Unit of Classification - Taxon - Systematics of Living Organisms - Biologi

Unit of Classification :

Species : Species is the principal natural taxonamic unit, ranking below a genus and denoted by latin binomial (considered as the basic) unit of classification that can interbreed under natural candition to produce fertile offspring. It was thought to be an indivisible, stable and static unit. However in the modern taxonomy, sub-division of species such as sub-species, varities and population are seen and give more importance.

Genus : Genus is a taxonomic rank or category larger than species used in the biological classification of living and fossil organisms. Genus is a group of species bearing close resemblance to one another in their morphological characters but they do not interbreed, e.g. Tiger, Leoard, Lion all three belong to same genus panthera. They have common characters yet are different from each other because their genus is same but species is different . Another example is genus Solanum. Brinjal and potato both belong to this genus.

Family : It is one of the major hierarchical taxonomic rank. A family represents a group of closely related genera. e.g. genera like Hibiscus, Gossypium, Sida, Bombox are included in same family Malvaceae. Cat also belongs to family of leopards, tigers and lions, family Felidae but dog belongs to different family Canidae.

Cahort / Order : It is taxonomic rank used in the classification of organisms and recognised by nomenclature codes. An order is a group of closely families showing definite affinities. Order this is a step above family in taxonomic hoerarchy. Members belonging to same order but different families may show very few dis similarities. e.g. family - Papavaraceae, Brassicaceae, Capparidance, etc with parietal plancentation are grouped in order Parietales. Families of dogs and cats though are different, they belong to same order Carnivora.

Calss : The calss is the distinct taxonomic rank of biological classification having its own distinctive name. A group of higher taxonomic rank than order. Class is the assemblage of closely allied orders. Orders Carnivora and order Primates belong to class Mammalia. This mankeys, gorillas, gibbons (Primats) and dogs, cats, tigers (Carnivora) belong to same class.

Division / Phylom : The division is a category composed of related classes e.g. division. Angiospermae includes two classes - Dicotyledonae and Monocotyledons (In animal classification division is a sub-unit of Category / Phylum).

Sub-kingdom : Different divisions having some similarities from sub-kingdom. e.g. The division Angiospermae and Gymnospermae will the sub-kingdom Phanerogams or Spermatophyta.

Kingdom :  It is the highest taxonomic category composed of different sub- kingdoms. e.g. sub-kingdom Phanerogams and Cryptogams from the Plant kingdom or Plantar which includes all the plants while all animals are included in kindom Animalia.

       The taxonomic Categories we have considered so far are broad categories. Scientists have added sub-categories to these in order to place organisms in more scientific manner. You will observe that as we go higher in taxonomical ladder, number of common characters go on decreasing.

If we are comparing two organisms that are related to each other only at division or phylum level, their classification may become difficult.

Taxonamic Hierarchy - Taxon - Systematics of Living Organisms - Biologi

Taxonamic Hierarchy :

Taxon : A taxon is the taxonomic group of any rank in the system of classification (H.J. Lam 1848) e.g. in plant kingdom each one of the following such as Angiosperms, Dicotyledonae, Polypetalae, Malvaceae represents a taxonomic group i.e. a taxon.

Taxonomic Categories - Systematics of Living Organisms - Biologi

Taxonamic Categories :

Classification is not a single step process but involves hierarchy of steps in which each step represents a rank or category. Since the category is a part of overall taxonomic arrangements 8t is called taxonomic category and all categories together constitute the taxonomic hoerarchy. Kingdom, division, class, order, family, genus, species are the categories in hirarchial sequence. These are compulsory categories. Besides, there are some facultative categories like sub-order, sub-family, etc. to be used as per need.

DNA barcoding - Systematics of Living Organisms - Biologi

DNA barcoding :

DNA barcoding, is a new method for the identification of any species based on its DNA sequence from a tiny tissue sample of the organism under study.

It help to study newly identified species as well as understanding ecological and evolutionary relationships between living beings. The process of DNA barcoding includes two basic steps: (a) collecting DNA barcode data of known species and (b)arching the barcode sequence of the unknown sample against the barcode library for identification. DNA barcoding has many applications. A few to mention are, protection of endangered species, preservation of natural resources, pest control in agriculture, identifying disease vectors, authentication of natural health products and identification of medicinal plants.

