Dr. Dileep Gangwar 9 The Living World
Dr. Dileep Gangwar 10 ERNST MAYR (1904-2004) Born on 5 July 1904, in Kempten, Germany. The Harvard University evolutionary biologist who has been called The Darwin of the 20 th century. He joined Harvard s Faculty of Arts and Sciences in 1953 and retired in 1975, assuming the title Alexander Agassiz Professor of Zoology Emeritus. Throughout his nearly 80-year career, his research spanned ornithology, taxonomy, zoogeography, evolution, systematics, and the history and philosophy of biology. He almost single-handedly made the origin of species diversity. He also pioneered the currently accepted definition of a biological species. He was awarded the three prizes widely regarded as the triple crown of biology - 1. The Balzan Prize in 1983. 2. The International Prize for Biology in 1994. 3. The Crafoord Prize in 1999.
Dr. Dileep Gangwar 11 What is Life? Life is unique, complicated organization of biomolecules, that shows different chemical reactions resulting in activities like growth, reproduction, development, metabolism, responsiveness & adaptations. All living things share certain key characteristics which separate them from non-living things. CHARACTERISTICS OF LIVING FORMS :- 1. Growth :- Increase in mass and increase in number of individuals are twin characteristics of growth. All living organisms grow. [it is a characteristic of living systems. A dead organism does not grow.] * A multicellular organism grows by cell division. * In plants, this growth by cell division occurs continuously throughout their life span. * In animals, this growth is seen only up to a certain age. However, cell division occurs in certain tissues to replace lost cells. * Unicellular organisms also grow by cell division. e.g., One can easily observe this in in vitro cultures by simply counting the number of cells under the microscope. In majority of higher animals and plants, growth and reproduction are mutually exclusive events. * One must remember that increase in body mass is considered as growth. * Non-living objects also grow if we take increase in body mass as a criterion for growth. Mountains, boulders and sand mounds do grow. However, this kind of growth exhibited by non-living objects is by accumulation of material on the surface. * In living organisms, growth is from inside. Growth, therefore, cannot be taken as defining feature of living organism.
Dr. Dileep Gangwar 12 2. Reproduction :- Reproduction refers to the production of progeny possessing features more or less similar to those of parents. It may be of two type - Asexual Reproduction (Without fusion of male & female gametes, And is always uniparental) Sexual Reproduction (With fusion of male & female gametes, And is mostly biparental) 1. By binary fission (&Multiple fission also) - * When an unicellular parent divides into two daughter cells by mitosis, it is called binary fission. e.g., Reproduction in all unicellular animals (both in prokaryotes & eukaryotes) Hence, in unicellular organisms, reproduction is synonymous with growth, i.e., increase in number of cells. 2. By budding :- * Observed in lower organisms like yeast and hydra [CPMT-96] 3. By spores :- e.g., Fungi multiply and spread easily due to the millions of asexual spores they produce. 4. By Fragmentation :- * When a fragmented organism regenerates the lost part of its body and becomes a new organism, it is called regeneration. e.g., * In Planaria (flat worms), we observe true regeneration. * Fungi, filamentous algae, protonema of mosses There are many organisms which do not reproduce (mules, sterile worker bees, infertile human couples, etc). Of course, no non-living object is capable of reproducing or replicating by itself. Hence, reproduction also cannot be an all-inclusive defining characteristic of living organisms. 3. Metabolism :- All living organisms are made of chemicals. These chemicals, small and big, belonging to various classes, sizes, functions, etc., are constantly being made and changed into some other biomolecules. These conversions are chemical reactions or metabolic reactions. e.g., There are thousands of metabolic reactions occurring simultaneously inside all living organisms (i.e., Plants, animals, fungi and microbes etc). The sum total of all the chemical reactions occurring in our body is metabolism. No non-living object exhibits metabolism. * Metabolic reactions can be demonstrated outside the body in cell-free systems. * An isolated metabolic reaction(s) outside the body of an organism, performed in a test tube is neither living nor non-living. Hence, metabolism is a defining feature of all living organisms without exception. Isolated metabolic reactions in vitro are not living things but surely living reactions.
