Several animals have curiosity but humans are particularly more curious about natural world and their surroundings, this feature that makes humans singularly different from other living organisms.
•We keep pets, nurture plants, visit zoological and botanical gardens, climb mountain peaks or divedeep into the sea and undertake trekking in the forests to enjoythe serenityof wilderness along with its vast living and non-living resources. All these activities reflect the innate attraction of humans fornatural world and their feeling of connectedness to living things.
•Inanimals,thisgrowthisseenonlyuptoacertainage(Determinategrowth).However,celldivision occurs in certain tissues to replace lost cells.
•Unicellular organisms multiply by cell division. One can easily observe this in in vitro cultures by simply counting the number of cells under the microscope.
•Onemustremember that increase in bodymassis considered asgrowth but non-living objects also grow if we take increase in body mass as a criterion for growth. e.g. 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.
•Conditions under which it can be observed in all living organisms have to be explained and then we understand that it is a characteristic of living systems. A dead organism does not grow.
2.REPRODUCTION
•In multicellular organisms, reproduction refers to the production of progeny possessing features moreor less similar to those of parents. Invariably and implicitly we refer to sexual reproduction.
When it comestounicellular organismslike bacteria, unicellular algae orAmoeba,reproduction is synonymous with growth, i.e., increase in number of cells.
•Hence, we notice that in single-celled organisms, we are not very clear about the usage of these two terms – growth and reproduction.
There are many organisms which do not reproduce (mules, sterile worker bees, infertile human couples, etc). Hence, reproduction also cannot be an all-inclusive defining characteristic of living organisms.
•These chemicals, small and big, belonging to various classes, sizes, functions, etc. are constantlybeing made and changed into some other biomolecules. These conversions are chemical reactions or metabolic reactions.
•There are thousands of metabolic reactions occurring simultaneously inside all living organisms, bethey unicellular or multicellular.
The sum total of all the chemical reactions occurring in our body is metabolism.
•Nonon-livingobjectexhibitsmetabolism.
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, while metabolism is a defining feature of all living organisms without exception, isolated metabolic reactions in vitro are not living things but surely living reactions.
•Perhaps, the most obvious and technically complicated feature of all living organisms is this ability to sense their surroundings or environment and respond to these environmental stimuli which could be physical, chemical or biological. We sense our environment through our sense organs.
•Plants respond to external factors like light, water, temperature, other organisms, pollutants, etc. All organisms, from the prokaryotes to the most complex eukaryotes can sense and respond to environmental cues.
Photoperiodaffects reproduction in seasonal breeders, both plants and animals.
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 observepatients 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.
•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.
•Therefore, we can say that living organisms are self-replicating, evolving and self-regulating interactive systems capable of responding to external stimuli.
•Taxonomy: The term Taxonomy used by A.P. de Candolle in his book ‘Theory of elementary de la botanqui’.
•Fatheroftaxonomy:CarolusLinnaeus
Characterization, identification, classification and nomenclature are the processes that are basicto taxonomy.
•Based on characteristics, all living organisms can be classified into different taxa. This process of classification is taxonomy.
•External (Morphology) and internal structure (Anatomy), along with the structure of cell (Cytology), development process and ecological information of organisms are essential and form the basis of modern taxonomic studies.
The word systematics is derived from the Latin word ‘systema’ which means systematic arrangement of organisms. Linnaeus used Systema Naturae as the title of his publication.
•It is the study of diversity and differentiation of organisms based on their phenotypic, genetic and phylogenetic relationships.
Systematicincludesidentification,nomenclature,classificationandevolutionaryrelationships between organisms.
SupportedbyLamark,Huxleyandother modern scientist.
New branches of systematics are as follows:
(a)Cytotaxonomy:
It is based on cytological information like chromosome number, chromosome structure and chromosome behaviour.
•Karyotaxonomyisthemostadvancedbranchoftaxonomy.
(b)Numerical Taxonomy (Phenetics or Taximetrics) or Adansonian Taxonomy:
•ItwasdevelopedbyAdanson.
It is based on all observable characteristic.
Each character is given equal importance.
Hundreds of character can be consider at the same time.
Number and code are assigned to all character and data and then processed usingcomputer
or statistical method.
