) Pteridophytes are used in horticulture, since they resist wilting so can be used in cut flower arrangements. (ii) Some ferns are used in handicrafts and basketery. (iii) Pteridium leaves are used in making green dyes. (iv) Club mosses are used for making industrial lubricant since their spores contain non-volatile oils. These spores are also used as fingerprint powder in forensic investigation. (v) Some pteridophytes are used as biofertiliser (Azolla) due to their nitrogen-fixing ability. (vi) Some pteridophytes are eaten as food. Gymnospermae (L. gymnos – naked; sperma – seed) Gymnosperms are naked seeded plants, which evolved earlier than the flowering plants. They have their seeds exposed on the megasporophylls, i.e., carpels. Probably, they are the first surviving seed plants (evolved during Jurassic period). General Characteristics (i) Plants are sporophytic, differ