SYSTEMATIC

There are more than 10 million kinds of living organisms like animals, plants, bacteria, viruses which are different from one another. Out of these, nearly 1.2 million animals and 0.5 million plant species have been studied. Many are still unknown. To study and remember each species is practically not possible. So, to make this simpler, Biologists name them. They use techniques for identifying, naming and grouping of organisms. (1.1) BIOLOGICAL CLASSIFICATION: -- To pick an organism of known characters from a huge variety of living organisms is not possible. They must be divided into groups and sub-groups with each having organisms of almost similar characters. Definition- The scientific ordering of organisms in hierarchical series of groups/ sub-groups on the basis of similarities/ differences and their relationships is called Biological Classification. Objectives of biological classification -: 1.to organize vast number of animals and plants into categories and then naming them. 2. To recognize basic unit of classification i.e. Species. Advantages of Biological classification: - 1.It makes identification and study of organisms convenient. 2. It shows relationships among various groups of organisms. 3. It shows evolutionary trend. 4. Study of a representative from each group gives a broad idea about whole group. 5. It helps in study of fossils for finding evolutionary relationships. Systematics/ Taxonomy (Gk.words) Systema-order. (taxis-arrangement nomos-law) Given by de Candolle in 1813. Deals with the identification, nomenclature and classification of organisms. Some scientists consider Systematics and Taxonomy as separate fields. According to G. Simpson (1961), Systematics is the study of diversity of organisms and all their comparative and evolutionary relationships based on comparative anatomy, ecology, physiology and Biochemistry. Whereas Taxonomy is the study of principles and procedures of classification. And Classification is the sub-topic of systematics dealing with ordering of organisms into groups. But all these terms are inter-related and so inter-changeable also. (1.2) HISTORY OF CLASSIFICATION: - Plants and animals existed before man evolved. But man was advanced species, so he started using plants and animals for its needs and even classified them in its own language. --According to Vedic literature (2500 BC-650BC), there are 740 plants and 250 animals. --While Chandayoga Upanishad classifies animals only --Susruta Samhita (600BC), a post-Vedic Indian literature classifies Theophrastus gave names and descriptions of 480 plants in his book ‘Historia Plantarum’. John Ray (1625-1705) described more than 18,600 plants and animals in his book Carolus Linnaeus (1707-1778) is the ‘Father of Taxonomy’. He published book ‘Systema Naturae’ in 1758, classified and arranged 4000 plant species on the basis of sexual characters in his book ‘Species Plantarum’ (1753). He gave system of Binomial Nomenclature’ according to which a scientific name has two parts- Genus and Species. E.g. Homo sapiens. Homo is genus and sapiens is species. Types of Taxonomy: - (1). Numerical Taxonomy: - (Phenetics) emerged since 1950.It uses numerical methods for evaluation of similarities and differences between the species. It is based upon proposals of Adanson (1763), that for classification, as many characters as possible must be taken, without extra emphasis on any particular character and all factors are given equal importance and weightage. As numerical Taxonomy is based on these principles, it is also called as Adansonian Classification. A family tree based upon phenetic classification is called Dendrogram.Computers and calculating machines are used in this method. (2) Phylogenetic Classification (Cladistics) - It classifies organisms according to the historical order in which evolution occurred. It led to emergence of ‘New Systematics’(Huxley 1940)/ Biosystematics. Cytotaxonomy :-It classifies organisms on the basis of information about cell like cell Structure, chromosome number, behaviour of chromosome during mitosis and meiosis etc.. (4) Chemotaxonomy :-It classifies organisms on the basis of its chemical constituents like amino acids, carbohydrates, alkaloids, calcium oxalate crystals (raphides),fragrances etc. (1.3) BASICS IN CLASSIFICATION :- Classification is ordering of organisms into groups. It has following three fundamental elements. (a) Nomenclature :-(L. nomen-name calarae-call) is giving distinct names to organisms so that they can be easily recognized and differentiated from others. There are universal rules and practices, which every taxonomist has to follow. Each organism is given a scientific name with two parts-Genus and Species. (b) Classification: - is arranging organism into categories according to systematic