(c)Chemotaxonomy or Biochemical taxonomy:
It is based on chemical constituent of plants.
•It involvestudy of biomolecules particularly secondary metabolites of the cell like betacyanin pigment in beet roots, raphides and cystolith crystals, sequencing of DNA and chemical nature of proteins.
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NOMENCLATURE
It is assigning of names to organisms. There is a need to standardize the naming of living organisms such that a particular organism is known by the same name all over the world. This process is called nomenclature.
•In ancient time organisms are given local names / vernacular names based on their characteristic or uses but local names vary from place to place, even within a country. e.g. Bottle guard is known by different name in different parts of country like – Louki, Dudhi, Ghiya etc.
Nomenclature or naming is only possible when the organism is described correctly and we know to what organism the name is attached to. This is identification.
ICZN (International Code of Zoological Nomenclature)ICBN(InternationalCodeforBotanicalNomenclature-1961) ICVN (International Code of Viral Nomenclature),
Each name has two components – the Generic name (Genus) and the specific epithet (Species).This system of providing a name with two components is called binomial nomenclature (L. bi: two; nomen: name). e.g. Mango – Mangifera indica; Honey bee – Apis indica
•Naturehas vastdiversityoflivingorganismssoitisnearlyimpossibletostudyallthelivingorganisms,it is necessary to devise some means to make this possible. This process is classification.
•It is the process by which anything is grouped into convenient categories (according to a systematic plan or an order) based on some easily observable characters. e.g. We recognize groups / categories like plant, animals, dog, cat, mammals, wheat etc. on the basis of certain associated characters called as taxa.
•Thepurpose of biologicalclassification is to organize the vast number of known plants and animals into categories that could be named, remembered and studied.
•The earliest classifications were based on the ‘uses’ of various organisms because in early days, human beings needed to find sources for their basic needs of food (e.g. oil yielding plants – Coconut, Mustard, Sesame), clothing (Cotton) and shelter (e.g. Medicinal plants – Turmeric, Rauwolfia).
•But now systematic is used for knowing more about different kinds of organisms and their diversities, and also the relationships among them.
•Classification is not a single step process but involves hierarchyof steps in which each step represents a rank or category.
TAXONOMIC CATEGORIES
•Thereare 7 main taxonomic categories (known as obligate or essential or broad categories)
which are essentially used in classification of organism.
•There are many intermediate categories like subkingdom, super phylum or super division, sub division, super class, sub-class, super order, sub order, super family, sub family, Tribe, sub species, variety etc. to facilitate more sound and scientific placement of various taxa.
e.g. Bryophyta is a taxon while division is a category. Similarly pea is a taxon while species is a category.
•The number of common character goes on decreasing from species (more common character) to kingdom (less common character). e.g. order being a higher category is the assemblage of families which exhibit a few similar character. And the similar character are less in number as compared to different genera included in family.
Kingdom
Species
Commoncharacterincreases
•Higher the category, greater is the difficulty of determining relationship to other taxa at the same levelso problem the classification become more complex.
•Biological species concept was given by Ernst Mayr. According to Mayr “species is group of organism with similar morphology which can interbreed among themselves and produce fertile offspring”. It is based on reproductive isolation.
B.GENUS
•Genus comprises a group of related species which has more characters in common in comparison to species of other genera.
•Each genus may have one or more than one specific epithets representing different organisms, but having morphological similarities.
•Genusmaybemonotypic(Singlespeciesinagenuse.g.Gregoriafenestrata)andPolytypic(many species in a genus).
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Tomato–Solanumlycopersicum
Solanum(Genus)
Brinjal–Solanummelongena
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Potato–Solanumtuberosum
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Lion–Pantheraleo
Panthera
Tiger–Pantheratigris
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Leopard–Pantherapardus
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Jaguar–Pantheraonca
Felis(Cat)andCanis(Dog)
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C.FAMILY (Suffix – aceae)
•Family has a group of related genera with still less number of similarities as compared to genus and species.
•Carolus Linnaeus (1707-1778): He proposed an artificial system of classification (Also called sexual system of classification) on the basis of few sexual characters like on the androecium structure (number of stamens), in his book Genera Plantarum. He classified plants into 24 classes. Out of them, 23 were of phanerogams and 24thclass was of cryptogams.