Dr. Dileep Gangwar 13 4. Consciousness (Response to stimuli) :- Consciousness is the ability of an organism to sense their surroundings (or environment) and respond to these environmental stimuli (which could be physical, chemical or biological). Perhaps, it is the most obvious and technically complicated feature of all living organisms. All organisms, from the prokaryotes to the most complex eukaryotes can sense and respond to environmental cues. e.g., * Photoperiod affects reproduction in seasonal breeders, both plants and animals. * All organisms handle chemicals entering their bodies. * Plants respond to external factors like light, water, temperature, other organisms, pollutants, etc. All organisms therefore, are aware of their surroundings. Human being is the only organism who is aware of himself, i.e., has self-consciousness. Consciousness therefore, becomes the defining property of living organisms. When it comes to human beings, it is all the more difficult to define the living state. We observe patients lying in coma in hospitals virtually supported by machines which replace heart and lungs. The patient is otherwise brain-dead. The patient has no self-consciousness. Are such patients who never come back to normal life, living or non-living? In higher classes, you will come to know that all living phenomena are due to underlying interactions. e.g., * Properties of tissues are not present in the constituent cells but arise as a result of interactions among the constituent cells. * Similarly, properties of cellular organelles are not present in the molecular constituents of the organelle but arise as a result of interactions among the molecular components comprising the organelle. * These interactions result in emergent properties at a higher level of organisation. This phenomenon is true in the hierarchy of organisational complexity at all levels. Therefore, we can say that - Living organisms are self-replicating, evolving and self-regulating interactive systems capable of responding to external stimuli. Subatomic particles (e-, H, n) + Atoms Molecules Cell Tissue Organs Organ System Organism Population Species Community Ecosystem Landscape Biome Biosphere
Dr. Dileep Gangwar 14
Dr. Dileep Gangwar 15 Diversity In The Living World As we know, a large variety of living organisms present on earth. i.e. * 1.7-1.8 million known species [1.3 million animal species + 0.5 million plant species] and * million unknown species [average 15000 new organisms are discovered every year] The number & types of organisms present on earth refers to biodiversity. The study of diversity of organisms along with all their comparative & evolutionary relationships is called Systematics. It is very difficult to study such a large number of organisms. For convenient study, it is necessary that organisms are placed into groups/categories so that study of one organism of a group may provide the idea about the rest members of that paticular group. The terms systematics, taxonomy and biological classification are often used as synonyms but technically they carry different meanings. Classification - * Is the process by which anything is grouped into convenient categories based on some easily observable characters. Taxonomy - * Deals with the rules & principles of classification. [CPMT-85, 91] Systematics - * Term systamatics was first used by Carolus Linnaeus in 1735. * The word systematics is derived from the Latin word systema which means systematic arrangement of organisms. * The scope of systematics was later enlarged to include taxonomy & phylogeny. * Systematics has following four steps - (I) Identification (ii) Nomenclature (iii) Classification Taxonomy ( is known as Linnaeus father of taxonomy). (iv) Establishment of evolutionary relationships. Phylogeny
Dr. Dileep Gangwar 16 Identification Identification is to determine the exact place or position of an organism in the set plan of classification. John Ray developed the taxonomic keys for the identification of animals. [MPPMT-99] Nomenclature It is the stablishment of a distinctive name to each species. Need of scientific names was felt because the same organism is having different common names in different parts of world. Nomenclature Vernacular name (= Local name) 1. These are common names given to organisms by residents of an area in local language. Scientific name 1. These are the names given by scientist in Latin language. 2. They differ from place to place & language to language. 3. There may be several vernacular names for an organism in a language. (Therefore they cannot be used by scientists.) New Systematics 2. Scientific names are universal & not liable to change with time or Language. 3. Some times different authors give different names to same species. According to Law of Priority oldest name is valid. (They are more precise & definite than common names.) Gauraiya : India Sparrow : England & America Haussperling : Germany Musch : Holland Pardal : Spain Suzune : Japan * There is three types of nomenclature - (i) Polynomial nomenclature - * Before 1750, biologists usually used this method for momenclature. * In this method, biologists use many Latin words (may be upto 15) for naming a species. e.g., Caryophyllum Caryophyllum saxatilis folis gramineus umbellatis corymbis * These name were lengthy & difficult to remember. (ii) Binomial nomenclature - * Bauhin was first who gave the idea of binomial nomenclature. * But its introduction is credited to Carolus Linnaeus. * In this method, biologists use only two Latin words for naming a species. e.g., Gauraiya ( Passer domesticus) Pyaz ( Allium cepa) Gurhal ( Hibiscus rosa-sinensis) (iii) Trinomial nomenclature - * It is employed to describe subspecies [JIPMER-93]. e.g., (i) Corvus splendens splendens (in India) (ii) Corvus splendens isolens (in Burma) (iii) Corvus splendens protegatus (in Sri Lanka)