plan. The categories are Kingdom, Phylum (in animals)/ Division (in plants), Class, Order, Family, Genus, Species. Each category is a unit called ‘Taxon’. (c) Identification :-It is finding of correct name and place of an organism in a system of classification. It helps in determining the similarity of an organism with an already known organism. (1.4) NOMENCLATURE:- It is the science of providing distinct and proper names to organisms so that they can be easily recognized and differentiated from others. Types: - It is of two types- (a) common / vernacular names –These are the names given to an organism in a particular language and region of the world like names in English, Hindi, Marathi, Gujarati, Bengali etc.e.g. Plant Gurhal (Hindi) is China Rose (in English), Padma charini (in Sanskrit), Jaba (in Bengali), Mandara (in Oriya) and Jaswand (in Marathi). Advantages of common names: - (i) Easy to learn, speak and write.      (ii) Are in local languages   (iii) are very short                              (iv) are familiar since childhood. Drawbacks: -  (i) These names vary in different countries and different languages which creates confusion in identifying an organism. (ii) Only animals and plants which are commonly found have been named. Small and insignificant organisms don’t have common names. (iii) They don’t have any scientific basis and are based on superficial characters like colour (e.g. Black Bird), habit (e.g. Flying Fish), habitat (e.g. Water Lily), use (e.g. Pearl Oyster) etc. (iv) Some names are misleading. e.g.Jelly Fish, Star Fish, , silvher fish but none of them is true fish. (v) Certain common names have no significance.E.g. Widow’s Tears (Tradescantia), Love in mist (Nigella damascena) (b) Scientific Names: - Given by Linnaeus (1751) in his book Philosophica Botanica. Names given by Linnaeus in 10th edition of his book Systema Naturae (published in 1758) were recognized internationally. System of Scientific Names: - (i) Polynomial Nomenclature: - Before 1750, names were given by adding many descript-ive words. So these were lengthy and difficult to remember.e.g.Caryophyllum saxatilis folis gramineus umbellatis corymbis was the name of Caryophyllym growing on rocks with grass like leaves and umbellate corymb arrangement of flowers. (ii) Binomial Nomenclature: -C.Linnaeus, in 1753, proposed Binomial System of Nomenclature in his book Species Plantarum. It was a better alternative to cumbersome polynomial nomenclature. So, it was accepted. According to this system, every organism has two names- first is Genus / Generic name and second is Species name.e.g.Mangifera indica is the scientific name of Mango. Mangifera represents Genus and indica is species. (iii) Trinomial Nomenclature: -According to this system, certain organisms have three names. First is Genus, second is Species and third is Sub-species (in animals) / variety (in plants). E.g. Homo sapiens sapiens (man, in general), Homo sapiens europeus (man of European race). Codes of Nomenclature: - There are three main international codes of nomenclature. (i) ICBN – International Code Of Botanical Nomenclature. In 1961 (ii) ICZN – International code of Zoological Nomenclature. In 1964. (iii) ICBN – International Code Of Bacteriological Nomenclature. There are ICVN (International Code of Viral Nomenclature) and ICNCP (International Code of Nomenclature for Cultivated Plants) also. The codes are established and improved upon at International Botanical and Zoological Congress from time to time. Advantages of Codes: - (i) Help in avoiding errors, duplication and confusion in scientific names. Rules of Nomenclature: -The codes of Nomenclature set rules and guidelines according to which scientific names are given to an organism. The rules are- (i) A scientific name has generally two words. First one denotes Genus & second Species. (ii) Scientific name should be in Latin language only. (iii) Names are either printed in italics or underlined separately. e.g. Homo sapiens or Homo  sapiens . (iv) Generic name always starts with capital letter and species name with small letter. (v) Generic name can be abbreviated by using its first initial. E.g. H. sapiens. (vi) The name of author is written in abbreviated form after species name. It is written in Roman language. E.g. Mangifera indica Linn.  