•Theearliestsystemsofclassificationusedonlygrosssuperficialmorphologicalcharacterssuchas habit, colour, number and shape of leaves, etc.
(b)The artificial systems gave equal weightage to vegetative and sexual characteristics; this is not acceptable since we know that often the vegetative characters are more easily affected by environment.
•Inthesesystemsorganismsareclassifiedonthebasisofmainlyexternalmorphologyandinternal feature like ultrastructure, anatomy, embryology features, phytochemistry etc.
•George Bentham and JD Hooker (1862–83) proposed a natural system of classification of angiosperms that was published in ‘Genera Plantarum’ in 3 volumes. It is based on A.P. de Candolle’s system.
•Evolutionary history of the organism is called Phylogeny (this term was coined by Lamarck). These systems are based on Phylogenetic relationships of organisms.
•Phylogenetic systems are also called Cladistics (Systematic classification based on evolutionary relationships of organisms in order of their assumed divergence from ancestral forms) and the graphic representation of evolutionary relationships is called family tree or Cladogram.
•Engler and Prantl proposed first phylogenetic classification (but it is very little phylogenetic) and published in their book “Die NaturlichenPflanzenfamilien” in 23 volumes.
•Later on well-developed phylogenetic systems of classification were created by Hutchinson, Tippo, Takhtajan, Robert Whitaker, Robert thorne and Cronquist.
•Oswald Tippoproposed biggest phylogenetic classification of plant kingdom and it is most acceptedfor books and study.
•Fossil records are most important evidences in systematics but if fossil record are not available then other branches of taxonomy like Karyotaxonomy, Cytotaxonomy, numerical, Chemotaxonomy etc. play important role to find out phylogeny
•Thallophyta includes those plants in which root, leaf and stem are not differentiated like fungi, Algaeand Bryophyta.
•Pteridophytsareconsideredasvascularcryptogams.
•Thallophyta, Bryophyta and Pteridophyta are zoodiogamous plants (Motile male gamete) while Gymnosperm and Angiosperms are siphonogamous plants (Pollen tube formation).
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BIOLOGICAL CLASSIFICATION:
On the basis of number of Kingdom.
1.TWO KINGDOM SYSTEM OF CLASSIFICATION:
•Proposed by C. Linnaeus and he classified all organisms into two kingdoms – Kingdom plantae and kingdom Animalia.
Kingdom plantae involves autotrophic, fixed organisms while kingdom Animalia includes motile, heterotrophic organisms. Microorganisms involved in both the kingdoms.
(i)Thissystem didnotdistinguishbetweentheeukaryotesandprokaryotes.e.g.Bacteriaand cyanobacteria are included under plants but the formers are prokaryotes.
(ii)Unicellularandmulticellularformshavebeenplacedinboththekingdomsthoughtheyhave different organisation.
(iii)Alargenumberoforganismsdidnotfallintoeithercategory. e.g.Virusesareneitherplants nor animals and placed at the border line of living and non-living.
(iv)Photosynthetic (green algae) and non-photosynthetic (fungi) organisms were placed together.
Thus two kingdom system of classification used for a long time was found inadequate.
•HeseparatedallonecelledEukaryotes(Algae,Slimemoulds,Protozoans,Fungi,bacteria)into separate kingdom Protista.
3.FOUR KINGDOM SYSTEM:
•ItwasproposedbyCopeland(1956).
•He established a new kingdom Monera for all acellular prokaryotes containing incipient nucleus like bacteria, blue green algae. The four kingdoms are monera, protista, plantae (metaphyta) and animalia (metazoa).
Issues and considerations that influenced the classification system:
Issues:
•Besides,gross morphology aneedwasalsofeltforincludingothercharacteristicslikecell structure, nature of wall, mode of nutrition, habitat, methods of reproduction, evolutionary relationships, etc.
•Earlierclassificationsystemsplantsincludedbacteria,bluegreenalgae,fungi,mosses,ferns, gymnosperms and the angiosperms because all of these have cell wall.
•Unicellular organism like Chlamydomonas and Spirogyra were placed together under algae which is multicellular.
•Heterotrophic / Saprotrophic group like fungi were classified autotrophic green plants though they also showed a characteristic difference in their walls composition – the fungi had chitin in their walls whilethe green plants had a cellulosic cell wall.