Phylogeny - Systematics of Living Organisms - Biologi

Phylogeny :

       It is evolutionary relationship of organism. It is an important tool in classification as it takes into account not merely the morphological status but also the relationship of one group of organism with order groups of life. The system helps to understand the evolution and also focuses on the similarities of their metabolic functioning. Woese's three domain concept as well as Whottaker's five kingdom system are very good examples of phylogenetic relationship.

Cladogram - Systematics of Living Organisms - Biologi

Cladogram : 

       It is a typical bronching pattern. As shown on previous page, a digram of three domains of life is a cladogram. It represents a hypothetical relationship denoting a comparison of organisms and their common ancestors.

Numerical taxonomy - Systematics of Living Organisms - Biologi

Numerical taxonomy :

       The system is besed on quantification of characters and developes an algorithm for classification. The basic aim of this taxonomy was to create a taxonomy using numeric algorithms like cluster analysis rather than using subjective evaluation of their propertise. This system was first proposed by Sokel and Sneath in 1963.

Chemotaxonomy - Systematics of Living Organisms - Biologi

Chemotaxonomy :

       It is method of biological classification based on similarities and differences in structure of certain compounds present among the organisms being classified. In short, it is the classification based on chemical constituents of organisms. e.g. Archaea cell wall is without peptidoglycan and that of Prokarya is with peptidoglycan. Among Eukarya, fungi have chitinous cell wall while plants have cellulosic cell wall.

Three domains of life - Systematics of Living Organisms - Biologi

Three domains of life : 

       It is believed that life originated on earth in its very simple form. Constant struggle of the early living beings gave rise to more and progress is evolution which led to formation of diverse life forms . Carl Worse in 1990 proposed three domains of life to classify life forms. They are Archaea, Bacteria and Eukarya. Domain is an unit larger than Kingdom in the system of classification.

       Bacteria and Archaea both have prokaryotic cells where as Eukarya heve eukaryotic cell. All the three domains have very unique ribosomal RNA (rRNA). Archaea are known for their survival in very extreme conditions like high temperature, salinity, acidic conditions, etc. Bateria , thought are prokaryotes differ from Archaea in structure of cell wall.

Classification - Systematics of Living Organisms - Biologi

Classification : 

       It is the arrangement of organisms or groups of organisms in distinct categories in accordance with a particular and we'll established plan . This classification is based on similarities and dissimilarities among the organisms.

Artificial :

 

       It is the classification that is based on few easily observable and non-evolutionary featurs such as habit, colour, form, etc., often irrespective of their affinity (relationship) with other organisms. e.g. Linnaeus system of classification.

Natural : 

       It is the classification which is based on objectively significant rather than being selected for convenience like artificial system of classification e.g. Bentham and Hooker's system of classification.

Phylogenetic : 

       It is the classification based on common evolutionary descent. e.g. Engler and prantles classification.

       In the system of classification the terms like ‘taxa' and ‘categories' are often used. Each category is referred to as a unit of classification. In fact, it represents a rank and is commonly termed as taxon.

Systematic - Systematics of Living Organisms - Biologi

Systematic :

   

       "Systematics is the study of kinds and diversity of organisms and their comparative and evolutionary relationship" (G. Simpson, 1961)

Taxonomy :

       Taxonomy means classification following certain rules or principles. Word Taxonomy comes from two Greek words, taxis - meaning arragement and nomous meaning law or rule. The term taxonomy was first introduced by A.P. de Candolle (Swiss Botanist) [1778-1841].

Systematics of Living Organisms - Biologi

There is great diversity of oraganisms around us. Since time immemorial, we humans have been exploiting this wealth for our own benefit. During this process man tried to differentiate between and identify the organisms. Eventually this evolved into a branch of biology known as systematic or classification. The methods of classification dates back to ancient time when Indian, Greek and Roman philosophers have contributed their might to systematised science.

Key - Living World Biology

Key :

       Key is taxonomical aid used for classification of plants and animals. The keys are based on contrasting characters. One of the contrasting characters gets accepted and other rejected. The statement in key is called a lead. Normally keys are analytical in nature . Let us study about classification of living organisms in next chapter.