Linn. is for Linnaeus. (vii) The date of species name published can also be added to the scientific name. Homo sapiens Linn. 1758. (viii) Each taxonomic group can have only one correct name. (ix) The name should be short, precise and easy to pronounce. (1.5) TAXONOMIC HIERARCHY :-    It is an arrangement by which taxonomic groups are arranged in definite order from higher to lower categories. This system was first proposed by Linnaeus, so it is also called as ‘Linnaean Hierarchy’. Nearer the categories in a hierarchy, the greater is the affinity between their individuals. In all categories, only species have real existence & rest are man made. There are seven major categories of classification. Their descending sequence for animals and plants with specific suffixes or endings is as given below. Kingdom                                                      : Phylum (in animals) / Division (in plants) :    -phyta  ,  -phytina Class                                                            :    -ae     ,  -opsida Order                                                           :    -ales Family                                                          :    -aceae Genus                                                          : Species                                                        : Kingdom is the highest category and Species is the lowest. The placement of an organism in sps., genus, phyla etc.is determined by similarities in their characters and relationships. The categories in hierarchy are therefore in ascending order as shown in diagram below: - Category: - It is a rank / level in a hierarchical classification of organism. There are seven categories. (i) Species :-It is the basic unit of classification. It is the group of individuals with similar morphological characters which interbreed among themselves and produce their own kind. There can be many sps. belonging to same genus. E.g. Tiger- Panthera tigris, Panthera leo. But individuals of two different species cannot interbreed. (ii) Genus: - It is a group of species, which are similar in broader features but differ in detail. E.g. Lion, tiger, Leopard, Jaguar have several common features and belong to one  Genus- Panthera.  Panthera leo (lion), P.tigris (tiger), P.pardus (leopard), P.onca (Jaguar). A genus can have single species (Monotypic) or many species (Polytypic). (iii) Family: - A family is a group of related genra. e.g. Genus Felis of cats and genus Panthera of Lion, Tiger, Leopard are placed in family Felidae as they have similar characters of retractile claws. (iv) Order: - It is a group of related families. E.g. Family Felidae of cats and Family Canidae of dogs are placed in same order Carnivora as these all have large canines & are  Flesh eaters. Family Solanaceae and Convolvulaceae in plants are put in one order Polemonial because of some same floral characters. (v) Class: - is a group of related orders. E.g. order Rodentia (of rats), Lagomorpha (of Rabbits) and Carnivora (of cats and dogs) all have hair, milk glands and are placed in same class Mammalia. (vi) Phyla / Divisions: -A group of related animal classes is called ‘Phylum’ whereas a group of related plant classes is called as ‘Division’.e.g. In animals, Phylum Chordata includes classes Amphibia, Pisces, Reptilia, Aves and mammals since all these classes have common characters like presence of notochord, dorsal hollow nervous system &  Pharynx with perforated gill slits. (vii) Kingdom :-It is a group of phyla / divisions with certain common characteristics. e.g.  all phyla of animals lack cell wall and chlorophyll. So these are placed in kingdom Animalia. All divisions of plants have cell wall and chlorophyll, so these are kept in Kingdom Plantae. Intermediate Categories: -There are smaller sub-categories also which can be added to explain finer distinctions wherever necessary. These sub-categories are sub-species (below species), sub-genra (below Genus), sub-family (below Family), Sub-order (below order), sub-class (between order and class), Sub-phylum (below phylum), sub-kingdom (Between phylum and kingdom). All these are called Intermediate Categories. (1.6) SYSTEMS OF BIOLOGICAL CLASSIFICATION :- There are three major systems of Biological classification. (1) Artificial System: -This is based upon few superficial resemblances in organism rather than natural or evolutionary relationships. It was introduced by Pliny, the elder (28-79AD). Aristotle (384-322BC) classified organism on the basis of habitat. E.g. Aquatic group (animals living in water), terrestrial (animals living on land) and Aerial (in air). E.g. two groups of animals –one, which can fly, and others, which cannot fly. Theophrastus followed him and classified plants as trees, shrubs and herbs on the basis of habit. Linnaeus also followed artificial system and classified plants on the basis of number, union, and length etc. of stamens.e.g.Monandria (1 stamen), Diandria (2 stamens), Triandria (3 stamens) and Polyandria (many stamens). Drawbacks: -(i) lacks natural relationship among organism. (ii) Leads to grouping of unrelated organisms like birds, bats, insects in flying animals. (iii) Related organisms get separated e.g. whales in aquatic animals and rats in terrestrial. (iv) Habits of certain animals change