Dr. Dileep Gangwar 17 Binomial System of nomenclature :- Linnaeus proposed binomial nomenclature for plants in his book Species plantarum published on 1 May 1753. He proposed binomial nomenclature for animals in 10th edition of his book Systema naturae published on 1 Aug 1758. Rules of Nomenclature :- * Linnaeus gave certain principles for the binomial nomenclature called Linnaen Principles. * There are five international codes for nomenclature of organisms. 1. ICBN; International code of Botanical nomenclature. [First accepted in 1961, after revision it was republished in 1978]. 2. ICZN; International code of Zoological nomenclature. [in 1964] 3. ICNB; International code for nomenclature of Bacteria. 4. ICVN; International code of Viral nomenclature. 5. ICNCP; International code of nomenclature for Cultivated Plants. * Universal rules of nomenclature are as follows : 1. Biological names are generally in Latin and written in italics. They are Latinised or derived from Latin irrespective of their origin. 2. The first word in a biological name represents the genus while the second component denotes the specific epithet. 3. Both the words in a biological name, when handwritten, are separately underlined, or printed in italics to indicate their Latin origin. 4. The first word denoting the genus starts with a capital letter while the specific epithet starts with a small letter. * Name of the author appears after the specific epithet in an abbreviated form, it is printid in Roman. e.g., Mango; Mangifera indica Linn. It indicates that this species was first described by Linnaeus. * If any scientist has proposed wrong name then his name should be written in bracket and the scientist who corrected the name should be written after the bracket. e.g., Siris; Albezzia lebbeck (Lin.) Benth * The names with same genus & species name are called tautonyms e.g., Rattus rattus * These are not recognised by botanists. * The names with same species & subspecies name are called autonyms e.g., Corvus splendens splendens * One name for two different plants are called homonyms e.g., Prunus dulcis (Almond & Plum)
Dr. Dileep Gangwar 18 Classification is not a single step process but involves hierarchy of steps in which each step represents a rank or category. Each category (referred to as a unit of classification) in fact, represents a rank and is commonly termed as taxon (pl.: taxa). Linnaeus used only 5 categories (class, order, genus, species & variety) to classify organisms. Later on the last one was discarded and three new were added, so that now there are 7 obligate categories. e.g., Classification of Radish Kingdom Division Categories Class Order Family Genus Species - Plantae - Spermatophyta - Dicotyledonae - Parietales - Brassicaceae - Raphanus - sativus Taxa Suffix for different taxon Kingdom - xxxxxxx Division - phyta Class - ae, phyceae, opsida. Order - ales Family - aceae Genus - xxxxxxx Species - xxxxxxx The descending (or ascending) sequence of these categories is called taxonomic hierarchy (= Linnaean Hierarchy). Taxonomists have also developed sub-categories in this hierarchy to facilitate more sound and scientific placement of various taxa. Kingdom > Division > Class > Series > Order > Family > Tribe > Genus > Species [CBSE-99, CET Kar.-01, AFMC-01] * As we go higher (from species to kingdom), the number of common characteristics goes on decreasing. [i.e., Lower the taxa, more are the characteristics that the members within the taxon share]. 1. Species :- Is a group of individual organisms with fundamental similarities and able to interbreed in natural conditions, and produce fertile offsprings (a definition according to Biological species concept given by Ernst Mayr). John Ray was the I st who introduce & define term Species & species concept. Species is the lowest category (or basic unit of classification). One should be able to distinguish one species from the other closely related species based on the distinct morphological differences. e.g., * Mangifera indica (Mango) * Solanum tuberosum (Potato) * Panthera leo (Lion) * Homo sapiens (Human) [In above names, term indica, tuberosum, leo and sapiens represent the specific epithets]. Some special type of species * Sibling species :- Related species which are reproductively isolated but morphologically similar. * Allopatric species :- Specieal inhabiting di? erent geographical areas. * Sympatric species :- Species inhabiting the same geographical area (identical or overlapping). * Palaeospecies :- Species known from fossils only. * Neontological species :- Living species. * Endemic species :- A species restricted to a given area. [CPMT-99] * Monotypic species :- Species without di? erentiation of subspecies/varieties. * Polytypic species :- Species with two or more subspecies/varieties. * Keystone species :- A species that plays a central role in the ecology of a place.
