Characteristics of a Living Thing

Class XI UNIT I Chapter 1 The Living World Characteristics of a Living thing All living organisms grow Increase in mass and increase in number of cells Growth is not the defining property of living organisms as non living things grow by accumulating materials on their surface. A dead organism does not grow. Reproduction is a characteristic of living organisms. Reproduction can be sexual or asexual Budding in Yeast and Hydra Fungi by asexual spores. Planaria regeneration Fragmentation is seen in fungi, algae and protonema of mosses. Sterile organisms are mules, sterile worker bees and infertile human couples. Metabolism All living organisms are made of chemicals. These chemicals are constantly being made or change in to bio molecules. These conversions are chemical reactions or metabolic reactions. The sum total of all chemical reactions occurring in our body is metabolism. No non living object performs metabolic reactions. Cellular organisation of the body is the defining feature of life forms. Consciousness is the defining property of living organisms. All living organisms have the ability to sense their surroundings or environment and respond to these environmental stimuli which could be physical, chemical or biological. Human being is the only organism who is aware of himself, i.e. has self consciousness. Living organisms are self-replicating, evolving and self regulating interactive systems capable of responding to external stimuli. DIVERSITY IN THE LIVING WORLD BIODIVERSITY It is the number and types of organisms present on earth. The number of species known and described ranges between 1.7 to 1.8 million. Nomenclature is the naming of living organisms such that a particular organism is known by the same name all over the world. Identification Naming is done when the organism is described correctly and a name is attached to it. This is the identification of that organism. ICBN International Code for Botanical Nomenclature ICZN International Code of Zoological Nomenclature The scientific name ensures that each organism has only one name. Description of any organism should enable the people to arrive at the same name. Same name has not been used for any other known organism. Binomial Nomenclature Each scientific name has two components – the Generic name and the specific epithet. This system of providing a name with two components is called Binomial nomenclature. Carolus Linnaeus gave binomial nomenclature. For ex scientific name of mango is Mangifera indica. Mangifera represents the genus while indica is specific epithet. Universal rules of nomenclature. 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. 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 and is written in an abbreviated form, Mangifera indica Linn. Classification is the process by which anything is grouped into convenient categories based on some easily observable characters. Taxa is the scientific term for convenient categories used to study organisms. For example plants and wheat both come under taxa. Taxonomy is classification of all living organisms based on their characteristics into different taxa. Basis of modern taxonomy: External and internal structure, structure of cell, development process and ecological information of organisms. Basic processes of taxonomy Characterisation, identification, classification and nomenclature. Systematics is the study of different kinds of organisms, their diversities and relationships among them. Systema means systematic arrangement of organisms. Systemae Naturae is the title of Linnaeus publication . Scope of systematics – identification, nomenclature, classification and evolutionary relationships between organisms. Taxonomic Categories An organism represents /occupies a place or position in the system of classification. There are many categories/ranks and are referred to as taxonomic categories or taxa. All categories together constitute taxonomic hierarchy. Basic requirement to place an organism in a category or taxa is the knowledge of characters of an individual or group of organisms. Species is a group of individual organisms with fundamental similarities. Each genus may have one or more than one specific epithets representing different organisms. Panthera leo, Panthera tigris, Solanum nigrum, Solanum tuberosum Genus is a group of related species which has more characteristics in common in comparison to species of other genera. Potato, tomato and brinjal are three different species but belong to genus Solanum . Family is a group of related genera with less number of similarities. Families are characterised on the basis of both vegetative and reproductive features. Two different genera Panthera and Felis are kept in the family Felidae. Cat family –Felidae Dog family-Cancidae Order is the assemblage of families which exhibit a few similar characters. Order Carnivora includes families like Felidae and Cancidae. Class includes related orders. Order Primata and Carnivora are kept in class Mammalia. Phylum comprises of different classes of animals Division is the higher category in plants. Kingdom is the highest category comprising phylums or divisions. As we go higher from species to kingdom, the number of common characteristics goes on decreasing. Lower the taxa, more are the characteristics that the members with in the taxon share. Taxonomical Aids Need of Aids Taxonomists have developed a variety of taxonomic aids to facilitate identification, naming and classification of organisms. Studies are carried out from the actual specimens, which are collected from the fields and preserved as referrals in the form of herbaria, museums and in botanical gardens and zoological parks. Herbarium It is a store house of collected plant specimens that are dried, pressed and preserved on sheets, according to classification. Sheets carry a label providing information about date and place of collection, English, local and botanical name, family, collector’s name etc. https://youtu.be/NMEluqHHs4A Botanical Gardens These specialised gardens have collection of living plants for reference. Each plant is labelled with local, botanical name and its family. Indian Botanical Garden (Howarh) National Botanical Research Institute (Lucknow) https://youtu.be/YhWewL6lEQ4 Museum Museums have collections of preserved plant and animal specimens for study and reference. Specimens are preserved in jars in preservative solutions, as dry specimens, insect boxes or as stuffed big animals. Zoological Parks These are the places where wild animals are kept in protected environments under human care to study their food habits and behaviour. Living conditions provided are similar to their natural habitat. Key is a taxonomical aid 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. Each statement in key is called Lead. Keys are analytical in nature. Other tools are FLORA, MANUALS, MONOGRAPHS and CATALOGUES. Flora contains actual account of habitat and distribution of plants of a given area. They provide the index to the plant species found in a particular area. Manuals provide information for identification of names of species found in an area. Monographs contain information on any one taxon. .

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