as they grow. E.g. Tadpoles are aquatic but when they grow as frog, they become amphibious. (v) It does not reflect evolution of organisms. (2) Natural System: - It was first proposed by John Ray (1627-1705) on basis of similarities and dissimilarities in plants and animals. A comparable study of number of characters is done in this system. It considers characters, which are relatively constant like morphological, cytological, anatomical characters. The latest natural system of classification of seed plants was proposed by George Bentham (1800-1884) and Joseph Dalton Hooker (1862-1883). Advantages: - (i) brings out natural relationship among organisms. (ii) Only related organisms are placed in a group. (iii) Unrelated organisms remain separate. (iv) It shows evolutionary relationship. (3) Phylogenetic system: -This system is based on evolutionary sequence as well as genetic relationship among organisms.e.g Hutchinson system, Engler and Prantl’s system. Etc. In this system, Organisms belonging to same taxa have a common ancestor & may be represented in form of a family tree-Cladogram. Adolf Engler and Karl A.E.Prantl (German) published their system in ‘Die naturlichen Pflanzenfamilien’ (1887-1899). According to them, flowers with only stamens or carpels formed the lowest grade of organization. They considered monocots to be primitive than dicots. Families were arranged according to increasing complexity of flower. Primitive forms have naked flowers and were kept in the beginning. The more advanced families have distinct perianth while highly evolved families have fused perianth. John Hutchinson (English Botanist) gave his phylogenetic classification in his book “Families of Flowering Plants” in 1959.According to him- -Trees and shrubs are considered to be more primitive than herbs. -Dicots are more primitive than monocots. -Polypetaly, Actinomorphic and Solitary flowers are considered more primitive than Gamopetaly, Zygomorphy and inflorescence respectively. (1.7) CLASSIFICATION OF ORGANISMS: - (1) Two Kingdom Classification: - It is the oldest system given by C.Linnaeus in1758. He divided living world into two kingdoms: (a) Plantae- includes plants. Are immobile, have autotrophic nutrition and rigid cell walls. (b) Animalia – includes animals. Are mobile, depend on plants or other organisms for food and have no cell wall. Shortcomings of two kingdom system: - (i) Higher organisms can be easily differentiated as plants and animals but lower organisms possess characters of both .So, it is difficult to place them in plants or animals. E.g. Euglena has autotrophic nutrition and chlorophyll. So, it resembles plants but it lacks cell wall and is mobile. So, it is like animals also. E.g. Sponges are immobile and branched like plants but they respond to stimuli, are holozoic and excrete nitrogenous waste material like animals. (ii) Fungi, Bread moulds, Mushrooms were placed in plants but these lack chlorophyll and do not synthesize their own food. (iii) Bacteria are included in plant kingdom but these lack well organized nucleus and are called prokaryotes in contrast to Eukaryotes, which have well defined nucleus. (iv) Viruses and Lichens have peculiar characters like viruses lack protoplasm and exhibit characters of living organism inside living cell. They don’t resemble plants but are kept in plant kingdom. Lichens have association of Algae and Fungi. So, these are neither plants nor animals. This system was inadequate. So, it was not fully accepted. (2) Three Kingdom Classification: - given by E.H. Haeckel. According to him, the three kingdoms are Protista included all unicellular microorganisms, which are either plants or animals. e.g. Bacteria, Algae ,Fungi and Protozoa were included in Protista. (3) Four Kingdom Classification: -By Copeland. According to him He placed Bacteria, Cyanobacteria in kingdom Monera. (3) Five Kingdom Classification: Given by Robert H. Whittaker in 1969. According to him five kingdoms are, Basis of Classification: - It is based on four factors. (i) Complexity of cell structure. (Prokaryotic or Eukaryotic) (ii) Complexity of organism’s body.  (Unicellular or multicellular). (iii) Mode of Nutrition (Autotrophic or Heterotrophic). (iv) Phylogenetic relationship. Complexity increased during evolution. Cells became prokaryotic to eukaryotic. Organisms became unicellular to multicellular. Mode of nutrition changed in multicellular kingdoms (Plantae, Fungi, Animalia). Plantae became Producers, Fungi were Decomposers and Animalia became Consumers. Kingdom Monera   (The Prokaryotes): - It includes single celled prokaryotic organisms like Bacteria, filamentous Bacteria (Archaebacteria) and Cyanobacteria (Blue Green Algae). They are most primitive with following characters: - - Are microscopic, found in deep ocean floor, hot deserts., hot springs and inside other Organisms. -Are either unicellular or occur in colonies. -Cells are prokaryotic with rigid cell walls. -Nucleus and other organelles lack membranes. -Nutrition is of different types. Most are heterotrophs, some Bacteria are autotrophs. -Reproduce mainly by Binary Fission. Sexual reproduction is absent. -Can survive in extreme environmental conditions like high salt concentration, high temp    erature, acidic / alkaline ph.can also survive in anaerobic conditions. Kingdom Protista (the unicellular Eukaryotes) :-It includes unicellular and multicellular forms found in aquatic habitats. They have following characters: - - Generally lack cell wall. If present, it is made up of cellulose. -Have membrane bound cell organelles like nucleus, mitochondria, and E.R. and Golgi   bodies. -May have cilia or flagella for their movement. -Show all modes of nutrition. Protistan algae are photosynthetic autotrophs. Unicellular Free-floating algae are called Phytoplanktons. Slime Moulds are decomposers. -Reproduce by sexual and asexual reproduction. Kingdom Fungi (multicellular Eukaryotes- Decomposers):- They have following characters: - -It is made up of thread like interwoven structures called ‘Hyphae’. Network of hyphae is called as ‘Mycelium’. -Are single celled as well as multicellular -Cell wall is made up of chitin-a nitrogen containing carbohydrate. -Are heterotrophs having either saprophytic or parasitic mode of nutrition. Some have Symbiotic association with algae or cyanobacteria (lichens) or roots of plants (Mycorrhiza). -Store reserve food as oil or Glycogen. -Hypha can undergo fragmentation & each fragment grows into new mycelium. -Reproduce asexually by spores like zoospores, Gonidia, Conidia, Ascospores and Basidiospores. Sexual reproduction occurs by fusion of similar (isogamy) or dissimilar gametes (oogamy). Types of Fungi: - On the basis of morphology of mycelium, mode of nutrition and mode of reproduction, fungi are of following types- (a) Myxomycetes :-occurs in damp places and are multinucleated. -Body is thallus shaped and is called Plasmodium. -Have pseudopodia for movement and engulfing food. -Body survives adverse dry conditions by becoming fruit like. -Multiply by fragmentation, asexually by zoospores, sexually by spores acting as Gametes. (b) Phycomycetes: -Found in water or decaying leaves. -Are multinucleated. -Reproduce asexually by ciliated zoospores and non-ciliated aplanospores.Sexual reproduction occurs by fusion of similar (Isogamy) gametes or dissimilar gametes (oogamy) e.g. Mucor, Albugo. (c) Ascomycetes: -are unicellular as well as multicellular -Asexual reproduction occurs by spores formed outside sporangium. Sexual reproduction occurs by ascospores formed within mycelium in sac like structure-Ascus. -After fusion of gametes, meiosis occurs to produce haploid ascospores. -Fruiting body is called Ascocarp. -e.g. Yeast,Penicillium ,Aspergillus. (d) Basidiomycetes: -are called ‘Club Fungi’ because of club shaped mycelium end kno       wn as Basidium. - Have multinucleated mycelium. -Asexual spores Basidiospores are produced outside. -Two compatible gametes fuse to form zygote, which undergoes meiosis to  produce four basidiospores. -Fruiting body is called ‘Basidiocarp’. -E.g. Mushroom, Smut, Rust. Kingdom Plantae (multicellular Eukaryotes- Producers) -Are multicellular and photosynthetic forms called Green plants, Algae etc. -Are non-motile except few Algae. -Have rigid cell wall of cellulose. -Reserve food is mainly Starch. -Algae reproduce asexually by motile and non-motile spores. -Are called ‘Photoautotrophs’or ‘Primary Producers’as they synthesize their food by  utilizing water, carbon di oxide, minerals in the presence of sunlight and chlorophyll.Some plants are total parasites (Cuscuta) or partial parasites (Viscum) also. Kingdom Animalia :-(Multicellular Eukaryotes- Consumers) -Comprise of animals, vertebrates and invertebrates. -Are multicellular without cell wall. -Lack chlorophyll, are heterotrophic with holozoic mode of nutrition. So these are also called as ‘Metazoa’. -Respond to external stimuli. -Have well developed control and co-ordination mechanism. - Reproduce sexually only. Some lower forms show asexual reproduction also. Significance of five kingdom classification: - (i) System is more natural as it shows gradual evolution of early organisms into plants & animals. (ii) It is based on cellular organization and modes of nutrition, which evolved very early in living world. (iii) Separate Kingdom Fungi is justified as it differs from plants morphologically as well as physiologically. (iv) Unicellular Eukaryotes like Euglena were earlier included in both plants and animals. But now placing them in separate kingdom Protista has eliminated this