Dr. Dileep Gangwar 19 2. Genus :- Is a group of related species. We can say that genera are aggregates of closely related species. e.g., * Panthera leo (Lion) * Panthera pardus (Leopard) * Panthera tigris (Tiger) * Solanum tuberosum (Potato) * Solanum melongena (Brinjal) 3. Family :- Is a group of related genera. e.g., * family Solanaceae has many genera like Solanum, Petunia and Datura etc. * family Felidae has many genera like Panthera, Felis (cats) etc. 4. Order :- Is the assemblage of families. e.g., * order, Polymoniales, includes families like Convolvulaceae, Solanaceae * order, Carnivora, includes families like Felidae (cats) and Canidae (dog) 5. Class :- includes related orders. e.g., Class Mammalia includes many orders like - * Insectivora * Lagomorpha (rabbit) * Carnivora (tiger, cat and dog) * Primata (monkey, gorilla & gibbon, human) 6. Phylum/Division :- includes related classes. e.g., Phylum chordata includes classes like - 1. Amphibia 2. Reptilia 3. Aves 4. Mammalia 7. Kingdom :- It is the highest category. includes related phyla. Whittaker grouped all the phyla of living beings into 5 kingdoms - 1. Monera 2. Protista 3. Fungi 4. Plantae 5. Animalia. Common Name Man Biological Name Homo sapiens Genus Homo Family Hominidae Order Primata Class Mammalia Phylum/ Division Chordata Housefly Musca domestica Musca Muscidae Diptera Insecta Arthropoda Mango Mangifera indica Mangifera Anacardiaceae Sapindales Dicotyledonae Angiospermae Wheat Triticum aestivum Triticum Poaceae Poales Monocotyledonae Angiospermae
Dr. Dileep Gangwar 20 Taxonomical aids Taxonomists have developed a variety of taxonomic aids to facilitate identification, naming and classification of organisms. These studies are carried out from the actual specimens which are collected from the field and preserved as referrals in the form of herbaria, museums and in botanical gardens and zoological parks. Taxonomists also prepare and disseminate information through manuals and monographs for further taxonomic studies. 1. Herbarium Herbarium is a store house of collected plant specimens that are dried, pressed and preserved on sheets. The standared size of herbarium sheet is 16.5 X 11.5 inch (or 41 X 29 cm). Further, these sheets are arranged according to a universally accepted system of classification [i.e., Bentham & Hooker s system of classification]. These specimens, along with their descriptions on herbarium sheets, become a store house or repository for future use. The herbarium sheets also carry a label providing information about - * date and place of collection * English, local and botanical names * family * Collector s name. etc. e.g., * Herbarium of Royal Botanical Garden, Kew (England) - * Greatest herbarium of world, * Having 6 millions specimens. [Wardha-01] * Herbarium of Indian Botanical Garden, Sibpur (Kolkata) - * Biggest herbarium of India * Having 1 million specimens (10 lakh). * Established by Robert Kyd. [AIIMS-96, 97] Herbaria also serve as quick referral systems in taxonomical studies.
Dr. Dileep Gangwar 21 2. Botanical Gardens These specialised gardens have collections of living plants for reference. Plant species in these gardens are grown for identification purposes and each plant is labelled indicating its botanical name and its family. e.g., * Royal Botanical Garden at Kew (England). * Indian Botanical Garden, Howrah (India) * National Botanical Research Institute, Lucknow (India). [Its old name is National Botanical Garden] 3. Museum Biological museums are generally set up in educational institutes such as schools and colleges. Museums have collections of preserved plant and animal specimens for study and reference. Specimens are preserved in the containers or jars in preservative solutions [such as formalin, alcohol etc] Plant and animal specimens may also be preserved as dry specimens. Insects are preserved in insect boxes after collecting, killing and pinning. Larger animals like birds and mammals are usually stuffed and preserved. Museums often have collections of skeletons of animals too. 4. Zoological Parks (= Zoo) These are the places where wild animals are kept in protected environments under human care. Objectives are public exhibition to understand wild life (their food habits and behaviour), recreation, education, in situ conservation and breeding of rare fauna. All animals in a zoo are provided, as far as possible, the conditions similar to their natural habitats. India has some 200 zoological parks being supervised by a Central Zoo Authority. Each big zoological park also has - * An aviary where birds are kept. * A serpentarium (Largest in Chennai) * A large aquarium (Largest in Mumbai). 5. Key Used for identification of plants and animals based on the similarities and dissimilarities. The keys are based on the contrasting characters generally in a pair called couplet. It represents the choice made between two opposite options. This results in acceptance of only one and rejection of the other. Each statement in the key is called a lead. Separate taxonomic keys are required for each taxonomic category such as family, genus and species for identification purposes. Keys are generally analytical in nature. Plant part Carpel Couplet (= A pair of contrasting characters) * Single ovuled ( Lead-I) * Many ovuled ( Lead-II) Leaves * Opposite ( Lead-I) * Alternate ( Lead-II) 7. Printed Records They also help in correct identification. These may be in the form of - (i) Flora - * Contains the actual account of habitat and distribution of plants of a given area. * These provide the index to the plant species found in a particular area. (ii) Manuals - * useful in providing information for identification of names of species found in an area. (iii) Monographs -* contain information on any one taxon (like family or genus or species etc). (iv) Catalogues -