UNIT I Diversity in the Living World CHAPTER 1 The Living World ???????????????? ?What is Living ?Diversity in the living world ?Taxonomic Categories ?Taxonomical Aids The living world is very wonderful. It contains wide range of life forms. 1. 1What is living – Living organisms are self-replicating, evolving and self-regulating interactive systems capable of responding to external stimuli. Living organisms exhibit following distinctive characteristics. All Living Organisms grow: ?Twin characters of growth are increase in (a) mass and (b) number of individuals.
Cell division leads to growth of an organism. ?External Growth is shown in non-living bodies where the accumulation of material on the surface takes place thereby increasing the mass. ?Internal Growth is a process in which the mass of living bodies grows by cell division. ?Growth – by Cell Division Animals – It is up to a certain age Plants – Continues through out their life span All Living Organisms Reproduce: ?Organisms reproduce or replicate both by sexual and asexual means. ?In unicellular organisms growth and reproduction are synonymous. Organisms such as sterile working bees, mules are living but don’t reproduce. So it can’t be a defining factor for life. ?No non-living organism is capable of reproducing itself. Metabolism ?All living organisms are made up of chemicals. ?These chemicals are constantly being made and changed into other bio-molecules. These conversions are chemical reactions or metabolic reactions. ?Thousands of metabolic reactions occur simultaneously in all the living organisms. The sum total of all the chemical reactions inside our body is metabolism. Cellular organization of body is the defining feature of life forms. Consciousness ?The most obvious and technically complicated feature of all living organisms is their ability to sense their surroundings and environment and respond to these environmental stimuli (physical, chemical, biological). ?Consciousness is also a defining feature of living organisms. All living phenomena are due to underlying interactions. Properties of tissues are not present in the constituent cells but arise as a result of interactions among the constituent cells.
Properties of cellular organelles are not present in the molecular constituents of the organelles but arise because of interactions among the molecular components comprising the organelle. This phenomenon is true for the hierarchy of organizational complexity at all levels. 1. 2Diversity in the living world ?We can see a large variety of living organisms around us. ?Species – each different kind of plant, animal or organism represents a species. ?The number of species that are known and described range between 1. 7 – 1. 8 million. ?Biodiversity – is the number and types of organisms present on earth.
Nomenclature – Is the process to standardize the naming of living organisms such that a particular organism is known by the same name all over the world. Identification: Describing an organism correctly and knowing to what organism the name is attached to. It is an essential function of nomenclature. ICBN – International Code for Botanical Nomenclature – for plants scientific names are based on agreed principles and criteria provided by ICBN. ICZN – International Code for Zoological Nomenclature – for animals scientific names are given by ICZN evolved by animal taxonomists.
Binomial Nomenclature ?Biologists follow universally accepted principles for providing scientific to living organisms. ?Each name has two components (a) the Generic name (b) the Specific Epithet. ?This system of providing the name with two components is called binomial nomenclature. ?This naming system, given by Carolus Linnaeus is being practices by biologists all over the world. Universal Rules of Nomenclature 1. Biological names are generally in Latin and written in italics. They are Latinized 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 hand written, 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. Example – Mangifera indica. Name of the author appears after the specific epithet i. e. at the end of the biological name and is written in an abbreviated form. Example – Mangifera indica Linn. It indicates that this species was first described by Linnaeus.
Classification – is the process by which anything is grouped into convenient categories based on some easily observable characters. Taxa – the convenient categories we use to study organisms are Taxa. Taxonomy – The classification of all living organisms based on characteristics into different taxa. ?Internal and external structure, along with the structure of cell, development process and ecological information of organisms are essential for modern taxonomic studies. ?Characterization, Identification, Classification and Nomenclature are the processes that are basic to taxonomy. Systematics (dr. systema’ Lt. systematic arrangement of organisms) – Knowing more about different kinds of organisms and their diversities and also the evolutionary relationships among them is known as systematics. 1. 3Taxonomic Categories – Category is a part of overall taxonomic arrangement, it is thus called taxonomic category. Each category represents a unit of classification, a rank and is commonly termed as Taxon (pl. : taxa). Taxonomic Hierarchy – All categories together constitute taxonomic hierarchy. 1. 3. 1Species – A group of individual organisms with fundamental similarities are known as species. Distinct morphological differences differentiate two species from one another. 1. 3. 2Genus – Comprises a group of related species which has more characters in common in comparison to species of other genera (are aggregates of closely related organisms). ?Each genus may have one or more than one specific epithets representing different organisms but having morphological similarities. 1. 3. 3Family – Family has group of related genera with still less number of similarities as compared to genus and species. ?Families are characterized on the basis of both vegetative and reproductive features of plant species. 1. 3. Order – Is the assemblage of families which exhibit a few similar characters which are comparatively less in number than of different genera included in a family. 1. 3. 5Class – This category includes related orders. 1. 3. 6Phylum – Classes comprising animals like fishes, amphibians, reptiles, birds along with mammals constitute the next higher category called phylum. ?In case plants, classes with a few similar characters are assigned to a higher category called division. 1. 3. 7Kingdom – All animals belonging to various phyla are assigned to the highest category called Kingdom Animalia in the classification system of animals. The Kingdom Plantae on the other hand is distinct and comprises all plants from various divisions. Species GenusFamilyOrderClassPhylum or DivisionKingdom 1. 4Taxonomic Aids – Identification of organisms requires intensive laboratory and field studies. The collection of actual specimens of plant and animal species is essential and is the prime source of taxonomic studies. Biologists have established certain procedures and techniques to store and preserve the information as well as the specimens. Some of these are: 1. 4. Herbarium – It is a store house of collected plant specimens that are dried, pressed and preserved on sheets. These sheets are arranged according to universally accepted system of classification. ?The specimens along with their descriptions on herbarium sheets become a store house or repository for future use. ?Herbarium sheets also carry a label providing information about date and place of collection, English, local and botanical names, family, collector’s name etc. 1. 4. 2Botanical Gardens – These specialized gardens have collections of living plants for reference.
Plants species in these gardens are grown for identification purposes and each plant is labeled indicating its botanical / scientific name and its family. ?Famous Botanical gardens – Kew (England), Indian Botanical Garden, Howrah (India) and National Botanical Research Institute, Lucknow (India). 1. 4. 3Museum – Biological museums have collections of preserved plant and animal specimens for study and reference. ?Biological museums are generally set up in educational institutions such as schools and colleges. ?Specimens are preserved in the containers or jars in preservative solutions. 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 have often collections skeletons of animals too. 1. 4. 4Zoological Parks – These are places where wild animals are kept in protected environment under human care and which enable us to learn about their food habits and behaviour. 1. 4. 5Key – Is a taxonomical aid used for identification of plants and animals based on similarities and dissimilarities. The keys are based on 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. More Taxonomical Aids 1Flora – contains the actual account of habitat and distribution of plants of a given area. 2Manuals – useful in providing information for identification of names of species found in an area. 3Monographs – contains information on any one taxon. 4Catalogues