anomaly. This system was better than all systems and resolved many problems also. But still, it was not perfect and had certain drawbacks like (i) Kingdom Monera and Protista are still heterogenous. Both include autotrophic and heterotrophic forms and organisms with or without cell wall. (ii) Phylogenetic relationship of lower organisms is not fully reflected. (iii) Slime moulds differ from other Protists with which they are combined. (iv) Multicellular Green algae cannot be phylogenetically separated from unicellular algae and therefore unicellular algae are placed in Plantae whereas these should be in Protista. (1.8) TAXONOMICAL AIDS :- Definition: The aids, which help in taxonomical studies, are called Taxonomical Aids. E.g. Herbarium, Museums. Some aids are- (1) Herbarium: -Definition-It is a collection of pressed, dried and preserved plants on paper sheet which are properly labelled, arranged and available for reference or study. Tools required in Herbarium: - (i) Digger for digging roots. (ii) Scissor for cutting twigs.   (iii) Knife for cutting woody twigs. (iv) Pole with a hook for collecting parts of tall trees. (v) Vasculum for keeping plant specimens. (vi) Plant Press for pressing parts of plants. Steps in preparation of Herbarium: -Regular field visits are done and specimens collected. Information about place, habitat, season and collection time is noted. The collected specimens are kept in a box called Vasculum to avoid loss of moisture and distortion. Specimens are spread out, dried in between folds of newspapers and pressed in Plant Press, which is a set of two boards with straps. Bigger specimens are folded in ‘n’ or ‘w’ form. Some leaves are spread to show dorsal surface and some to show ventral surface. Dried specimens are pasted on herbarium sheets of standard size (29 x 41 cms.). All pasted specimens are sprayed with fungicides like 0.1% mercuric chloride. Heavier plant parts like seed, fruits are put in a packet and attached to the sheet. Technique of Herbarium  (i) Pressed and dried specimens are mounted on thick paper with some adhesive. (ii) Small paper envelopes ‘Fragment Packets’ containing seeds/fruits are attached to herbarium sheet. (iii) Sheet is labelled on right corner with following information- Name of Institution – Scientific name of Plant- Common / Vernacular Name- Family - Locality - Date of collection - Collection Number- Name of Collector- (iv) Pesticides are sprayed on specimens to keep them pest free. (v) Mounted, labelled and treated specimens are stored in herbarium cabinets, which are insect and dust proof. (vi) An Index register is maintained to locate desired specimens easily. (2) Botanical Gardens: - Definition- It is a place where plants of various groups are grown for scientificstudy, conervation, public education, aesthetics and recreation. Major botanical Gardens-There are thousands of Botanical Gardens in the world. About 800 are listed in International Directory of Botanical Gardens published by Henderson in 1983. In India- (i) Indian Botanical Garden, Kolkata. (ii) National Botanical Research Institute, Lucknow. (iii) Garden of Forest Research Institute, Dehradun. In World- (i) New York Botanical Garden, USA. (1801) (ii) Royal Botanical Garden, London. (1600) (iii) Main Botanical Garden, Moscow. (iv) Botanical Garden, Montreal, Canada. (3) Museums: -Definition-It is a place where preserved plants and animals are kept for reference and study. Plants like Algae, Fungi, Gymnosperms, which cannot be kept in herbaria, are kept in museums. Plant and animal specimens are fixed in chemical solution identified and are labelled to be preserved for longer duration. Museums help in taxonomic studies. (4) Zoological Parks (Zoo/Zoological Garden): -Definition-It is an enclosed space where live wild animals are kept for public exhibition. There are over 3000 zoological parks in India. Aim of Zoological parks: -The main purpose is to breed those animals, which are facing threat in their natural habitat. Information about common names and scientific names is also displayed. Keys: - Definition:-A scheme for identifying plants and animals is called ‘Key’. It is based on contrasting characters. Separate keys are required for different categories like family, Genus, species. Types: - It is of two types: (a) Indented (Yoked)- In this, two or more statements of characters of species are given to make choices. E.g. To identify Genra in family Ranunculaceae, characters of carpels and fruit of specimen can be considered as Indented Keys. The first choice starts with carpels. (b) Bracketed – Pair of contrasting statements are used for identification. Animals can also be identified by using Keys. Distinguishing features are recorded for each group. Questions are framed and answers are given in yes or no.