Biodiversity parks- Living World Biology

Biodiversity parks :

       It is an ecological assemblage of species that form self-sustaining communities on degraded / barren landscape e.g. Late  Uttamrao Patil biodiversity parks Gureghar Mahabaleshwar. This park is the best model for conservation of natural heritage in urban landscape.

       Systematic classification of living organisms is helpful in understanding the interrelations. In order to understand interrelations between organisms and maintain harmony on planet earth, study of biodiversity is a must.

ZOOLOGICAL PARKS - Living World Biology

Zoological Parks :

       Zoological Park generally known as zoo, is a place of interest for common man. In a zoo, wild animals are kept in captivity. They are protected and care is taken to provide conditions similar to their natural habitat. (ex - situ) In a zoo, a naturalist can study food habits and behavior of animals.

       Flora, manuals, Monographs and Catalogue are some other tools of maintaining biodiversity records. Flora is the plant life occurring in a particular any one selected biological group where as manual provides information, keys about identification of species found in a particular area.

MUSEUM - Living World Biology

Museum :

       Museums are the places where, collections of preserved plant and animal specimens are kept. Plant and animal specimens may be preserved in formalin (10% to 40% formaldehyd) in transperent jars. Jars are labelled. Larger animals like birds and mammals are usually stuffed and preserved. This science is known as taxidermy. Specimens in dried form are also kept in museum.

       We can even find systematic collections of shells, skeletons of animals, insect boxes in museums.

       Thus, biological museums in educational institutes are reference hubs of biodiversity studies.

BOTANICAL GARDENS - Living World Biology

Batanical Gardens :

       Botanical gardes are the places where plants of different varieties collected from different parts of the world, are grown in a scientific and systematic in a in vivo manner. Plants are labeled. The label-board shows scientific as well as common name of the plant.

HARBARIUM - LIVING WORLD BIOLOGY

Herbarium : 

       The word herbarium (plural-herbaria) was coined by Pitton de Tournefort in the book `Elemens'. The art of herbarium was initiated by an Italian taxonomist Luca Ghini (1490-1556). Herbaria are effective tools in taxonomic studies. A herbarium is essentially a dried plant specimen that is pressed, treated and mounted on standard size sheet in order to preserve it.

      Data, place of collection along with detailed classification and highlighting with its ecological peculiarities, characters of the plant are name of the collector may be added. This information is given at lower right corner of sheet and is called `label'.

Basic principles of life - Living World for Biologi

Basic principles of life:

A. The living beings once produced / born has to servive. For survival, it needs energy and many chemical molecules. For energy, it has to perform metabolism. Metabolism is breaking of molecules (catabolism) and making of new molecules (anabolism).

B. From birth onwards, organisms show tendency of growth and development. This growth is a well-orchestrated process. You might have observed sand mounds, boulders grow, etc. This growth is not from within and hence these are not living beings.

C. Growth and development are not the processes which have unlimited time span. At certain point of time, the molecules, organs, systems begin to loose their effective working and become old . This is ageing process of the body.

D. Life has to continue hence the organism tries to produce a young one like itself. It is possible due to repraduction (asexual or sexual). This ensures continuity of race. Mules, sterile worker bees do not reproduce; yet are living. Can we call reproduction as inclusive characteristic of life?

E. As the body looses it's capacity to perform metabolism, the organism dies.

F. Any living being responds to thermal, chemical or biological changes in the surrounding or biological changes in the surrounding. This is unique property of living beings.

        There are immense diversity in living organisms. Since time immemorial, variety of organisms are Living together on earth. In order to understand the interrelations between living and non-living as well as between living beings or groups, systematic study of these is essential. This data is also important for various industries and agriculture. Intensive laboratory and organisms from strong basis for meaningful use of the collected data. If we need to study this diversity, certain aids called taxonomical aids can be used. These includes herbaria, botanical gardens, museums, biodiversity parks, etc.

Living World - Importants note for Biologi

       Planet earth is made up of abiotic and biotic components. The biotic compo6are obviously the living beings present around us. The question is why do we call them living and how do they differ from non-living?