•All prokaryotic organisms were grouped together under Kingdom Monera and the unicellular eukaryotic organisms were placed in Kingdom Protista.
•It has put together organisms which, in earlier classifications, were placed in different kingdoms. e.g. KingdomProtistahasbroughttogetherChlamydomonas,Chlorella(earlierplacedinAlgaewithinPlants and both having cell walls) with Paramoeciumand Amoeba (which were earlier placed in the animal kingdom which lack cell wall).
•This happened because the criteria for classification changed with time and this kind of changes will also take place in future too depending on the improvement in our understanding of characteristics and evolutionary relationships.
•Though plant and animal kingdoms have been a constant under all different systems, theunderstanding of what groups/organisms be included under these kingdoms have been changing; the number and nature of other kingdoms have also been understood differently by different scientists over the time.
All Eukaryotic forms like Algae, Fungi, Protista,Plants andAnimals
TAXONOMICAL AIDS
•Taxonomic studies of various species of plants, animals and other organisms are usefulin agriculture, forestry, industry and in general in knowing our bioresources and their diversity.
•Itis used for classification of an organism, and the informationgathered is also storedalong with the specimens. In some cases the specimen is preserved for future studies.
•Biologists haveestablishedcertainproceduresandtechniques tostore andpreservetheinformationas well as the specimens. Some of these are explained to help you understand the usage of these aids.
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A.HERBARIUM:
Herbarium isa storehouseofcollectedplantspecimens thataredried, pressedandpreserved on sheets. Further, these sheets are arranged according to auniversallyacceptedsystem of classification.
•Thesespecimens,alongwiththeirdescriptionsonherbariumsheets,becomeastorehouseorrepository for future use.
Theherbarium sheets(standardsize16.5×11.5inch.) alsocarrya label providinginformation about date and place of collection, English, local and botanical names, family, collector’s name, etc.
•In the field, one requires digger for digging roots, scissors for cutting twigs, knife for woody twigs and a pole with a hook for collecting parts of tall trees.
•The collected specimens are carried in a box called vasculum to avoid loss of moisture and distortions by drying and shriveling up.
•Museumshavecollectionsofpreservedplantandanimalspecimensforstudyandreference. Specimens are preserved in the containers or jars in preservative solutions.
•These are the places where wild animals are kept in protected environments under human care and which enable us to learn about their food habits and behavior.
•Allanimalsinazooareprovided,asfaraspossible,theconditionssimilartotheirnaturalhabitats. Children love visiting these parks, commonly called Zoos.
E.KEY:
Keyisanothertaxonomicalaidusedforidentificationofplantsandanimalsbasedonthe similarities and dissimilarities.
•Theindentedkeyprovides sequenceofchoicesbetweentwoormorestatementsofcharactersof species. The user has to make correct choice for identification.
(b)Bracketedkey(Morepopular).
•In the bracketed key, the pairs of contrasting statements are used for identification. The number on the right indicates the next choice of paired contrasting statements.
ResonatetheConcept
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F.FLORA:
•Flora contains the actualaccount of habitatand distribution and indexto theplantspecies found in a particular area.
•The branch of biology which deals with the study of animals is called zoology (zoon: animal; logos: to discourse). Aristotle is regarded as Father of Zoology. Book – Historia animalia.
•The study of plants is called Botany (botane: plant). Theophrastus (370-287 B.C.) prepared a list of500 plants and is called “Father of Botany”. Book – Historia plantarum.
•In Chandyogya Upanishad animals were classified into 3 categories i.e. Jivaja (Viviparous), Andaja (Oviparous) Udbhija (Vegetal origin).
•Charaka was the first physician to present the concepts of digestion, metabolism and immunity. According to him, a body functions because it contains three doshas,namely, bile (pitta), phlegm (cough) and wind (vata) and illness is caused when the balance among the three doshas in a human bodyis disturbed. These are the basis of the indigenous system of medicine in India which is known as Ayurveda.
•C. Linneaus: Books – Species plantarum (1753, 5900 plant species) and Systema naturae (1758, 4326 animal species). He also gave term systematics and class.
•Apoplasmic substances are non-living components formed bycell e.g. Cell wall, fibers in connective tissue, matrix of bone etc.
